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For a project, we're using Django to generate a textual report. For readability, it is in monospace text. And we've done it in reStructuredText (RST) so we can generate an HTML document from it as well. A table in RST might look like this: +-----------+-------+ | car brand | users | +===========+=======+ | Peugeot | 2 | +-----------+-------+ | Saab | 1 | +-----------+-------+ | Volvo | 4 | +-----------+-------+ Transforming this to HTML with a rst2html(1) generates a table similar to this:

My Python code that interfaces with a serial port stopped working when refactoring the code to use asyncio. It started raising Invalid argument exceptions from tcsetattr(3). Why would asynchronous Python misbehave? Was there a bug in serial_asyncio? TL;DR: When interfacing with an openpty(3) pseudoterminal — which I used to emulate a real serial port — setting parity and bytesize is not supported. But an error would only show up when tcsetattr(3) was called twice, which happened only in the asyncio case.

2021 – het jaar waarin alles ingehaald wordt. Zo eindigde de recap van vorig jaar. Iets té optimistisch naar nu blijkt. De pandemie duurt voort en heeft zijn weerslag gehad op allerlei processen. Contact met onze klanten speelde nu noodgedwongen nog vaker digitaal af. Maar de OSSO-workflow kon grotendeels gehandhaafd blijven. Hier volgen wat downs en (gelukkig vooral) ups van het afgelopen jaar. Challenges 😢Onze gewaardeerde collega Edgar besloot werk aan te nemen dat dichter bij huis was.

On getting regular ZFS mount points to work with systemd dependency ordering. ZFS on Ubuntu is nice. And so is systemd. But getting them to play nice together sometimes requires a little extra effort. A problem we were facing was that services would get started before their respective mount points had all been made available. For example, for some setups, we have a local-storage ZFS zpool that holds the /var/lib/docker directory.

Today, when trying to import a newly created ZFS pool, we had to supply the -d DEV argument to find the pool. # zpool import no pools available to import But I know it's there. # zpool import local-storage cannot import 'local-storage': no such pool available And by specifying -d with a device search path, it can be found: # zpool import local-storage -d /dev/disk/by-id Success! # zpool list -oname NAME bpool local-storage rpool Manually specifying a search path is not real convenient.

On getting LetsEncrypt certificates to work on Debian/Jessie or Cumulus Linux 3 again. Since last Thursday the 30th, the old LetsEncrypt certificate root stopped working at 14:01 UTC. This was a known and anticipated issue. All certificates had long been double signed by a new root that doubled as intermediate. Unfortunately, this does not mean that everything worked on older platforms with OpenSSL 1.0.1 or 1.0.2. See this Debian/Jessie box — we see similar behaviour on Cumulux Linux 3.

The other day I learned — the hard way — that umount -l can be dangerous. Using the --make-slave mount option makes it safer. The scenario went like this: A virtual machine on our Proxmox VE cluster wouldn't boot. No biggie, I thought. Just mount the filesystem on the host and do a proper grub-install from a chroot: # fdisk -l /dev/zvol/zl-pve2-ssd1/vm-215-disk-3 /dev/zvol/zl-pve2-ssd1/vm-215-disk-3p1 * 2048 124999679 124997632 59.6G 83 Linux /dev/zvol/zl-pve2-ssd1/vm-215-disk-3p2 124999680 125827071 827392 404M 82 Linux swap / Solaris # mount /dev/zvol/zl-pve2-ssd1/vm-215-disk-3p1 /mnt/root # cd /mnt/root # for x in dev proc sys; do mount --rbind /$x $x; done # chroot /mnt/root There I could run the necessary commands to fix the boot procedure.

When running the iKVM software on the BMC of SuperMicro machines, we regularly see an interesting "singal" typo. (For the interested, we use a helper script to access the KVM console: ipmikvm. Without it, you need Java support enabled in your browser, and that has always given us trouble. The ipmikvm script logs on to the web interface, downloads the required Java bytecode and runs it locally.) Connect to somewhere, wait for the KVM console to open, close it, and you might see something like this:

When using mariabackup (xtrabackup/innobackupex) for your MySQL/MariaDB backups, you get a snapshot of the mysql lib dir. This is faster than doing an old-style mysqldump, but it is slightly more complicated to restore. Especially if you just want access to data from a single table. Assume you have a big database, and you're backing it up like this, using the mariadb-backup package: # ulimit -n 16384 # mariabackup \ --defaults-file=/etc/mysql/debian.cnf \ --backup \ --compress --compress-threads=2 \ --target-dir=/var/backups/mysql \ [--parallel=8] [--galera-info] .

If you're running an older Debian or Ubuntu, you may sometimes want to check out a newer version of a package, to see if a particular bug has been fixed. I know, this is not supported, but this scheme Generally Works (*): replace the current release name in /etc/apt/sources.list, with the next release — e.g. from bionic to focal do an apt-get update and an apt-get install SOME-PACKAGE You can test the package while replacing the sources.