Search Results: "ag"

4 May 2020

Dima Kogan: Redirection and /dev/stderr

I just hit some unexpected unix-ism (or maybe Linux-ism?) that I'd like to mention here. I found a workaround, but if anybody knows what's actually happening and can enlighten me, please send me an email, and I'll update the post. OK, so I have a program that does stuff, and outputs its progress to stderr. And I'm invoking this from a shell script that also outputs stuff to stderr. A minimized sample: 
echo "Outer print 1111" > /dev/stderr
perl -E 'say STDERR ("1111 1111 1111 1111 1111 1111 1111 1111\n")'
echo "Outer print 2222" > /dev/stderr
perl -E 'say STDERR ("2222 2222 2222 2222 2222 2222 2222 2222\n")'
Let's call this dothing.sh. This works just fine. Now let's say I want to log the output to a file. Naturally I do this: 
./dothing.sh 2> /tmp/log
Surprisingly, this does not work: 
$ bash dothing.sh 2> /tmp/log && cat /tmp/log
Outer print 2222
2222 2222 2222 2222 2222 2222 2222 2222
$ bash dothing.sh 2> /tmp/log && xxd /tmp/log
0000000: 4f75 7465 7220 7072 696e 7420 3232 3232  Outer print 2222
0000010: 0a00 0000 0000 0000 0000 0000 0000 0000  ................
0000020: 0000 0000 0000 0000 0032 3232 3220 3232  .........2222 22
0000030: 3232 2032 3232 3220 3232 3232 2032 3232  22 2222 2222 222
0000040: 3220 3232 3232 2032 3232 3220 3232 3232  2 2222 2222 2222
0000050: 0a0a                                     ..
The 1111 prints are gone, and we now have a block of binary 0 bytes in there for some reason. I had been assuming that writes to stderr block until they're finished. So I can, without thinking about it, mix writing to fd 2 and opening, and then writing to /dev/stderr. Apparently the right way to do this is to write to fd 2 in the script directly, instead of opening /dev/stderr: 
echo "Outer print 1111" >&2
perl -E 'say STDERR ("1111 1111 1111 1111 1111 1111 1111 1111\n")'
echo "Outer print 2222" >&2
perl -E 'say STDERR ("2222 2222 2222 2222 2222 2222 2222 2222\n")'
Why?

Update So I poked at it for a bit more, and it turns out that the obvious scapegoat (buffering) is actually not the issue. The problem is this: 

$ ls -l /dev/stderr(:A)
-rw-r--r-- 1 dima dima 36 May  4 17:02 /tmp/log
:A is the zsh syntax for recursive link-following. /dev/stderr is thus ultimately a link to /tmp/log. So the file on disk /tmp/log is being opened for writing and written-to twice at the same time
  • once in the outer 2>/tmp/log redirection
  • again in the inner >/dev/stderr redirection
Now we know. Thanks to Larry Doolittle for pointers.

Christoph Berg: arm64 on apt.postgresql.org

The apt.postgresql.org repository has been extended to cover the arm64 architecture. We had occasionally received user request to add "arm" in the past, but it was never really clear which kind of "arm" made sense to target for PostgreSQL. In terms of Debian architectures, there's (at least) armel, armhf, and arm64. Furthermore, Raspberry Pis are very popular (and indeed what most users seemed to were asking about), but the raspbian "armhf" port is incompatible with the Debian "armhf" port. Now that most hardware has moved to 64-bit, it was becoming clear that "arm64" was the way to go. Amit Khandekar made it happen that HUAWEI Cloud Services donated a arm64 build host with enough resources to build the arm64 packages at the same speed as the existing amd64, i386, and ppc64el architectures. A few days later, all the build jobs were done, including passing all test-suites. Very few arm-specific issues were encountered which makes me confident that arm64 is a solid architecture to run PostgreSQL on. We are targeting Debian buster (stable), bullseye (testing), and sid (unstable), and Ubuntu bionic (18.04) and focal (20.04). To use the arm64 archive, just add the normal sources.list entry: 
deb https://apt.postgresql.org/pub/repos/apt buster-pgdg main
Ubuntu focal At the same time, I've added the next Ubuntu LTS release to apt.postgresql.org: focal (20.04). It ships amd64, arm64, and ppc64el binaries. 
deb https://apt.postgresql.org/pub/repos/apt focal-pgdg main
Old PostgreSQL versions Many PostgreSQL extensions are still supporting older server versions that are EOL. For testing these extension, server packages need to be available. I've built packages for PostgreSQL 9.2+ on all Debian distributions, and all Ubuntu LTS distributions. 9.1 will follow shortly. This means people can move to newer base distributions in their .travis.yml, .gitlab-ci.yml, and other CI files.

Russ Allbery: Review: Seraphina

Review: Seraphina, by Rachel Hartman
Series: Seraphina #1
Publisher: Ember
Copyright: 2012
ISBN: 0-375-89658-9
Format: Kindle
Pages: 360
Forty years ago, dragons and humans negotiated a fragile truce. The fighting stopped, the dragon-killing knights were outlawed, and dragons were allowed to visit the city in peace, albeit under stringent restrictions. Some on both sides were never happy with that truce and now, as the anniversary approaches, Prince Rufus has been murdered while hunting. His head was never found, and not a few members of the court are certain that it was eaten. Sixteen-year-old Seraphina had no intention of being part of that debate. She's desperately trying to keep a low profile as the assistant court music director and music tutor to a princess. Her father is furious that she's at court at all, since that they are hiding a family secret that cannot get out. But Seraphina has a bad habit of being competent in ways that are hard to ignore: improving the princess's willingness to learn music beyond all expectations, performing memorably at Prince Rufus's funeral, and then helping, with her dragon tutor, a newskin dragon (one new to shapeshifting) who was attacked by a mob. This brings her to the attention of Prince Lucian Kiggs: royal bastard, fiance of the princess, head of the royal guard, and observant investigator. For Seraphina and her secrets, that's a threat, but she has made more friends at court than she realizes. I probably should spoil Seraphina's secret, since it's hard to talk about this book without it and Hartman reveals it relatively early, but I try to avoid spoilers. I'll instead say that Seraphina is in danger from both the court and the dragons if her secret is uncovered, but she has an ability that will prove more useful than she ever expected in helping the kingdom avoid war. That ability is not something flashy; it lies in listening, understanding, and forming connections. As you have probably guessed from the age of the protagonist, this is a young adult fantasy. It has that YA shape; Seraphina is uncertain but brave, gets into trouble by being unable to keep her mouth shut or stand by when she can prevent bad things from happening, and is caught by surprise when others find those characteristics likable. The cast is small despite an epic fantasy setup, and the degree to which Seraphina ends up at the heart of the kingdom's affairs is perhaps a touch unrealistic. Like a lot of YA, Seraphina is very centered on its main character. Your enjoyment of this book will likely hinge on how much you like her mix of uncertainty, determination, and ethics. I liked her. I also appreciated the way that Hartman had her stumble into the plot through a series of accidents and entanglements with her past and her secret, despite her own best intentions. Seraphina is trying to avoid attention, not get into the middle of a novel, but she's naturally the sort of person who rushes towards danger to help others whenever events happen too fast for her to think. She has also attracted the attention (and unexpected friendship) of critical members of the royal family who like to meddle, which is bad for her attempts to hide. This could have felt artificial and too coincidental, but it didn't. The one thing that did bother me about this book, though, was the nature of dragons, although it's possible that I'm being unfair. Dragons in Hartman's world can shapeshift into human form, but they don't understand (and deeply distrust) human emotions, finding them overwhelming and impure. This bit of world-building is not original to this book, and perhaps I should attribute it to the ubiquitous influence of Spock and Vulcans. But I kept stumbling over the feeling like dragons were based partly on stereotypes of the autism spectrum, which hurt my ability to engross myself in the story. It would not surprise me if I had this all wrong, Hartman didn't intend anything of the sort, and no one else will read it that way. But it still seemed worth mentioning. Seraphina's dynamic with Kiggs becomes the core of the story, but it's slow and stumbling and occasionally frustrating when Seraphina is more cautious than the reader thinks she needs to be. The payoff is mostly worth the frustration, though. I wish Seraphina had been a bit more curious about her abilities, a bit more willing to notice the obvious (the bit with the dancers drug on far too long), and a bit more trusting of people who deserve her trust, and I wish Hartman had taken a different approach with the dragon attitude towards emotions. But this was fun. Recommended if you want a good-hearted story where doing the right thing is rewarded and people in positions of power notice when someone is a good person. Followed by Shadow Scale. Rating: 7 out of 10

3 May 2020

Enrico Zini: Tech links

Debops (2014) Hacker News
debian devel archive.org
2020-05-04
The way developers somehow think DevOps is (or should be) an abbreviation of "Developers doing/replacing Operations" is terrifying to me.I'm also in the same boat as the author, in that I recommend and target Debian Stable + Backports (and some vendor/community repos when required).
What nobody tells you about documentation - Blog - Divio
devel archive.org
2020-05-04
However hard you work on documentation, it won't work for your software - unless you do it the right way.
Eagle's Path: (2019-11-09)
devel python archive.org
2020-05-04
I'm going to preach the wonders of Python dataclasses, but for reasons of interested to those who have already gone down the delightful rabbit-hole of typed Python. So let me start with a quick plug for mypy if you haven't heard about it.
Encoding your WiFi access point password into a QR code
howto security archive.org
2020-05-04
Subscribe in a reader Subscribe by Email
My Abandonware: because old video games were better
games history archive.org
2020-05-04
Database of 15500 abandonware games free. One of the most complete video games museum. Take a trip down Memory Lane now! Warning: whole weekends can be lost.

Dirk Eddelbuettel: #0: Introducing T^4: Tips, Tricks, Tools, and Toys

For way too long now something I had meant to start was a little series about tips, tricks, tools, and toys. I had mentioned the idea a few times to a friend or two, and generally received a thumbs up or a go for it . But it takes a little to get over the humb and get going. And it turns out that last week s r^4 talk on upgrading to R 4.0.0 hit some latent demand as we are now at 1400 views on YouTube. Wowser. So hence without further ado, let s kick off T^4. Similar in spirit to R^4, but broader in scope and going beyond R. The opening slides explaining what we plan to do are here, and the video link follows below:

With some luck we should have the first actual talk next week. See you then! If you like this or other open-source work I do, you can now sponsor me at GitHub. For the first year, GitHub will match your contributions.

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. Please report excessive re-aggregation in third-party for-profit settings.

Sean Whitton: Processing mail from discussion lists differently

I realised this week that for some years I have been applying Inbox Zero indiscriminately to all e-mail that I receive, but this does not make sense, and has some downsides. My version of Inbox Zero works very well when applied to mail addressed directly to me, and for mail to certain mailing lists, where each post to the list might as well be addressed directly to me, in addition to the list. However, I also receive by e-mail the following things to which I now believe Inbox Zero should not be applied: I believe that applying Inbox Zero to these sorts of things is not only incorrect but is actually harming my engagement with these mediums. Let us distinguish
  1. processing e-mail this means applying the Inbox Zero decision procedure to incoming messages, at set times during the day (I do it once, around 4pm)
  2. browsing and sometimes catching up RSS articles and list mail looking through unread items, replying if I think I have something useful to say, leaving things for later, and occasionally marking all as read if I ve not had time for that group of lists lately.
These should be kept apart. The easy case to see is why you shouldn t apply the browsing/catching up approach to e-mail which should rather be processed that s just the original wisdom of Inbox Zero. And clearly you don t want ever to have to resort to just marking all mail addressed directly to you as read. What goes wrong, then, if you misapply the processing mentality to e-mail which should, rather, be browsed/caught up? Well, the core of Inbox Zero is deciding whether to read and reply to something right now, add it to your todo list to handle later, or decide the mail cannot be dealt with quickly but is not important enough to go on that todo list. If you apply this to RSS articles and discussion list mail, then the third option is basically ruled out, because almost nothing on mailing lists or on blogs that I follow is important enough to go on my list of Real Tasks. But then you re faced with either reading the article/post right now, or discarding it. There is no option to leave the item marked as unread and then maybe come back to it, or postpone discarding it until you ve decided to catch up the group. Applying Inbox Zero to discussion lists and RSS feeds creates a false sense of urgency. I ve realised that my implicit response to this has been reluctance to subscribe to new mailing lists and feeds, because I don t have things set up to allow me to read them in a leisurely way. But then I m missing out on discussions and writing that might be relevant and beneficial to me if I could only approach them when I m in a frame of mind other than time to get my inbox down to zero . This also means that subscribing to new mailing lists just in order to post something has an unreasonably high cost: introducing all mail on those lists into my Inbox Zero processing window. So, what s needed is to make the virtual folder views which I use to read new mail correspond cleanly to the distinction between mail to be processed and mail to be browsed. I.e. for each virtual folder it should be clear whether mail there is to be processed or to be browsed. Then I can continue to use my processing views once per day, and access the browsing views at leisure. (Indeed, I ve created a keybinding to cycle through the new browsing views, and another to catch them up.) As I mentioned, some list mail ought to be processed. For example, I want to process rather than browse the debian-policy mailing list, as one of the Policy Editors. With notmuch, it s easy to include this mail in the relevant processing views (I ve long had one processing view for weekdays and another for weekends). Additionally, I ve used a bit of Emacs Lisp to create a dynamic uncategorised unread view which catches mail to be browsed which (i) doesn t show up in one of the other virtual folders for mail to be browsed, and (ii) doesn t show up in one of the processing views. So now subscribing to a mailing list is cheap: mail will end up in the uncategorised view, and I can decide whether to leave it there for a low traffic list; create a new virtual folder for the list (trivial as it s all just more Emacs Lisp, no actual moving of files required); or unsubscribe. I ve been experiencing nostalgia for my time in secondary school when my friends and I had all sorts of interesting stuff flowing into our mailstores, from RSS feeds to each other s blogs where we d post both our own content and links elsewhere, RSS feeds to stranger s blogs, and e-mails sent to each other with links. We didn t have to worry about processing anything back then, as our e-mail accounts were used for intellectual enrichment but not the completion of tasks. I think I can recapture something of that with my new virtual folders for browsing.

Iain R. Learmonth: Hetzner Dedicated Server Reverse DNS + Ansible

Continuing on the path towards all my stuff being managed by Ansible, I ve figured out a method of managing the reverse DNS entries for subnets on the Hetzner Dedicated Server. There s a bunch of Ansible modules for handling Hetzner Cloud, but these servers are managed in Robot which the Cloud API doesn t cover. Instead, you need to use the Robot Webservice. Ansible does have a module for doing pretty arbitrary things with web APIs though, so using that I ve got the following playbook figured out to keep the reverse DNS entries in sync: 
---
- hosts:
  - vmhost_vm1
  gather_facts: False
  tasks:
  - name: import hetzner webservice credentials
    include_vars:
      file: "hetzner_ws.yml"
  - name: set rdns for hetzner hosts
    block:
    - name: get current rdns entry
      uri:
        user: "  hetzner_ws_user  "
        password: "  hetzner_ws_password  "
        url: "https://robot-ws.your-server.de/rdns/  vmip4  "
        status_code: [200, 404]
      register: rdns_result
    - name: update incorrect rdns entry
      uri:
        user: "  hetzner_ws_user  "
        password: "  hetzner_ws_password  "
        url: "https://robot-ws.your-server.de/rdns/  vmip4  "
        method: "POST"
        body_format: form-urlencoded
        body:
          ptr: "  inventory_hostname  "
        status_code: [200, 201]
      when: '"rdns" not in rdns_result.json or inventory_hostname != rdns_result.json.rdns.ptr'
      changed_when: True
    delegate_to: localhost
The host groups this runs on are currently hardcoded as the VMs that live in the Hetzner Dedicated Server. A future iteration of this might use some inventory plugin to look up the subnets that are managed on Hetzner and create a group for all of those. Right now it won t be setting the reverse DNS for the router interface on that subnet, and won t automatically include new server s subnets. Gathering facts is disabled because all of these run locally. There is at least one VM running on this server that I can t log in to because I host it for someone else, so running locally is a necessity. The webservice credentials are stored in an Ansible Vault encrypted YAML file and loaded explicitly. An important note: the webservice username and password is not the same as your regular Robot username and password. You need to create a webservice user in Robot under Settings; Webservice and app settings . If you attempt to authenticate with an incorrect username and password 3 times in a row, your IP address will be blocked for 10 minutes. There are 6 hosts in this group, so I did this a few times before I realised there was a different user account I needed to create. I d suggest limiting to a single host while you re testing to get the authentication figured out. The actual calls to the webservice take place in a block just to avoid having to specify the delegate_to: localhost twice. The first step looks up the current PTR record, and accepts success if it gives either a 200 or 404 status code (it will be 404 if there is no existing pointer record). The result of this is used to conditionally create/update the PTR record in the next task. If nothing needs to be done, nothing will be changed and the second task will be skipped. If a change is needed, the second step is successful if either the PTR record is updated (status 200) or created (status 201). This was actually a lot easier than I thought it would be, and the uri module looks to be really flexible, so I bet there are other things that I could easily integrate into my Ansible playbooks.

Evgeni Golov: Remote management for OpenWRT devices without opening inbound connections

Everyone is working from home these days and needs a decent Internet connection. That's especially true if you need to do video calls and the room you want to do them has the worst WiFi coverage of the whole flat. Well, that's exactly what happened to my parents in law. When they moved in, we knew that at some point we'll have to fix the WiFi - the ISP provided DSL/router/WiFi combo would not cut it, especially not with the shape of the flat and the elevator shaft in the middle of it: the flat is essentially a big C around said shaft. But it was good enough for email, so we postponed that. Until now. The flat has wired Ethernet, but the users MacBook Air does not. That would have been too easy, right? So let's add another access point and hope the situation improves. Luckily I still had a TP-Link Archer C7 AC1750 in a drawer, which I could quickly flash with a fresh OpenWRT release, disable DHCPd and configure the same SSID and keys as the main/old WiFi. But I didn't know which channels would be best in the destination environment. Under normal circumstances, I'd just take the AP, drive to my parents in law and finish the configuration there. Nope, not gonna happen these days. So my plan was to finish configuration here, put the AP in a box and on the porch where someone can pick it up. But this would leave me without a way to further configure the device once it has been deployed - I was not particularly interested in trying to get port forwarding configured via phone and I was pretty sure UPnP was disabled in the ISP router. Installing a Tor hidden service for SSH was one possibility, setting up a VPN and making the AP a client another. Well, or just creating a reverse tunnel with SSH! sshtunnel Creating a tunnel with OpenSSH is easy: ssh -R127.0.0.1:2222:127.0.0.1:22 server.example.com will forward localhost:2222 on server.example.com to port 22 of the machine the SSH connection originated from. But what happens if the connection dies? Adding a while true; do ; done around it might help, but I would really like not to reinvent the wheel here! Thankfully, somebody already invented that particular wheel and OpenWRT comes with a sshtunnel package that takes care of setting up and keeping up such tunnels and documentation how to do so. Just install the sshtunnel package, edit /etc/config/sshtunnel to contain a server stanza with hostname, port and username and a tunnelR stanza referring said server plus the local and remote sides of the tunnel and you're good to go. 
config server home
  option user     user
  option hostname server.example.com
  option port     22
config tunnelR local_ssh
  option server         home
  option remoteaddress  127.0.0.1
  option remoteport     2222
  option localaddress   127.0.0.1
  option localport      22
The only caveat is that sshtunnel needs the OpenSSH client binary (and the package correctly depends on it) and OpenWRT does not ship the ssh-keygen tool from OpenSSH but only the equivalent for Dropbear. As OpenSSH can't read Dropbear keys (and vice versa) you'll have to generate the key somewhere else and deploy it to the OpenWRT box and the target system. Oh, and OpenWRT defaults to enabling password login via SSH, so please disable that if you expose the box to the Internet in any way! Using the tunnel After configuring and starting the service, you'll see the OpenWRT system logging in to the configured remote and opening the tunnel. For some reason that connection would not show up in the output of w -- probably because there was no shell started or something, but logs show it clearly. Now it's just a matter of connecting to the newly open port and you're in. As the port is bound to 127.0.0.1, the connection is only possible from server.example.com or using it as a jump host via OpenSSH's ProxyJump option: ssh -J server.example.com -p 2222 root@localhost. Additionally, you can forward a local port over the tunneled connection to create a tunnel for the OpenWRT webinterface: ssh -J server.example.com -p 2222 -L8080:localhost:80 root@localhost. Yes, that's a tunnel inside a tunnel, and all the network engineers will go brrr, but it works and you can access LuCi on http://localhost:8080 just fine. If you don't want to type that every time, create an entry in your .ssh/config: 
Host openwrt
  ProxyJump server.example.com
  HostName localhost
  Port 2222
  User root
  LocalForward 8080 localhost:80
And we're done. Enjoy easy access to the newly deployed box and carry on.

Fran ois Marier: Backing up to a GnuBee PC 2

After installing Debian buster on my GnuBee, I set it up for receiving backups from my other computers.

Software setup I started by configuring it like a typical server but without a few packages that either take a lot of memory or CPU: I changed the default hostname:
  • /etc/hostname: foobar
  • /etc/mailname: foobar.example.com
  • /etc/hosts: 127.0.0.1 foobar.example.com vogar localhost
and then installed the avahi-daemon package to be able to reach this box using foobar.local. I noticed the presence of a world-writable directory and so I tightened the security of some of the default mount points by putting the following in /etc/rc.local: 
mount -o remount,nodev,nosuid /etc/network
mount -o remount,nodev,nosuid /lib/modules
chmod 755 /etc/network
exit 0

Hardware setup My OS drive (/dev/sda) is a small SSD so that the GnuBee can run silently when the spinning disks aren't needed. To hold the backup data on the other hand, I got three 4-TB drives drives which I setup in a RAID-5 array. If the data were valuable, I'd use RAID-6 instead since it can survive two drives failing at the same time, but in this case since it's only holding backups, I'd have to lose the original machine at the same time as two of the 3 drives, a very unlikely scenario. I created new gpt partition tables on /dev/sdb, /dev/sdbc, /dev/sdd and used fdisk to create a single partition of type 29 (Linux RAID) on each of them. Then I created the RAID array: 
mdadm /dev/md127 --create -n 3 --level=raid5 -a /dev/sdb1 /dev/sdc1 /dev/sdd1
and waited more than 24 hours for that operation to finish. Next, I formatted the array: 
mkfs.ext4 -m 0 /dev/md127
and added the following to /etc/fstab: 
/dev/md127 /mnt/data/ ext4 noatime,nodiratime 0 2
To reduce unnecessary noise and reduce power consumption, I also installed hdparm: 
apt install hdparm
and configured all spinning drives to spin down after being idle for 10 minutes by putting the following in /etc/hdparm.conf: 
/dev/sdb  
       spindown_time = 120
 
/dev/sdc  
       spindown_time = 120
 
/dev/sdd  
       spindown_time = 120
and then reloaded the configuration: 
 /usr/lib/pm-utils/power.d/95hdparm-apm resume
Finally I setup smartmontools by putting the following in /etc/smartd.conf: 
/dev/sda -a -o on -S on -s (S/../.././02 L/../../6/03)
/dev/sdb -a -o on -S on -s (S/../.././02 L/../../6/03)
/dev/sdc -a -o on -S on -s (S/../.././02 L/../../6/03)
/dev/sdd -a -o on -S on -s (S/../.././02 L/../../6/03)
and restarting the daemon: 
systemctl restart smartd.service

Backup setup I started by using duplicity since I have been using that tool for many years, but a 190GB backup took around 15 hours on the GnuBee with gigabit ethernet. After a friend suggested it, I took a look at restic and I have to say that I am impressed. The same backup finished in about half the time.

User and ssh setup After hardening the ssh setup as I usually do, I created a user account for each machine needing to backup onto the GnuBee: 
adduser machine1
adduser machine1 sshuser
adduser machine1 sftponly
chsh machine1 -s /bin/false
and then matching directories under /mnt/data/home/: 
mkdir /mnt/data/home/machine1
chown machine1:machine1 /mnt/data/home/machine1
chmod 700 /mnt/data/home/machine1
Then I created a custom ssh key for each machine: 
ssh-keygen -f /root/.ssh/foobar_backups -t ed25519
and placed it in /home/machine1/.ssh/authorized_keys on the GnuBee. On each machine, I added the following to /root/.ssh/config: 
Host foobar.local
    User machine1
    Compression no
    Ciphers aes128-ctr
    IdentityFile /root/backup/foobar_backups
    IdentitiesOnly yes
    ServerAliveInterval 60
    ServerAliveCountMax 240
The reason for setting the ssh cipher and disabling compression is to speed up the ssh connection as much as possible given that the GnuBee has avery small RAM bandwidth. Another performance-related change I made on the GnuBee was switching to the internal sftp server by putting the following in /etc/ssh/sshd_config: 
Subsystem      sftp    internal-sftp

Restic script After reading through the excellent restic documentation, I wrote the following backup script, based on my old duplicity script, to reuse on all of my computers: 
# Configure for each host
PASSWORD="XXXX"  # use  pwgen -s 64  to generate a good random password
BACKUP_HOME="/root/backup"
REMOTE_URL="sftp:foobar.local:"
RETENTION_POLICY="--keep-daily 7 --keep-weekly 4 --keep-monthly 12 --keep-yearly 2"
# Internal variables
SSH_IDENTITY="IdentityFile=$BACKUP_HOME/foobar_backups"
EXCLUDE_FILE="$BACKUP_HOME/exclude"
PKG_FILE="$BACKUP_HOME/dpkg-selections"
PARTITION_FILE="$BACKUP_HOME/partitions"
# If the list of files has been requested, only do that
if [ "$1" = "--list-current-files" ]; then
    RESTIC_PASSWORD=$PASSWORD restic --quiet -r $REMOTE_URL ls latest
    exit 0
# Show list of available snapshots
elif [ "$1" = "--list-snapshots" ]; then
    RESTIC_PASSWORD=$GPG_PASSWORD restic --quiet -r $REMOTE_URL snapshots
    exit 0
# Restore the given file
elif [ "$1" = "--file-to-restore" ]; then
    if [ "$2" = "" ]; then
        echo "You must specify a file to restore"
        exit 2
    fi
    RESTORE_DIR="$(mktemp -d ./restored_XXXXXXXX)"
    RESTIC_PASSWORD=$PASSWORD restic --quiet -r $REMOTE_URL restore latest --target "$RESTORE_DIR" --include "$2"   exit 1
    echo "$2 was restored to $RESTORE_DIR"
    exit 0
# Delete old backups
elif [ "$1" = "--prune" ]; then
    # Expire old backups
    RESTIC_PASSWORD=$PASSWORD restic --quiet -r $REMOTE_URL forget $RETENTION_POLICY
    # Delete files which are no longer necessary (slow)
    RESTIC_PASSWORD=$PASSWORD restic --quiet -r $REMOTE_URL prune
    exit 0
# Catch invalid arguments
elif [ "$1" != "" ]; then
    echo "Invalid argument: $1"
    exit 1
fi
# Check the integrity of existing backups
RESTIC_PASSWORD=$PASSWORD restic --quiet -r $REMOTE_URL check   exit 1
# Dump list of Debian packages
dpkg --get-selections > $PKG_FILE
# Dump partition tables from harddrives
/sbin/fdisk -l /dev/sda > $PARTITION_FILE
/sbin/fdisk -l /dev/sdb > $PARTITION_FILE
# Do the actual backup
RESTIC_PASSWORD=$PASSWORD restic --quiet --cleanup-cache -r $REMOTE_URL backup / --exclude-file $EXCLUDE_FILE
I run it with the following cronjob in /etc/cron.d/backups: 
30 8 * * *    root  ionice nice nocache /root/backup/backup-machine1-to-foobar
30 2 * * Sun  root  ionice nice nocache /root/backup/backup-machine1-to-foobar --prune
in a way that doesn't impact the rest of the system too much. Finally, I printed a copy of each of my backup script, using enscript, to stash in a safe place: 
enscript --highlight=bash --style=emacs --output=- backup-machine1-to-foobar   ps2pdf - > foobar.pdf
This is actually a pretty important step since without the password, you won't be able to decrypt and restore what's on the GnuBee.

2 May 2020

Jonathan Carter: Free Software Activities for 2020-04

Debian project leader This month contained the first week and a half or so of my term as Debian Project Leader. So far my focus has been getting up to speed and keeping the gears turning with day to day DPL tasks. The updates listed here will also be available on the DPL blog, where I aim to make more frequent updates. During May, Debian Brazil will host Debian talks throughout the month which they will stream to their YouTube channel. You can find the schedule in this git repository, most of the talks will be in Portuguese, but on the 4th of May at 21:00 UTC, I ll be covering some Debian project topics for an hour or so and take some questions if there s time left. 2020-04-19: Handover session with Sam, our outgoing DPL. We covered a lot of questions I had and main areas that the DPL works in. Thanks to Sam for having taken the time to do this. 2020-04-21: First day of term! Thank you to everybody who showed support and have offered to help! 2020-04-21: Request feedback from the trademark team on an ongoing trademark dispute. 2020-04-21: Join the GNOME Advisory Board as a representative from Debian. 2020-04-21: Reply on an ongoing community conflict issue. 2020-04-21: Update Debian project summary for SPI annual report. 2020-04-21: Received a great e-mail introduction from Debian France and followed up on that. 2020-04-21: Posted Bits from the new DPL to debian-devel-announce. 2020-04-22: Became Debian s OSI Affilliate representative. 2020-04-22: Reply to a bunch of media inquiries for interviews, will do them later when initial priorities are on track. 2020-04-23: Resign as Debian FTP team trainee and mailing list moderator. In both these areas there are enough people taking care of it and I intend to maximise available time for DPL and technical areas in the project. 2020-04-25: Review outgoing mail for trademark team. 2020-04-25: Answer some questions in preparation for DAM/Front Desk delegation updates. 2020-04-26: Initiated wiki documentation for delegation updates process. 2020-04-27: Update delegation for the Debian Front Desk team. 2020-04-29: Schedule video call with Debian treasurer team. 2020-04-29: OSI affiliate call. Learned about some Open Source projects including OpenDev, OpenSourceMatters, FOSS Responders and Democracy Labs.

Debian Social Work on the Debian Social project is progressing, we plan to start a separate blog syndicated to Planet Debian that contains progress and status updates. I ve been terrible at tracking the work we ve been doing on this, so for now, here are some micro updates:

MiniDebConf Online In the DebConf video team, we ve been wondering whether we have all the tools required to successfully host a DebConf (or even a mini DebConf) entirely online. There s really just one way to know for sure, so we re going to host MiniDebConf Online from 28 May to 31 May. The first two days will be an online MiniDebCamp, where we can try to hold online spints, meetings and general chit-chat. The last two days will be for talks and lightnight talks, with BoFs likely to take place throughout the 4 days (this will probably be decided once we have a content team). Announcements should go out within the next week, in the meantime, save the dates.

Debian package uploads 2020-04-07: Upload package flask-autoindex (0.6.6-1) to Debian unstable. 2020-04-07: Upload package gamemode (1.5.1-1) to Debian unstable. 2020-04-08: Accept MR#2 for live-tasks (add usbutils to live-task-standard). 2020-04-08: Upload package live-tasks (11.0.2) to Debian unstable (Closes: #955526, #944578, #942837, #942834). 2020-04-08: Close live-config bug #655198 (Only affects squeeze which is no longer supported). 2020-04-08: Upload package live-config (11.0.1) to Debian unstable. 2020-04-08: Upload package calamares (3.2.22-1) to Debian unstable. 2020-04-15: Upload package xabacus (8.2.6-1) to Debian unstable. 2020-04-16: Merge MR#1 for gnome-shell-extension-dashtodock (new upstream release). 2020-04-16: Upload package gnome-shell-extension-dashtodock (67+git20200225-1) to Debian unstable. 2020-04-16: Merge MR#1 for gnome-shell-extension-hard-disk-led (fix some lintian issues). 2020-04-16: Merge MR#1 for gnome-shell-extension-system-monitor (fix some lintian issues). 2020-04-17: Upload package calamares (3.2.23-1) to Debian unstable. 2020-04-17: Upload package catimg (2.6.0-1) to Debian unstable (Closes: #956150). 2020-04-17: Upload package fabulous (0.3.0+dfsg1-7) to Debian unstable (Closes: #952242). 2020-04-17: Upload package gnome-shell-extension-system-monitor (38+git20200414-32cc79e-1) to Debian unstable (Closes: #956656, #956171). 2020-04-17: Upload package gnome-shell-extension-arc-menu (45-1) to Debian unstable (Closes: #956168). 2020-04-18: Upload package toot (0.26.0-1) to Debian unstable. 2020-04-23: Update packaging for gnome-shell-extension-tilix-shortcut, upstream section needs some additional work before release is possible. 2020-04-23: Upload package xabacus (8.2.7-1) to Debian unstable. 2020-04-27: Upload package gnome-shell-extension-dash-to-panel (37-1) to Debian unstable (Closes: #956162, #954978). 2020-04-27: Upload package gnome-shell-extension-dash-to-panel (37-2) to Debian unstable. 2020-04-27: Upload package gnome-shell-extension-dashtodock (68-1) to Debian unstable. 2020-04-30: Merge MR#8 for gamemode (add symbol files) (Closes: #952425). 2020-04-30: Merge MR#9 for gamemode (reduce number of -dev packages generated). 2020-04-30: Merge MR#10 for gamemode (deal better with upgrades on a buggy version). 2020-04-30: Manually merge changes from MR#11 for gamemode (packaging fixes). 2020-04-30: Upload package gamemode (1.5.1-2) to Debian unstable.

Sylvain Beucler: Debian LTS and ELTS - April 2020

Debian LTS Logo Here is my transparent report for my work on the Debian Long Term Support (LTS) and Debian Extended Long Term Support (ELTS), which extend the security support for past Debian releases, as a paid contributor. In April, the monthly sponsored hours were split evenly among contributors depending on their max availability - I was assigned 28.75h for LTS (out of 30 max; all done) and 7.75h for ELTS (out of 20 max; I did 2.75). Escalation procedures were (internally) documented with a focus on discussing issues with team coordinator(s) first. Debian LTS had its first team meeting through IRC and lots of workflow question were discussed. This should help discuss questions that are a bit hard to bring up, and ensure everybody participates. There were lots of topics and it was a bit rushed, but this is something we want to repeat monthly now, possibly with audio/video in a couple months. Remarks from last month's report were discussed, strengthening the Front-Desk role. 10% of the global funding is now reserved for infrastructure work. What kind of work, and who (LTS or external) will do the work, will be discussed further. A fellow DD suggested (in a private conversation) that LTS may be taking time from the Debian Security team, due to additional commits to review. Conversely, this is another opportunity to mention all the global, non-LTS-specific work that LTS provides, which I usually highlight in my reports, and maybe I should be even more ;) ELTS - Wheezy LTS - Jessie Documentation/Scripts

1 May 2020

Paul Wise: FLOSS Activities April 2020

Changes

Issues

Review

Administration
  • myrepos: fix the forum
  • Debian: restart non-responsive tor daemon, restart processes due to OOM, apply debian.net changes for DD with expired key
  • Debian wiki: approve accounts
  • Debian QA services: deploy changes, auto-disable oldoldstable pockets

Communication

Sponsors The purple-discord work was sponsored by my employer. All other work was done on a volunteer basis.

Utkarsh Gupta: FOSS Activites in April 2020

Here s my (seventh) monthly update about the activities I ve done in the F/L/OSS world.

Debian
It s been 14 months since I ve started contributing to Debian. And 4 months since I ve been a Debian Developer. And in this beautiful time, I had this opprotunity to do and learn lots of new and interesting things. And most importantly, meet and interact with lots of lovely people!
Debian is $home.

Uploads:

Other $things:
  • Attended Ruby team meeting. Logs here.
  • Attended Perl team LHF. Report here.
  • Sponsored a lot of uploads for William Desportes and Adam Cecile.
  • Mentoring for newcomers.
  • FTP Trainee reviewing.
  • Moderation of -project mailing list.
  • Applied for DUCI project for Google Summer of Code 2020.

Ruby2.7 Migration:
Ruby2.7 was recently released on 25th December, 2019. Santa s gift. Believe it or not. We, the Debian Ruby team, have been trying hard to make it migrate to testing. And it finally happened. The default version in testing is ruby2.7. Here s the news! \o/
Here s what I worked on this month for this transition.

Upstream: Opened several issues and proposed patches (in the form of PRs):
  • Issue #35 against encryptor for Ruby2.7 test failures.
  • Issue #28 against image_science for removing relative paths.
  • Issue #106 against ffi-yajl for Ruby2.7 test failures.
  • PR #5 against aggregate for simply using require.
  • PR #6 against aggregate for modernizing CI and adding Ruby 2.5 and 2.7 support.
  • Issue #13 against espeak-ruby for Ruby2.7 test failures.
  • Issue #4 against tty-which for test failures in general.
  • Issue #11 against packable for Ruby2.7 test failures. PR #12 has been proposed.
  • Issue #10 against growl for test failures and proposed an initial patch.

Downstream: I fixed and uploaded the following packages in Debian:

Debian LTS
Debian Long Term Support (LTS) is a project to extend the lifetime of all Debian stable releases to (at least) 5 years. Debian LTS is not handled by the Debian security team, but by a separate group of volunteers and companies interested in making it a success.
This was my seventh month as a Debian LTS paid contributor. I was assigned 24.00 hours and worked on the following things:

CVE Fixes and Announcements:

Other LTS Work:

Other(s)
Sometimes it gets hard to categorize work/things into a particular category.
That s why I am writing all of those things inside this category.
This includes two sub-categories and they are as follows.

Personal: This month I could get the following things done:
  • Most importantly, I finally migrated to a new website. Huge UI imporvement! \o/
    From Jekyll to Hugo, it was not easy. But it was worth it! Many thanks to Luiz for writing hugo-coder, Clement, and Samyak!
    If you find any flaws, issues and pull requests are welcomed at utkarsh2102/utkarsh2102.com
  • Wrote battery-alert, a mini-project of my own to show battery alerts at <10% and >90%.
    Written in shell, it brings me all the satisfaction as it has saved my life on many occasions.
    And guess what? It has more users than just myself!
    Reviews and patches are welcomed \o/
  • Mentored in HackOn Hackathon. Thanks to Manvi for reaching out!
    It was fun to see people developing some really nice projects.
  • Thanks to Ray and John, I became a GitLab Hero!
    (I am yet to figure out my role and responibility though)
  • Atteneded Intro Sec Con and had the most fun!
    Heard Ian s keynote and attended other talks and learned how to use WireShark!

Open Source: Again, this contains all the things that I couldn t categorize earlier.
Opened several issues and pull requests:
  • Issue #297 against hugo-coder, asking to enable RSS feed for blogs.
  • PR #316 for hugo-coder for fixing the above issue myself.
  • Issue #173 against arbre for requesting a release.
  • Issue #104 against combustion, asking to relax dependency on rubocop. Fixed in this commit.
  • Issue #16 against ffi-compiler for requesting to fix homepage and license.
  • Issue #57 against gographviz for requesting a release.
  • Issue #14 against crb-blast, suggesting compatability with bio 2.0.x.
  • Issue #58 against uniform_notifier for asking to drop the use of ruby-growl.
  • PR #2072 for polybar, adding installation instructions on Debian systems.
Until next time.
:wq for today.

30 April 2020

Chris Lamb: Free software activities in April 2020

Here is my monthly update covering what I have been doing in the free software world during April 2020 (previous month's report). Looking it over prior to publishing, I am surprised how much I got done this month I felt that I was not only failing to do all the extra things I had planned, but I was doing far less than normal. But let us go easy on ourselves; nobody is nailing this. In addition, I did more hacking on the Lintian static analysis tool for Debian packages:
Reproducible builds One of the original promises of open source software is that distributed peer review and transparency of process results in enhanced end-user security. However, whilst anyone may inspect the source code of free and open source software for malicious flaws, almost all software today is distributed as pre-compiled binaries. This allows nefarious third-parties to compromise systems by injecting malicious code into ostensibly secure software during the various compilation and distribution processes. The motivation behind the Reproducible Builds effort is to ensure no flaws have been introduced during this compilation process by promising identical results are always generated from a given source, thus allowing multiple third-parties to come to a consensus on whether a build was compromised. The initiative is proud to be a member project of the Software Freedom Conservancy, a not-for-profit 501(c)(3) charity focused on ethical technology and user freedom. Conservancy acts as a corporate umbrella allowing projects to operate as non-profit initiatives without managing their own corporate structure. If you like the work of the Conservancy or the Reproducible Builds project, please consider becoming an official supporter. Elsewhere in our tooling, I made the following changes to diffoscope, our in-depth and content-aware diff utility that can locate and diagnose reproducibility issues, including preparing and uploading versions 139, 140, 141 and 142 to Debian: Lastly, I made a large number of changes to our website and documentation in the following categories:
Debian LTS This month I have contributed 18 hours to Debian Long Term Support (LTS) and 7 hours on its sister Extended LTS project. You can find out more about the project via the following video:
Debian I only filed three bugs in April, including one against snapshot.debian.org to report that a Content-Type HTTP header is missing when downloading .deb files (#956471) and to report build failures in the macs & ruby-enumerable-statistics packages:

Jonathan McDowell: Let's talk about work/life balance in lock down

A SYNCNI article passed by on my Twitter feed this morning, talking about balancing work life balance while working from home in these times of COVID-19 inspired lock down. The associated Twitter thread expressed an interest in some words of advice from men to other men (because of course the original article has the woman having to do all the balancing). This post does not contain the words of advice searched for, but it hopefully at least offers some reassurance that if you re finding all of this difficult you re not alone. From talking to others I don t think there s anything particularly special we re doing in this house; a colleague is taking roughly the same approach, and some of the other folk I ve spoken to in the local tech scene seem to be doing likewise. First, the situation. Like many households both my wife and I work full time. We have a small child (not even a year and a half old yet). I work for a software startup, my wife is an HR business partner for a large multinational, dealing with employees all over the UK and Ireland. We re both luckily able to work from home easily - our day to day work machines are laptops, our employers were already setup with the appropriate VPN / video conferencing etc facilities. Neither of us has seen any decrease in workload since lock down; there are always more features and/or bugs to work on when it comes to a software product, and, as I m sure you can imagine, there has been a lot more activity in the HR sphere over the past 6 weeks as companies try to work out what to do. On top of this our childcare arrangements, like everyone else s, are completely gone. Nursery understandably shut down around the same time as the schools (slightly later, but not by much) and contact with grandparents is obviously out (which they re finding hard). So we re left with trying to fit 2 full time jobs in with full time childcare, of a child who up until recently tried to go down stairs by continuing to crawl forward. Make no mistake, this is hard. I know we are exceptionally lucky in our situation, but that doesn t mean we re finding it easy. We ve adopted an approach of splitting the day up. I take the morning slot (previously I would have got up with our son anyway), getting him up and fed while my wife showers. She takes over for a bit while I shower and dress, then I take over again in time for her to take her daily 8am conference call. My morning is mostly taken up with childcare until nap time; I try to check in first thing to make sure there s nothing urgent, and get a handle on what I might have to work on later in the day. My local team mates know they re more likely to get me late morning and it s better to arrange meetings in the afternoon. Equally I work with a lot of folk on the US West coast, so shifting my hours to be a bit later is not a problem there. After nap time (which, if we re lucky, takes us to lunch) my wife takes over. As she deals with UK/Ireland folk she often ends up having to take calls even while looking after our son; generally important meetings can be moved to the morning and meetings with folk who understand there might be a lot of pot banging going on in the background can happen in the afternoon. Having started late I generally work late - past the point where I d normally get home; if I m lucky I pop my head in for bath time, but sometimes it s only for a couple of minutes. We alternate cooking; usually based on work load + meetings. For example tonight I m cooking while my wife catches up on some work after having put our son to bed. Last night I had a few meetings so my wife cooked. So what s worked for us? Splitting the day means we can plan with our co-workers. We always make sure we eat together in the evening, and that generally is the cut-off point for either of us doing any work. I m less likely to be online in the evening because my study has become the place I work. That means I m not really doing any of my personal projects - this definitely isn t a case of being at home during lock down and having lots of time to achieve new things. It s much more of case of trying to find a sustainable way to get through the current situation, however long it might last.

Mike Gabriel: My Work on Debian LTS (April 2020)

Due to sickness I was not able to complete my 8 hours of work on Debian LTS as planned. I only worked 1.5 hours this month, moving the remaining 6.5 hours over to May. LTS Other security related work for Debian

29 April 2020

Ian Jackson: subdirmk 1.0 - ergonomic preprocessing assistant for non-recursive make

I have made the 1.0 release of subdirmk. subdirmk is a tool to help with writing build systems in make, without use of recursive make. Why Peter Miller's 1997 essay Recursive Make Considered Harmful persuasively argues that it is better to arrange to have a single make invocation with the project's complete dependency tree, rather than the conventional $(MAKE) -C subdirectory approach. This has become much more relevant with modern projects which tend to be large and have deep directory trees. Invoking make separately for each of these subdirectories can be very slow. Nowadays everyone needs to run a parallel build, but with the recursive make approach great discipline is needed to avoid introducing races which cause the build to sometimes fail. There are various new systems which aim to replace make. My general impression of these is that they mostly threw away the good parts of make (often, they discard the flexibility, and the use of the shell command as the basic unit of execution, making them hard to extend), or make other unfortunate assumptions. And there are a lot of programming-language-specific systems - a very unsatisfactory development. Having said all that, I admit I haven't properly evaluated every make competitor. Other reasons for staying with make including that it is widely available, relatively widely understood, and has a model relatively free of high-level abstract concepts. (I like my languages with high-level concepts, but not my build systems.) But, with make, I found that actually writing a project's build system in non-recursive make was not very ergonomic. So with some help and prompting from Mark Wooding, I have made a tool to help. What subdirmk is a makefile preprocessor and aggregator, typically run from autoconf. subdirmk provides convenience syntaxes for references to per-directory variables and pathnames. It also helps by providing a little syntactic sugar for GNU make's macro facilities, which are awkward to use in raw make. subdirmk's features are triggered by the sigil &. The syntax is carefully designed to avoid getting in the way of makefile programming (and programming of shell commands in make rules). subdirmk is fully documented in the README. There is a demo in the example directory (which also serves as part of the test suite). What's new The version number. I have not felt the need to make any changes since releasing 0.4 in mid-February. The last non-docs change was a (backwards-compatible) extension, in late January, to pass through unaltered GNU make's new grouped multiple targets syntax. Advantages and disadvantages of subdirmk Compared to recursive make, subdirmk is easier and simpler, although you do have to decorate a lot of your variables and filenames with & to indicate that they are directory-local. It is much easier to avoid writing parallel make bugs. You naturally get properly working per-subdirectory targets. subdirmk-based nonrecursive make is much, much faster than recursive make. Compared to many other recent build system tools, subdirmk retains all the flexibility and extensibility of make, and operates at a fairly low level of abstraction. subdirmk-based makefiles can easily invoke other build systems. make knows it's not the only thing in the universe. You can adopt subdirmk incrementally or partially, gradually bringing your recursive submakefiles into the unified build. The build system code in subdirmk's Dir.sd.mk files will be readily navigable by most readers; much will be familiar. Because subdirmk is a small collection of (fairly simple) scripting and makefile code, there is no need to build it; you can simply ship it with your project using git-subtree. For an autoconf-based project, there need be no change to how your users and downstreams invoke your build. On the other hand the price you (continue to) pay is make's punctation soup, which subdirmk adds a new sigil to. subdirmk-based makefiles are terse and help you use make's facilities to abstract away repetition, but that can make them dense. The new & sigil will faze some readers. Currently, the provided mechanism for incorporating subdirmk into your project assumes you are using autoconf but not automake. It would be possible to use subdirmk with autoconf-less projects, or with automake-based ones, but I haven't done the glue work to make that easy. subdirmk does require GNU make and it assumes you have perl installed. But GNU make is very portable, and perl is very widely available. (The perl used is very conservative.) The make competitors are, themselves, even less standard build tools. I don't think a build-dependency on GNU make, or perl, is a significant barrier nowadays, for most projects. Note about comment moderation I have deliberately been vague about other build systems and avoided specific criticisms or references. I don't want the comments to become a build system advocacy debate. Comments may be screened and moderated accordingly. Pointers to other obscure build system tools are very welcome. If you want to write a survey of build tools, or a critique of subdirmk, please do so on your own blog; I would be happy to consider linking to it.

comment count unavailable comments

Craig Small: Sending data in a signal

The well-known kill system call has been around for decades and is used to send a signal to another process. The most common use is to terminate or kill another process by sending the KILL or TERM signal but it can be used for a form of IPC, usually around giving the other process a kick to do something. One thing that isn t as well known is besides sending a signal to a process, you can send some data to it. This can either be an integer or a pointer and uses similar semantics to the known kill and signal handler. I came across this when there was a merge request for procps. The main changes are using sigqueue instead of kill in the sender and using a signal action not a signal handler in the receiver. To illustrate this feature, I have a small set of programs called sender and receiver that will pass an integer between them. The Sender The sender program is extremely simple, use a random(ish) from time masked to two bytes, put it in the required union and send the lot to sendqueue. 
# include <signal.h>
# include <stdlib.h>
# include <stdio.h>
# include <time.h>
int main(int argc, char **argv)
 
    union sigval sigval;
    pid_t pid;
    if (argc < 2   (pid = atoi(argv[1])) < 0)
	return EXIT_FAILURE;
    sigval.sival_int = time(NULL) &amp; 0xff;
    printf("sender: sending %d to PID %d\n",
        sigval.sival_int, pid);
    sigqueue(pid, SIGUSR1, sigval);
    return EXIT_SUCCESS;
The key lines are 13 and 16 where the random (ish) integer is stored in the sigval union and then sent to the other process with the sigqueue. The receiver The receiver just sets up the signal handler, sends its PID (so I know what to tell the sender) and sits in a sleeping loop. 
# include <stdio.h>
# include <stdlib.h>
# include <sys/types.h>
# include <unistd.h>
# include <signal.h>
void signal_handler(int signum, siginfo_t *siginfo, void *ucontext)
 
    if (signum != SIGUSR1) return;
    if (siginfo->si_code != SI_QUEUE) return;
    printf("receiver: Got value %d\n",
	    siginfo->si_int);
 
int main(int argc, char **argv)
 
    pid_t pid = getpid();
    struct sigaction signal_action;
    printf("receiver: PID is %d\n", pid);
    signal_action.sa_sigaction = signal_handler;
    sigemptyset (&amp;signal_action.sa_mask);
    signal_action.sa_flags = SA_SIGINFO;
    sigaction(SIGUSR1, &amp;signal_action, NULL);
    while(1) sleep(100);
    return EXIT_SUCCESS;
Lines 16-26 setup the signal handler. The main difference here is SA_SIGINFO used for the signal flags and sigaction references a sa_sigaction function rather than sa_handler. We need to use a different function because the sigaction only is passed the signal number but we need more information, including the integer that the sender process stored in sigval. Lines 7-14 are the signal handler function itself. It first checks that the receiver process got the correct signal (SIGUSR1 in this case) and that we got this signal from sigqueue because the type is SI_QUEUE. Checking the type of signal is important because different signals give you different data. For example, if you signalled this process with kill then si_int is undefined. The result As a proof of concept, the results are not terribly exciting. We see the sender say what it will be sending and the receiver saying it got it. It was useful to get some results, especially when things went wrong. 
$ ./receiver &amp;
[1] 370216
receiver: PID is 370216
$ ./sender 370216
sender: sending 133 to (gdPID 370216
receiver: Got value 133
Gotchas While testing the two process there was two gotchas I encountered. GDB and the siginfo structure The sigaction manual page shows a simple siginfo_t structure, however when looking at what is passed to the signal handler, it s much more complicated. 
(gdb) p *siginfo
$2 =  si_signo = 10, si_errno = 0, si_code = -1, __pad0 = 0, _sifields =  _pad =  371539, 1000, 11, 32766, 0 <repeats 24 times> , _kill =  si_pid = 371539, si_uid = 1000 , _timer =  si_tid = 371539, 
      si_overrun = 1000, si_sigval =  sival_int = 11, sival_ptr = 0x7ffe0000000b , _rt =  si_pid = 371539, si_uid = 1000, si_sigval =  sival_int = 11, sival_ptr = 0x7ffe0000000b , _sigchld =  
      si_pid = 371539, si_uid = 1000, si_status = 11, si_utime = 0, si_stime = 0 , _sigfault =  si_addr = 0x3e80005ab53, si_addr_lsb = 11, _bounds =  _addr_bnd =  _lower = 0x0, _upper = 0x0 , _pkey = 0 , 
    _sigpoll =  si_band = 4294967667539, si_fd = 11 , _sigsys =  _call_addr = 0x3e80005ab53, _syscall = 11, _arch = 32766 
(gdb) p siginfo->_sifields._rt.si_sigval.sival_int
$3 = 11
So the integer is stored in a union in a structure in a structure. Much harder to find than just simply sival_int. The pointer is just a pointer So perhaps sending an integer is not enough. The sigval is a union with an integer and a pointer. Could a string be sent instead? I changed line 13 of the sender so it used a string instead of an integer. 
    sigval.sival_ptr = "Hello, World!"
The receiver needed a minor adjustment to print out the string. I tried this and the receiver segmentation faulted. What was going on? The issue is the set of system calls does a simple passing of the values. So if the sender sends a pointer to a string located at 0x1234567 then the receiver will have a pointer to the same location. When the receiver tries to dereference the sival_ptr, it is pointing to memory that is not owned by it but by another process (the sender) so it segmentation faults. The solution would be to use shared memory between the processes. The signal queue would then use the pointer to the shared memory and, in theory, all would be well.

Petter Reinholdtsen: GnuCOBOL, a free platform to learn and use COBOL - nice free software

The curiosity got the better of me when Slashdot reported that New Jersey was desperately looking for COBOL programmers, and a few days later it was reported that IBM tried to locate COBOL programmers. I thus decided to have a look at free software alternatives to learn COBOL, and had the pleasure to find GnuCOBOL was already in Debian. It used to be called Open Cobol, and is a "compiler" transforming COBOL code to C or C++ before giving it to GCC or Visual Studio to build binaries. I managed to get in touch with upstream, and was impressed with the quick response, and also was happy to see a new Debian maintainer taking over when the original one recently asked to be replaced. A new Debian upload was done as recently as yesterday. Using the Debian package, I was able to follow a simple COBOL introduction and make and run simple COBOL programs. It was fun to learn a new programming language. If you want to test for yourself, the GnuCOBOL Wikipedia page have a few simple examples to get you startet. As I do not have much experience with COBOL, I do not know how standard compliant it is, but it claim to pass most tests from COBOL test suite, which sound good to me. It is nice to know it is possible to learn COBOL using software without any usage restrictions, and I am very happy such nice free software project as this is available. If you as me is curious about COBOL, check it out. As usual, if you use Bitcoin and want to show your support of my activities, please send Bitcoin donations to my address 15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

28 April 2020

Steve Kemp: I'm a contractor, available for work

For the foreseeable future I'm working for myself, as a contractor, here in sunny Helsinki, Finland. My existing contract only requires me to work 1.5-2.0 days a week, meaning my week looks something like this: It does mean that I'm available for work Wednesday-Friday though, in the event I can find projects to work upon, or companies who would be willing to accept my invoices. I think of myself as a sysadmin, but I know all about pipelines, automation, system administration, and coding in C, C++, Perl, Ruby, Golang, Lua, etc. On the off-chance anybody reading this has a need for small projects, services, daemons, or APIs to be implemented then don't hesitate to get in touch. I did manage to fill a few days over the past few weeks completing an online course from Helsinki Open University, Devops with Docker, it is possible I'll find some more courses to complete in the future. (There is an upcoming course Devops with Kubernetes which I'll definitely complete.)

Next.

Previous.