Would the systemd inhibit interface be an option?
https://www.freedesktop.org/wiki/Software/systemd/inhibit/
It was designed for that use case after all.
Am Mo., 29. Aug. 2022 um 14:01 Uhr schrieb Mantas Mikulėnas <graw...@gmail.com>:
>
> On Mon, Aug 29, 2022 at 1:31 PM Henning Moll <newssc...@gmx.de> wrote:
>>
>> Hi,
>>
>> back in the rcX days I configured a backup system which blocks a system
>> shutdown in a certain state (network and mounts still active) if a backup is
>> still running. The init script looks like this:
>>
>> ...
>> case "$1" in
>> ...
>> stop)
>> plymouth --ping
>> if [ $? -ne 0 ]; then
>> log_daemon_msg "waiting for running backup" "backup"
>> else
>> plymouth message --text="waiting for running backup"
>> fi
>> sleep 10
>> logger -t backup "rcS: trying to get lock..."
>> exec {FD}<>"$LOCKFILE"
>> {
>> logger -t backup "locked rsync_wrapper: waiting for lock"
>> flock ${FD}
>> }
>> logger -t backup "rcS: continue shutdown..."
>> plymouth message --text=""
>>
>> ...
>> esac
>> ...
>>
>> The strategy is to wait for a successful lock on a shared LOCKFILE.
>>
>> Now, I want to solve this with systemd. I've read tons of documentation but
>> I don't get it, all my experiments failed. I am using Linux Mint 21
>> "Vanessa", which is based on Ubunut 22.04.
>>
>> I am looking for a solution which
>>
>> * "pauses" a shutdown or reboot attempt as long as the LOCK cannot be
>> obtained (which means the backup is still running)
>> * while the network connection (ethernet) is still active
>> * and all mounts (local, usb and cifs) are still active
>> * openssh-server still running
>> * The logging functionality (plymouth / log_daemon) would be nice. so the
>> system should be allowed to shutdown to a stage where plymouth is already
>> visible
>>
>> Can you please help me?
>>
>> Best regards
>> Henning
>
>
> Probably similar to what you already have – create a service that starts on
> boot (doing nothing) and delays the *stop* action. (You'll probably need to
> start with [Service] Type=oneshot, RemainAfterExit=yes, TimeoutStopSec=1d.)
> If you list After=ssh.service as a dependency, then your service will be
> started after OpenSSH and *stopped before OpenSSH*, same with NetworkManager.
> (I'm not sure if there's a dependency that can be used to target manually
> done SMB mounts, although remote-fs.target might work for the ones in fstab?)
>
> Not sure how it works with Plymouth, but in its default console output,
> systemd itself will already show which services are waiting to be stopped.
> Syslog (journald) should be available the entire time.
>
> The backup system should also run under `systemd-inhibit --what=shutdown` as
> an additional layer of precaution – that way the user will know that
> something is still running *before* they initiate the actual shutdown.
>
> --
> Mantas Mikulėnas
