I have the following content in in /etc/udev/rules.d/81-external-disk.rules:
ENV{ID_FS_UUID}=="6826692e-79f4-4423-8467-cef4d5e840c5", RUN{program}+="/bin/mount -o nofail,x-systemd.device-timeout=1 -t ext4 -U 6826692e-79f4-4423-8467-cef4d5e840c5 /backup/external"
After running:
udevadm control --reload ; udevadm trigger /dev/sdb1
It does nothing at all. However if II change the mount command for something such as /bin/touch /tmp/xyz it works.
Versions:
[<a href="https://getridbug.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="394b56564d79515c554a50575250">[email protected]</a> rules.d]# rpm -qa | grep udev libgudev1-219-19.el7_2.12.x86_64 python-pyudev-0.15-7.el7_2.1.noarch [<a href="https://getridbug.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="2654494952664e434a554f484d4f">[email protected]</a> rules.d]# rpm -qa | grep systemd systemd-libs-219-19.el7_2.12.x86_64 systemd-219-19.el7_2.12.x86_64 systemd-sysv-219-19.el7_2.12.x86_64 [<a href="https://getridbug.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="fc8e939388bc9499908f95929795">[email protected]</a> rules.d]# cat /etc/redhat-release CentOS Linux release 7.2.1511 (Core)
Answers:
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Method 1
This is a systemd feature. The original udev command has been replaced by systemd-udevd (see its man page). One of the differences is that it creates its own filesystem namespace, so your mount is done, but it is not visible in the principal namespace. (You can check this by doing systemctl status systemd-udevd to get the Main PID of the service, then looking through the contents of /proc/<pid>/mountinfo for your filesystem).
If you want to go back to having a shared instead of private filesystem namespace, then create a file /etc/systemd/system/systemd-udevd.service with contents
.include /usr/lib/systemd/system/systemd-udevd.service [Service] MountFlags=shared
or a new directory and file /etc/systemd/system/systemd-udevd.service.d/myoverride.conf with just the last 2 lines, i.e.
[Service] MountFlags=shared
and restart the systemd-udevd service. I haven’t found the implications of doing this.
Method 2
This same problem occurs in Ubuntu 18.04 with the same underlying cause. To fix it we create an override file for systemd-udevd:
sudo systemctl edit systemd-udevd
And insert into it:
[Service] MountFlags=shared
(on Ubuntu 20.04, replace MountFlags=shared with PrivateMounts=no.)
Save the file and then execute:
sudo systemctl daemon-reload sudo service systemd-udevd --full-restart
All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0