Systemd does not start UDEV after remounting root

[Taniwha]

Systemd under zesty starts udev before the root file system has been made writeable.

This means that every insertion script (from /lib/udev/rules.d) that is subsequently run, even long after system boot, is unable to change anything in the world (for example can't create locks in /run/lock, device files in /dev etc etc) can't even write to /tmp;

In my case scripts run at device insertion (including an attempt to log data to /tmp) fail:

Oct 1 21:45:02 rata systemd-udevd[21055]: '/sbin/onerng.sh ttyACM0'(err) '/sbin/onerng.sh: 2: /sbin/onerng.sh: cannot create /tmp/yy: Read-only file system'
Oct 1 21:45:02 rata systemd-udevd[21055]: '/sbin/onerng.sh ttyACM0'(err) 'warning: commands will be executed using /bin/sh'
Oct 1 21:45:02 rata systemd-udevd[21055]: '/sbin/onerng.sh ttyACM0'(err) 'Cannot open lockfile /var/spool/cron/atjobs/.SEQ: Read-only file system'

This breaks add-on products already in the field that worked with previous versions of Ubuntu

One can use "/etc/init.d/udev restart" to restart udev and everything works great after that - but devices that were discovered since udev was originally started will already have had their startup scripts run and fail - works great for devices that are only inserted after system boot, fails for devices that were already present at boot time

The solution is to make sure that udev is started after the system directories are remoutned RW

[Dan Streetman (ddstreet)]

please reopen if this is still an issue