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You sound very knowledgable on systemd, could ypu share some suggestions for learning resources? I would like to push a better use of it in my org, but besides

You sound very knowledgable on systemd, could ypu share some suggestions for learning resources? I would like to push a better use of it in my org, but besides some unit file messing about and using all the cool anaylysis tools, I don't know as much as I'd like.

ilyt 4y ago
Well, I've written a blogpost on dependencies [1] but really reading all of the man pages (the most useful ones [2][3][4]) will get you a good idea on what it can do, I had many "oh, we can use THAT" moments with it. They are written pretty well. The directives we got most use in org are probably Restart* family and RequiresMountsFor, althought the last one is more and more common in distro packages so it is not even needed that often. The usecase being "don't start DB if mount fails" usually. Overrides are probably the most used feature overall, we often find that the standard distro unit just needs a little bit of tweaking for our purpose (like adding restart), so we just create file /etc/systemd/system/servicename.service.d/01-restart.conf with [Service] Restart=always RestartSec=30 and voila, service now auto-restarts and that behaviour won't break when package updates, as we're not changing any package file. The few other modifications of existing ones included adding new read-write dirs or adding env variables for proxy. Technically you can even go as far as making services into little containers with all the options for limiting permissions but I haven't got that far. Most apps don't exactly need it either, have readonly/readwrite dir + some limits and it is pretty safe out of the box, I've also noticed many distro packages going that way. * [1] https://devrandom.eu/blog/post/2022-02-27_increasing_system_robustness_with_systemd_dependencies https://devrandom.eu/blog/post/2022-02-27_increasing_system_... * [2] https://www.freedesktop.org/software/systemd/man/systemd.exec.html https://www.freedesktop.org/software/systemd/man/systemd.exe... * [3] https://www.freedesktop.org/software/systemd/man/systemd.unit.html https://www.freedesktop.org/software/systemd/man/systemd.uni... * [4] https://www.freedesktop.org/software/systemd/man/systemd.service.html https://www.freedesktop.org/software/systemd/man/systemd.ser...

ilyt 4y ago

Well, I've written a blogpost on dependencies [1] but really reading all of the man pages (the most useful ones [2][3][4]) will get you a good idea on what it can do, I had many "oh, we can use THAT" moments with it. They are written pretty well. The directives we got most use in org are probably Restart* family and RequiresMountsFor, althought the last one is more and more common in distro packages so it is not even needed that often. The usecase being "don't start DB if mount fails" usually. Overrides are probably the most used feature overall, we often find that the standard distro unit just needs a little bit of tweaking for our purpose (like adding restart), so we just create file /etc/systemd/system/servicename.service.d/01-restart.conf with [Service] Restart=always RestartSec=30 and voila, service now auto-restarts and that behaviour won't break when package updates, as we're not changing any package file. The few other modifications of existing ones included adding new read-write dirs or adding env variables for proxy. Technically you can even go as far as making services into little containers with all the options for limiting permissions but I haven't got that far. Most apps don't exactly need it either, have readonly/readwrite dir + some limits and it is pretty safe out of the box, I've also noticed many distro packages going that way. * [1] https://devrandom.eu/blog/post/2022-02-27_increasing_system_robustness_with_systemd_dependencies https://devrandom.eu/blog/post/2022-02-27_increasing_system_... * [2] https://www.freedesktop.org/software/systemd/man/systemd.exec.html https://www.freedesktop.org/software/systemd/man/systemd.exe... * [3] https://www.freedesktop.org/software/systemd/man/systemd.unit.html https://www.freedesktop.org/software/systemd/man/systemd.uni... * [4] https://www.freedesktop.org/software/systemd/man/systemd.service.html https://www.freedesktop.org/software/systemd/man/systemd.ser...