Re: [systemd-devel] What is the shutdown sequence with systemd and dracut?
On Sa, 13.08.22 20:46, Patrick Schleizer (patrick-mailingli...@whonix.org) wrote: > 2. /lib/systemd/system-shutdown (shutdown.c) runs Still, this binary is called systemd-shutdown, i.e. with one more 'd'. > 4. /lib/systemd/system-shutdown performs further cleanup (similar to > dracut, probably some functionality duplicated with dracut, includes > kill all remaining processes, unmount remaining file systems) I am not sure dracut has another killing spree. > 6. /run/initramfs/shutdown (which is at time of writing only implemented > in dracut) attempts to kill all remaining processes, unmount remaining > file systems and calls kernel. I think the arch initrd also implements this scheme. And IIRC they use a neat trick, and chainload systemd-shutdown from the initrd, so that it runs again, and does the actual final shutdown, but that time without transitioning back into an initrd env. Hence for them PID 1 during shutdown first transitions from the service manager into systemd-shutdown, and then from there into into the initrd script, and then back into systemd-shutdown. I like their approach. Lennart -- Lennart Poettering, Berlin
Re: [systemd-devel] What is the shutdown sequence with systemd and dracut?
On Mo, 08.08.22 12:24, Patrick Schleizer (patrick-mailingli...@whonix.org) wrote: > Hi! > > This is what I think but please correct me if I am wrong. > > 1. systemd runs systemd units for systemd shutdown.target > > 2. /lib/systemd/system-shutdown (shutdown.c) runs I presume you mean /usr/lib/systemd/systemd-shutdown? (i.e. there's a *d* in the file name; and the path outside of /usr/ is only done by legacy distros, who still stick to spit /usr/ setups, which we do not support anymore) > 3. /lib/systemd/system-shutdown executes /run/initramfs/shutdown (which > is dracut) systemd-shutdown runs as PID 1 at this time, and it then chain loads /run/initramfs/shutdown also as PID1 – if it exists. Thus, at that moment no systemd code runs anymore, dracut is the only userspace code remaining. > 4. dracut shutdown.sh performs various cleanup tasks (such as kill all > remaining processes and unmount root disk) It should have been systemd-shutdown between steps 2 and 3 above which should have already killed everything. But yeah, dracut is supposed to detach the root fs. > 5. /lib/systemd/system-shutdown runs scripts in the > /usr/lib/systemd/system-shutdown/ folder This is actually done before step 3 above. > 6. /lib/systemd/system-shutdown performs further cleanup (similar to > dracut, probably some functionality duplicated with dracut, includes > kill all remaining processes, unmount the root risk) and eventually > halt/reboot/poweroff/kexec. Nah, the killing of processes it already did between steps 2 and 3. Also, as mentioned systemd-shutdown doesn't run at this time anymore. Lennart -- Lennart Poettering, Berlin
Re: [systemd-devel] What is the shutdown sequence with systemd and dracut?
On 08.08.2022 15:24, Patrick Schleizer wrote: > Hi! > > This is what I think but please correct me if I am wrong. > > 1. systemd runs systemd units for systemd shutdown.target > > 2. /lib/systemd/system-shutdown (shutdown.c) runs > > 3. /lib/systemd/system-shutdown executes /run/initramfs/shutdown (which > is dracut) > > 4. dracut shutdown.sh performs various cleanup tasks (such as kill all > remaining processes and unmount root disk) > > 5. /lib/systemd/system-shutdown runs scripts in the > /usr/lib/systemd/system-shutdown/ folder > > 6. /lib/systemd/system-shutdown performs further cleanup (similar to > dracut, probably some functionality duplicated with dracut, includes > kill all remaining processes, unmount the root risk) and eventually > halt/reboot/poweroff/kexec. > No. The sequence is 1, 2, 5, 6 (up to halt/reboot/poweroff/kexec). Then if /run/initramfs/shutdown is present, systemd-shutdown executes it. What happens later is completely outside of systemd scope, there is no return. If this fails or /run/initramfs/shutdown is not present, systemd-shutdown calls kernel to actually perform halt/reboot/poweroff/kexec. Dracut shutdown script attempts to unmount remaining filesystems and calls kernel.
