Systemd: how to get into rescue mode

[Tom H]

On Sat, Jan 11, 2020 at 5:33 PM Little Girl <littlergirl at gmail.com> wrote:
> Tom H wrote:
>
> >"procps" ships "/etc/sysctl.d/10-magic-sysrq.conf" which sets
> >"kernel.sysrq = 176" and this setting prevents using "e" and "i"
> >among others.
>
> >What's "cat /proc/sys/kernel/sysrq" on your system? If it's not "176"
> >either you or MATE (?) are overriding it.
>
> It returns 176 on my system.
>
> A bit of research on "kernel.sysrq = 176" turned up that the
> Alt+SysRq+REISUB and Alt+SysRq+REISUO key combinations no longer take
> control of the keyboard away from the X server, no longer send the
> SIGTERM signal to all processes, and no longer send the SIGKILL
> signal to all processes. They do, however, still sync all mounted
> filesystems, remount all mounted filesystems in read-only mode, and
> shut off the system or reboot it without unmounting or syncing
> filesystems.
>
> When I did those key combinations, apparently the REI key presses
> were simply ignored and the SUB and SUO key presses were obeyed. Now
> the question becomes whether we should just be using the SUB or SUO
> key combinations in emergencies or whether there's a new and improved
> way of handling such situations. If you were dealing with a frozen
> system (which wasn't the case with the OP in this thread), I suppose
> Systemd commands would be useless, since you probably wouldn't be
> able to issue them.

If you're not on the console (usually vt1), you won't see the error
messages; unless you check the output of "journalctl".