My main desktop/server machine (running Debian sid) at home has been running XFS on mdadm raid-1 on a pair of SSDs for the last few years. A few days ago, one of the SSDs died. I ve been planning to switch to ZFS as the root filesystem for a while now, so instead of just replacing the failed drive, I took the opportunity to convert it. NOTE: at this point in time, ZFS On Linux does NOT support TRIM for either datasets or zvols on SSD. There s a patch almost ready (TRIM/Discard support from Nexenta #3656), so I m betting on that getting merged before it becomes an issue for me. Here s the procedure I came up with: 1. Buy new disks, shutdown machine, install new disks, reboot. The details of this stage are unimportant, and the only thing to note is that I m switching from mdadm RAID-1 with two SSDs to ZFS with two mirrored pairs (RAID-10) on four SSDs (Crucial MX300 275G at around $100 AUD each, they re hard to resist). Buying four 275G SSDs is slightly more expensive than buying two of the 525G models, but will perform a lot better. When installed in the machine, they ended up as /dev/sdp, /dev/sdq, /dev/sdr, and /dev/sds. I ll be using the symlinks in /dev/disk/by-id/ for the zpool, but for partition and setup, it s easiest to use the /dev/sd? device nodes. 2. Partition the disks identically with gpt partition tables, using gdisk and sgdisk. I need:

• A small partition (type EF02, 1MB) for grub to install itself in. Needed on gpt.
• A small partition (type EF00, 1MB) for EFI System. I m not currently booting with UEFI but I want the option to move to it later.
• A small partition (type 8300, 2GB) for /boot. I want /boot on a separate partition to make it easier to recover from problems that might occur with future upgrades. 2GB might seem excessive, but as this is my tftp & dhcp server I can t rely on network boot for rescues, so I want to be able to put rescue ISO images in there and boot them with grub and memdisk. This will be mdadm RAID-1, with 4 copies.
• A larger partition (type 8200, 4GB) for swap. With 4 identically partitioned SSDs, I ll end up with 16GB swap (using zswap for block-device backed compressed RAM swap)
• A large partition (type bf07, 210GB) for my rootfs
• A small partition (type bf08, 2GBB) to provide ZIL for my HDD zpools
• A larger partition (type bf09, 32GB) to provide L2ARC for my HDD zpools

ZFS On Linux uses partition type bf08 ( Solaris Reserved 1 ) natively, but doesn t seem to care what the partition types are for ZIL and L2ARC. I arbitrarily used bf08 ( Solaris Reserved 2 ) and bf09 ( Solaris Reserved 3 ) for easy identification. I ll set these up later, once I ve got the system booted I don t want to risk breaking my existing zpools by taking away their ZIL and L2ARC (and forgetting to zpool remove them, which I might possibly have done once) if I have to repartition. I used gdisk to interactively set up the partitions:

# gdisk -l /dev/sdp
GPT fdisk (gdisk) version 1.0.1
Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present
Found valid GPT with protective MBR; using GPT.
Disk /dev/sdp: 537234768 sectors, 256.2 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 4234FE49-FCF0-48AE-828B-3C52448E8CBD
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 537234734
Partitions will be aligned on 8-sector boundaries
Total free space is 6 sectors (3.0 KiB)
Number  Start (sector)    End (sector)  Size       Code  Name
   1              40            2047   1004.0 KiB  EF02  BIOS boot partition
   2            2048         2099199   1024.0 MiB  EF00  EFI System
   3         2099200         6293503   2.0 GiB     8300  Linux filesystem
   4         6293504        14682111   4.0 GiB     8200  Linux swap
   5        14682112       455084031   210.0 GiB   BF07  Solaris Reserved 1
   6       455084032       459278335   2.0 GiB     BF08  Solaris Reserved 2
   7       459278336       537234734   37.2 GiB    BF09  Solaris Reserved 3

I then cloned the partition table to the other three SSDs with this little script: clone-partitions.sh

#! /bin/bash
src='sdp'
targets=( 'sdq' 'sdr' 'sds' )
for tgt in "$ targets[@] "; do
  sgdisk --replicate="/dev/$tgt" /dev/"$src"
  sgdisk --randomize-guids "/dev/$tgt"
done

3. Create the mdadm for /boot, the zpool, and and the root filesystem. Most rootfs on ZFS guides that I ve seen say to call the pool rpool, then create a dataset called "$(hostname)-1" and then create a ROOT dataset under that. so on my machine, that would be rpool/ganesh-1/ROOT. Some reverse the order of hostname and the rootfs dataset, for rpool/ROOT/ganesh-1. There might be uses for this naming scheme in other environments but not in mine. And, to me, it looks ugly. So I ll use just $(hostname)/root for the rootfs. i.e. ganesh/root I wrote a script to automate it, figuring I d probably have to do it several times in order to optimise performance. Also, I wanted to document the procedure for future reference, and have scripts that would be trivial to modify for other machines. create.sh

#! /bin/bash
exec &> ./create.log
hn="$(hostname -s)"
base='ata-Crucial_CT275MX300SSD1_'
md='/dev/md0'
md_part=3
md_parts=( $(/bin/ls -1 /dev/disk/by-id/$ base *-part$ md_part ) )
zfs_part=5
# 4 disks, so use the top half and bottom half for the two mirrors.
zmirror1=( $(/bin/ls -1 /dev/disk/by-id/$ base *-part$ zfs_part    head -n 2) )
zmirror2=( $(/bin/ls -1 /dev/disk/by-id/$ base *-part$ zfs_part    tail -n 2) )
# create /boot raid array
mdadm "$md" --create \
    --bitmap=internal \
    --raid-devices=4 \
    --level 1 \
    --metadata=0.90 \
    "$ md_parts[@] "
mkfs.ext4 "$md"
# create zpool
zpool create -o ashift=12 "$hn" \
    mirror "$ zmirror1[@] " \
    mirror "$ zmirror2[@] "
# create zfs rootfs
zfs set compression=on "$hn"
zfs set atime=off "$hn"
zfs create "$hn/root"
zpool set bootfs="$hn/root"
# mount the new /boot under the zfs root
mount "$md" "/$hn/root/boot"

If you want or need other ZFS datasets (e.g. for /home, /var etc) then create them here in this script. Or you can do that later after you ve got the system up and running on ZFS. If you run mysql or postgresql, read the various tuning guides for how to get best performance for databases on ZFS (they both need their own datasets with particular recordsize and other settings). If you download Linux ISOs or anything with bit-torrent, avoid COW fragmentation by setting up a dataset to download into with recordsize=16K and configure your BT client to move the downloads to another directory on completion. I did this after I got my system booted on ZFS. For my db, I stoppped the postgres service, renamed /var/lib/postgresql to /var/lib/p, created the new datasets with:

zfs create -o recordsize=8K -o logbias=throughput -o mountpoint=/var/lib/postgresql \
  -o primarycache=metadata ganesh/postgres
zfs create -o recordsize=128k -o logbias=latency -o mountpoint=/var/lib/postgresql/9.6/main/pg_xlog \
  -o primarycache=metadata ganesh/pg-xlog

followed by rsync and then started postgres again. 4. rsync my current system to it. Logout all user sessions, shut down all services that write to the disk (postfix, postgresql, mysql, apache, asterisk, docker, etc). If you haven t booted into recovery/rescue/single-user mode, then you should be as close to it as possible everything non-esssential should be stopped. I chose not to boot to single-user in case I needed access to the web to look things up while I did all this (this machine is my internet gateway). Then:

hn="$(hostname -s)"
time rsync -avxHAXS -h -h --progress --stats --delete / /boot/ "/$hn/root/"

After the rsync, my 130GB of data from XFS was compressed to 91GB on ZFS with transparent lz4 compression. Run the rsync again if (as I did), you realise you forgot to shut down postfix (causing newly arrived mail to not be on the new setup) or something. You can do a (very quick & dirty) performance test now, by running zpool scrub "$hn". Then run watch zpool status "$hn". As there should be no errorss to correct, you should get scrub speeds approximating the combined sequential read speed of all vdevs in the pool. In my case, I got around 500-600M/s I was kind of expecting closer to 800M/s but that s good enough .the Crucial MX300s aren t the fastest drive available (but they re great for the price), and ZFS is optimised for reliability more than speed. The scrub took about 3 minutes to scan all 91GB. My HDD zpools get around 150 to 250M/s, depending on whether they have mirror or RAID-Z vdevs and on what kind of drives they have. For real benchmarking, use bonnie++ or fio. 5. Prepare the new rootfs for chroot, chroot into it, edit /etc/fstab and /etc/default/grub. This script bind mounts /proc, /sys, /dev, and /dev/pts before chrooting: chroot.sh

#! /bin/sh
hn="$(hostname -s)"
for i in proc sys dev dev/pts ; do
  mount -o bind "/$i" "/$ hn /root/$i"
done
chroot "/$ hn /root"

Change /etc/fstab (on the new zfs root to) have the zfs root and ext4 on raid-1 /boot:

/ganesh/root    /         zfs     defaults                                         0  0
/dev/md0        /boot     ext4    defaults,relatime,nodiratime,errors=remount-ro   0  2

I haven t bothered with setting up the swap at this point. That s trivial and I can do it after I ve got the system rebooted with its new ZFS rootfs (which reminds me, I still haven t done that :). add boot=zfs to the GRUB_CMDLINE_LINUX variable in /etc/default/grub. On my system, that s:

GRUB_CMDLINE_LINUX="iommu=noagp usbhid.quirks=0x1B1C:0x1B20:0x408 boot=zfs"

NOTE: If you end up needing to run rsync again as in step 4. above copy /etc/fstab and /etc/default/grub to the old root filesystem first. I suggest to /etc/fstab.zfs and /etc/default/grub.zfs 6. Install grub Here s where things get a little complicated. Running install-grub on /dev/sd[pqrs] is fine, we created the type ef02 partition for it to install itself into. But running update-grub to generate the new /boot/grub/grub.cfg will fail with an error like this:

/usr/sbin/grub-probe: error: failed to get canonical path of  /dev/ata-Crucial_CT275MX300SSD1_163313AADD8A-part5'.

IMO, that s a bug in grub-probe it should look in /dev/disk/by-id/ if it can t find what it s looking for in /dev/ I fixed that problem with this script: fix-ata-links.sh

#! /bin/sh
cd /dev
ln -s /dev/disk/by-id/ata-Crucial* .

After that, update-grub works fine. NOTE: you will have to add udev rules to create these symlinks, or run this script on every boot otherwise you ll get that error every time you run update-grub in future. 7. Prepare to reboot Unmount proc, sys, dev/pts, dev, the new raid /boot, and the new zfs filesystems. Set the mount point for the new rootfs to / umount-zfs-root.sh

#! /bin/sh
hn="$(hostname -s)"
md="/dev/md0"
for i in dev/pts dev sys proc ; do
  umount "/$ hn /root/$i"
done
umount "$md"
zfs umount "$ hn /root"
zfs umount "$ hn "
zfs set mountpoint=/ "$ hn /root"
zfs set canmount=off "$ hn "

8. Reboot Remember to configure the BIOS to boot from your new disks. The system should boot up with the new rootfs, no rescue disk required as in some other guides the rsync and chroot stuff has already been done. 9. Other notes

• If you re adding partition(s) to a zpool for ZIL, remember that ashift is per vdev, not per zpool. So remember to specify ashift=12 when adding them. e.g.

  zpool add -o ashift=12 export log \
    mirror ata-Crucial_CT275MX300SSD1_163313AAEE5F-part6 \
           ata-Crucial_CT275MX300SSD1_163313AB002C-part6
  

  Check that all vdevs in all pools have the correct ashift value with:

  zdb   grep -E 'ashift vdev type'   grep -v disk
  

10. Useful references Reading these made it much easier to come up with my own method. Highly recommended.

• http://wiki.complete.org/ConvertingToZFS
• http://www.thecrosseroads.net/2016/02/booting-a-zfs-root-via-uefi-on-debian/
• https://github.com/zfsonlinux/zfs/wiki/HOWTO-install-Debian-GNU-Linux-to-a-Native-ZFS-Root-Filesystem
• http://open-zfs.org/wiki/Performance_tuning

Converting to a ZFS rootfs is a post from: Errata

This weekend, I traveled to Columbus, Ohio to attend Ohio Linux Fest. I departed San Francisco early on Thursday. It was interesting getting to experience the luxurious side of flying as I enjoyed a mimosa in the American Express Centurion lounge for the first time. I even happend to cross paths with Corey Quinn, who was on his way to [DevOpsDays Boise]. While connecting in Houston, I met up with the always awesome Jos Antonio Rey, who was to be my travel companion for this trip. The long day of travel took its toll on us, so we had a lazy Friday morning before checking in for the conference around lunch time. I was not that interested in the afternoon sessions, so I spent the majority of the first day helping out at the Ubuntu booth and catching up with friends and colleagues. The day ended with a nice Happy Hour sponsored by Oracle. Saturday was the main day for the conference. Ethan Galstad, Founder and CEO of Nagios, started the day with a Keynote about Becoming the Next Tech Entrepreneur. Next up was Elizabeth K. Joseph with A Tour of OpenStack Deployment Scenarios. While I ve read plenty about OpenStack, I ve never actually used it before. As a result, this demo and introduction was great to watch. It was entertaining to watch her login to CirrOS with the default password of cubswin:), as the Chicago Cubs are currently playing the San Francisco Giants in the National League Divisional Series (and winning). Unfortunately, I was not able to win a copy of her new Common OpenStack Deployments book, but it was great getting to watch her signing copies for other attendees after all of the hard work that went into writing the book. For lunch, Jos , Elizabeth, and Svetlana Belkin all gathered together for an informal Ubuntu lunch. Finally, it was time for me to give my talk. This was the same talk I gave at FOSSCON, but this time, I had a significantly larger audience. Practice definitely makes perfect, as my delivery was a lot better the second time giving this talk. Afterwards, I had a number of people come up to me to let me know that they really enjoyed the presentation. Pro Tip: If you ever attend a talk, the speaker will really appreciate any feedback you send their way. Even if it is a simple, Thank You , it really means a lot. One of the people who came up to me after the talk was Unit193. We have known each other through Ubuntu for years, but there has never been an opportunity to meet in person. I am proud to be able to say with 99% confidence that he is not a robot, and is in fact a real person. Next up was a lesson about the /proc filesystem. While I ve explored it a bit on my own before, I still learned a few tips and tricks about information that can be gained from the files in this magical directory. Following this was a talk about Leading When You re Not the Boss. It was even partially taught by a dummy (the speaker was a ventriloquist). The last regular talk of the day was one of the more interesting ones I attended. It was a talk by Patrick Shuff from Facebook about how they have built a load balancer than can handle a billion users. The slide deck was well-made with very clear diagrams. The speaker was also very knowledgeable and dealt with the plethora of questions he received. Prior to the closing keynote was a series of lightning talks. These served as a great means to get people laughing after a long day of talks. The closing keynote was given by father and daughter Joe and Lilly Born about The Democratization of Invention. Both of them had very interesting stories, and Lily was quite impressive given her age. We skipped the Nagios After Party in favor of a more casual pizza dinner. Overall, it was a great conference, and I am very glad to have had the opportunity to attend. A big thanks to Canonical and the Ubuntu Community for fudning my travel through the Ubuntu Community Fund and to the Ohio Linux Fest staff for allowing me the opportunity to speak at such a great conference.

This post is long past due, but I figured it is better late than never. At the start of the year, I set a goal to get more involved with attending and speaking at conferences. Through work, I was able to attend the Southern California Linux Expo (SCALE) in Pasadena, CA in January. I also got to give a talk at O'Relly's Open Source Convention (OSCON) in Austin, TX in May. However, I really wanted to give a talk about my experience contributing in the Ubuntu community. Jos Antonio Rey encouraged me to submit the talk to FOSSCON. While I've been aware of FOSSCON for years thanks to my involvement with the freenode IRC network (which has had a reference to FOSSCON in the /motd for years), I had never actually attended it before. I also wasn't quite sure how I would handle traveling from San Francisco, CA to Philadelphia, PA. Regardless, I decided to go ahead and apply. Fast forward a few weeks, and imagine my surprise when I woke up to an email saying that my talk proposal was accepted. People were actually interested in me and what I had to say. I immediately began researching flights. While they weren't crazy expensive, they were still more money than I was comfortable spending. Luckily, Jos had a solution to this problem as well; he suggested applying for funding through the Ubuntu Community Donations fund. While I've been an Ubuntu Member for over 8 years, I've never used this resource before. However, I was happy when I received a very quick approval. The conference itself was smaller than I was expecting. However, it was packed with lots of friendly and familiar faces of people I've interacted with online and in person over the years at various Open Source events. I started off the day by learning from Jos how to use Juju to quickly setup applications in the cloud. While Juju has definitely come a long way over the last couple of years, and it appears t be quite easy to learn and use, it still appears to be lacking some of the features needed to take full control over how the underlying applications interact with each other. However, I look forward to continuing to watch it grow and mature. Net up, we had a lunch break. There was no catered lunch at this conference, so we decided to get some cheesesteak at Abner's (is any trip to Philadelphia complete without cheesesteak?). Following lunch, I took some time to make a few last minute changes to my presentation and rehearse a bit. Finally, it was time. I got up in front of the audience and gave my presentation. Overall, I was quite pleased. It was not perfect, but for the first time giving the talk, I thought it went pretty well. I will work hard to make it even better for next tme. Following my talk was a series of brief lightning talks prior to the closing keynote. Another long time friend of mine, Elizabeth Krumbach Joseph, was giving the keynote about listening to the needs of your global open source community. While I have seen her speak on several other occassions, I really enjoyed this particular talk. It was full of great examples and anecdotes that were easy for the audience to relate to and start applying to their own communities. After the conference, a few of us went off and played tourist, paying the Liberty Bell a visit before concluding our trip in Philadelpha. Overall, I had a great time as FOSSCON. It was great being re-united with so many friends. A big thank you to Jos for his constant support and encouragement and to Canonical and the Ubuntu Community for helping to make it possible for me to attend this conference. Finally, thanks to the terrific FOSSCON staff for volunteering so much time to put on this great event.

People keep ignoring the status of the Pacemaker HA stack in Debian Jessie. Most people think that they should stick to Debian Wheezy. Why does this happen? Perhaps little or none publicity of the situation. Since some time now, Debian contains a Pacemaker stack which is ready to use in both Debian Jessie and in Debian Stretch. Anyway, let s see what we have so far:

1. The pacemaker stack was updated in Debian unstable around Feb 2016.
2. They migrated to Debian testing by that time as well.
3. Most of the key packages were backported to jessie-backports (if not all).
4. Therefore, Stretch is ready for the HA stack, and so is Jessie (using backports).

The packages I m refering to are those which I consider the key components of the stack, and by the time of this blogpost, the versions are:

package	jessie-backports	stretch	sid	upstream
corosync	2.3.6	2.3.6	2.3.6	2.4.1
pacemaker	1.1.14	1.1.15	1.1.15	1.1.15
crmsh	2.2.0	2.2.1	2.2.1	2.4.1
libqb	1.0	1.0	1.0	1.0

How can you check this by yourself? Here some pointers:

• Debian HA packaging team overview: link
• Package tracker for corosync: link
• Package tracker for pacemaker: link
• Package tracker for crmsh: link
• Package tracker for libqb: link

I m sure we even have the chance to improve a bit the packages before the release of stretch. There are some packages which are a bit behind the upstream version. In any case: Yes! you can move from Debian Wheezy to Debian Jessie!

What happened in the Reproducible Builds effort between Sunday September 25 and Saturday October 1 2016: Statistics For the first time, we reached 91% reproducible packages in our testing framework on testing/amd64 using a determistic build path. (This is what we recommend to make packages in Stretch reproducible.) For unstable/amd64, where we additionally test for reproducibility across different build paths we are at almost 76% again. IRC meetings We have a poll to set a time for a new regular IRC meeting. If you would like to attend, please input your available times and we will try to accommodate for you. There was a trial IRC meeting on Friday, 2016-09-31 1800 UTC. Unfortunately, we did not activate meetbot. Despite this participants consider the meeting a success as several topics where discussed (eg changes to IRC notifications of tests.r-b.o) and the meeting stayed within one our length. Upcoming events Reproduce and Verify Filesystems - Vincent Batts, Red Hat - Berlin (Germany), 5th October, 14:30 - 15:20 @ LinuxCon + ContainerCon Europe 2016. From Reproducible Debian builds to Reproducible OpenWrt, LEDE & coreboot - Holger "h01ger" Levsen and Alexander "lynxis" Couzens - Berlin (Germany), 13th October, 11:00 - 11:25 @ OpenWrt Summit 2016. Introduction to Reproducible Builds - Vagrant Cascadian will be presenting at the SeaGL.org Conference In Seattle (USA), November 11th-12th, 2016. Previous events GHC Determinism - Bartosz Nitka, Facebook - Nara (Japan), 24th September, ICPF 2016. Toolchain development and fixes Michael Meskes uploaded bsdmainutils/9.0.11 to unstable with a fix for #830259 based on Reiner Herrmann's patch. This fixed locale_dependent_symbol_order_by_lorder issue in the affected packages (freebsd-libs, mmh). devscripts/2.16.8 was uploaded to unstable. It includes a debrepro script by Antonio Terceiro which is similar in purpose to reprotest but more lightweight; specific to Debian packages and without support for virtual servers or configurable variations. Packages reviewed and fixed, and bugs filed The following updated packages have become reproducible in our testing framework after being fixed:

• ara/1.0.32 by Chris Lamb, original patch by Chris Lamb.
• fracplanet/0.4.0-5 by Chris Lamb, original patch by Reiner Herrman.
• gnarwl/3.6.dfsg-8 by Bernhard Schmidt, original patch by Chris Lamb.
• kgb-bot/1.34-1 by gregor herrmann, original patch by gregor herrmann.
• survex/1.2.29-1 by Olly Betts.
• zpaq/1.10-3 by Chris Lamb, original patch by Reiner Herrman.
• fig2dev/1:3.2.6-3 by Roland Rosenfeld.
• luxio/11-1 by Daniel Silverstone.
• monkeysign/2.1.1 by Antoine Beaupr , original patch by Daniel Kahn Gillmor.
• openarena-085-data/0.8.5split-9 by Simon McVittie.
• openarena-088-data/0.8.8-7 by Simon McVittie.
• openarena-data/0.8.5split-9 by Simon McVittie.
• rc/1.7.4-1 by Reiner Herrmann, original patch by Chris Lamb.

The following updated packages appear to be reproducible now for reasons we were not able to figure out. (Relevant changelogs did not mention reproducible builds.)

• gkrellm/2.3.8-1 by Sandro Tosi
• glassfish/1:2.1.1-b31g+dfsg1-4 by Emmanuel Bourg

Some uploads have addressed some reproducibility issues, but not all of them:

• apache2/2.4.23-5 by Rapha l Hertzog
• freeradius/3.0.11+dfsg-1 by Michael Stapelberg
• libnss-ldap/265-4 by Chris Lamb
• lift/2.5.0-1 by Nicolas Delvaux
• linux/4.8~rc8-1~exp1 by Ben Hutchings
• nose2/0.6.5-2 by Barry Warsaw
• postgresql-9.6/9.6.0-1 Christoph Berg
• strace/4.13-0.1 by Nicolas Braud-Santoni
• yersinia/0.7.3-3 by No l K the

Patches submitted that have not made their way to the archive yet:

• #838888 filed against dh-haskell by Chris Lamb.
• #838971 filed against slang2 by Chris Lamb.
• #839587 filed against sympa by Chris Lamb.
• #839181 filed against transmission-remote-gtk by Chris Lamb.
• #838829 filed against vala by Sebastian Reichel.
• #838970 filed against webkit2pdf by Chris Lamb.
• #831569 filed against websockets by Chris Lamb.
• #839347 filed against xml-core by Lucas Nussbaum.
• #839526 filed against xml-core by Adrian Bunk.

Reviews of unreproducible packages 77 package reviews have been added, 178 have been updated and 80 have been removed in this week, adding to our knowledge about identified issues. 6 issue types have been updated:

• Added clilibs_line_order, records_build_flags and hevea_captures_build_path.
• Removed locale_dependent_symbol_order_by_lorder, fixed in bsdmainutils/9.0.11.
• Updated diffoscope_runs_forever, captures_build_path.

Weekly QA work As part of reproducibility testing, FTBFS bugs have been detected and reported by:

• Adrian Bunk (3)
• Chris Lamb (12)
• Lucas Nussbaum (3)
• Sebastian Reichel (1)

diffoscope development A new version of diffoscope 61 was uploaded to unstable by Chris Lamb. It included contributions from:

• Ximin Luo:
  • Improve the CLI --help text and add an --output-empty option.
• Chris Lamb:
  • Add a progress bar and show it if stdout is a TTY. You can read more about it here. It can also be read by higher-level programs via the --status-fd CLI option.
• Maria Glukhova:
  • Behaviour improvements in the case of OS-level errors.
• Mattia Rizzolo:
  • Testing and packaging improvements.

Post-release there were further contributions from:

• Chris Lamb:
  • Code architecture improvements.
• Maria Glukhova:
  • Testing improvements.

reprotest development A new version of reprotest 0.3.2 was uploaded to unstable by Ximin Luo. It included contributions from:

• Ximin Luo:
  • Add a --diffoscope-arg CLI option to pass extra args to diffoscope.

Post-release there were further contributions from:

• Chris Lamb:
  • Code quality improvements.

tests.reproducible-builds.org

• Hans-Christoph Steiner continued work on setting up reproducible tests for F-Droid.
• Holger cleaned up the script creating the page showing breakages, so that it now also cleans up some of the breakage it finds.
• IRC notifications about diffoscope crashes and artifacts available for investigations have been dropped; instead the breakages page has a permanent pointer. (h01ger)
• IRC notifications from the automatic package scheduler and status changes for packages have been moved -- as a temporary trial -- to #debian-reproducible-changes on irc.oftc.net (Mattia).

Misc. This week's edition was written by Ximin Luo, Holger Levsen & Chris Lamb and reviewed by a bunch of Reproducible Builds folks on IRC.

Previously: v4.7. Here are a bunch of security things I m excited about in Linux v4.8: SLUB freelist ASLR Thomas Garnier continued his freelist randomization work by adding SLUB support. x86_64 KASLR text base offset physical/virtual decoupling On x86_64, to implement the KASLR text base offset, the physical memory location of the kernel was randomized, which resulted in the virtual address being offset as well. Due to how the kernel s -2GB addressing works (gcc s -mcmodel=kernel ), it wasn t possible to randomize the physical location beyond the 2GB limit, leaving any additional physical memory unused as a randomization target. In order to decouple the physical and virtual location of the kernel (to make physical address exposures less valuable to attackers), the physical location of the kernel needed to be randomized separately from the virtual location. This required a lot of work for handling very large addresses spanning terabytes of address space. Yinghai Lu, Baoquan He, and I landed a series of patches that ultimately did this (and in the process fixed some other bugs too). This expands the physical offset entropy to roughly $physical_memory_size_of_system / 2MB bits. x86_64 KASLR memory base offset Thomas Garnier rolled out KASLR to the kernel s various statically located memory ranges, randomizing their locations with CONFIG_RANDOMIZE_MEMORY. One of the more notable things randomized is the physical memory mapping, which is a known target for attacks. Also randomized is the vmalloc area, which makes attacks against targets vmalloced during boot (which tend to always end up in the same location on a given system) are now harder to locate. (The vmemmap region randomization accidentally missed the v4.8 window and will appear in v4.9.) x86_64 KASLR with hibernation Rafael Wysocki (with Thomas Garnier, Borislav Petkov, Yinghai Lu, Logan Gunthorpe, and myself) worked on a number of fixes to hibernation code that, even without KASLR, were coincidentally exposed by the earlier W^X fix. With that original problem fixed, then memory KASLR exposed more problems. I m very grateful everyone was able to help out fixing these, especially Rafael and Thomas. It s a hard place to debug. The bottom line, now, is that hibernation and KASLR are no longer mutually exclusive. gcc plugin infrastructure Emese Revfy ported the PaX/Grsecurity gcc plugin infrastructure to upstream. If you want to perform compiler-based magic on kernel builds, now it s much easier with CONFIG_GCC_PLUGINS! The plugins live in scripts/gcc-plugins/. Current plugins are a short example called Cyclic Complexity which just emits the complexity of functions as they re compiled, and Sanitizer Coverage which provides the same functionality as gcc s recent -fsanitize-coverage=trace-pc but back through gcc 4.5. Another notable detail about this work is that it was the first Linux kernel security work funded by Linux Foundation s Core Infrastructure Initiative. I m looking forward to more plugins! If you re on Debian or Ubuntu, the required gcc plugin headers are available via the gcc-$N-plugin-dev package (and similarly for all cross-compiler packages). hardened usercopy Along with work from Rik van Riel, Laura Abbott, Casey Schaufler, and many other folks doing testing on the KSPP mailing list, I ported part of PAX_USERCOPY (the basic runtime bounds checking) to upstream as CONFIG_HARDENED_USERCOPY. One of the interface boundaries between the kernel and user-space are the copy_to_user()/copy_from_user() family of functions. Frequently, the size of a copy is known at compile-time ( built-in constant ), so there s not much benefit in checking those sizes (hardened usercopy avoids these cases). In the case of dynamic sizes, hardened usercopy checks for 3 areas of memory: slab allocations, stack allocations, and kernel text. Direct kernel text copying is simply disallowed. Stack copying is allowed as long as it is entirely contained by the current stack memory range (and on x86, only if it does not include the saved stack frame and instruction pointers). For slab allocations (e.g. those allocated through kmem_cache_alloc() and the kmalloc()-family of functions), the copy size is compared against the size of the object being copied. For example, if copy_from_user() is writing to a structure that was allocated as size 64, but the copy gets tricked into trying to write 65 bytes, hardened usercopy will catch it and kill the process. For testing hardened usercopy, lkdtm gained several new tests: USERCOPY_HEAP_SIZE_TO, USERCOPY_HEAP_SIZE_FROM, USERCOPY_STACK_FRAME_TO,
USERCOPY_STACK_FRAME_FROM, USERCOPY_STACK_BEYOND, and USERCOPY_KERNEL. Additionally, USERCOPY_HEAP_FLAG_TO and USERCOPY_HEAP_FLAG_FROM were added to test what will be coming next for hardened usercopy: flagging slab memory as safe for copy to/from user-space , effectively whitelisting certainly slab caches, as done by PAX_USERCOPY. This further reduces the scope of what s allowed to be copied to/from, since most kernel memory is not intended to ever be exposed to user-space. Adding this logic will require some reorganization of usercopy code to add some new APIs, as PAX_USERCOPY s approach to handling special-cases is to add bounce-copies (copy from slab to stack, then copy to userspace) as needed, which is unlikely to be acceptable upstream. seccomp reordered after ptrace By its original design, seccomp filtering happened before ptrace so that seccomp-based ptracers (i.e. SECCOMP_RET_TRACE) could explicitly bypass seccomp filtering and force a desired syscall. Nothing actually used this feature, and as it turns out, it s not compatible with process launchers that install seccomp filters (e.g. systemd, lxc) since as long as the ptrace and fork syscalls are allowed (and fork is needed for any sensible container environment), a process could spawn a tracer to help bypass a filter by injecting syscalls. After Andy Lutomirski convinced me that ordering ptrace first does not change the attack surface of a running process (unless all syscalls are blacklisted, the entire ptrace attack surface will always be exposed), I rearranged things. Now there is no (expected) way to bypass seccomp filters, and containers with seccomp filters can allow ptrace again. That s it for v4.8! The merge window is open for v4.9

2016, Kees Cook. This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 License.

Once a month I am involved in running an informal session, loosely affiliated with Open Rights Group and FSFE, called Cryptonoise. Cryptonoise explores methods for protecting your digital rights, with a leaning towards focusing on privacy, and provides a venue for like minded people to meet up and discuss the state of the digital landscape and those that may try to infringe on the rights of digital citizens. We ve all made it easy for large enterprises and governments to collect masses of data about our online activities because we perform most of those activities in the same place. Facebook, Google and Twitter spring to mind as examples of companies that have grown to dangerous sizes with little competition. This is not paranoia. This is real. We make it a lot more difficult when we spread out. Our meetups are held at 57North Hacklab and at the last meetup on the 29th September I set up a GNU Social instance for the members of 57North. GNU Social provides the same functionality as Twitter but as a decentralised federated network. Federation is a feature that is found in protocols like E-Mail, XMPP and SIP. It doesn t matter which server you re using, you can still talk to all the other users on all the other servers. While I m using social.57north.org.uk I can still follow FSF on status.fsf.org, for example, with no prior coordination with system administrators or anything complicated. It all just works. People have pointed out that I ve just introduced another point of centralisation but I don t see it necessarily as a bad thing. I think too many users in a single service starts to look dangerous but as long as user counts don t go too high I believe that the benefits of sharing the administrative workload (performing updates, monitoring, keeping the TLS cert current, etc.) far outweigh the effects of having a few extra users. I think 100 is probably about the maximum number I would be comfortable with, although I ll admit I ve not based this on anything and it s chosen arbitrarily. The jabber.ccc.de server is an example of a service that grew too large. It was set up by members of CCC and made available to all, but ended up becoming the de facto service for hackers. The jabber.ccc.de team have made appeals for others to set up their own servers, and you should. For a great overview and guide for setting up your own real-time commmunication servers, check out the RTC Quick Start Guide. This work was enabled by Shell who had previously set up a Central Authentication Service, which GNU Social already had a plugin to use as the authentication backend. No one likes to have a whole load of different passwords for different services and integration with this allows for identities to be consistent across the 57North services. She has also setup a Matrix homeserver, another step towards decentralisation and an end of reliance on centralised giants. If you have an account on a GNU Social instance, you can follow me here.

I have been working quite hard, along with my friend and colleague Richard Maw, on getting Gitano ready for a release suitable for inclusion into Debian Stretch. You can see how we're doing on the various Trello boards for:

• Gitano
• Clod
• Gall
• Lace
• Tongue
• Supple

As Richard and I work toward a version of Gitano we're prepared to support long-term in Debian we are making many changes to make our lives easier. For those of you who have been using Gitano over the past few years, you'll need to pay attention to some postings which will be coming soon about how to make the changes you need so as to not explode horribly when you upgrade to the version we're releasing soon. For those of you who are not yet using Gitano but feel like you might want to; I'll also be producing some postings about getting started with the packages. And for those happily running current HEAD of Gitano already, I'll be posting about some of the new features over the next little while in case you're not aware of them.

IMPORTANT: If you're using Gitano already and have any issues or feature requests then please please please let me know ASAP otherwise they're unlikely to be resolved/implemented before 1.0. irl already asked for the facility to verify GPG signed commits and tags, but if you want anything else considering then I need to know v. soon. (Ideally email me, but you may comment on this posting too if you must)

Shipping Position Independent Executables and using read-only Global Offset Table was already possible for packages but needed package maintainers to opt-in for each package (see Hardening wiki) using the pie and bindnow Dpkg hardening flags. Many critical packages enabled the extra flags but there are still way more left out according to Lintian hardening-no-bindnow and hardening-no-pie warnings. Now we can change that. We can make those hardening flags the default for every package.
We already have the needed patches for GCC (#835148) and dpkg (#835146, #835149). We already have all packages rebuilt once to test which breaks (Thanks to Lucas Nussbaum!). The Release Team already asked porters if they feel their ports ready for enabling PIE and most ports tentatively opted-in (Thanks to Niels Thykier for pushing this!). What is left is fixing the ~75 open bugs found during the test rebuilds and this is where You can help, too! Please check if your packages are affected or give a helping hand to other maintainers who need it. (See PIEByDefaultTransition wiki for hints on fixing the bugs.) Many thanks to those who already fixed their packages! If we can get past those last bugs we can enable those badly needed security features and make Stretch the most secure release ever!

Trust is important in any kind of interpersonal relationship. It's inevitable that there will be cases where something you do will irritate or upset others, even if only to a small degree. Handling small cases well helps build trust that you will do the right thing in more significant cases, whereas ignoring things that seem fairly insignificant (or saying that you'll do something about them and then failing to do so) suggests that you'll also fail when there's a major problem. Getting the small details right is a major part of creating the impression that you'll deal with significant challenges in a responsible and considerate way.

This isn't limited to individual relationships. Something that distinguishes good customer service from bad customer service is getting the details right. There are many industries where significant failures happen infrequently, but minor ones happen a lot. Would you prefer to give your business to a company that handles those small details well (even if they're not overly annoying) or one that just tells you to deal with them?

And the same is true of software communities. A strong and considerate response to minor bug reports makes it more likely that users will be patient with you when dealing with significant ones. Handling small patch contributions quickly makes it more likely that a submitter will be willing to do the work of making more significant contributions. These things are well understood, and most successful projects have actively worked to reduce barriers to entry and to be responsive to user requests in order to encourage participation and foster a feeling that they care.

But what's often ignored is that this applies to other aspects of communities as well. Failing to use inclusive language may not seem like a big thing in itself, but it leaves people with the feeling that you're less likely to do anything about more egregious exclusionary behaviour. Allowing a baseline level of sexist humour gives the impression that you won't act if there are blatant displays of misogyny. The more examples of these "insignificant" issues people see, the more likely they are to choose to spend their time somewhere else, somewhere they can have faith that major issues will be handled appropriately.

There's a more insidious aspect to this. Sometimes we can believe that we are handling minor issues appropriately, that we're acting in a way that handles people's concerns, while actually failing to do so. If someone raises a concern about an aspect of the community, it's important to discuss solutions with them. Putting effort into "solving" a problem without ensuring that the solution has the desired outcome is not only a waste of time, it alienates those affected even more - they're now not only left with the feeling that they can't trust you to respond appropriately, but that you will actively ignore their feelings in the process.

It's not always possible to satisfy everybody's concerns. Sometimes you'll be left in situations where you have conflicting requests. In that case the best thing you can do is to explain the conflict and why you've made the choice you have, and demonstrate that you took this issue seriously rather than ignoring it. Depending on the issue, you may still alienate some number of participants, but it'll be fewer than if you just pretend that it's not actually a problem.

One warning, though: while building trust in this way enhances people's willingness to join your community, it also builds expectations. If a significant issue does arise, and if you fail to handle it well, you'll burn a lot of that trust in the process. The fact that you've built that trust in the first place may be what saves your community from disintegrating completely, but people will feel even more betrayed if you don't actively work to rebuild it. And if there's a pattern of mishandling major problems, no amount of getting the details right will matter.

Communities that ignore these issues are, long term, likely to end up weaker than communities that pay attention to them. Making sure you get this right in the first place, and setting expectations that you will pay attention to your contributors, is a vital part of building a meaningful relationship between your community and its members.

comments

This would be a longish post. I had bought a Samsung Galaxy J-5/500 just a few days before Debconf16 which I had written about a bit earlier as well. As can be seen in the specs there isn t much to explore other than A-GPS. There were a couple of temperature apps. which I wanted to explore before buying the smartphone but as there were budget constraints and there weren t any good budget smartphones with environmental sensors built-in had to let go of those features. I was looking for a free app. which would have OSM support and came across osmand . I was looking for an app. which would have support for OSM and support for the gpx format. I was planning to use osmand in South Africa but due to the over-whelming nature of meeting people, seeing places and just being didn t actually get the time and place to try it. Came back home and a month and a half passed. In-between I had done some simple small tracks but nothing major. This week-end I got the opportunity as I got some free data balance from my service provider (a princely 50 MB) as well an opportunity to go about 40 odd kms. from the city. I had read about osmand and was looking if the off-line method worked or not from the webpage Works online (fast) or offline (no roaming charges when you are abroad) So armed with a full battery I started the journey which took about an hour and half even though technically it was a holiday. On the way back, got a different route and recorded that as well. The app. worked flawlessly. I was able to get the speed of the vehicle and everything. The only thing I haven t understood till date is how to select waypoints but other than that I got the whole route on my mobile. What was cool to see that on most roads, at least through the app. there were speed limits. Now I don t know from where the data was getting there. Most city roads had 65 and some roads had 55 at the maximum. I am assuming that it was at km/hr as also shared later. Just for fun I also looked at the gpx file after copying it from mobile to hdd (an extract) https://paste.debian.net/853231/ While it s not a complete extract, What was interesting for me to note here is the time was in UTC . What was also interesting is that in the gpx tracks I also saw some entries about speed as can be seen in the paste above. Although it doesn t say whether it was in km/hr or mph, I believe it probably is km/hr. as that is the unit I defined in the app. Anyways, the next step was trying to see which tool was good enough to show me the tracks with tiles underneath and labels of places, paths etc. I tried three tools 1. jmapviewer this didn t work at all.
2. gnome-maps this worked remarkably well but has numerous gtk3.0 warnings [shirish@debian] - [~/osmand] - [10149]
[$] gnome-maps 2016-10-01_08-11_Sat.gpx (gnome-maps:21017): Gtk-WARNING **: Theme parsing error: gtk.css:63:28: The :prelight pseudo-class is deprecated. Use :hover instead. (gnome-maps:21017): Gtk-WARNING **: Theme parsing error: gtk.css:73:35: The :prelight pseudo-class is deprecated. Use :hover instead. (gnome-maps:21017): Gtk-WARNING **: Theme parsing error: application.css:14:30: The style property GtkButton:image-spacing is deprecated and shouldn't be used anymore. It will be removed in a future version (gnome-maps:21017): Gtk-WARNING **: Theme parsing error: application.css:15:31: The style property GtkWidget:interior-focus is deprecated and shouldn't be used anymore. It will be removed in a future version (gnome-maps:21017): Gdk-WARNING **: /build/gtk+3.0-Tod2iD/gtk+3.0-3.22.0/./gdk/x11/gdkwindow-x11.c:5554 drawable is not a native X11 window (gnome-maps:21017): Gdk-WARNING **: /build/gtk+3.0-Tod2iD/gtk+3.0-3.22.0/./gdk/x11/gdkwindow-x11.c:5554 drawable is not a native X11 window (gnome-maps:21017): Gdk-WARNING **: /build/gtk+3.0-Tod2iD/gtk+3.0-3.22.0/./gdk/x11/gdkwindow-x11.c:5554 drawable is not a native X11 window (gnome-maps:21017): Gdk-WARNING **: /build/gtk+3.0-Tod2iD/gtk+3.0-3.22.0/./gdk/x11/gdkwindow-x11.c:5554 drawable is not a native X11 window (gnome-maps:21017): Gdk-WARNING **: /build/gtk+3.0-Tod2iD/gtk+3.0-3.22.0/./gdk/x11/gdkwindow-x11.c:5554 drawable is not a native X11 window (gnome-maps:21017): Gdk-WARNING **: /build/gtk+3.0-Tod2iD/gtk+3.0-3.22.0/./gdk/x11/gdkwindow-x11.c:5554 drawable is not a native X11 window (gnome-maps:21017): Gtk-WARNING **: GtkClutterOffscreen 0x4c4f3f0 is drawn without a current allocation. This should not happen. (gnome-maps:21017): Gtk-WARNING **: GtkImage 0x4ed4140 is drawn without a current allocation. This should not happen. Now I m not sure whether all of those are gtk3+ issues or me running them under Debian MATE. I know that there are issues with mate and gtk3+ as had been told/shared a few times in p.d.o. Anyways, one of the issues I encountered is that gnome-maps doesn t work in offline-mode, saw https://bugzilla.gnome.org/show_bug.cgi?id=708799 . Also saw ~/.cache/champlain/osm-mapquest and the listing underneath is gibberish in the sense you don t know what it meant to do
[shirish@debian] - [~/.cache/champlain/osm-mapquest] - [10163]
[$] ll -h drwx------ 6 shirish shirish 4.0K Jun 11 2015 10
drwx------ 26 shirish shirish 4.0K Oct 24 2014 11
drwx------ 10 shirish shirish 4.0K Jun 11 2015 12
drwx------ 11 shirish shirish 4.0K Jun 11 2015 13
drwx------ 12 shirish shirish 4.0K Jun 11 2015 14
drwx------ 12 shirish shirish 4.0K Jun 11 2015 15
drwx------ 27 shirish shirish 4.0K Oct 24 2014 16
drwx------ 25 shirish shirish 4.0K Oct 24 2014 17
drwx------ 4 shirish shirish 4.0K Mar 4 2014 3
drwx------ 5 shirish shirish 4.0K Mar 4 2014 8
drwx------ 9 shirish shirish 4.0K Mar 29 2014 9
What was/is interesting to see things like this As I was in a moving vehicle, it isn t easy to know if the imagery is at fault or was it app. , sensor of my mobile ? Did see http://learnosm.org/en/josm/correcting-imagery-offset/ but as can be seen that requires more effort from my side. The last tool proved to be the most problematic 3. JOSM Getting the tracks into josm which was easily done. While firing up josm came across https://josm.openstreetmap.de/ticket/13735 which I subsequently filed. One of the other first things which has been a major irritant for a long time is JOSM is, for a lack of better term, ugly. See the interface, especially the one having preferences, all cluttered look and specifically see the plugins corner/tab The part about it being ugly, I dunno but have seen most java apps are a bit ugly. It is a bit generalist I know but that has been my experience with whatever little java apps. I have used. I don t know what the reasons for that are, maybe because java is known/rumoured to use lot of memory which seems true in my case as well OR it doesn t have toolkits like gtk3+ or qt quick, although have to say that the looks have improved from before when I used it last some years ago
[shirish@debian] - [~] - [10340]
[$] ps -eo size,pid,user,command awk ' hr=$1/1024 ; printf("%13.6f Mb ",hr) for ( x=4 ; x<=NF ; x++ ) printf("%s ",$x) print "" ' grep josm 0.324219 Mb /bin/sh /usr/bin/josm
419.468750 Mb /usr/lib/jvm/java-8-openjdk-amd64/bin/java -Djosm.restart=true -Djava.net.useSystemProxies=true -jar /usr/share/josm/josm.jar
This is when I m just opening josm and have not added any tracks or done any work. Now I wanted to explore the routing in good amount of detail on josm. This was easily said than done. When trying to get imagery I got the Download area too large issue/defect . Multiple tries didn t get me anywhere. Then hunting on the web came across the continous-download plugin which is part of the plugin infrastructure . This I found to be a very good tool. It downloads the tiles and puts them in ~/.josm/cache/tiles
[shirish@debian] - [~/.josm/cache/tiles] - [10147]
[$] ll -h total 28M
-rw-r--r-- 1 shirish shirish 28M Oct 2 02:13 TMS_BLOCK_v2.data
-rw-r--r-- 1 shirish shirish 290K Oct 3 12:59 TMS_BLOCK_v2.key
-rw-r--r-- 1 shirish shirish 4 Oct 3 12:59 WMS_BLOCK_v2.key
-rw-r--r-- 1 shirish shirish 4 Oct 3 12:59 WMTS_BLOCK_v2.key
While unfortunately I cannot see this/make sense of it I m guessing it is some sort of database with key and data files. What did become apparent is that the OSM needs lots more love if it is to become something which can be used everyday. At the end I had to change the open-source gpx track file to a Google map kml file to be able to make sense as there are whole areas which need to be named, numbered etc. One of the newbie mistakes that I did was trying to use the slippy map in josm (using Openstreetmap/Mapnik at the back-end) to move/pan using the left-hand mouse button. It took me quite sometime to figure out that it is with right-hand mouse button that you can make the slippy map pan. This is different from almost all maps, gnome-maps uses the traditional left-hand button, Google maps also uses the same. I have filed it in upstream as https://josm.openstreetmap.de/ticket/13751 . So at least, in these rounds it is gnome-maps which has kind of won even though it doesn t do any of the things that josm claims to do. I am sure there might be some interesting tricks and tips that people might have to share about mapping
Filed under: Miscellenous Tagged: #Debconf16, #GNOME-MAPS, #JOSM, OSM

Review: Winds of Fury, by Mercedes Lackey

Series:	Mage Winds #3
Publisher:	DAW
Copyright:	August 1994
ISBN:	0-88677-612-0
Format:	Mass market
Pages:	427

This is the concluding book of the Mage Winds trilogy and a direct sequel to Winds of Change. This series doesn't make sense to read out of order. In traditional fantasy trilogies of this type, the third book is often the best. The author can stop developing characters, building the world, and setting the scene and can get to the meat of the story. All the guns on the mantles go off, all the twists the author has been saving can be used, and there's usually a lot more action than in the second book of a trilogy. That is indeed the case here. I'm not sure Winds of Fury rises to the level of a good book, but if you're invested in the Valdemar story, it works better than the previous books of this series. As one might expect, the protagonists do return to Valdemar, finally. The method of that return makes sense of some things that happened in Winds of Change and is an entertaining surprise, although I wish more had been done with it through the rest of the book and we'd gotten more world-building details. I also like how Lackey handles the Valdemar reactions to the returning protagonists, and their own reactions to Valdemar. Lackey's characters might fit some heavy-handed stereotypes a bit too neatly, but they do grow and change over the course of a series, and the return home is a good technique for showing that. Lackey also throws in her final twist for the villains of this series at the start of this book, and it's a good one (if typical Lackey; she does love her abused youth characters). The villains are still far too one-dimensional and far too stereotyped evil, but the twist (which I'll avoid spoiling) does make that dynamic a bit more interesting. And she manages to get the reader to root for one evil over another, since one of them is at least competent. You'd think from the direction the series was taking that Winds of Fury would culminate in another epic war of magic, but not this book. Lackey takes a more personal and targeted approach, heavier on characterization and individual challenge. This gives Firesong a chance to grow into an almost-likable character and earn some of that empathy and insight that he'd gotten for free. Unfortunately, it sidelines Nyara a lot, and pushes her back into a stereotyped role, which made me sad. The series otherwise emphasizes the importance of magic users who know their own limitations and can thoughtfully use the power they have, but rarely extends that to Nyara herself. I would have much rather seen her play a role like that in the final climax instead of the one she played. This is partly made up for by centering Need in the story and having her play the key connecting role between two different threads of effort. Those are probably the best parts of this book. I wish the entire series had been told from Need's perspective, with a heavy helping of exasperated grumbling, although I don't think Lackey could have written that series. But what we get of her is a delight. The gryphons, sadly, are relegated to fairly minor roles, but we get a few more tantalizing hints about the Companions to make up for it. (Although not enough to figure out their great mystery, which isn't revealed until future books.) This series is nowhere near as good as I remembered, sadly, but I did enjoy bits of it. If you like Valdemar in general, the world building is fairly important and reveals quite a lot about the underpinnings and power dynamics of Lackey's universe. I'm not sure that makes up for some tedious characters, poor communication, and some uncomfortable and dragging sections, but if you're trying to get the whole Valdemar story, the events here are rather important. And this ending was at least entertaining, if not great fiction. Rating: 6 out of 10

I was asked whether it would be safe to open a link in a spam message with wget. So here are some thoughts about wget security and web browser security in general. Wget Overview Some spam messages are designed to attack the recipient s computer. They can exploit bugs in the MUA, applications that may be launched to process attachments (EG MS Office), or a web browser. Wget is a very simple command-line program to download web pages, it doesn t attempt to interpret or display them. As with any network facing software there is a possibility of exploitable bugs in wget. It is theoretically possible for an attacker to have a web server that detects the client and has attacks for multiple HTTP clients including wget. In practice wget is a very simple program and simplicity makes security easier. A large portion of security flaws in web browsers are related to plugins such as flash, rendering the page for display on a GUI system, and javascript features that wget lacks. The Profit Motive An attacker that aims to compromise online banking accounts probably isn t going to bother developing or buying an exploit against wget. The number of potential victims is extremely low and the potential revenue benefit from improving attacks against other web browsers is going to be a lot larger than developing an attack on the small number of people who use wget. In fact the potential revenue increase of targeting the most common Linux web browsers (Iceweasel and Chromium) might still be lower than that of targeting Mac users. However if the attacker doesn t have a profit motive then this may not apply. There are people and organisations who have deliberately attacked sysadmins to gain access to servers (here is an article by Bruce Schneier about the attack on Hacking Team [1]). It is plausible that someone who is targeting a sysadmin could discover that they use wget and then launch a targeted attack against them. But such an attack won t look like regular spam. For more information about targeted attacks Brian Krebs article about CEO scams is worth reading [2]. Privilege Separation If you run wget in a regular Xterm in the same session you use for reading email etc then if there is an exploitable bug in wget then it can be used to access all of your secret data. But it is very easy to run wget from another account. You can run ssh otheraccount@localhost and then run the wget command so that it can t attack you. Don t run su otheraccount as it is possible for a compromised program to escape from that. I think that most Linux distributions have supported a switch user functionality in the X login system for a number of years. So you should be able to lock your session and then change to a session for another user to run potentially dangerous programs. It is also possible to use a separate PC for online banking and other high value operations. A 10yo PC is more than adequate for such tasks so you could just use an old PC that has been replaced for regular use for online banking etc. You could boot it from a CD or DVD if you are particularly paranoid about attack. Browser Features Google Chrome has a feature to not run plugins unless specifically permitted. This requires a couple of extra mouse actions when watching a TV program on the Internet but prevents random web sites from using Flash and Java which are two of the most common vectors of attack. Chrome also has a feature to check a web site against a Google black list before connecting. When I was running a medium size mail server I often had to determine whether URLs being sent out by customers were legitimate or spam, if a user sent out a URL that s on Google s blacklist I would lock their account without doing any further checks. Conclusion I think that even among Linux users (who tend to be more careful about security than users of other OSs) using a separate PC and booting from a CD/DVD will generally be regarded as too much effort. Running a full featured web browser like Google Chrome and updating it whenever a new version is released will avoid most problems. Using wget when you have to reason to be concerned is a possibility, but not only is it slightly inconvenient but it also often won t download the content that you want (EG in the case of HTML frames).

• [1] https://www.schneier.com/blog/archives/2016/04/how_hacking_tea.html
• [2] https://krebsonsecurity.com/2016/04/fbi-2-3-billion-lost-to-ceo-email-scams/

Review: Winds of Change, by Mercedes Lackey

Series:	Mage Winds #2
Publisher:	DAW
Copyright:	August 1993
ISBN:	0-88677-563-9
Format:	Mass market
Pages:	475

Winds of Change is a direct sequel to Winds of Fate. This is a more closely connected trilogy than the previous Valdemar books. It's not the sort of thing you want to read out of order. The events of Winds of Fate predictably left the multiple protagonists united and with some breathing space, but none of their problems are resolved. The Heartstone is still a mess; in fact, it may be getting worse. Elspeth needs to learn how to wield the magical power she apparently has. And there are a lot of interpersonal tensions, lingering hurt feelings, and (in the case of Elspeth and Darkwind) a truly prodigious quantity of whining that has to be worked through before the protagonists can feel safe and happy. Winds of Change is the training montage book, and wow did my memory paper over a lot of flaws in this series. This is 475 pages of not much happening, occasionally in very irritating ways. Yes, we do finally meander to a stronger conclusion than the last book, and there is much resolving of old hurts and awkward interactions, as well as a bit of discovery of true love (this is Lackey, after all). But far, far too much of the book is Elspeth and Darkwind sniping at each other, being immature, not communicating, and otherwise being obnoxious while all the people around them try to gently help. Lackey's main characterization flaw for me is that she tends to default into generating characters who badly need to be smacked upside the head, and then does so in ways and for things at odd angles to the reasons why I think they should be smacked. It can make for frustrating reading. The introduction of Firesong as a character about halfway through this book does not help. Firesong is a flamboyant, amazingly egotistical, and stunningly arrogant show-off who also happens to be a magical super-genius and hence has "earned" his arrogance. This is an intentional character design, not my idiosyncratic reaction to the character, since every other character in the book finds him insufferable as well at first. But he's also a deeply insightful healing Adept by, honestly, authorial fiat, so by the end of the novel he's helped patch up everyone's problems and the other characters have accepted his presentation as a character quirk. Sigh. So, okay, one doesn't read popcorn fantasy for its deep characterization or realistic grasp of human subtlety. But this is just way more than I can swallow. Lackey's concept of a healing Adept (which I like a great deal as a bit of world-building) necessarily involves both deep knowledge and deep empathy and connection with other people. Firesong is so utterly full of himself that there's simply no way that he could have the empathy required to do what he is shown to do here. (Lackey does try to explain this away in the book, but the explanation didn't work for me.) Every time he successfully intervenes in other people's emotional lives, he does so with a sudden personality change, some stunning insight that he previously showed no evidence of ability to understand, and somehow only enough arrogance in his presentation to prickle but not to close people's mind to whatever he's trying to say. That's not how this works. That's not how any of this works. Lackey always treats psychology as a bit of a blunt instrument, and one either learns to tolerate that or gives up on her series, but Firesong is flatly the most unbelievable emotional mentor figure in any of her books I've read. (One of the more satisfying, if slight, bits of this series comes up in the next book, where Firesong runs into someone else who can do the same thing but has actually earned the empathy the hard way, and is a bit taken aback by it.) My other complaint with this book is that Lackey adds more chapters from the viewpoint of the big bad of the series. These are deeply unpleasant, since he's a deeply unpleasant person, and seem largely unnecessary. It's vaguely interesting to follow the magical maneuverings from both sides, but there are more of these scenes than strictly necessary for that purpose, and the sheer unmitigated evil of Lackey's evil characters is a bit hard to take. Also, he somehow has vast resources of staff and assistants, and much suspension of disbelief is required to believe that anyone would continue working for this person. It's one thing to imagine people being drawn to a charismatic Hitler type; it's quite another when the boss is a brooding, imperious asshole who roams the hallways and tortures random people to death whenever he's bored. Fear and magic only go so far in maintaining a large following when you do that, and he generates dead bodies at a remarkable rate. The best characters in this series continue to be Nyara, Need, and the gryphons. I'd rather read a book just about them. Need does use a bit too much of Lackey's tough love technique (another recurring theme of this larger series), but from Need that's wholly believable; her gruff and dubious empathy is in line with her character and history and fits a talking sword extremely well. But they, despite having a bit of their own training montage, are a side story here. The climax of the story is moderately satisfying, but the book takes far too long to get to it. I remember liking this series when I first read it, and I still like some aspects of Lackey's world-building and a few of the characters, but it's much weaker than I had remembered. I can't really recommend it. Followed by Winds of Fury. Rating: 5 out of 10

I sent this email to debian-private a few days ago, on the 10th anniversary of my Debian account creation:

Date: Fri, 14 Aug 2015 19:37:20 +0200
From: David Moreno 
To: debian-private@lists.debian.org
Subject: Retiring from Debian
User-Agent: Mutt/1.5.23 (2014-03-12)
[-- PGP output follows (current time: Sun 23 Aug 2015 06:18:36 PM CEST) --]
gpg: Signature made Fri 14 Aug 2015 07:37:20 PM CEST using RSA key ID 4DADEC2F
gpg: Good signature from "David Moreno "
gpg:                 aka "David Moreno "
gpg:                 aka "David Moreno (1984-08-08) "
[-- End of PGP output --]
[-- The following data is signed --]
Hi,
Ten years ago today (2005-08-14) my account was created:
https://nm.debian.org/public/person/damog
Today, I don't feel like Debian represents me and neither do I represent the
project anymore.
I had tried over the last couple of years to retake my involvement but lack of
motivation and time always got on the way, so the right thing to do for me is
to officially retire and gtfo.
I certainly learned a bunch from dozens of Debian people over these many years,
and I'm nothing but grateful with all of them; I will for sure carry the project
close to my heart   as I carry it with the Debian swirl I still have tattooed
on my back ;)
http://damog.net/blog/2005/06/29/debian-tattoo/
I have three packages left that have not been updated in forever and you can
consider orphaned now: gcolor2, libperl6-say-perl and libxml-treepp-perl.
With all best wishes,
David Moreno.
http://damog.net/
[-- End of signed data --]

I received a couple of questions about my decision here. I basically don t feel like Debian represents my interests and neither do I represent the project this doesn t mean I don t believe in free software, to the contrary. I think some of the best software advancements we ve made as society are thanks to it. I don t necessarily believe on how the project has evolved itself, whether that has been the right way, to regain relevancy and dominance, and if it s remained primarily a way to feed dogmatism versus pragmatism. This is the perfect example of a tragic consequence. I was very happy to learn that the current Debian Conference being held in Germany got the highest attendance ever, hopefully that can be utilized in a significant and useful way. Regardless, my contributions to Debian were never noteworthy so it s also not that big of a deal. I just need to close cycles myself and move forward, and the ten year anniversary looked like a significant mark for that. Poke me in case you wanna discuss some more. I ll always be happy to. Specially over beer :) Peace.

There has been a great deal of comment among my friends recently about a particularly British cookery program called "The Great British Bake Off". There has been some controversy as the program is moving from the BBC to a commercial broadcaster.

Part of this discussion comes from all the presenters, excepting Paul Hollywood, declining to sign with the new broadcaster and partly because of speculation the BBC might continue with a similar format show with a new name.

Rob Kendrick provided the start to this conversation by passing on a satirical link suggesting Samuel L Jackson might host "cakes on a plane"

This caused a large number of suggestions for alternate names which I will be reporting but Rob Kendrick, Vivek Das Mohapatra, Colin Watson, Jonathan McDowell, Oki Kuma, Dan Alderman, Dagfinn Ilmari Manns ke, Lesley Mitchell and Daniel Silverstone are the ones to blame.

• Strictly come baking
• Stars and their pies
• Baking with the stars
• Bake/Off.
• Blind Cake
• Cake or no cake?
• The cake is a lie
• Bake That.
• Bake Me On
• Bake On Me
• Bakin' Stevens.
• The Winner Bakes It All
• Bakerloo
• Bake Five
• Every breath you bake
• Every bread you bake
• Unbake my heart
• Knead and let prove
• Bake me up before you go-go
• I want to bake free
• Another bake bites the dust
• Cinnamon whorl is not enough
• The pie who loved me
• The yeast you can do.
• Total collapse of the tart
• Bake and deliver
• You Gotta Bake
• Bake's Seven
• Natural Born Bakers
• Bake It Or Leaven It
• Driving the last pikelet
• Pie crust on the dancefloor
• Tomorrow never pies
• Murder on the pie crust
• The pie who came in from the cold.
• You only bake twice (Every body has to make one sweet and one savoury dish).

So that is our list, anyone else got better ideas?

Previously: v4.5. The v4.6 Linux kernel release included a bunch of stuff, with much more of it under the KSPP umbrella. seccomp support for parisc Helge Deller added seccomp support for parisc, which including plumbing support for PTRACE_GETREGSET to get the self-tests working. x86 32-bit mmap ASLR vs unlimited stack fixed Hector Marco-Gisbert removed a long-standing limitation to mmap ASLR on 32-bit x86, where setting an unlimited stack (e.g. ulimit -s unlimited ) would turn off mmap ASLR (which provided a way to bypass ASLR when executing setuid processes). Given that ASLR entropy can now be controlled directly (see the v4.5 post), and that the cases where this created an actual problem are very rare, means that if a system sees collisions between unlimited stack and mmap ASLR, they can just adjust the 32-bit ASLR entropy instead. x86 execute-only memory Dave Hansen added Protection Key support for future x86 CPUs and, as part of this, implemented support for execute only memory in user-space. On pkeys-supporting CPUs, using mmap(..., PROT_EXEC) (i.e. without PROT_READ) will mean that the memory can be executed but cannot be read (or written). This provides some mitigation against automated ROP gadget finding where an executable is read out of memory to find places that can be used to build a malicious execution path. Using this will require changing some linker behavior (to avoid putting data in executable areas), but seems to otherwise Just Work. I m looking forward to either emulated QEmu support or access to one of these fancy CPUs. CONFIG_DEBUG_RODATA enabled by default on arm and arm64, and mandatory on x86 Ard Biesheuvel (arm64) and I (arm) made the poorly-named CONFIG_DEBUG_RODATA enabled by default. This feature controls whether the kernel enforces proper memory protections on its own memory regions (code memory is executable and read-only, read-only data is actually read-only and non-executable, and writable data is non-executable). This protection is a fundamental security primitive for kernel self-protection, so making it on-by-default is required to start any kind of attack surface reduction within the kernel. On x86 CONFIG_DEBUG_RODATA was already enabled by default, but, at Ingo Molnar s suggestion, I made it mandatory: CONFIG_DEBUG_RODATA cannot be turned off on x86. I expect we ll get there with arm and arm64 too, but the protection is still somewhat new on these architectures, so it s reasonable to continue to leave an out for developers that find themselves tripping over it. arm64 KASLR text base offset Ard Biesheuvel reworked a ton of arm64 infrastructure to support kernel relocation and, building on that, Kernel Address Space Layout Randomization of the kernel text base offset (and module base offset). As with x86 text base KASLR, this is a probabilistic defense that raises the bar for kernel attacks where finding the KASLR offset must be added to the chain of exploits used for a successful attack. One big difference from x86 is that the entropy for the KASLR must come either from Device Tree (in the /chosen/kaslr-seed property) or from UEFI (via EFI_RNG_PROTOCOL), so if you re building arm64 devices, make sure you have a strong source of early-boot entropy that you can expose through your boot-firmware or boot-loader. zero-poison after free Laura Abbott reworked a bunch of the kernel memory management debugging code to add zeroing of freed memory, similar to PaX/Grsecurity s PAX_MEMORY_SANITIZE feature. This feature means that memory is cleared at free, wiping any sensitive data so it doesn t have an opportunity to leak in various ways (e.g. accidentally uninitialized structures or padding), and that certain types of use-after-free flaws cannot be exploited since the memory has been wiped. To take things even a step further, the poisoning can be verified at allocation time to make sure that nothing wrote to it between free and allocation (called sanity checking ), which can catch another small subset of flaws. To understand the pieces of this, it s worth describing that the kernel s higher level allocator, the page allocator (e.g. __get_free_pages()) is used by the finer-grained slab allocator (e.g. kmem_cache_alloc(), kmalloc()). Poisoning is handled separately in both allocators. The zero-poisoning happens at the page allocator level. Since the slab allocators tend to do their own allocation/freeing, their poisoning happens separately (since on slab free nothing has been freed up to the page allocator). Only limited performance tuning has been done, so the penalty is rather high at the moment, at about 9% when doing a kernel build workload. Future work will include some exclusion of frequently-freed caches (similar to PAX_MEMORY_SANITIZE), and making the options entirely CONFIG controlled (right now both CONFIGs are needed to build in the code, and a kernel command line is needed to activate it). Performing the sanity checking (mentioned above) adds another roughly 3% penalty. In the general case (and once the performance of the poisoning is improved), the security value of the sanity checking isn t worth the performance trade-off. Tests for the features can be found in lkdtm as READ_AFTER_FREE and READ_BUDDY_AFTER_FREE. If you re feeling especially paranoid and have enabled sanity-checking, WRITE_AFTER_FREE and WRITE_BUDDY_AFTER_FREE can test these as well. To perform zero-poisoning of page allocations and (currently non-zero) poisoning of slab allocations, build with:

CONFIG_DEBUG_PAGEALLOC=n
CONFIG_PAGE_POISONING=y
CONFIG_PAGE_POISONING_NO_SANITY=y
CONFIG_PAGE_POISONING_ZERO=y
CONFIG_SLUB_DEBUG=y

and enable the page allocator poisoning and slab allocator poisoning at boot with this on the kernel command line:

page_poison=on slub_debug=P

To add sanity-checking, change PAGE_POISONING_NO_SANITY=n, and add F to slub_debug as slub_debug=PF . read-only after init I added the infrastructure to support making certain kernel memory read-only after kernel initialization (inspired by a small part of PaX/Grsecurity s KERNEXEC functionality). The goal is to continue to reduce the attack surface within the kernel by making even more of the memory, especially function pointer tables, read-only (which depends on CONFIG_DEBUG_RODATA above). Function pointer tables (and similar structures) are frequently targeted by attackers when redirecting execution. While many are already declared const in the kernel source code, making them read-only (and therefore unavailable to attackers) for their entire lifetime, there is a class of variables that get initialized during kernel (and module) start-up (i.e. written to during functions that are marked __init ) and then never (intentionally) written to again. Some examples are things like the VDSO, vector tables, arch-specific callbacks, etc. As it turns out, most architectures with kernel memory protection already delay making their data read-only until after __init (see mark_rodata_ro()), so it s trivial to declare a new data section ( .data..ro_after_init ) and add it to the existing read-only data section ( .rodata ). Kernel structures can be annotated with the new section (via the __ro_after_init macro), and they ll become read-only once boot has finished. The next step for attack surface reduction infrastructure will be to create a kernel memory region that is passively read-only, but can be made temporarily writable (by a single un-preemptable CPU), for storing sensitive structures that are written to only very rarely. Once this is done, much more of the kernel s attack surface can be made read-only for the majority of its lifetime. As people identify places where __ro_after_init can be used, we can grow the protection. A good place to start is to look through the PaX/Grsecurity patch to find uses of __read_only on variables that are only written to during __init functions. The rest are places that will need the temporarily-writable infrastructure (PaX/Grsecurity uses pax_open_kernel()/pax_close_kernel() for these). That s it for v4.6, next up will be v4.7!

2016, Kees Cook. This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 License.

Here is my monthly update covering what I have been doing in the free software world (previous month):

• Fixed a number of instances in the Django web development framework where methods had mutable defaults arguments such as lists or dictionaries. (#7253)
• Made a large number of improvements to travis.debian.net, my hosted service for projects that host their Debian packaging on GitHub to use the Travis CI continuous integration platform to test builds on every update:
  • Worked with Evgeni Golov to run autopkgtest and autodep8 tests after builds. (#23, #24 & #25)
  • Ensured that all remote branches are created locally so that packages that specify options such as pristine_tar=True in debian/gbp.conf work as expected. (commit)
  • Fixed an issue where checking out other branches did not reliably not work due to Travis cloning the repository with --depth=50. (#21)
  • Updated the documentation after prompting from Valerie Young. (db7238 & 470d24)
• Improved my Chrome extension for the FastMail web interface to collapse whitespace when appending to the subject. (#9)
• Submitted a pull request for the Handbrake video transcoder to make the build reproducible. (#320)
• Updated the configuration for my OpenWRT-based router (a device I use as a range extender and to save tedious reconfiguration of all my wifi devices in new locales) to enter a "fallback" mode if it cannot connect to the client network. This works around a longstanding "wontfix" upstream issue. (diff)
• Updated django-agpl, my reusable Django application to assist in releasing projects under the GNU Affero General Public License:
  • Merged support from defivelo to support Django 1.8. (#1)
  • Improved the code quality & testability throughout the package. (diff)
• Filed in issue in Mailvelope (a browser extension for OpenPGP encryption) to support composing/viewing messages in a fixed-width font. (#422)
• Blogged about how to write your first Lintian check as well as on the progress bar I added to Diffoscope.

---

Previously: v4.4. Some things I found interesting in the Linux kernel v4.5: CONFIG_IO_STRICT_DEVMEM The CONFIG_STRICT_DEVMEM setting that has existed for a long time already protects system RAM from being accessible through the /dev/mem device node to root in user-space. Dan Williams added CONFIG_IO_STRICT_DEVMEM to extend this so that if a kernel driver has reserved a device memory region for use, it will become unavailable to /dev/mem also. The reservation in the kernel was to keep other kernel things from using the memory, so this is just common sense to make sure user-space can t stomp on it either. Everyone should have this enabled. (And if you have a system where you discover you need IO memory access from userspace, you can boot with iomem=relaxed to disable this at runtime.) If you re looking to create a very bright line between user-space having access to device memory, it s worth noting that if a device driver is a module, a malicious root user can just unload the module (freeing the kernel memory reservation), fiddle with the device memory, and then reload the driver module. So either just leave out /dev/mem entirely (not currently possible with upstream), build a monolithic kernel (no modules), or otherwise block (un)loading of modules (/proc/sys/kernel/modules_disabled). ptrace fsuid checking Jann Horn fixed some corner-cases in how ptrace access checks were handled on special files in /proc. For example, prior to this fix, if a setuid process temporarily dropped privileges to perform actions as a regular user, the ptrace checks would not notice the reduced privilege, possibly allowing a regular user to trick a privileged process into disclosing things out of /proc (ASLR offsets, restricted directories, etc) that they normally would be restricted from seeing. ASLR entropy sysctl Daniel Cashman standardized the way architectures declare their maximum user-space ASLR entropy (CONFIG_ARCH_MMAP_RND_BITS_MAX) and then created a sysctl (/proc/sys/vm/mmap_rnd_bits) so that system owners could crank up entropy. For example, the default entropy on 32-bit ARM was 8 bits, but the maximum could be as much as 16. If your 64-bit kernel is built with CONFIG_COMPAT, there s a compat version of the sysctl as well, for controlling the ASLR entropy of 32-bit processes: /proc/sys/vm/mmap_rnd_compat_bits. Here s how to crank your entropy to the max, without regard to what architecture you re on:

for i in "" "compat_"; do f=/proc/sys/vm/mmap_rnd_$ i bits; n=$(cat $f); while echo $n > $f ; do n=$(( n + 1 )); done; done

strict sysctl writes Two years ago I added a sysctl for treating sysctl writes more like regular files (i.e. what s written first is what appears at the start), rather than like a ring-buffer (what s written last is what appears first). At the time it wasn t clear what might break if this was enabled, so a WARN was added to the kernel. Since only one such string showed up in searches over the last two years, the strict writing mode was made the default. The setting remains available as /proc/sys/kernel/sysctl_writes_strict. seccomp UM support Micka l Sala n added seccomp support (and selftests) for user-mode Linux. Moar architectures! seccomp NNP vs TSYNC fix Jann Horn noticed and fixed a problem where if a seccomp filter was already in place on a process (after being installed by a privileged process like systemd, a container launcher, etc) then the setting of the no new privs flag could be bypassed when adding filters with the SECCOMP_FILTER_FLAG_TSYNC flag set. Bypassing NNP meant it might be possible to trick a buggy setuid program into doing things as root after a seccomp filter forced a privilege drop to fail (generally referred to as the sendmail setuid flaw ). With NNP set, a setuid program can t be run in the first place. That s it! Next I ll cover v4.6 Edit: Added notes about iomem=

2016, Kees Cook. This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 License.

A new postdoc student arrived at our department this semester, and after learning that he uses GNU/Linux for all his computing, I invited him along to TFUG. During some of our meetings people asked how could I do X on my GNU/Linux desktop? and, jokingly, the postdoc would respond the answer to your question is do you really need to do that? Sometimes the more experienced GNU/Linux users at the table would respond to questions by suggesting that the user should simply give up on doing X, and the postdoc would slap his thigh and laugh and say see? I told you that s the answer! The phenomenon here is that people who have at some point made a commitment to at least try to use GNU/Linux for all their computing quickly find that they have come to value using GNU/Linux more than they value engaging in certain activities that only work well/at all under a proprietary operating system. I think that this is because they get used to being treated with respect by their computer. And indeed, one of the reasons I ve almost entirely given up on computer gaming is that computer games are non-free software. Are you sure you need to do that? starts sounding like a genuine question rather than simply a polite way of saying that what someone wants to do can t be achieved. I suggest that this is a blessing in disguise. The majority of the things that you can only do under a proprietary operating system are things that it would be good for you if you were to switch them out for other activities. I m not suggesting that switching to a GNU/Linux is a good way to give up on the entertainment industry. It s a good way of moderating your engagement with the entertainment industry. Rather than logging onto Netflix, you might instead pop in a DVD of a movie. You can still engage with contemporary popular culture, but the technical barriers give you an opportunity to moderate your consumption: once you ve finished watching the movie, the software won t try to get you to watch something else by making a calculation as to what you re most likely to assent to watching next based on what you ve watched before. For this behaviour of the Netflix software is just another example of non-free software working against its user s interests: watching a movie is good for you, but binge-watching a TV series probably isn t. In cases like this, living in the world of Free Software makes it easier to engage with media healthily.