Hello Config::Model::Dpkg project (a Debian source package model based on Config::Model) is partly based on a ParseRec::Descent grammar. This grammar is used to parse the dependency of a Debian source package. This article will show how such a grammar is written, its limitation regarding error handling and how to improve the situation. Debian package main data is described in debian/control file. This file can feature a list of dependencies, i.e. a list of package that must be installed for the package to work. These dependencies are declared in fields like Build-Depends , or Depends as a list of package. For Dpkg model purpose, I needed only to parse one item of a dependency list at a time. This dependency item can be a simple package name: foo or a package name with a version requirement: foo ( > 1.24 ) or a package name with architectures restrictions: foo [alpha amd64 hurd-arm linux-armeb] or both: foo ( > 1.24 ) [alpha amd64 hurd-arm linux-armeb] or a list of alternate choices combining the possibilities above: foo ( > 1.24 ) bar [ linux-any] baz ( << 3.14 ) [ ! hurd-armel !hurd-armeb ] or a variable that is replaced during package build: $ perl-depends Writing a Parse::RecDescent grammar to parse this is relatively straightforward. The first production handles alternate dependencies separated by and raises an error if some text was not consumed by the dependencies:

dependency_item: depend(s /\ /) eofile  

A dependency as explained above is expressed as:

depend: pkg_dep   variable

A variable like $ foo or $ bar -1.24~ is parsed with:

variable: /\$ [\w:\-]+ [\w\.\-~+]*/

This rule handles a package name with optional version or arch restriction:

pkg_dep: pkg_name dep_version(?) arch_restriction(?) 
pkg_name: /[a-z0-9][a-z0-9\+\-\.]+/

The remaining rules are quite simple:

dep_version: '(' oper version ')' 
oper: '<<'   '<='   '='   '>='   '>>'
version: variable   /[\w\.\-~:+]+/
arch_restriction: '[' arch(s) ']'
arch:  /!?[\w-]+/
eofile: /^\Z/

The grammar above works well to parse the dependency. You can test it with this small Perl script:

#!/usr/bin/perl
use strict;
use warnings;
use 5.010 ;
use Parse::RecDescent ;
my $parser = Parse::RecDescent->new(join('',));
my $dep = shift ;
say "parsing '$dep'";
my $ret = $parser->dependency_item($dep) ;
say "result is ", $ret if $ref ;
__DATA__
# insert grammar here !!!

Unfortunately, any error in the optional parts (i.e version requirements and arch restriction) leads to an error message which is not very helpful. The error message only mention that some text could not be parsed:

parsing 'foo ( != 1.24 )   bar'
       ERROR (line 1): Invalid dependency item: Was expecting /\ / but found
                       "( != 1.24 )   bar" instead

or

parsing 'foo [ arm & armel]   bar'
       ERROR (line 1): Invalid dependency item: Was expecting /\ / but found
                       "[ arm & armel]   bar" instead

The problem comes from the fact that version requirements or arch restrictions are optional. For instance if a version requirement has a syntax error, Parse::RecDescent will try to parse it as an arch restriction. This arch restriction rule will also fail and the last terminal ( eofile ) will fail. So the error message does not hint at the actual syntax problem. To generate better error messages, I improved the suggestion made in Parse::RecDescent FAQ. Instead of calling a plain subroutine, I use a sub reference that will store the error messages in a closure. This sub ref is declared in a start-up action. Note that the sub ref explicitly returns undef. I ll explain why later.

 
    my @dep_errors ;
    my $add_error = sub  
        my ($err, $txt) = @_ ;
        push @dep_errors, "$err: '$txt'" ;
        return ;
      ;
 

The following production always fails while ensuring that the error list is reset. This production is always run at the beginning of the dependency parsing:

dependency:   @dep_errors = ();  

Here s the actual dependency production that is run when dependency method is called on the parser. It will return an array ref containing (1, data) if the dependency is valid or (0, errors) otherwise:

dependency: depend(s /\ /) eofile
   
    $return = [ 1 , @ $item[1]  ] ;
   
   
   
    push( @dep_errors, "Cannot parse: '$text'" ) unless @dep_errors ;
    $return =  [ 0, @dep_errors ];
   

The following productions don t change much:

depend: pkg_dep   variable
variable: /\$ [\w:\-]+ [\w\.\-~+]*/
pkg_dep: pkg_name dep_version(?) arch_restriction(?) 
dep_version: '(' oper version ')'

The first rule of this production parses the package name which must be followed by a space, end of string ( or ['. A positive look-ahead assertion is used so only the package name is consumed. If the first rule fails, the second rule provides a meaningful error message. The second rule will match anything which is not a space and create an error message. Since $add_error returns undef, the second rule returns undef and the production fails. So the text stored in the error message is not consumed:

pkg_name: /[a-z0-9][a-z0-9\+\-\.]+(?=\s \Z \( \[)/
      /\S+/   $add_error->("bad package name", $item[1]) ; 

The same trick is used with these productions:

oper: '<<'   '='   '>>'
      /\S+/   $add_error->("bad dependency version operator", $item[1]) ; 
version: variable   /[\w\.\-~:+]+(?=\s \) \Z)/
      /\S+/   $add_error->("bad dependency version", $item[1]) ; 

The action of this production is a little bit more tricky. The action ensures that '!' are either added before all arch or not at all. Otherwise an error message is generated and added to the list of errors:

arch_restriction: '[' osarch(s) ']'
     
        my $mismatch = 0;
        # $ref contains ['!',os,arch] or ['',os,arch]
        my $ref = $item[2] ;
        for (my $i = 0; $i < $#$ref -1 ; $i++ )  
            $mismatch  = ($ref->[$i][0] xor $ref->[$i+1][0]) ;
         
        my @a = map   ($_->[0]   '') . ($_->[1]   '') . $_->[2]   @$ref ;
        if ($mismatch)  
            $add_error->("some names are prepended with '!' while others aren't.", "@a") ;
         
        else  
            $return = 1 ;
         
     

The check above is possible only if the "osarch" production returns an array ref containing something like ('!','linux','any') for "!linux-any' or ('','linux','any') for "linux-any":

osarch: not(?) os(?) arch
     
        $return =  [ $item[1][0], $item[2][0], $item[3] ];
     
      /.?(?=\s \] \Z)/   $add_error->("bad arch specification: ", $item[1]) ;  
not: '!'

Here's the remaining of the grammar:

os: /(any uclibc-linux linux kfreebsd knetbsd etc...)-/
     /\w+/ '-'   $add_error->("bad os in architecture specification", $item[1]) ; 
arch: / (any  alpha amd64  arm\b  arm64  etc... )
        (?=(\]  ))
      /x
        /\w+/   $add_error->("bad arch in architecture specification", $item[1]) ; 
eofile: /^\Z/

That's all for grammar 2.0... Before someone yells: "Show me the message ! ", here are some example of bad dependencies and their error message generated by the parser:

parse 'foo ( != 1.24 )   bar'
result is: 0 bad dependency version operator: '!='
parsing 'foo [ arm & armel]   bar'
result is: 0 bad arch specification: : '&'
parsing 'foo [ arm armel ]   bar [!moo]'
result is: 0 bad arch specification: : ']' bad arch in architecture specification: 'moo'

The 2 first error messages are spot on the actual error. The second one has a false positive (']' is correct) but correctly highlights the wrong arch name ('moo'). Mission accomplished. In order to keep this post (relatively) simple, I've removed the part that actually store parsed data. They don't really matter for error handling. Nevertheless, you may see the whole grammar in Config::Model::Dpkg::Dependency module. All the best
Tagged: Config::Model, debian, dpkg, package, Parse::RecDescent, Perl

Migrating a Debian installation between architectures has always been difficult. The recommended way to crossgrade an i386 Debian to amd64 Debian was to reinstall the system, move over data and configuration. For the more brave, in-place crossgrades usually involved chroots, rescue CDs, a lot of ar p tar xf - data.tar.gz and luck. I have never been brave when it comes to system administration, have done a lot of architecture migrations with reinstallation, and have always taken the opportunity to clear out the contamination that accumulates itself when a system is running for a long time. I would even recommend doing this to most people even now. However, I have a few very ugly systems in place that are still on i386 because I didn t dare going the reinstallation path. Doing in-place crossgrades has become a lot easier since wheezy s release, since once now can have both i386 and amd64 libraries installed in parallel, which allows to replace foo:i386 with foo:amd64 without influencing the other parts of the system. The process is still full of pitfalls:

• apt removes a package before it reinstalls its new counterpart. This results in apt calling dpkg to remove dpkg, and then calling dpkg again to install dpkg. Guess which operation fails and the state of the system after this failure. Same applies to coreutils, which leaves the system without rm, which in turn dpkg of either architecture doesn t like. Using apt-get --download-only install to resolve dependencies and downloading the debs, followed by a traditional dpkg --install solves this issue since multiarch dpkg will replace a package with another one without deinstalling the first one first.
• At least for the process, you need a kernel that can run both 32bit and 64bit binaries for the i386 architecture. AFAIR, setting CONFIG_64BIT, CONFIG_X86_64 and CONFIG_IA32_EMULATION in the kernel configuration takes care of this.
• During the process, apt wants to remove the better part of your system. It is important to not let it do this, as it wants to deinstall essential packages as well.
• It looks like the process is not always exactly reproducible. During the first tries, I found myself without an initrd at all, with an initrd that lacked the ext[234].ko kernel modules, without working e2fstools and in a number of other undesireable states of the system.

I have only tried this yet with a freshly installed minimal wheezy server system. I do not, however, expect surprises when it comes to using this process with real life systems. I will document other pitfalls I have fallen into here at a later time. My minimal wheezy system was running in a KVM VM with its virtual disk as a LVM LV in the host system. I took a snapshot before beginning and used lvconvert --merge numerous time to return my LV to the original state. Be aware that lvconvert --merge removes the snapshot after merging it, so you ll need to re-create the snapshot before trying again. During the process, I discussed things with Paul Tagliamonte, who has done this before, but on a live system and with a slightly more invasive approach. He has blogged about this. Thank you very much, your hints were very helpful. Here is a commented typescript of what I have done. Be warned: This was a lab setting with a rather minimal system. If you re going to try this with a production system, have a backup, or, if you re on snapshottable infrastructure, take snapshots and be prepared to roll back if anything goes wrong. First let s see what we have and save a list of installed packages.

mh@swivel:~$ ssh wheezyarch.zugschlus.de
$ uname -a
Linux wheezyarch 3.9.4-zgsrv2008064 #2 SMP PREEMPT Wed Jun 5 12:57:51 UTC 2013 x86_64 GNU/Linux
$ dpkg --print-architecture
i386
$ dpkg --print-foreign-architectures
$ dpkg --list   grep i386   wc -l
175
$ dpkg --list   grep amd64   wc -l
0
$ sudo dpkg --get-selections   grep install   awk  print $1    sed  s/:.*//;s/$/:amd64
install/;  > get-selections.pre

So we have an i386 system running an x86_64 kernel. Next, we add amd64 as an additional architecture which allows us to install amd64 packages. We download the amd64 packages files. Note that dpkg still considers this an i386 system with amd64 as a foreign arch.

$ sudo dpkg --add-architecture amd64
$ sudo apt-get update
Get:1 http://security.debian.org wheezy/updates Release.gpg [836 B]
( )
Fetched 6.155 kB in 4s (1.400 kB/s)
Reading package lists... Done
$ dpkg --print-architecture
i386
$ dpkg --print-foreign-architectures
amd64
$ dpkg --list   grep i386   wc -l
175
$ dpkg --list   grep amd64   wc -l
0

Next, download everything that is necessary to migrate dpkg and apt from i386 and amd64. We cannot directly apt things as the remove-install cycle used by apt will leave us without working dpkg. One could work around this by un-aring the dpkg.deb and directly forcing the amd64 files upon the system, but I think this approach is much cleaner. apt-get download will not resolve dependices while apt-get --download install does. After the download, dpkg --install the packages. dpkg is not particularly smart about installation order, so Pre-Depends may fail or not. If they fail, dpkg will give a list of deb files that were affected, which is an easy help to finish their installation. One could also choose the easy way (which I did here) and repeat the dpkg --install *.deb command. Since the Pre-Depends will already be installed, the second install run will succeed.

$ sudo apt-get --download-only install dpkg:amd64 apt:amd64
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following extra packages will be installed:
  gcc-4.7-base:amd64 libapt-pkg4.12:amd64 libbz2-1.0:amd64 libc6:amd64
  libgcc1:amd64 liblzma5:amd64 libselinux1:amd64 libstdc++6:amd64
  zlib1g:amd64
Suggested packages:
  aptitude:amd64 synaptic:amd64 wajig:amd64 dpkg-dev:amd64 apt-doc:amd64
  python-apt:amd64 glibc-doc:amd64 locales:amd64
The following packages will be REMOVED:
  apt cron-apt dpkg
The following NEW packages will be installed:
  apt:amd64 dpkg:amd64 gcc-4.7-base:amd64 libapt-pkg4.12:amd64
  libbz2-1.0:amd64 libc6:amd64 libgcc1:amd64 liblzma5:amd64 libselinux1:amd64
  libstdc++6:amd64 zlib1g:amd64
0 upgraded, 11 newly installed, 3 to remove and 0 not upgraded.
Need to get 10,0 MB of archives.
After this operation, 14,9 MB of additional disk space will be used.
Do you want to continue [Y/n]? 
Get:1 http://debian.debian.zugschlus.de/debian/ wheezy/main gcc-4.7-base amd64 4.7.2-5 [144 kB]
( )
Fetched 10,0 MB in 2s (3.535 kB/s)
Download complete and in download only mode
$ sudo dpkg --install /var/cache/apt/archives/*.deb
(Reading database ... 16586 files and directories currently installed.)
Preparing to replace apt 0.9.7.8 (using .../archives/apt_0.9.7.8_amd64.deb) ...
Unpacking replacement apt ...
dpkg: regarding .../dpkg_1.16.10_amd64.deb containing dpkg, pre-dependency problem:
 dpkg pre-depends on libbz2-1.0
dpkg: error processing /var/cache/apt/archives/dpkg_1.16.10_amd64.deb (--install):
 pre-dependency problem - not installing dpkg
Selecting previously unselected package gcc-4.7-base:amd64.
( )
Errors were encountered while processing:
 /var/cache/apt/archives/dpkg_1.16.10_amd64.deb
$ sudo dpkg --install /var/cache/apt/archives/*.deb
(Reading database ... 16905 files and directories currently installed.)
Preparing to replace apt 0.9.7.8 (using .../archives/apt_0.9.7.8_amd64.deb) ...
Unpacking replacement apt ...
( )
$

From dpkg s point of view, the system is now already amd64, with i386 being a foreign arch. However, the majory of packages is still i386.

$ dpkg --print-architecture
amd64
$ dpkg --print-foreign-architectures
i386
$ dpkg --list   grep i386   wc -l
173
$ dpkg --list   grep amd64   wc -l
11
$ 

The apt resolver is currently in a very bad broken state since the system is missing most essential packages in its native architecture. This is not easily solved by apt-get -f install, as this would zap most of the existing system . We let apt-get --download-only -f install download the packages that it wants to replace with its amd64 counterparts and their dependencies, and, again, use dpkg --install *.deb to install them.

$ sudo apt-get --download-only -f install
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Correcting dependencies... Done
The following packages were automatically installed and are no longer required:
  cpio gettext-base:i386 klibc-utils libapt-inst1.5 libasprintf0c2:i386
  libcurl3-gnutls:i386 libfreetype6:i386 libfuse2:i386 libklibc
  libreadline5:i386
Use  apt-get autoremove  to remove them.
The following extra packages will be installed:
  acpid aide bsd-mailx cpio cron curl daemon dctrl-tools exim4-base
  exim4-daemon-light initscripts insserv kbd klibc-utils less libbsd0
  libcomerr2 libcurl3 libdb5.1 libexpat1 libgcrypt11 libgdbm3 libgnutls26
  libgpg-error0 libgssapi-krb5-2 libidn11 libk5crypto3 libkeyutils1 libklibc
  libkmod2 libkrb5-3 libkrb5support0 libldap-2.4-2 liblockfile1 libncursesw5
  libnewt0.52 libp11-kit0 libpam-modules libpam0g libpcre3 libpopt0
  libreadline6 librtmp0 libsasl2-2 libslang2 libsqlite3-0 libssh2-1
  libssl1.0.0 libtasn1-3 libterm-readkey-perl libtinfo5 openssl perl
  perl-base python2.7 python2.7-minimal sysvinit-utils whiptail
Suggested packages:
  libarchive1 anacron logrotate checksecurity debtags mail-reader eximon4
  exim4-doc-html exim4-doc-info spf-tools-perl swaks bootchart2 rng-tools
  krb5-doc krb5-user libpam-doc perl-doc make python2.7-doc binutils
  binfmt-support bootlogd sash
Recommended packages:
  exim4 postfix mail-transport-agent psmisc mailx ca-certificates
  krb5-locales libgpm2 libfribidi0 libsasl2-modules libpng12-0
The following packages will be REMOVED:
  acpid:i386 aide:i386 aptitude:i386 bsd-mailx:i386 cpio:i386 cron:i386
  curl:i386 daemon:i386 dctrl-tools:i386 debsecan dmsetup:i386 e2fsprogs:i386
  exim4-base:i386 exim4-daemon-light:i386 git:i386 grub-common:i386
  grub-pc:i386 grub-pc-bin:i386 grub2-common:i386 ifupdown:i386
  initramfs-tools initscripts:i386 insserv:i386 ippl:i386 jed:i386 kbd:i386
  klibc-utils:i386 less:i386 libdevmapper-event1.02.1:i386
  libdevmapper1.02.1:i386 libklibc:i386 libnewt0.52:i386
  libparted0debian1:i386 libterm-readkey-perl:i386 lsof:i386 lvm2:i386
  molly-guard ntp:i386 openssh-server:i386 openssl:i386 parted:i386 perl:i386
  perl-base:i386 procps:i386 python-apt:i386 python2.7:i386
  python2.7-minimal:i386 rsyslog:i386 sysvinit:i386 sysvinit-utils:i386
  udev:i386 util-linux:i386 whiptail:i386
The following NEW packages will be installed:
  acpid aide bsd-mailx cpio cron curl daemon dctrl-tools exim4-base
  exim4-daemon-light initscripts insserv kbd klibc-utils less libbsd0
  libcomerr2 libcurl3 libdb5.1 libexpat1 libgcrypt11 libgdbm3 libgnutls26
  libgpg-error0 libgssapi-krb5-2 libidn11 libk5crypto3 libkeyutils1 libklibc
  libkmod2 libkrb5-3 libkrb5support0 libldap-2.4-2 liblockfile1 libncursesw5
  libnewt0.52 libp11-kit0 libpam-modules libpam0g libpcre3 libpopt0
  libreadline6 librtmp0 libsasl2-2 libslang2 libsqlite3-0 libssh2-1
  libssl1.0.0 libtasn1-3 libterm-readkey-perl libtinfo5 openssl perl
  perl-base python2.7 python2.7-minimal sysvinit-utils whiptail
0 upgraded, 58 newly installed, 53 to remove and 0 not upgraded.
Need to get 23,4 MB of archives.
After this operation, 17,5 MB disk space will be freed.
Do you want to continue [Y/n]? Y
Get:1 http://security.debian.org/debian-security/ wheezy/updates/main libgnutls26 amd64 2.12.20-7 [619 kB]
( )
Fetched 23,4 MB in 11s (2.038 kB/s)                                           
Download complete and in download only mode
$ sudo dpkg --install /var/cache/apt/archives/*.deb
(Reading database ... 16905 files and directories currently installed.)
Preparing to replace acpid 1:2.0.16-1+deb7u1 (using .../acpid_1%3a2.0.16-1+deb7u1_amd64.deb) ...
( )
Selecting previously unselected package libpam-modules:amd64.
dpkg: regarding .../libpam-modules_1.1.3-7.1_amd64.deb containing libpam-modules:amd64, pre-dependency problem:
 libpam-modules pre-depends on libdb5.1
  libdb5.1:amd64 is unpacked, but has never been configured.
dpkg: error processing /var/cache/apt/archives/libpam-modules_1.1.3-7.1_amd64.deb (--install):
 pre-dependency problem - not installing libpam-modules:amd64
Selecting previously unselected package libpcre3:amd64.
Unpacking libpcre3:amd64 (from .../libpcre3_1%3a8.30-5_amd64.deb) ...
( )
Errors were encountered while processing:
 /var/cache/apt/archives/libpam-modules_1.1.3-7.1_amd64.deb
$ sudo dpkg --install /var/cache/apt/archives/libpam-modules_1.1.3-7.1_amd64.deb
(Reading database ... 17007 files and directories currently installed.)
Unpacking libpam-modules:amd64 (from .../libpam-modules_1.1.3-7.1_amd64.deb) ...
Setting up libpam-modules:amd64 (1.1.3-7.1) ...
$ sudo apt-get clean
$ dpkg --print-architecture
amd64
$ dpkg --print-foreign-architectures
i386
$ dpkg --list   grep i386   wc -l
151
$ dpkg --list   grep amd64   wc -l
66
$ 

The concluding apt-get clean prevents packages from being reinstalled again in the next dpkg --install *.deb run. Now, the apt resolver is kind of fixed, but apt will still want to remove most of the system. I haven t found a way to get out of this mess short of allowing apt to de-install those packages and to manually install their amd64 counterparts later. First, we see what apt wants to do, and paste the The following packages will be removed part of apt-get s output into a sed expression which fixes the architecture strings for us so that we can use the resulting file as input for the following installation procedure. After that, we let apt-get do what itself considers a bad thing and requires us to type a consent sentence. The key is that this deinstallation of essential packages breaks the system, but not apt and dpkg, which allows us to un-break the system afterwards.

$ sudo apt-get -f install
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Correcting dependencies... Done
The following packages were automatically installed and are no longer required:
  gettext-base:i386 libapt-inst1.5 libasprintf0c2:i386 libcurl3-gnutls:i386
  libfreetype6:i386 libfuse2:i386 libreadline5:i386
Use  apt-get autoremove  to remove them.
The following extra packages will be installed:
  sysvinit-utils:i386
Suggested packages:
  bootlogd:i386 sash:i386
The following packages will be REMOVED:
  adduser aide-common aptitude:i386 bsd-mailx console-common console-data
  console-log cron curl debian-goodies debsecan dmsetup:i386 e2fsprogs:i386
  exim4-base exim4-config exim4-daemon-light git:i386 grub-common:i386
  grub-pc:i386 grub-pc-bin:i386 grub2-common:i386 ifupdown:i386
  initramfs-tools initscripts ippl:i386 jed:i386 libcurl3
  libdevmapper-event1.02.1:i386 libdevmapper1.02.1:i386 liberror-perl
  libfile-find-rule-perl libnumber-compare-perl libparted0debian1:i386
  libswitch-perl libterm-readkey-perl libterm-readline-perl-perl
  libtext-glob-perl libtimedate-perl locales lsof:i386 lvm2:i386 molly-guard
  ntp:i386 openssh-client:i386 openssh-server:i386 openssl openssl-blacklist
  openssl-blacklist-extra parted:i386 perl perl-modules procps:i386
  python-apt:i386 rsyslog:i386 stow sysv-rc sysvinit:i386 sysvinit-utils
  tzdata ucf udev:i386 util-linux:i386
The following NEW packages will be installed:
  sysvinit-utils:i386
WARNING: The following essential packages will be removed.
This should NOT be done unless you know exactly what you are doing!
  e2fsprogs:i386 util-linux:i386 (due to e2fsprogs:i386) sysvinit:i386
  sysvinit-utils tzdata (due to util-linux:i386)
0 upgraded, 1 newly installed, 62 to remove and 0 not upgraded.
Need to get 97,1 kB of archives.
After this operation, 131 MB disk space will be freed.
You are about to do something potentially harmful.
To continue type in the phrase  Yes, do as I say!  ? (abort with Ctrl-C)
$ sed  s/:i386//g  > removedpkg (paste  The following packages will be REMOVED:  stanza here and
type Ctrl-D afterwards)
  adduser aide-common aptitude:i386 bsd-mailx console-common console-data
  console-log cron curl debian-goodies debsecan dmsetup:i386 e2fsprogs:i386
  exim4-base exim4-config exim4-daemon-light git:i386 grub-common:i386
  grub-pc:i386 grub-pc-bin:i386 grub2-common:i386 ifupdown:i386
  initramfs-tools initscripts ippl:i386 jed:i386 libcurl3
  libdevmapper-event1.02.1:i386 libdevmapper1.02.1:i386 liberror-perl
  libfile-find-rule-perl libnumber-compare-perl libparted0debian1:i386
  libswitch-perl libterm-readkey-perl libterm-readline-perl-perl
  libtext-glob-perl libtimedate-perl locales lsof:i386 lvm2:i386 molly-guard
  ntp:i386 openssh-client:i386 openssh-server:i386 openssl openssl-blacklist
  openssl-blacklist-extra parted:i386 perl perl-modules procps:i386
  python-apt:i386 rsyslog:i386 stow sysv-rc sysvinit:i386 sysvinit-utils
  tzdata ucf udev:i386 util-linux:i386
$ cat removedpkg 
  adduser aide-common aptitude bsd-mailx console-common console-data
  console-log cron curl debian-goodies debsecan dmsetup e2fsprogs
  exim4-base exim4-config exim4-daemon-light git grub-common
  grub-pc grub-pc-bin grub2-common ifupdown
  initramfs-tools initscripts ippl jed libcurl3
  libdevmapper-event1.02.1 libdevmapper1.02.1 liberror-perl
  libfile-find-rule-perl libnumber-compare-perl libparted0debian1
  libswitch-perl libterm-readkey-perl libterm-readline-perl-perl
  libtext-glob-perl libtimedate-perl locales lsof lvm2 molly-guard
  ntp openssh-client openssh-server openssl openssl-blacklist
  openssl-blacklist-extra parted perl perl-modules procps
  python-apt rsyslog stow sysv-rc sysvinit sysvinit-utils
  tzdata ucf udev util-linux
$ sudo apt-get -f install
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Correcting dependencies... Done
The following packages were automatically installed and are no longer required:
  gettext-base:i386 libapt-inst1.5 libasprintf0c2:i386 libcurl3-gnutls:i386
  libfreetype6:i386 libfuse2:i386 libreadline5:i386
Use  apt-get autoremove  to remove them.
The following extra packages will be installed:
  sysvinit-utils:i386
Suggested packages:
  bootlogd:i386 sash:i386
The following packages will be REMOVED:
  adduser aide-common aptitude:i386 bsd-mailx console-common console-data
  console-log cron curl debian-goodies debsecan dmsetup:i386 e2fsprogs:i386
  exim4-base exim4-config exim4-daemon-light git:i386 grub-common:i386
  grub-pc:i386 grub-pc-bin:i386 grub2-common:i386 ifupdown:i386
  initramfs-tools initscripts ippl:i386 jed:i386 libcurl3
  libdevmapper-event1.02.1:i386 libdevmapper1.02.1:i386 liberror-perl
  libfile-find-rule-perl libnumber-compare-perl libparted0debian1:i386
  libswitch-perl libterm-readkey-perl libterm-readline-perl-perl
  libtext-glob-perl libtimedate-perl locales lsof:i386 lvm2:i386 molly-guard
  ntp:i386 openssh-client:i386 openssh-server:i386 openssl openssl-blacklist
  openssl-blacklist-extra parted:i386 perl perl-modules procps:i386
  python-apt:i386 rsyslog:i386 stow sysv-rc sysvinit:i386 sysvinit-utils
  tzdata ucf udev:i386 util-linux:i386
The following NEW packages will be installed:
  sysvinit-utils:i386
WARNING: The following essential packages will be removed.
This should NOT be done unless you know exactly what you are doing!
  e2fsprogs:i386 util-linux:i386 (due to e2fsprogs:i386) sysvinit:i386
  sysvinit-utils tzdata (due to util-linux:i386)
0 upgraded, 1 newly installed, 62 to remove and 0 not upgraded.
Need to get 97,1 kB of archives.
After this operation, 131 MB disk space will be freed.
You are about to do something potentially harmful.
To continue type in the phrase  Yes, do as I say! 
 ?] Yes, do as I say! (actually type this!)
Get:1 http://debian.debian.zugschlus.de/debian/ wheezy/main sysvinit-utils i386 2.88dsf-41 [97,1 kB]
Fetched 97,1 kB in 0s (687 kB/s)    
(Reading database ... 17050 files and directories currently installed.)
Removing aide-common ...
( )
dpkg: warning: overriding problem because --force enabled:
 This is an essential package - it should not be removed.
Removing e2fsprogs ...
Removing sysv-rc ...
dpkg: warning: overriding problem because --force enabled:
 This is an essential package - it should not be removed.
Removing sysvinit ...
dpkg: warning: overriding problem because --force enabled:
 This is an essential package - it should not be removed.
Removing sysvinit-utils ...
dpkg: warning: overriding problem because --force enabled:
 This is an essential package - it should not be removed.
Removing ucf ...
dpkg: warning: overriding problem because --force enabled:
 This is an essential package - it should not be removed.
dpkg: warning: overriding problem because --force enabled:
 This is an essential package - it should not be removed.
dpkg: warning: overriding problem because --force enabled:
 This is an essential package - it should not be removed.
dpkg: warning: overriding problem because --force enabled:
 This is an essential package - it should not be removed.
dpkg: warning: overriding problem because --force enabled:
 This is an essential package - it should not be removed.
Removing libdevmapper1.02.1:i386 ...
Removing libswitch-perl ...
Removing perl ...
dpkg: warning: overriding problem because --force enabled:
 This is an essential package - it should not be removed.
Removing dmsetup ...
Removing perl-modules ...
dpkg: warning: overriding problem because --force enabled:
 This is an essential package - it should not be removed.
Removing util-linux ...
Removing tzdata ...
Processing triggers for mime-support ...
Selecting previously unselected package sysvinit-utils.
(Reading database ... 9802 files and directories currently installed.)
Unpacking sysvinit-utils (from .../sysvinit-utils_2.88dsf-41_i386.deb) ...
Setting up sysvinit-utils (2.88dsf-41) ...
$ sudo apt-get install $(cat removedpkg)
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  libasprintf0c2:i386 libcurl3-gnutls:i386 libfreetype6:i386 libfuse2:i386
  libreadline5:i386
Use  apt-get autoremove  to remove them.
The following extra packages will be installed:
  e2fslibs gettext-base libapt-inst1.5 libasprintf0c2 libattr1 libblkid1
  libboost-iostreams1.49.0 libcap2 libcurl3-gnutls libcwidget3 libedit2
  libept1.4.12 libfreetype6 libfuse2 libgpm2 libncurses5 libopts25 libprocps0
  libreadline5 libsepol1 libsigc++-2.0-0c2a libss2 libudev0 libuuid1 libwrap0
  libxapian22 logrotate
Suggested packages:
  liblocale-gettext-perl tasksel debtags unicode-data anacron checksecurity
  popularity-contest xdg-utils zenity gpart e2fsck-static mail-reader eximon4
  exim4-doc-html exim4-doc-info spf-tools-perl swaks git-daemon-run
  git-daemon-sysvinit git-doc git-el git-arch git-cvs git-svn git-email
  git-gui gitk gitweb multiboot-doc grub-emu xorriso desktop-base
  isc-dhcp-client dhcp-client ppp rdnssd net-tools gpm libcwidget-dev fuse
  libparted0-dev libparted0-i18n xapian-tools ntp-doc ssh-askpass libpam-ssh
  keychain monkeysphere rssh ufw parted-doc perl-doc make libpod-plainer-perl
  python-apt-dbg python-gtk2 python-vte python-apt-doc rsyslog-mysql
  rsyslog-pgsql rsyslog-doc rsyslog-gnutls rsyslog-gssapi rsyslog-relp
  doc-base sysv-rc-conf bum bootlogd sash util-linux-locales dosfstools
Recommended packages:
  aptitude-doc-en aptitude-doc apt-xapian-index libparse-debianchangelog-perl
  exim4 postfix mail-transport-agent psmisc mailx patch rsync ssh-client
  os-prober busybox busybox-initramfs busybox-static ca-certificates
  uuid-runtime xauth ncurses-term iso-codes usbutils
The following packages will be REMOVED:
  gettext-base:i386 libboost-iostreams1.49.0:i386 libcwidget3:i386
  libept1.4.12:i386 libopts25:i386 libxapian22:i386 logrotate:i386
  sysvinit-utils:i386
The following NEW packages will be installed:
  adduser aide-common aptitude bsd-mailx console-common console-data
  console-log cron curl debian-goodies debsecan dmsetup e2fslibs e2fsprogs
  exim4-base exim4-config exim4-daemon-light gettext-base git grub-common
  grub-pc grub-pc-bin grub2-common ifupdown initramfs-tools initscripts ippl
  jed libapt-inst1.5 libasprintf0c2 libattr1 libblkid1
  libboost-iostreams1.49.0 libcap2 libcurl3 libcurl3-gnutls libcwidget3
  libdevmapper-event1.02.1 libdevmapper1.02.1 libedit2 libept1.4.12
  liberror-perl libfile-find-rule-perl libfreetype6 libfuse2 libgpm2
  libncurses5 libnumber-compare-perl libopts25 libparted0debian1 libprocps0
  libreadline5 libsepol1 libsigc++-2.0-0c2a libss2 libswitch-perl
  libterm-readkey-perl libterm-readline-perl-perl libtext-glob-perl
  libtimedate-perl libudev0 libuuid1 libwrap0 libxapian22 locales logrotate
  lsof lvm2 molly-guard ntp openssh-client openssh-server openssl
  openssl-blacklist openssl-blacklist-extra parted perl perl-modules procps
  python-apt rsyslog stow sysv-rc sysvinit sysvinit-utils tzdata ucf udev
  util-linux
WARNING: The following essential packages will be removed.
This should NOT be done unless you know exactly what you are doing!
  sysvinit-utils:i386
0 upgraded, 89 newly installed, 8 to remove and 0 not upgraded.
Need to get 55.3 MB of archives.
After this operation, 134 MB of additional disk space will be used.
You are about to do something potentially harmful.
To continue type in the phrase  Yes, do as I say! 
 ?] Yes, do as I say! (actually type this!)
Get:1 http://debian.debian.zugschlus.de/debian/ wheezy/main e2fslibs amd64 1.42.5-1.1 [197 kB]
( )
Fetched 55.3 MB in 20s (2648 kB/s)                                            
perl: warning: Setting locale failed.
( )

This process may re-ask some debconf questions that you have already answered during initial system setup. I find it comforting to actually see that my answers were preserved, but you can always export DEBIAN_FRONTEND=noninteractive if you want installation to be silent. If you know how this step can be done more elegantly, please comment. We now, finally, have the resolver in a consistent state.

$ sudo apt-get -f install
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  libasprintf0c2:i386 libcurl3-gnutls:i386 libfreetype6:i386 libfuse2:i386
  libreadline5:i386
Use  apt-get autoremove  to remove them.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
$ dpkg --print-architecture
amd64
$ dpkg --print-foreign-architectures
i386
$ dpkg --list   grep i386   wc -l
121
$ dpkg --list   grep amd64   wc -l
119
$ 

Now we can force-crossgrade all i386 packages that are still left on the system. Again, we use the apt-get --download install, dpkg --install stunt as coreutils gets crossgraded at this step and dpkg is less than happy if it finds itself without /bin/rm. Remember, with --download, nothing is actually removed during this step even if apt-get claims to remove things. Apt will also complain that many of these packages are already installed. Those are libs that were pulled in previously. The first dpkg --install run in this step will complain about gazillions of dependency problems, which will all be resolved in concluding apt-get -f install after the second dpkg --install run, this time a manual one.

$ sudo apt-get --download-only install $(dpkg --list   awk  if( $1 ==  ii  && $4 ==
 i386  )   print $2     sed  s/:i386// )
Reading package lists... Done
Building dependency tree       
Reading state information... Done
( )
The following packages were automatically installed and are no longer required:
  libasprintf0c2:i386 libcurl3-gnutls:i386 libfreetype6:i386 libfuse2:i386
  libreadline5:i386
Use  apt-get autoremove  to remove them.
Suggested packages:
  powermgmt-base bash-doc bzip2-doc diffutils-doc wdiff mlocate locate
  gnupg-doc xloadimage imagemagick eog libpcsclite1 iproute-doc resolvconf
  avahi-autoipd nfs-common ncompress indent
Recommended packages:
  bsdmainutils gnupg-curl libatm1
The following packages will be REMOVED:
  anacron:i386 apt-utils:i386 base-files:i386 base-passwd:i386 bash:i386
( )
The following NEW packages will be installed:
  anacron apt-utils base-files base-passwd bash bsdutils busybox bzip2
( )
0 upgraded, 56 newly installed, 49 to remove and 0 not upgraded.
Need to get 24,1 MB of archives.
After this operation, 2.030 kB of additional disk space will be used.
Do you want to continue [Y/n]? y
Get:1 http://debian.debian.zugschlus.de/debian/ wheezy/main kmod amd64 9-3 [60,5 kB]
( )
Fetched 24,1 MB in 11s (2.120 kB/s)                                           
Download complete and in download only mode
$ sudo dpkg --install /var/cache/apt/archives/*.deb
(Reading database ... 17098 files and directories currently installed.)
Preparing to replace adduser 3.113+nmu3 (using .../adduser_3.113+nmu3_all.deb) ...
Unpacking replacement adduser ...
( )
Errors were encountered while processing:
 /var/cache/apt/archives/bash_4.2+dfsg-0.1_amd64.deb
 /var/cache/apt/archives/coreutils_8.13-3.5_amd64.deb
 initscripts
 lvm2
 procps
 rsyslog
 sysvinit
 sysv-rc
 udev
 util-linux
 aide-common
 dmsetup
 e2fsprogs
 ifupdown
 initramfs-tools
 libdevmapper1.02.1:amd64
 libdevmapper-event1.02.1:amd64
 libparted0debian1:amd64
 molly-guard
 openssh-server
 parted
 grub-common
 grub-pc
 grub-pc-bin
 grub2-common
$ sudo dpkg --install /var/cache/apt/archives/bash_4.2+dfsg-0.1_amd64.deb
/var/cache/apt/archives/coreutils_8.13-3.5_amd64.deb
(Reading database ... 17129 files and directories currently installed.)
Preparing to replace bash 4.2+dfsg-0.1 (using .../bash_4.2+dfsg-0.1_amd64.deb) ...
Unpacking replacement bash ...
Preparing to replace coreutils 8.13-3.5 (using .../coreutils_8.13-3.5_amd64.deb) ...
Unpacking replacement coreutils ...
Setting up bash (4.2+dfsg-0.1) ...
update-alternatives: using /usr/share/man/man7/bash-builtins.7.gz to provide /usr/share/man/man7/builtins.7.gz
(builtins.7.gz) in auto mode
Setting up coreutils (8.13-3.5) ...
$ sudo apt-get -f install
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Correcting dependencies... Done
The following packages were automatically installed and are no longer required:
  libasprintf0c2:i386 libcurl3-gnutls:i386 libfreetype6:i386 libfuse2:i386
  libreadline5:i386
Use  apt-get autoremove  to remove them.
The following extra packages will be installed:
  sysvinit-utils
Suggested packages:
  bootlogd sash
The following packages will be REMOVED:
  libslang2-modules:i386 sysvinit-utils:i386
The following NEW packages will be installed:
  sysvinit-utils
WARNING: The following essential packages will be removed.
This should NOT be done unless you know exactly what you are doing!
  sysvinit-utils:i386
0 upgraded, 1 newly installed, 2 to remove and 0 not upgraded.
23 not fully installed or removed.
Need to get 0 B/99,5 kB of archives.
After this operation, 328 kB disk space will be freed.
You are about to do something potentially harmful.
To continue type in the phrase  Yes, do as I say! 
 ?] Yes, do as I say! (actually type this!)
dpkg: warning: overriding problem because --force enabled:
 This is an essential package - it should not be removed.
(Reading database ... 17129 files and directories currently installed.)
Removing sysvinit-utils ...
Selecting previously unselected package sysvinit-utils.
(Reading database ... 17105 files and directories currently installed.)
Unpacking sysvinit-utils (from .../sysvinit-utils_2.88dsf-41_amd64.deb) ...
Setting up sysvinit-utils (2.88dsf-41) ...
Setting up sysv-rc (2.88dsf-41) ...
Setting up initscripts (2.88dsf-41) ...
Setting up util-linux (2.20.1-5.3) ...
Setting up e2fsprogs (1.42.5-1.1) ...
Setting up sysvinit (2.88dsf-41) ...
sysvinit: restarting... done.
(Reading database ... 17129 files and directories currently installed.)
Removing libslang2-modules:i386 ...
Setting up ifupdown (0.7.8) ...
Setting up procps (1:3.3.3-3) ...
[ ok ] Setting kernel variables ... /etc/sysctl.conf...done.
Setting up udev (175-7.2) ...
[ ok ] Stopping the hotplug events dispatcher: udevd.
[ ok ] Starting the hotplug events dispatcher: udevd.
update-initramfs: deferring update (trigger activated)
Setting up rsyslog (5.8.11-3) ...
[ ok ] Stopping enhanced syslogd: rsyslogd.
[ ok ] Starting enhanced syslogd: rsyslogd.
Setting up aide-common (0.15.1-8) ...
Setting up initramfs-tools (0.109.1) ...
update-initramfs: deferring update (trigger activated)
Setting up openssh-server (1:6.0p1-4) ...
[ ok ] Restarting OpenBSD Secure Shell server: sshd.
Setting up molly-guard (0.4.5-1) ...
Setting up libdevmapper1.02.1:amd64 (2:1.02.74-7) ...
Setting up libdevmapper-event1.02.1:amd64 (2:1.02.74-7) ...
Setting up libparted0debian1:amd64 (2.3-12) ...
Setting up grub-common (1.99-27+deb7u1) ...
Setting up grub2-common (1.99-27+deb7u1) ...
Setting up grub-pc-bin (1.99-27+deb7u1) ...
Setting up grub-pc (1.99-27+deb7u1) ...
Installation finished. No error reported.
Generating grub.cfg ...
Found linux image: /boot/vmlinuz-3.9.4-zgsrv2008064
Found initrd image: /boot/initrd.img-3.9.4-zgsrv2008064
done
Setting up parted (2.3-12) ...
Setting up dmsetup (2:1.02.74-7) ...
update-initramfs: deferring update (trigger activated)
Setting up lvm2 (2.02.95-7) ...
[ ok ] Setting up LVM Volume Groups...done.
update-initramfs: deferring update (trigger activated)
Processing triggers for initramfs-tools ...
update-initramfs: Generating /boot/initrd.img-3.9.4-zgsrv2008064
Found 12 processes using old versions of upgraded files
( )
$ sudo apt-get -f install
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  libasprintf0c2:i386 libcurl3-gnutls:i386 libfreetype6:i386 libfuse2:i386
  libreadline5:i386
Use  apt-get autoremove  to remove them.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
$ dpkg --print-architecture
amd64
$ dpkg --print-foreign-architectures
i386
$ dpkg --list   grep i386   wc -l
72
$ dpkg --list   grep amd64   wc -l
175
$ 

We have completed the actual crossgrade. All non-multiarch packages are now amd64. The resolver is now fine as well. At this current state, all i386 packages that are still installed should be unneeded libs. We can safely nuke them. Careful minds may inspect the list of packages to be removed for important or non-lib items. After completion of the command, a second call of the same command verifies that we were successful.

$ sudo apt-get remove $(dpkg --list   awk  if( $1 ==  ii  && $4 ==  i386  )   print $2
  )
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages will be REMOVED:
  e2fslibs:i386 gcc-4.7-base:i386 libacl1:i386 libapt-inst1.5:i386
  libapt-pkg4.12:i386 libasprintf0c2:i386 libattr1:i386 libblkid1:i386
  libbsd0:i386 libbz2-1.0:i386 libc6:i386 libcap2:i386 libcomerr2:i386
  libcurl3:i386 libcurl3-gnutls:i386 libdb5.1:i386 libedit2:i386
  libexpat1:i386 libfreetype6:i386 libfuse2:i386 libgcc1:i386
  libgcrypt11:i386 libgdbm3:i386 libgnutls26:i386 libgpg-error0:i386
  libgpm2:i386 libgssapi-krb5-2:i386 libidn11:i386 libk5crypto3:i386
  libkeyutils1:i386 libkmod2:i386 libkrb5-3:i386 libkrb5support0:i386
  libldap-2.4-2:i386 liblockfile1:i386 liblzma5:i386 libmagic1:i386
  libncurses5:i386 libncursesw5:i386 libp11-kit0:i386 libpam-modules:i386
  libpam0g:i386 libpci3:i386 libpcre3:i386 libpng12-0:i386 libpopt0:i386
  libprocps0:i386 libreadline5:i386 libreadline6:i386 librtmp0:i386
  libsasl2-2:i386 libselinux1:i386 libsemanage1:i386 libsepol1:i386
  libsigc++-2.0-0c2a:i386 libslang2:i386 libsqlite3-0:i386 libss2:i386
  libssh2-1:i386 libssl1.0.0:i386 libstdc++6:i386 libtasn1-3:i386
  libtinfo5:i386 libudev0:i386 libusb-0.1-4:i386 libustr-1.0-1:i386
  libuuid1:i386 libwrap0:i386 linux-image-3.9.4-zgsrv2008064:i386 zlib1g:i386
0 upgraded, 0 newly installed, 70 to remove and 0 not upgraded.
After this operation, 67,5 MB disk space will be freed.
Do you want to continue [Y/n]? y
(Reading database ... 17111 files and directories currently installed.)
Removing e2fslibs:i386 ...
( )
$ sudo apt-get remove $(dpkg --list   awk  if( $1 ==  ii  && $4 ==  i386  )   print $2
  )
Reading package lists... Done
Building dependency tree       
Reading state information... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
$ dpkg --print-architecture
amd64
$ dpkg --print-foreign-architectures
i386
$ dpkg --list   grep i386   wc -l
70
$ dpkg --list   grep amd64   wc -l
175
$ 

To finally make the packages really vanish from the system, we purge all packages that dpkg --list still reports in state rc , which means removed, configuration still present . Thankfully, dpkg seems to handle the case where a dpkg-conffile belongs to a transitioned package gracefully.

$ sudo dpkg --purge $(dpkg --list   awk  if ($1 ==  rc )   print $2  )
(Reading database ... 15868 files and directories currently installed.)
Removing e2fslibs:i386 ...
Purging configuration files for e2fslibs:i386 ...
( )
$ dpkg --print-architecture
amd64
$ dpkg --print-foreign-architectures
i386
$ dpkg --list   grep i386   wc -l
0
$ dpkg --list   grep amd64   wc -l
175
$ 

We now verify that all packages we have are either arch all or arch amd64.

$ dpkg --list   grep -v  \(amd64 all\) 
Desired=Unknown/Install/Remove/Purge/Hold
  Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
 / Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
 / Name                            Version                   Architecture Description
+++-===============================-=========================-============-========================================================================

As I found myself suddenly without e2fsprogs during one of my experiments, I check for e2fsprogs being present. If this package is missing, you ll only find out after rebooting.

$ dpkg --list e2fsprogs
Desired=Unknown/Install/Remove/Purge/Hold
  Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
 / Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
 / Name           Version      Architecture Description
+++-==============-============-============-=================================
ii  e2fsprogs      1.42.5-1.1   amd64        ext2/ext3/ext4 file system utilit

My locally built amd64 kernel with 32 bit support was an arch i386 package as well, so it got zapped in the migration process. Replace it with a real amd64 kernel. This step will vary if you use Debian kernels. Do not forget the firmwares.

$ sudo apt-get -t wheezy-zg-experimental install kernel-image-zgserver linux-firmware-image
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following extra packages will be installed:
  cpio initramfs-tools kernel-image-zgsrv20080 klibc-utils libklibc
  linux-image-3.9.4-zgsrv20080
Suggested packages:
  libarchive1
The following NEW packages will be installed:
  cpio initramfs-tools kernel-image-zgserver kernel-image-zgsrv20080
  klibc-utils libklibc linux-firmware-image linux-image-3.9.4-zgsrv20080
0 upgraded, 8 newly installed, 0 to remove and 0 not upgraded.
Need to get 11,2 MB of archives.
After this operation, 30,5 MB of additional disk space will be used.
Do you want to continue [Y/n]? 
Get:1 http://zg20110.debian.zugschlus.de/ wheezy-zg-experimental/main linux-image-3.9.4-zgsrv20080 amd64
3.9.4.20130605.0 [10,4 MB]
( )

I now make sure that the initrd I have built contains all file system modules and is of the right architecture:

$ cd /tmp
$ < /boot/initrd.img-3.9.4-zgsrv20080 gunzip   cpio -i
32053 blocks
$ find . -name  *ext*.ko 
./lib/modules/3.9.4-zgsrv20080/kernel/fs/ext3/ext3.ko
./lib/modules/3.9.4-zgsrv20080/kernel/fs/ext2/ext2.ko
./lib/modules/3.9.4-zgsrv20080/kernel/fs/ext4/ext4.ko
$ file ./lib/modules/3.9.4-zgsrv20080/kernel/fs/ext4/ext4.ko
./lib/modules/3.9.4-zgsrv20080/kernel/fs/ext4/ext4.ko: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV),
BuildID[sha1]=0x259a642448805c9597932ee25c62c8e6a00a32ad, not stripped
$ cd

As the last step, remove i386 as an architecture and reboot into the newly migrated system. We verify that the system considers itself amd64 with no foreign architectures.

$ sudo dpkg --remove-architecture i386
$ dpkg --print-architecture
amd64
$ 
$ dpkg --print-foreign-architectures
$ dpkg --list   grep i386   wc -l
0
$ dpkg --list   grep amd64   wc -l
181
$ sudo shutdown -r now
Broadcast message from root@wheezyarch (pts/0) (Wed Jun 12 16:09:24 2013):
The system is going down for reboot NOW!
$ Connection to wheezyarch.zugschlus.de closed by remote host.
Connection to wheezyarch.zugschlus.de closed.
$ ssh wheezyarch.zugschlus.de
Linux wheezyarch 3.9.4-zgsrv20080 #2 SMP PREEMPT Wed Jun 5 13:12:04 UTC 2013 x86_64
$ dpkg --print-architecture
amd64
$

We now check whether we have lost any packages in this process:

$ sudo dpkg --get-selections   grep install   awk  print $1    sed  s/:.*//;s/$/:amd64
install/;  > get-selections.post
$ wc -l get-selections.*
  234 get-selections.post
  226 get-selections.pre
$ diff --unified=0 get-selections.pre get-selections.post 
--- get-selections.pre  2013-06-12 19:47:40.278176000 +0200
+++ get-selections.post 2013-06-12 20:28:51.389874000 +0200
@@ -22,0 +23 @@
+cpio:amd64 install
@@ -58,0 +60 @@
+initramfs-tools:amd64 install
@@ -68,0 +71,3 @@
+kernel-image-zgserver:amd64 install
+kernel-image-zgsrv20080:amd64 install
+klibc-utils:amd64 install
@@ -108,0 +114 @@
+libklibc:amd64 install
@@ -163,0 +170,2 @@
+linux-firmware-image:amd64 install
+linux-image-3.9.4-zgsrv20080:amd64 install

So we have not actually lost things, but we have gained the pure amd64 kernel and the packages that are needed to build a proper initrd. These were missing from the initial install of the i386 test VM. The downside of the process is that we have lost most of the automatically installed markers in aptitude which make sure to remove a library once nothing depends on it any more. If you make a point in having those markers correctly set, as I do, this is tedious work to set it on every package in the aptitude curses interface, making aptitude suggest removing the entire system, and then again remove it from the packages you actually intend to keep. This should not result in anything being removed, otherwise you have goofed previously. All Done! I am now off perfecting my upgrade process so that the i386 lenny and squeeze machines can first be moved to wheezy and then to amd64.

So I'd previously talked about migrating machines. From having one virtual machine running "mail" + "web" + "stuff" I've now got three hosts:

ssh.steve.org.uk

This is supposed to be used solely for shell access, email reading, IRC. Sadly it still hosts one website, the web interface to my Mercurial repositories. This can't be moved without moving the repositories which is a step too far. Although I don't particularly want people browsing my code/changes I do want them to be able to clone them. If I could get anonymous-SSH checkouts working, sanely, then I'd be happy, but I don't see how to do that.

skx-web

This hosts all my websites except for two. The two that are excluded are my mercurial repositories, which still lives on ssh.steve.org.uk, and my blogspam service.

blogspam

This runs my blogspam.net service. I wish I could retired this, since it uses cruftly XML::RPC. I'd rather see a RESTful application sending/receiving JSON. Sadly I can't kill it without annoying a lot of people. So it must remain.

I chose to add the blogspam guest, because that service does really take over an IP, and it just seemed simplest to move it to one machine. As a quick hack both http://repository.steve.org.uk & http://blogspam.net/ run under Apache. Although the other websites run under their own UID with thttpd + my proxy. Now time to change the subject entirely. I've recently joined gym. Which isn't as horrible as I thought it might be, though as a matter of policy I refuse to go on any of those fancy running/jogging machines. The first three weeks I just alternated between the cycling machines and the rowing machines. Initially ten minutes on each, then twenty, then thirty. Now I'm being all brave and adventurous, using new machines and pieces of equipment. Writing this I've got a dull ache in both my arms, after doing seated-dips with 100Lbs. So I guess I'm starting to make progress. No specific goals in mind, but I've been paying slightly more attention to my diet over the past month and I think if I'm a "little fitter" and have "slightly nicer arms" then I'll be happy enough. I've no desire to go all anal and count calories, or give up chocolate and beer. So it is almost hard to explain why I'm going, but .. it is fun, and watching the numbers change is fun too. I'll probably post more about this in the future.

The third wheezy based alpha release of Debian Edu was wrapped up today. This is the release announcement: New features for Debian Edu 7.0.0 alpha2 released 2013-06-10 This is the release notes for for Debian Edu / Skolelinux 7.0.0 edu alpha2, based on Debian with codename "Wheezy". About Debian Edu and Skolelinux Debian Edu, also known as Skolelinux, is a Linux distribution based on Debian providing an out-of-the box environment of a completely configured school network. Immediately after installation a school server running all services needed for a school network is set up just waiting for users and machines being added via GOsa , a comfortable Web-UI. A netbooting environment is prepared using PXE, so after initial installation of the main server from CD, DVD or USB stick all other machines can be installed via the network. The provided school server provides LDAP database and Kerberos authentication service, centralized home directories, DHCP server, web proxy and many other services. The desktop contains more than 60 educational software packages and more are available from the Debian archive, and schools can choose between KDE, Gnome, LXDE and Xfce desktop environment. This is the third test release based on Debian Wheezy. Basically this is an updated and slightly improved version compared to the Squeeze release. Software updates

• Iceweasel was updated from 10 to 17. (DSA 2699-1)
• Updated libxv (DSA-2674), libxvmc (DSA-2675), libxfixes (DSA-2676), libxrender (DSA-2677), mesa (DSA-2678), xserver-xorg-video-openchrome (DSA-2679), libxt (DSA-2680), libxcursor (DSA-2681), libxext (DSA-2682), libxi (DSA-2683), libxrandr (DSA-2684), libxp (DSA-2685), libxcb (DSA-2686), libfs (DSA-2687), libxres (DSA-2688), libxtst (DSA-2689), libxxf86dga (DSA-2690), libxinerama (DSA-2691), libxxf86vm (DSA-2692), libx11 (DSA-2693), chromium-browser (DSA-2695), gnutls26 (DSA-2697), wireshark (DSA-2700), krb5 (DSA-2701), telepathy-gabble (DSA-2702) and subversion (DSA-2703).
• Switched xrdp on thin client servers to use tightvncserver instead of xvnc4.
• Now install software oscilloscope xoscope by default.
• Now install music tools gtick, lingot and pianobooster by default.

Other changes

• The subnet-change script is now able to change all files needing a change on the main-server when changing the IP network used.
• Updated translation of the installation.
• New Romanian translation.
• Fix security problem causing root and first user password to no longer show up in /var/cache/debconf/templates.dat.
• Fix roaming workstation setup (Closed in libpam-mklocaluser/0.8, libpam-mklocaluser/0.8~deb7u1: #706753: libpam-mklocaluser: Fail to create local user during first login).
• Made roaming workstation setup more robust in non-Debian Edu environments.
• New script debian-edu-bless to transform a Debian installation to a Debian Edu profile.
• Adjust Iceweasel setup to improve performance when $HOME is on NFS.
• More testsuite tests.
• Make automatic proxy configuration more robust.
• Adjust GOsa GUI configuration.
• Update thin client and diskless workstation setup to work with LTSP in Wheezy.
• Diskless workstations now run out of the box -- no need to set them up with GOsa .
• Update IMAP server setup.
• Fix login into Skolelinux Backup Tool (Closed in slbackup-php/0.4.4-1: #700257: slbackup-php: Fails to submit correctly entered password).

Known issues

• DVD binary and source images are not yet ready.
• No mass import of user account data in GOsa (ldif or csv) available yet (Open in gosa/2.7.4-4: #698840: gosa-plugin-ldapmanager: missing import feature).
• Missing artwork for the KDE desktop (and probably a few others).
• KDE Debian submenu lacks icons (Closed: #502192: menu-xdg: invents own icon names instead of using existing). This will remain unfixed.

Where to get it To download the multiarch netinstall CD release you can use

• ftp://ftp.skolelinux.org/skolelinux-cd/wheezy/debian-edu-7.0+edu0~a2-CD.iso
• http://ftp.skolelinux.org/skolelinux-cd/wheezy/debian-edu-7.0+edu0~a2-CD.iso
• rsync -avzP ftp.skolelinux.org::skolelinux-cd/wheezy/debian-edu-7.0+edu0~a2-CD.iso .

The MD5SUM of this image is: 27bbcace407743382f3c42c08dbe8178
The SHA1SUM of this image is: e35f7d7908566cd3075375b3721fa10ee420d419 How to report bugs http://wiki.debian.org/DebianEdu/HowTo/ReportBugs

One of the various ways to measure an open source project is the way it encourages and accepts patches from community members (or future members). The various open source projects I m involved with have many ways to send patches: mailing list, bug tracking systems and more recently pre-commit tools for peer review (such as gerrit). Another popular option is to use github s pull request feature for this. Personally, I find it too complex for simple patches and would prefer gerrit over it. As part of my work at Zend, I try to make sure patches are sent back upstream. Comparing to other open source projects I know, it seems to me that PHP isn t open enough for contributions. This might be just my private case, but if not, it would be discouraging people to contribute and blocking the community from expanding. 6 Months ago I submitted patch to #36103 (patch is at #63767), but no response. A month ago I submitted a simple patch to FPM s shell script (#64764), and no response there as well. To ease things up, I ve created a github fork of the php-src repository and sent pull requests with each of the patches (as suggested at http://php.net/git-php.php). Even edited the bugs reports with the pull request details (as they provide such integration). I m waiting to see if this will trigger a more rapid review process from the project. For the simple patch, I got a response very fast from a user, but still waiting for a core member to check it. Going over the pull requests (both open and closed), I m not too optimistic about having the patches merged, judging by past merged patches (most of them are at least 2 months) and by the open patches (e.g. a typos fix patch is waiting for month).
Filed under: PHP

It has been a while since my last English Debian Edu and Skolelinux interview last November. But the developers and translators are still pulling along to get the Wheezy based release out the door, and this time I managed to get an interview from one of the French translators in the project, C dric Boutillier. Who are you, and how do you spend your days? I am 34 year old. I live near Paris, France. I am an assistant professor in probability theory. I spend my daytime teaching mathematics at the university and doing fundamental research in probability in connexion with combinatorics and statistical physics. I have been involved in the Debian project for a couple of years and became Debian Developer a few months ago. I am working on Ruby packaging, publicity and translation. How did you get in contact with the Skolelinux / Debian Edu project? I came to the Debian Edu project after a call for translation of the Debian Edu manual for the release of Debian Edu Squeeze. Since then, I have been working on updating the French translation of the manual. I had the opportunity to make an installation of Debian Edu in a virtual machine when I was preparing localised version of some screen shots for the manual. I was amazed to see it worked out of the box and how comprehensive the list of software installed by default was. What amazed me was the complete network infrastructure directly ready to use, which can and the nice administration interface provided by GOsa . What pleased me also was the fact that among the software installed by default, there were many "traditional" educative software to learn languages, to count, to program... but also software to develop creativity and artistic skills with music (Ardour, Audacity) and movies/animation (I was especially thinking of Stopmotion). I am following the development of Debian Edu and am hanging out on #debian-edu. Unfortunately, I don't much time to get more involved in this beautiful project. What do you see as the advantages of Skolelinux / Debian Edu? For me, the main advantages of Skolelinux/Debian Edu are its community of experts and its precise documentation, as well as the fact that it provides a solution ready to use. I would add also the fact that it is based on the rock solid Debian distribution, which ensures stability and provides a huge collection of educational free software. What do you see as the disadvantages of Skolelinux / Debian Edu? Maybe the lack of manpower to do lobbying on the project. Sometimes, people who need to take decisions concerning IT do not have all the elements to evaluate properly free software solutions. The fact that support by a company may be difficult to find is probably a problem if the school does not have IT personnel. One can find support from a company by looking at the wiki dokumentation, where some countries already have a number of companies providing support for Debian Edu, like Germany or Norway. This list is easy to find readily from the manual. However, for other countries, like France, the list is empty. I guess that consultants proposing support for Debian would be able to provide some support for Debian Edu as well. Which free software do you use daily? I am using the KDE Plasma Desktop. But the pieces of software I use most runs in a terminal: Mutt and OfflineIMAP for emails, latex for scientific documents, mpd for music. VIM is my editor of choice. I am also using the mathematical software Scilab and Sage (built from source as not completely packaged for Debian, yet). Do you have any suggestions for teachers interested in using the free software in Debian to teach mathematics and statistics? I do not have any "nice" recommendations for statistics. At our university, we use both R and Scilab to teach statistics and probabilistic simulations. For geometry, there are nice programs:

• drgeo and kig to do constructions in planar geometry
• kali to discover symmetry groups (the so-called wallpapers and frieze groups), although the interface looks a bit old.

I like also cantor, which provides a uniform interface to SciLab, Sage, Octave, etc... Which strategy do you believe is the right one to use to get schools to use free software? My suggestions would be to

• advertise the reduction of costs when free software is used.
• communicate about the quality of free software projects, using well known examples like Firefox, ThunderBird and OpenOffice.org/LibreOffice.
• advertise the living and strong community around the project.
• show that it is not more difficult to use than any other system.

I recently made a routine analysis of my kitchen. (Of course I make a routine analysis of my kitchen; don t you?) In it, I discovered these items, still usable, but approaching that magic throw it out date:

• Baby carrots
• Potatoes
• Lemons
• Green beans
• Corn

So, I thought, what can I make that would use all of these? And I realized I had some shrimp in the freezer, so: a shrimp boil! I tossed it all, plus some various seasonings and a few other veggies, into the Dutch oven, and boiled. Jacob and Oliver watched the activity with interest. Well, except for the potato-peeling part. For that, they went and played with their toy school buses. But the rest was good. They carefully observed me adding some spices, some vegetables, the shrimp, and watched it all simmer. Then it was time to eat. Excitement! Of course, it did take a few minutes to boil, so Jacob got down his whiteboard while Oliver looked on. They enjoyed learning how to peel the shell from the shrimp and devoured their food. And another night recently, Jacob unexpectedly showed up in the kitchen at 10PM. He said he was thirsty, so I got him some water. He asked, Dad, did you make ice cream? Earlier that day, I had prepared ice cream with Oliver, but it was a kind that had to be cooked (lemon with pureed strawberries and peaches) and it wasn t cool enough to finish before their bedtime. I did let them help add the ice and salt to the ice cream freezer just before they went to bed. So I told Jacob that yes, the ice cream was done. He stood there, tiredly, considering, with this oh he ll never say yes to ice cream at 10PM look on his face. So I said, would you like one bite right now? The look of delight on his face was amazing; a broad smile, a twinkle in his eyes, and a clap. So I got out the big bowl of ice cream and scooped up one big spoonful. He loved it. Then I said, should we go look at the stars? I carried Jacob outside to the porch. We stood there, looking up. I used to do this with him periodically, but it had been about a year. So he was thrilled. It was a partially overcast night, but there were still some stars visible. He had no idea there were some stars missing. To him, it was amazing and wonderful and infinite. Oh dad, there are way too many stars to count! He stayed there, arms around my neck, for a minute or two, then was ready to go back inside. I set him down, gave him a hug, said Goodnight, Jacob. And off he trotted, back upstairs, wearing a contented smile, and he fell asleep almost immediately. All it takes to delight children is a bit a shrimp or some stars. And those things delight me, too.

Included in Debian Edu / Skolelinux, there are quite a lot of educational software. Created to help teachers teach, and pupils learn. We have tried to tag them all using debtags use::learning and role::program, and using the debtags I was happy to be able to create a collage of the educational software packages installed by default, sorted by the debtag field. Here it is. Click on a image to learn more about the program. field::arts field::astronomy field::biology:structural field::chemistry [viewmol] field::electronics [gpsim] field::geography field::linguistics field::mathematics [geomview] field::physics field::TODO In total, 61 applications. 3 of them lacked screen shots on screenshot.debian.net. If you know of some packages we should install by default, please let us know on IRC, #debian-edu on irc.debian.org, or our mailing list debian-edu@.

I like Drupal. It's a very, very flexible CMS that evolved into a full-fledged Web development framework. Mind you, it's written in PHP, and that makes it a nightmare to develop for (in ~6 years I have used it for all of my important websites I have only got around to develop a set of related modules for it once). PHP programming sucks and makes my eyes and fingers bleed, but happily there are people who disagree with me And they tend to write code. All the better! Minor upgrades with Drupal are quite easy to handle. Not as easy as I'd like (i.e. whenever I upgrade the core system or a module, I have to log in as root^Wadmin^WUser #1 to ~15 different sites and run http://someurl/update.php It very seldom causes any pain. The updates that have to be run via this URL are usually on the database's structures, so I understand they have to be started (and watched) by a human. And yes, I know I could do that with Drush, the Drupal shell, but it is not very friendly to Debian-packaged Drupal... But easy enoguh. But major updates are a royal pain, and they usually amount to quite a bit. First, disable all of the modules and revert to a known-safe theme. Ok, it makes sense. Second, check whether the modules exist for the newer version (as they won't work Drupal changes enough between major versions that not only it's API-incompatible, I'd classify it as API-unrecognizable). Ok, all set? Now for the live migration itself... It has to be triggered from the browser. So yes, I am now staring at a window making clever AJAX status updates. I am sitting at 46 of 199, but following the lovely ways of programmers, it's impossible to forsee whether update #47 will just be an UPDATE foo SET bar=0 WHERE bar IS NULL or a full-scale conversion between unspeakable serialized binary structures while rearranging the whole database structure. And yes, while the meter progresses I stand in fear that update #n+1 will bomb giving me an ugly red error. I must keep the magic AJAX running, or the update might be botched. And, of course, the update has sat at #69 all while I wrote the last two paragraphs. Sometimes the updates can progress after an interruption... And it seems I have no choice but to interrupt it. /me crosses fingers... [update] Wow... I am happy I got bored of looking at the meter and decided to write this blog post: After several minutes, and just as I was about to launch a second update session (130 updates to go), the meter advanced! I'm now sitting watching it at #75. Will it ever reach 199? [update] And so it had to be... At around 115, I now got: *sigh* The update process was aborted prematurely while running update #7000 in biblio.module...

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Yesterday, the first milestone of the Havana developement branch of Ceilometer has been released and is now available for testing and download. This means the first quarter of the OpenStack Havana development has passed! New features Ten blueprints have been implemented as you can see on the release page. I'm going to talk through some of them here, that are the most interesting for users. Ceilometer can now counts the scheduling attempt of instances done by nova-scheduler. This can be useful to eventually bill such information or for audit (implemented by me for eNovance). People using the HBase backend can now do requests filtering on any of the counter fields, something we call metadata queries, and which was missing for this backend driver. Thanks to Shengjie Min (Dell) for the implementation. Counters can now be sent over UDP instead of the Oslo RPC mechanism (AMQP based by default). This allows counter transmission to be done in a much faster way, though less reliable. The primary use case being not audit or billing, but the alarming features that we are working on (implemented by me for eNovance). The initial alarm API has been designed and implemented, thanks to Mehdi Abaakouk (eNovance) and Angus Salkled (RedHat) who tackled this. We're now able to do CRUD actions on these. Posting of meters via the HTTP API is now possible. This is now another conduct that can be used to publish and collector meter. Thanks to Angus Salkled (RedHat) for implementing this. I've been working on an somewhat experimental notifier driver for Oslo notification that publishes Ceilometer counters instead of the standard notification, using the Ceilometer pipeline setup. Sandy Walsh (Rackspace) has put in place the base needed to store raw notifications (events), with the final goal of bringing more functionnalities around these into Ceilometer. Obviously, all of this blueprint and bugfixes wouldn't be implemented or fixed without the harden eyes of our entire team, reviewing code and advising restlessly the developers. Thanks to them! Bug fixes Thirty-one bugs were fixed, though most of them might not interest you so I won't elaborate too much on that. Go read the list if you are curious. Toward Havana 2 We now have 21 blueprints targetting the Ceilometer's second Havana milestone, with some of them are already started. I'll try to make sure we'll get there without too much trouble for the 18th July 2013. Stay tuned!

A few days ago we the Qt/KDE team uploaded a new tool in the Qt ecosystem: qtchooser.

This tool is a wrapper tool used to select between different Qt versions. Of course, the first and easiest example is choosing between Qt4 and Qt5. But it doesn't end there: it can also be used to select a user's build of Qt.

To experienced Debian users, at first sight, it might resemble Debian's alternatives system. But it goes much further than that, allowing users (not sysadmins) to decide their defaults, and even adding new ones, user-wide. All this can be done using different methods like command line arguments, environment variables and configuration files.

Apart from all that, this is the recommended upstream way of managing Qt, being picked up by several (if not all) distributions, so it can easily be supported by upstream in their documentation.

My Qt4 package in Debian does not uses qtchooser, do I need to change anything?No, we have tried to make things as smooth as possible. Your Qt4 packages should be safe. There will be more info on this later.

Review: The Making of the Indebted Man, by Maurizio Lazzarato

Translator:	Joshua David Jordan
Publisher:	Semiotext(e)
Copyright:	2011, 2012
Printing:	2012
ISBN:	1-58435-115-2
Format:	Trade paperback
Pages:	199

This is a continuation of my effort to catch up on Marxist thought while pondering workplace governance, this time following the recommendations of a friend after a related conversation (about pension systems and basic income guarantee in a Usenet group Usenet isn't dead yet). As opposed to Democracy at Work, which is a popularization, The Making of the Indebted Man has more of the density of a scholarly text. The version I'm reading is also in translation, which I suspect makes it even harder going in places. The basic thesis, though, is clear: debt is far more central to the way that we construct not only economic systems but social systems and even internal models of our own nature than is often realized. We prefer to think of societies as structured around mutual exchange, but in practice they're more often constructed around concepts of debt and credit that have been fully internalized and used to construct a moral code for a responsible debtor. And this is not a neutral construction; rather, it is a key support mechanism of capitalism and of the financial and economic status quo, used (both intentionally and accidentally) to reduce uncertainty and to support exploitation and economic domination. This is one of those perspectives that didn't occur to me prior to reading this book but which is startlingly obvious in retrospect. Once Lazzarato starts pointing it out, the prevelance and universality of debt as a basic structure of social and economic life is striking. The creditor and debtor concept extends not just to obvious examples, such as consumer credit or mortgages, but also to education (via student loans), law enforcement ("pay one's debt to society"), employment (most employers, particularly during economic downturns, have successfully inverted the natural direction of the creditor relationship and have made employees feel in debt to the employer for having a job), and social services (unemployment and welfare benefits come with significant, if often unstated, debt-like requirements). Debt is also the great leveller. It now cuts across race, gender, and social class. Apart from a small handful of extremely rich individuals and corporations, Lazzarato claims, convincingly, that nearly everyone is enmeshed to some extent in a network of debt, or at least in in attitudes and moral pressures of a debtor. Nor is this a static situation. The role of debt in our social lives seems to be constantly increasing. The past fifteen years in particular have seen drastic increases in debt during a debt-funded economic boom combined with debt-funded asset bubbles. Even after the financial collapse, much of that growth of debt persists. Lazzarato, probably in part because he's Italian, focuses on national debt (more on that in a moment); as an American, I'd identify student loan debt as a more compelling example in the United States. Other countries probably have their own examples. For a system to be this widespread, it must serve some social purpose. Lazzarato sees it as an instrument of control. Debt has been very effectively built up as a moral obligation, and (unlike a society of mutual support) it's a very one-sided moral obligation that strongly favors existing power. The debtor is held to a tight moral standard of repayment of debts, and is morally condemned by all of society, including their peers, for a failure to repay. But there is little or no corresponding moral pressure on the creditor: perhaps a half-hearted dislike of high interest rates or occasional pressure to not change previously agreed terms, but nothing like the moral pressure applied to the debtor. To be a creditor is to have an agreed-upon, one-sided right to dictate to the debtor the terms on which they must conduct a portion of their life, and the larger the debt, the larger the portion. The debtor is expected to realign their life, at least in part, around paying off the debt, including choice of profession, decisions about when to quit a job, about how to prioritize personal spending, and so forth. This is all so automatic and so deeply ingrained that, even while writing this, I'm nodding along and thinking "well, of course." Lazzarato offers an opportunity to take a step back and think about the implications, particularly of the deeply one-sided web of obligations this creates. A Marxist analysis adds another level of consideration. One of the basic questions of Marxist thought is why workers put up with exploitation by capitalists. In a Marxist analysis, workers provide the productive output of society, which is then redirected and controlled by a relatively small capitalists. The workers massively outnumber the capitalists. Why would they be content for this situation to continue? Marx, of course, thought they wouldn't be, that the periodic crises of capitalism would eventually result in a socialist revolution by the workers. But by and large this hasn't happened. Why? Lazzarato offers debt as a partial explanation. The profits redirected by capitalists are returned to workers to some extent, but as debt rather than payment. This allows workers to participate to some extent in the growth of societal wealth from constantly increasing productivity, while simultaneously entangling workers in a system of moral control. Company stores, starvation wages, and other confiscatory practices are clear mechanisms of external control that provoke directed outrage. Debt is something that the debtor has nominally agreed to (however much the situation is manipulated to make that agreement almost inevitable), and to which attaches a deep tradition of moral responsibility. The worker has respected grounds on which to object to inequitable treatment; the debtor is wholly responsible for repayment, and is rarely considered to have grounds to complain about the debt. Most of the historical attempts to balance those scales, such as laws and religious rules against usury or the historical Jewish rule of Jubilee, have fallen by the wayside. This is a rather extended summary of what I got out of the book. I'm doing that in part because the book itself is somewhat heavy going. Lazzarato makes extensive use of specialized terms (often not defined) and fills the book with references to other works without much in the way of useful summary. It's the sort of book where, if you're not already well-versed in the field, you may need to just keep reading through some passages to find a point of reference that makes the argument retroactively make sense. I had a particular difficulty with "subjectivation," a term that Wikipedia tells me is from the writings of Michel Foucault (a major source for this book), which Lazzarato uses extensively but never adequately defines. Some external research indicates that this is a very difficult term to define, which explains why I was never quite comfortable with my understanding. I think Lazzarato is using it to get at the process of internalization of the morality of debt and the way that a debt society forces individuals into a mode of economic individualism in which many of their personal choices are bent towards making themselves better (more reliable, more trustworthy) debtors. But I'm not completely sure. There are also places in which I think Lazzarato takes his argument too far, although one of those, I think, reflects a difference in national economic status. He makes quite a lot of national debt in this book, placing it in the universal position of the overarching debt that turns every citizen into a debtor even if they've avoided other debts. This is possibly true in countries whose national debts are held in other currencies, or in countries like Italy that are part of the Euro (which, if one is not Germany or France, amounts to much the same thing). It's a dubious assertion for countries like the UK, Japan, or the United States, where the national debt is held in their own free-floating currency and is largely owed domestically, and partly plays into some frustratingly incorrect political rhetoric. One of the key dynamics of debt, namely the extreme power imbalance between debtor and creditor, is missing in countries with sovereign debt in their own currency, since those countries can always (if they're willing to pay the inflation price) simply print money to pay off national debt. Creditors know this, and therefore interest rates are much lower, the amount of leverage the creditor has is quite limited, and the sorts of debt crises seen in Italy and elsewhere in the Euro periphery are not seen. Lazzarato is understandably writing from the Italian perspective, but I think he weakens his argument by lumping national debt so completely into the same category as the other types of exploitative debt he discusses. The principle does feel universal to me, but the best examples of debt vary by country, so one has to be careful about generalizing specific examples. Another place where I simply disagree with his conclusions is around some of the more dramatic presentations of subjectivation. Lazzarato talks, at one point, about how debt reduces debtors to mechanical components, and uses as an example an ATM machine, which he portrays as uniquely dehumanizing through the mechanical process that someone has to follow to withdraw money. There may be some point here about the dehumanization of debt and its subsumption into the foundation of day-to-day social interaction, but he lost me entirely with the unwarranted technophobia of the specific example. The idea that machines and automation make us less human is an old argument that's orthogonal to the thrust of his argument. It reminded me of old contentions that human relationships made on-line aren't real, which is nonsense. Overall, this is a fascinating and insightful discussion hampered by a difficult and sometimes overly elliptical presentation, a bit too much drama and grand theorizing, and a few poor choices of examples. I found the basic idea extremely valuable, but the amount of work required to extract it occasionally irritating. (This could be partly due to the limits of translation, but I suspect most of the difficulty was present in the original.) I'm not sure that I would recommend the book, but I definitely recommend considering the underlying ideas. Debt now works alongside the employment relationship as a primary means of reinforcing economic and social control and hierarchy. This is likely via accidental development rather than any grand plan, but it's now being actively exploited by the creditors of society, large corporations most notably. Viewed in that light, the explosive growth of student loan debt in the United States is particularly frightening. After Lazzarato's extensive examination of the distortive effects of permanent debt, not just on economics and society but on our own conceptions of our selves and our duties and roles in life, the idea of trapping a generation in debt from the moment of their financial independence is deeply troubling, even nauseating. Rating: 6 out of 10

Almost every bug tracker for free software projects has a section for wishlist bugs. Often this results in ever growing lists of wishes, most of which will never be fulfilled. A long list of bugs, even if it is wishlist bugs, is rarely useful. It's hard to keep track of what is there, and so the information is not kept up to date when things change. Even if a wishlist bug gets implemented, the bug is often overlooked, and remains on the list. Joel Spolsky calls this a software inventory. Carrying a large inventory has costs, and usually results in slowed-down development. It increases the friction of doing things in a project. I have some quite old wishlists for my own projects. I have even more wishlists hidden in my own GTD system. I am not happy about either, and I'm going to have to do something about that. Just closing all wishlist bugs immediately would be bad manners. Keeping them open indefinitely, just in case someone will some day decide to look through the list in order to hack on something, is wishful thinking: that rarely happens. So I'm thinking of a compromise: keep wishlist bugs open for a while, perhaps a few months, and if nothing is happening to them, close them with an apology.

Cameron Russell (who works as an underwear model) gave an interesting TED talk about beauty [1]. Ben Goldacre gave an interesting and energetic TED talk about bad science in medicine [2]. A lot of the material is aimed at non-experts, so this is a good talk to forward to your less scientific friends. Lev wrote a useful description of how to disable JavaScript from one site without disabling it from all sites which was inspired by Snopes [3]. This may be useful some time. Russ Allbery wrote an interesting post about work and success titled The Why? of Work [4]. Russ makes lots of good points and I m not going to summarise them (read the article, it s worth it). There is one point I disagree with, he says You are probably not going to change the world . The fact is that I ve observed Russ changing the world, he doesn t appear to have done anything that will get him an entry in a history book but he s done a lot of good work in Debian (a project that IS changing the world) and his insightful blog posts and comments on mailing lists influence many people. I believe that most people should think of changing the world as a group project where they are likely to be one of thousands or millions who are involved, then you can be part of changing the world every day. James Morrison wrote an insightful blog post about what he calls Penance driven development [5]. The basic concept of doing something good to make up for something you did which has a bad result (even if the bad result was inadvertent) is probably something that most people do to some extent, but formalising it in the context of software development work is a cencept I haven t seen described before. A 9yo boy named Caine created his own games arcade out of cardboard, when the filmmaker Nirvan Mullick saw it he created a short movie about it and promoted a flash mob event to play games at the arcade [6]. They also created the Imagination Foundation to encourage kids to create things from cardboard [7]. Tanguy Ortolo describes how to use the UDF filesystem instead of FAT for USB devices [8]. This allows you to create files larger than 2G while still allowing the device to be used on Windows systems. I ll keep using BTRFS for most of my USB sticks though. Bruce Schneier gave an informative TED talk about security models [9]. Probably most people who read my blog already have a good knowledge of most of the topics he covers. I think that the best use of this video is to educate less technical people you know. Blaine Harden gave an informative and disturbing TED talk about the concentration camps in North Korea [10]. At the end he points out the difficult task of helping people recover from their totalitarian government that will follow the fall of North Korea. Bruce Schneier has an interesting blog post about the use of a motherboard BMC controller (IPMI and similar) to compromise a server [11]. Also some business class desktop systems and laptops have similar functionality. Russ Allbery wrote an insightful article about the failures of consensus decision-making [12]. He compares the Wikipedia and Debian methods so his article is also informative for people who are interested in learning about those projects. The TED blog has a useful reference article with 10 places anyone can learn to code [13]. Racialicious has an interesting article about the people who take offense when it s pointed out that they have offended someone else [14]. Nick Selby wrote an interesting article criticising the Symantic response to the NYT getting hacked and also criticises anti-viru software in general [15]. He raises the point that most of us already know, anti-virus software doesn t do much good. Securing Windows networks is a losing game. Joshua Brindle wrote an interesting blog post about security on mobile phones and the attempts to use hypervisors for separating data of different levels [16]. He gives lots of useful background information about how to design and implement phone based systems.

• [1] http://tinyurl.com/be6eel3
• [2] http://www.ted.com/talks/ben_goldacre_battling_bad_science.html
• [3] http://levlafayette.com/node/383
• [4] http://www.eyrie.org/~eagle/journal/2013-01/021.html
• [5] http://www.sorced.com/2012/03/penance-driven-development.html
• [6] http://cainesarcade.com/
• [7] http://www.imagination.is/
• [8] http://tanguy.ortolo.eu/blog/article93/usb-udf
• [9] http://www.ted.com/talks/bruce_schneier.html
• [10] http://www.youtube.com/watch?v=8SAWKDRHZuw
• [11] http://www.schneier.com/blog/archives/2013/01/the_eavesdroppi.html
• [12] http://www.eyrie.org/~eagle/journal/2013-01/026.html
• [13] http://blog.ted.com/2013/01/29/10-places-where-anyone-can-learn-to-code/
• [14] http://tinyurl.com/q2vl2fv
• [15] http://tinyurl.com/awtv7ka
• [16] http://securityblog.org/2013/02/11/security-anti-pattern-mobile-hypervisors/

For a long time it was widely regarded that SCSI was the interface for all serious drives that were suitable for Enterprise Use or for anything else which requires reliable operation. On the other hand IDE was for cheap disks that were only suitable for home use. The SCSI vs IDE issue continues to this day but now we have SAS and SATA filling the same market niches with the main difference between the current debate and the debate a decade ago being that a SATA disk can be connected on a SAS bus. Both SAS and SATA have a single data cable for each disk which avoids the master/slave configuration on IDE and the issue of bus device ID number (from 0-7 or 0-15) and termination on SCSI. Termination When a high speed electrical signal travels through a cable some portion of the signal will be reflected from any cable end point or any point of damage. To prevent the signal reflection from the end of a cable you can have a set of resistors (or some other terminating device) at the end of the cable, see the Terminator(electrical) Wikipedia page [1] for a brief overview. As an aside I think that page could do with some work, if you are an EE with a bit of spare time then improving that page would be a good thing. SCSI was always designed to have termination while IDE never was. I presume that this was largely due to the cable length (18 for IDE vs 1.5m to 25m for SCSI) and the number of devices (2 for IDE vs 7 or 15 for SCSI). I also presume that some of the problems that I ve had with IDE systems have been related to signal problems that could have been avoided with a terminated bus. My first encounter with SCSI was when working for a small business that focused on WindowsNT software development. Everyone in the office knew a reasonable amount about computers and was happy to adjust the hardware of their own workstation. A room full of people who didn t understand termination who fiddled with SCSI buses tended to give a bad result. On the up-side I learned that a SCSI bus can work most of the time if you have a terminator in the middle of the cable and a hard drive at the end. There have been two occasions when I ve been at ground zero for a large deployment of servers from a company I ll call Moon Computers. In both cases there were two particularly large and expensive servers in a cluster and one of the cluster servers had data loss from bad SCSI termination. This is particularly annoying as the terminators have different colours, all that was needed to get the servers working was to change the hardware to make them look the same. As an aside the company with no backups [2] had one of the servers with bad SCSI termination. Heat SCSI disks and now SAS disks tend to be designed for higher performance, this usually means greater heat dissipation. A disk that dissipates a lot of heat won t necessarily work well in a desktop case with small and quiet fans. This can become a big problem if you have workstations running 24*7 in a hot place (such as any Australian city that s not in Tasmania) and turn the air-conditioner off on the weekends. One of my clients lost a few disks before they determined that IDE disks are the only option for systems that are to survive Australian heat without any proper cooling. Differences between IDE/SATA and SCSI/SAS In 2009 I wrote about vibration and SATA performance [3]. Rumor has it that SCSI/SAS disks are designed to operate in environments where there is a lot of vibration (servers with lots of big fans and fast disks) while IDE/SATA disks are designed for desktop and laptop systems in quiet environments. One thing I d like to do is to test performance of SATA vs SAS disks in a server that vibrates. SCSI/SAS disks have apparently been designed for operation in a RAID array and therefore will give a faster timeout on a read error (so another disk can return the data). While IDE/SATA disks are designed for a non-RAID situation and will spend longer trying to read the data. There are also various claims about the error rates from SCSI/SAS disks being better than those of IDE/SATA disks. But I think that in all cases the error rates are small enough not to be a problem if you use a filesystem like ZFS or BTRFS but they are also large enough to be a significant risk with modern data volumes if you have a lesser filesystem. Data Loss from Storage Failure In the data loss that I ve personally observed from storage failures the loss from SCSI problems (termination and heat) is about equal to all the hardware related data loss I ve seen on IDE disks. Given that the majority of disks I ve been responsible for have been IDE and SATA that s a bad sign for SCSI use in practice. But all serious data loss that I ve seen has involved the use of a single disk (no RAID) and inadequate backups. So a basic RAID-1 or RAID-5 installation will solve most hardware related data loss problems. There was one occasion when heat caused two disks in a RAID-1 to give errors at the same time, but by reading from both disks I managed to get almost all the data back, RAID can save you from some extreme error conditions. That situation would have been ideal for BTRFS or ZFS to recover data. Conclusion SCSI and SAS are designed for servers, using them in non-server systems seems to be a bad idea. Using SATA disks in servers can have problems too, but not typically problems that involve massive data loss. Using technology that is too complex for the people who install it seems risky. That includes allowing programmers to plug SCSI disks into their workstations and whoever it was from Moon computers or their resellers who apparently couldn t properly terminate a SCSI bus. It seems that the biggest advantage of SAS over SCSI is that SAS is simple enough for most people to be able to correctly install it. Making servers similar to the systems that the system administrators use at home seems like a really good idea. I think that one of the biggest benefits of using x86 systems as servers is that skills learned on home PCs can be transferred to administration of servers. Of course it would also be a good idea to have test servers that are identical to servers in production so that the sysadmin team can practice and make mistakes on systems that aren t mission critical, but companies seem to regard that as a waste of money apparently the risk of down-time is cheaper.

• [1] http://en.wikipedia.org/wiki/Terminator_(electrical)
• [2] http://etbe.coker.com.au/2013/05/21/no-backups-wtf/
• [3] http://etbe.coker.com.au/2009/04/22/vibration-strange-sata-performance/

Review: Advanced Perl Programming, by Sriram Srinivasan

Publisher:	O'Reilly
Copyright:	August 1997
ISBN:	1-56592-220-4
Format:	Trade paperback
Pages:	392

The problem with buying lots of books is that one frequently doesn't read them soon after purchase. And while nearly all fiction and most non-fiction doesn't have a time limit, technical books are more of a problem. As you might have guessed from the publication date and subject matter of this book, it's one I waited too long to read. I picked up Advanced Perl Programming not too long after it was first published in 1997. I bought it primarily for the chapters on XS programming, since I was just starting to develop and help maintain code that built Perl interfaces for C libraries. And then it sat on my bookshelf in the office, and then at home, until it was 16 years old. That's problematic for a general Perl programming guide; it's particularly troublesome for a book that dives deep into internals. That said, I still got some interesting information from it. Advanced Perl Programming is something of a grab bag of different and largely unrelated topics. It starts with a data structures overview (which is mostly about references), covers typeglobs and the Perl symbol table, briefly discusses closures, and then dives deeper into eval. That's followed by an overview of modules and object-oriented programming in Perl. The general Perl topics close with a solid (if outdated) discussion of tied objects and a somewhat rambling and remarkably general discussion of persistance. Srinivasan then covers some recommended module APIs for networking and graphics (Tk, specifically) while working through some complex examples, takes a deeper dive into eval and code generation, and concludes with three chapters on XS and embedded Perl interpreters. This is all solid material, but a lot of it is at least partly obsolete. The chapters on modules and object-oriented programming fare the worst; you'll find much better guides to those topics elsewhere. Data structures also fare poorly, partly because Srinivasan is still happy to use symbolic references, now considered bad style due to lack of compile-time checking. (That does mean, though, that this is one of the best introductions to symbolic references that you'll find, since few other Perl programmers discuss them.) But the rest of the book is fairly solid, if limited by age. If I'd read it when I first started with XS, it would have indeed helped. Advanced Perl Programming contains a succinct and clear overview of Perl internals and data representation (assuming, of course, it's not changed drastically, but I didn't notice any significant issues from what I know of internals from quite a lot of XS programming), particularly when combined with the earlier chapter on typeglobs and the symbol table. It is interesting, though, to see how much accepted Perl style has changed. Srinivasan is quite fond of eval with a scalar argument to construct code at runtime, something that most current authors recommend against when it can be avoided. The loss of static syntax checking means the technique is often hard to debug and can cause surprising runtime errors. Several of the more advanced tricks in this book are built on that framework, including a moderately interesting templating system that he constructs from scratch in this book. The examples here are also missing the focus on use strict, warnings, and avoiding special variables and unusual constructs that you see in more recent Perl books. This is a very thoughtful book, with several structural techniques that I appreciated and would like to see more technical writers use. One is the comparisons to the approaches of other languages at the end of most chapters. It puts Perl's approach in a broader context and encourages thought about alternative ways to view a particular feature and implementation tradeoffs in Perl's choices. Another is the careful discussion of design approaches and possibilities during the construction of larger examples. I think there's a tendency in technical books to spend a lot of time developing the best possible implementation of something and then show that completed example. Even with a detailed analysis of its construction, this can be less useful than a broader discussion of possible approaches, including dead ends. The problem, of course, is that 16 years is a long time, even for a relatively mature programming language, and Perl has changed. There are significant improvements not only to the standard library but to Perl core functionality that have happened since this book was written. The chapter on tying, which is otherwise excellent, is badly out of date on what functionality and methods are available and is no longer a reliable guide to using that feature except for simple cases. Similar problems plague the chapter on persistence, which develops the concept from basics that most programmers reading an advanced book no longer need, and which has been rendered mostly obsolete by further developments in the Perl module ecosystem. I think the best parts of this book, the ones that cover material that I think is still relatively accurate and that are not well-covered by other resources, are the chapters on typeglobs and on XS. The typeglob discussion is both clear and informative, covering material and techniques that are used in a few core Perl modules and that I've never seen adequately addressed elsewhere. I'd subsequently picked up XS and Perl embedding the hard way: lots of trial and error and reading difficult POD documentation. I wish I'd read this book earlier, since Srinivasan does a great job of basic orientation. He doesn't go far enough for me (the book I probably wanted was Extending and Embedding Perl by Jenness and Cozens, published five years later), but I would have been up and running with basic XS much faster by starting here. If this were 1997, or even 2000, I would probably recommend this book, albeit with a few caveats. Higher Order Perl is the place you should go for discussion of closures, rather than here (although of course it didn't exist then). I wasn't fond of string eval even in 1997, and I still think it produces code that, while efficient and quite powerful, is horribly difficult to understand. And the introduction to modules is adequate but not compelling; most other introductions to object-oriented programming and module construction in Perl are better. But even discarding those chapters (and the mostly unnecessary Tk reference), there's a lot of great material here that would have been quite helpful in 2000. Unfortunately, this is not the sort of technical book that ages well, and while I did pick up some useful background knowledge and a much better understanding of typeglobs, I mostly read this book because I wanted to salvage some knowledge from a book that sat for far too long on my shelves. There's really no reason to buy it today. If you run across it in a library, there are a few chapters that are still worth reading, but by and large if you know enough Perl to know where to be careful of landmines due to changes in Perl since the book was written, you also know enough Perl to not really need this book. Rating: 5 out of 10