Start a systemd service inside chroot

A well-known problem in systemd distros (Arch Linux, OpenSUSE, Fedora).

Systemd replaces sysvinit, and provides one great advantage over this. In sysvinit, when you ask a service to start, it inherits the execution context of the person invoking the script, which includes environment variables, ulimits, and so on. Systemd improves on this at the contrary by notifying a daemon, which will start the service in a well-defined, healthy, constant environment, where of course the performances of the services are much easier to predict, since the environment is always the same.

This implies that, when I call systemctl from within the chroot, it is irrelevant that I am inside chroot, the environment that will be inherited is still that of PID 1, not my current one. But it gets worse than this: since communication sockets are placed inside /run/systemd, a process in a chroot will not even be able to talk to the init system!

So how do you go about chroot'ing in systemd distros?

1. If all you want to do is have a Linux container, this Arch Wiki page will tell you how to set up a Linux container in less than 30 seconds, thanks to systemd-nspawn.

2. If instead you really want a chroot environment, this beautiful and crystal clear Web page will provide you with two working solutions (the second one is a modified version of the one offered at point #1).

Several years laters I must admit there is only one solution to most Systemd practical problems. Because the error is Systemd itself

I am really fed up with Systemd as I had problems that I never faced with things like Upstart or Openrc :

• The enforcing of a kernel requiring cgroups support (instead of being made optional but enabled by default inside a config file) even for embedded systems with only 24Mb of ram and no writable storage.
  While proponents argue that not being able to use it in such case is the wanted behavior since it wasn’t designed for such case, the reality is the other init systems also don’t care while in systemd such feature isn’t a separate project which highlights once again the consequences of not following kiss.
• Despite the claim of being modular, at runtime the dependency hell makes it a strong god object : want to boot over a single reiser4 rootfs ? It’s not possible because many programs requires systemd-udevd which requires systemd-init which requires the systemd-boot package which can’t be installed at the same time than grub2 nor can read kernel images from a reiser4 partition.
• Want to connect to internet through Bluetooth dialup ? If it doesn’t work with your samsung java me phone, then you aren’t able to run the scripts and command line software that previously worked manually because of networkd.
• Though I recognize the biggest problem is if you are building and maintaining your own Linux distribution : the systemd init module itself has so much dependencies that you can’t propose to choose an other init system through different install packages.
• The default use of Google dns for systemd if no resolver is defined in terms of privacy.
• The inability to launch a background non serive process and log out as there are no simple way to do it in a new systemd scope.
• Good luck for viewing logs if you can’t chroot in your system or if you upgraded from libdb4.8 (whereas at least, in worst case Microsoft have it’s log files in xml format).

The only solution :

Systemd is unessary complex for solving problems : like alsa instead of ossv4. So if you have something that uses systemd just wipe all the data :

dd if=/dev/urandom of=/dev/dm−0 bs=1M

and install something that don’t uses it at all while solving problems of SysV Init like Gentoo with Openrc.
Concerning my question systemd makes things like the Windows® registry : if a part of it gets screwed up, then it’s over.

systemd only ignores "services", so I just run the daemon commands manually.

So instead of

service sshd start

I use

/usr/sbin/sshd -D &