How can I mount a device with specific user rights on start up? I still have some problems figuring it out. I would like to mount the divide with uid=1000 and gid=1000. My current entry to the /etc/fstab/ file looks like this:

dev /var/www vboxsf rw, suid, dev, exec, auto, nouser, async, uid=1000
  • Don't forget gui=1000. Also, what is the ownership/rights to /var/www. It should be owned by root. – skub Aug 8 '11 at 12:57
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    @skub: The owner of /var/www/ is root. dev /var/www vboxsf rw, suid, dev, exec, auto, nouser, async, uid=1000 gui=1000 didin't work so well (Ubuntu removed the entry after a failed restart). – wowpatrick Aug 8 '11 at 21:14
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    Your mount source is "dev"?? – James T Snell Aug 8 '11 at 21:51
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    @skub: It's a VirtualBox shared folder, so /dev is is right. I figured it out by now, sudo mount -t vboxsf -o umask=0022,gid=33,uid=33 dev /var/www works just fine. – wowpatrick Aug 8 '11 at 23:16
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    I've been messing around with this problem in vbox for a while now too. From what I've gathered, the correct solution (to the question you aren't asking) is to add your user into the vboxsf group, and then it doesn't matter who the owner of the files are - you will have permission to edit them. alcobrov.blogspot.com/2012/06/… – stevemidgley Aug 23 '14 at 0:00

To mount a device with certain rights, you can use the -o Option directive while mounting the device. To mount the device you described, run:

 mount -t deviceFileFormat -o umask=filePermissions,gid=ownerGroupID,uid=ownerID /device /mountpoint

For example mounting a VirtualBox shared folder to /var/www with www-data as owner would look like this:

mount -t vboxsf -o umask=0022,gid=33,uid=33 dev /var/www

If you want to mount the device on startup, you can add the following entry to your /etc/fstab file:

 /device /mountpoint deviceFileFormat umask=filePermissions,gid=ownerGroupID,uid=ownerUserID

Again, with the same example the entry to the /etc/fstab file would look like this:

dev /var/www vboxsf umask=0022,gid=33,uid=33

For filesystems that does not support mounting as a specific user (like ext4) the above will give the error

Unrecognized mount option "uid=33" or missing value

to change the owner of an ext4 mount simply run

chown username /mountpoint

after it has been mounted.

  • I was able to use the uid/gid option on ext4. – CMCDragonkai Dec 9 '15 at 9:45
  • This doesn't seem to work with mount --bind , i'm using a btrfs file system – Northstrider Mar 18 '17 at 16:48
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    Shouldn't the umask be umask=0077 instead of umask=0022 to give permission only owner to read or write? It seems that umask=0022 will give read permissions to others if I am reading it correctly. I want that only the user who mount the disk should have read or write permission. – Mian Asbat Ahmad Jan 9 '19 at 14:00

For a file-system like ext3 or ext4, after doing

    chown -R username:group /mountpoint

to change the owner of the currently existing files you can set the group id bit to have new files created with the specific group (doesn't work for the user id under Linux):

    find /mountpoint -type d -exec chmod g+ws {} \;

The Wikipedia entry on setuid and setgid is quite informative, see the section on directories.

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    Changing the ownership of all the files on the device is very invasive. Since there is a -o option for mount, it is the better way. – lmat - Reinstate Monica Apr 29 '13 at 15:16
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    -o unfortunately doesn't work for ext4, as explained in the answer by @wowpatrick. – js. Aug 18 '14 at 20:55
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    chowning the contents of the mounted drive to some other user is ridiculous. You have no idea what you might break for any applications on that drive. It may be fine if all of the contents belong to your user, but this is a very big no-no... – carlspring Apr 12 '15 at 1:56
  • The device in question is /dev/www, it is easy to control which applications have access to it (probably only a WWW server, which you can turn off during the operation). Even if the app using it is still running, it will keep running, since that is the point of the operation. – js. Apr 13 '15 at 7:40
  • bindfs allows you to mount a directory with different user and group ownership - this can be helpful to avoid chown'ing all the files - although I found this question hoping to find a more elegant approach than bindfs. – Steve Kroon Apr 14 '20 at 13:05

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