systemd

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Systemd boot messages. Systemd boot messages.

It's been nagging me for a while. I knew that it would happen at some point. I read the blogs, the reviews, the flames. The future of PID1 is here.

I've been putting this off for a while, udev-200 was the first visible change. I practiced the upgrade a few times, so I was ready when it stabilised. Replace all instances of eth0 with enpXsY. It seemed harmless enough. For my generic images, adding dhcpcd to the default runlevel, and not creating the net.* specific scripts tends to do well. Hostnames (dhcp/dns coupling) are a bit erratic but some tweaks to the runlevel order fixes those.

This is something a bit more invasive. I can't upgrade this easily.  

It's all about choice


Gentoo is on the verge of quite a few major upgrades. The devs have been assuring users that there is no need to make the jump, everything still works and we all have the choice to not migrate over.

SysV+openrc has some really odd corner cases where I find myself spending too much time googling around and not finding an answer. For instance, /etc/init.d/* stop scripts not stopping gunicorn workers (even if the master is killed!). Daemons are forking  too many times for PID (and process group id) tracking to be useful. In gentoo's init scripts you can specify

stop() {
...
kill -TERM -$(cat /run/${SVCNAME}.pid)
...
}

to kill the process group, but that isn't 100% reliable.

Systemd places processes into cgroups keeping track of all children, no matter how naughty they are.

There's also some other cool linux features that systemd exposes, better support for process isolation, socket activated daemons (a cool feature for another blog post), faster boot times? It is the future of linux distros (fedora and arch are fully supported, even SailfishOS!).

I also find that systemd units are easier to automate than sysv (drop a unit file, add a symlink and recalculate default.target). This isn't so bad in gentoo with declarative init scripts.

When writing daemons the 12factors are also well respected. A statement that I will leave with no extra comment until a future post.

WTF?!


It's not all fun and giggles. There's some funny NIH with system configuration.
root@localhost ~ # qlist systemd|grep -e bin |grep ctl
/usr/bin/systemctl
/usr/bin/localectl
/usr/bin/hostnamectl
/usr/bin/timedatectl
/usr/bin/bootctl
/usr/bin/loginctl
/usr/bin/systemd-coredumpctl
/usr/bin/journalctl
/bin/systemctl

You get used to them once you figure out that they can be used to deprecate files like /etc/hosts and /etc/fstab. Not all of the utilities are fully working yet, so I can't recommend that everyone switches to systemd right now.

Stage3 Tarballs


There are currently no official gentoo systemd stage3 tarballs. I'm working on creating a stage3 of my own which is probably worth another blog post.   You still need openrc installed as a crutch, even if it isn't running as PID1.

Update: I have a stage3 tarball.

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systemd stage3 | Fragments 7 months, 3 weeks ago

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