I'm trying to do something that I hope is relatively simple, namely to run a simple kexec -l ... command on system shutdown before the /boot file system is unmounted. I'm trying this on two different machines, both of which are running current versions of arch linux with systemd 204. The machines are configured very similarly, except that one has a serial console and some NFS mounts, while the other does not. Unfortunately, I cannot find a single script that works on both machines.
On the machine with a serial console, the following unit file seems to work (in /etc/systemd/system/kexec-load@.service, enabled with systemctl enable kexec-load@linux). This is a slightly modified version of a suggestion on the arch linux wiki: [Unit] Description=load %i kernel into the current kernel Documentation=man:kexec(8) DefaultDependencies=no Before=shutdown.target umount.target final.target After=sysinit.target [Service] Type=oneshot ExecStart=/usr/bin/kexec -l /boot/vmlinuz-%i --initrd=/boot/initramfs-%i.img --reuse-cmdline [Install] WantedBy=kexec.target However, when I try this script on the machine without a serial console, the script gets run at the very end of the shutdown process, after all the file systems are unmounted (and hence at a point where the new kernel image is unavailable). I can boot with systemd.log_level=debug, but since there's no serial console and I can't get my job to fire before the journal system is shutdown, it's hard for me to capture all the output on shutdown. Conversely, I devised a kind of hacky way to make it work on the non-serial-console machine what doesn't work on the serial console one. Here my idea is to have a job whose ExecStop loads the new kernel. I'm not sure why that job fires only on startup and not shutdown of the serial console machine, but if I solve one of these problems, I'd rather get the WantedBy=kexec.target approach working, if that's possible, so I'll omit the details for now. For what it's worth, here's a relevant subset of the output of the systemd --test command on the machine that does not work (i.e., the non-serial console) with the above unit file: /usr/lib/systemd/systemd --system --test --unit=kexec.target -> By units: -> Unit shutdown.target: After: kexec-load@linux.service ReferencedBy: kexec-load@linux.service -> Unit systemd-journald.socket: Before: kexec-load@linux.service ReferencedBy: kexec-load@linux.service -> Unit sysinit.target: Before: kexec-load@linux.service ReferencedBy: kexec-load@linux.service -> Unit final.target: After: kexec-load@linux.service ReferencedBy: kexec-load@linux.service -> Unit umount.target: After: kexec-load@linux.service ReferencedBy: kexec-load@linux.service -> Unit kexec.target: Wants: kexec-load@linux.service References: kexec-load@linux.service -> Unit kexec-load@linux.service: Name: kexec-load@linux.service Fragment Path: /etc/systemd/system/kexec-load@.service -> ExecStart: Command Line: /usr/bin/kexec -l /boot/vmlinuz-%i --initrd=/boot/initramfs-%i.img --reuse-cmdline So here the dependencies seem fine. Yet when I look at the "by jobs" category: -> By jobs: -> Job 3: Action: kexec.target -> start State: waiting Forced: no Irreversible: no -> Job 4: Action: systemd-kexec.service -> start State: waiting Forced: no Irreversible: no -> Job 5: Action: shutdown.target -> start State: waiting Forced: no Irreversible: no -> Job 83: Action: umount.target -> start State: waiting Forced: no Irreversible: no -> Job 88: Action: boot.mount -> stop State: waiting Forced: no Irreversible: no -> Job 90: Action: final.target -> start State: waiting Forced: no Irreversible: no -> Job 91: Action: kexec-load@linux.service -> start State: waiting Forced: no Irreversible: no [end of file] Job 91 is the very last job. So while I'm not 100% sure how to parse this output, it sure looks as though kexec-load is getting started *after* boot.mount is stopped, which is indeed the behavior I see when rebooting my machine with "systemctl kexec". On the other hand, maybe "waiting" means these jobs are waiting for dependencies? At any rate, I'd be grateful for any advice on what the problem is, or even better for any meta-advice on how to debug these things in general. (In a sense, debugging my dependencies and solving the problem are the same thing, as getting my shutdown script to run while the journal service is active would solve the problem.) Also, in order to short-circuit some potentially redundant discussion, I should say that I've also tried adding various permutations of the following to my unit file, all to no avail: RequiresMountsFor=/boot RequiresMountsFor=/boot/vmlinuz-linux Requires=boot.mount After=boot.mount Thanks. _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel