Comment 5 for bug 1392637

Thanks Didier! Some remarks:

+ * Add systemd-emergency-tmpfs to force tmp.mount (tmpfs) enablement if the
 ... "generator"?
Also, s/enablement/startup/? (We don't permanently enable the unit, that could be misleading)

+avail=`df -BM -P /tmp/ | awk 'NR==2 { print substr($4, 0, length($4)-1) }'`

This needs guarding against /tmp not existing. Strange, I know, but let's better be correct. tmpfiles.d/tmp will create it later on if it's missing.

Also, this generator will trigger if tmp.mount is already (manually) enabled, right? In this case you wouldn't have an overflow in /tmp as it's overmounted later on, and that unit should stay inert. You could check for enablement symlinks in /etc, /lib, and /run, but that gets a bit fiddly... Perhaps the "After=tmp.mount" emergency-tmp.service was less intrusive after all?