How to force OS reload of fstab?

Question

mount -a works fine as a one-time action. But auto-mount of removable media reverts to settings that were in fstab at the last reboot.

How to make the OS reload /etc/fstab so auto-mounts use the new settings when media is connected?

The specific example seen with Raspbian (Debian) Stretch:

FAT-formatted SD card; configured fstab to auto-mount; rebooted; volume auto-mounts, but read-only.
Changed umask options in /etc/fstab; mount -a while media is connected, and volume is now read-write.
Unmount and re-insert the media; auto-mount works, but using the options in /etc/fstab from the last reboot, so volume is read-only.
Reboot; OS loads updated /etc/fstab; auto-mount works when media is connected, and volume is read-write. How to get this effect without a reboot?

FWIW, the (updated) /etc/fstab syntax was:

/dev/sdb1   /Volumes/boot   vfat    rw,user,exec,nofail,umask=0000  0   0

score 33 · Accepted Answer · answered Oct 25 '18 at 18:24

33

I suspect this is caused by systemd’s conversion of /etc/fstab; traditional mount doesn’t remember the contents of /etc/fstab.

To refresh systemd’s view of the world, including changes to /etc/fstab, run

systemctl daemon-reload

answered Oct 25 '18 at 18:24

Stephen Kitt

434,908

Sigh. An auto-generated comment in the top of /etc/fstab reminding/advising people it has now been deprecated - and how to update systemd - would go a long way. – Chris Davies Oct 25 '18 at 20:14
2

Thanks! You can imagine Google returned nothing but 'mount -a' hits for this query. Are there any unwanted side-effects when doing this on-the-fly re-gen of the tables? Doesn't seem to be. – RichardH Oct 25 '18 at 21:45
For more, see https://unix.stackexchange.com/a/236968/5132 and https://unix.stackexchange.com/questions/90723/ . Note that the Debian service that used to run mount -a is nowadays masked. – JdeBP Oct 26 '18 at 00:03

score 24 · Answer 2 · edited Mar 12 '24 at 12:18

24

To elaborate the answer from @Stephen Kitt: for example I have this entry in /etc/fstab:

vnetsvr-home:/etc/skel   /etc/skel    nfs4   sec=krb5p,noauto,x-systemd.automount,x-systemd.idle-timeout=10min   0   0

and only doing sudo systemctl daemon-reload doesn't reloaded the fstab. I have to do:

sudo systemctl daemon-reload
sudo systemctl restart remote-fs.target

To reload an entry to mount a local filesystem, you should use:

sudo systemctl daemon-reload
sudo systemctl restart local-fs.target

edited Mar 12 '24 at 12:18

bryant1410

131

answered Apr 01 '20 at 17:46

Ingo

626

This answer worked for me in regards to Ubuntu 16.04 while the accepted answer did not. – Dmitrii Volosnykh Dec 30 '20 at 10:17
Even this answer does not help me when removing entries from /etc/fstab. So, I opt for the reboot. – Dmitrii Volosnykh Dec 30 '20 at 10:24
If you're using "noauto" option, this answer resolves the issue. – Ahmet May 19 '21 at 05:21
This answer worked for me in RedHat 8, however, the accepted answer did not. – caot Mar 23 '22 at 16:47
This answer worked for me in Ubuntu 18.04 – Tiana987642 Nov 01 '22 at 03:42

score 0 · Answer 3 · answered Oct 03 '21 at 16:09

I know that these solutions might not work in every linux distro and version. However this method would generally works for all Linux versions.
1- Do your configuration and change the fstab file
2- Use this command to remount the device_file you have changed its configuration in the fstab file:
# mount -o remount [device_file]
This way you will mount the partition with its new configuration read from "fstab" file.
If you removed a partition from "fstab" file, simply umount [device_file]. Be sure, the partition stays unmounted after the reboot.

Any time you can check the result by running mount command.

How to force OS reload of fstab?

3 Answers3