Klaus Knopper answers your Linux questions

Systemd Update

What's up with systemd in Knoppix 7.4 and Debian?

Debian is going to switch the startup system to systemd [6]. Although systemd claims to be able to work as a "drop-in replacement for sysvinit," the startup procedure and configuration differ a lot from the traditional SysV init startup [7]. Although systemd-sysv features parallelizing startup of services, it uses different paths and flow of execution, and it adds more complexity because the systemd modules also replace or change interfaces like ConsoleKit, powerd, and acpid. For embedded systems and customized boot procedures  – such as the one Knoppix uses, which basically consists of only two or three scripts for fast startup – this raises a lot of issues.

Unfortunately, as of this writing, it is no longer possible to keep the traditional SysV init (which has been renamed sysvinit-core) in parallel with other systemd features that are required by various services like network-manager or session management. Installing the required systemd-sysv will remove sysvinit-core and, thus, change the boot procedure completely.

Apparently systemd will be a basic requirement for Debian to work properly starting from the "jessie" release, but I prefer to keep my customized boot scripts that take care of parallelizing and fallbacks on their own. Thus, I'm using a forked SysV init package as a workaround for keeping the SysV init startup while still providing the now necessary systemd modules. To provide systemd's session management as well, systemd-logind is also started, so network-manager and other packages that rely on it will continue to work.

The workaround is (probably) temporary until systemd integration in Debian is stabilized. I may have to redesign the Knoppix start scripts to run as systemd services in the future. This means /etc/inittab will go away, but the main hardware detection and the fast startup script /etc/init.d/knoppix-autoconfig won't.

Because the handling of systemd dependencies in Debian is still a work in progress, I expect many things to break upon upgrade. Thus, the currently installed versions of essential packages have been put on hold, so they won't be upgraded accidentally when attempting to update packages.

Another difference between Knoppix systemd integration and Debian/unstable is disabling systemd's attempt to take over hot keys and events that were formerly handled by acpid – such as closing the notebook lid or pressing the poweroff button. These actions usually lead to a (non-recoverable without password) lockup of the display caused by systemd or an immediate shutdown, both of which have been disabled by configuration in Knoppix.

In summary, Knoppix 7.4 is mostly prepared for systemd, whereas the startup process is still using SysV init (or rather BSD) style.

The Author

Klaus Knopper is the creator of Knoppix and co-founder of LinuxTag expo. He currently is a Professor, Dipl. Ing., at the University of Applied Sciences Kaiserslautern. If you have a configuration problem, or if you just want to learn more about how Linux works, send your questions to: klaus@linux-magazine.com

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