We have a beaglebone where we want to place it into a readonly mode in case of power off in some circumstances. To do this we created a sleep.target and run systemctl isolate sleep.target, which will end up ending services that write to disk. Then we can run mount to remount / as readonly to wait safely for power loss.
We have two problems:
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connmand opens files on disk, so we have to stop it. When connmand stops, the bone’s Ethernet goes offline, we haven’t found a way around this.
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By default, systemd-journald does not write to disk unless you make a /var/log/journal. When you do it writes all buffered data there. This is super cool. But I haven’t found a reliable way to either stop journald or, even better, make it go back into its buffering mode, so we can remount /.
So the questions: -
Is it possible to run connmand on a read-only file system?
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Is it possible to make systemd-journald revert back to the buffering mode it was in before /var was mounted read-write, so it releases /var?
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Is the sleep.target followed by a call to mount -o remount,ro the proper way to do this?