specify user in fstab

Jimmy2027 · n00b Joined: 12 May 2020 Posts: 34

Hello, I want to mount an external hard drive such that only user "larry" and root can access it. Is there a way to do this in the fstab file?

Also another somehow related question: Is there a way to change access rights of a folder in an external hard drive?
For example, if I have a folder that should only be accessible by user "larry" in a mounted external hard drive that is accessible by all users?
If I try to run `chown larry my_folder` as root in the mounted hard drive, I get the error:
`chown: changing ownership of my_folder: Operation not permitted`

NeddySeagoon · Posted: Tue Oct 13, 2020 1:37 pm Post subject:

Jimmy2027,

The user= option to mount, however its called, only works with non *NIX filesystems that do not support *NIX permissions.
It will work for vfat and ntfs and a few others.

Change the permissions on the mount point while the filesystem is not mounted.

A word of warning. Linux uses UIDs everywhere. User names are for display only.
If you want this to work on several systems, larry must have the same UID on every system.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

Tony0945 · Posted: Tue Oct 13, 2020 3:39 pm Post subject:

Hu · Administrator Joined: 06 Mar 2007 Posts: 21724

What filesystem type is used by the external drive? Do you require that the access control apply regardless of the computer used to access the drive, or is it sufficient that the Gentoo Linux system in question enforces it? In the latter case, someone could move the drive to a different system and allow users other than root and larry to access it.

Jimmy2027 · n00b Joined: 12 May 2020 Posts: 34

Thanks for the replies! I have tried to add user=hendrik to the fstab, however after unmounting and mounting the external drive, all users could still access it.
My fstab entry looks like the following, with 1000 my user uid:
LABEL=my_external_drive /mnt/my_external_drive exfat user=1000 0 0

The external drive uses the exfat file system and should in theory never change place. It would be enough if the Gentoo Linux system it is mounted on would enforce the access rights.
However out of curiosity, how could one make sure that for any system only root or user larry can access the external drive?

toralf · Posted: Tue Oct 13, 2020 5:54 pm Post subject:

NeddySeagoon · Posted: Tue Oct 13, 2020 8:57 pm Post subject:

Jimmy2027,

user allows any single user to mount the filesystem and that same user to unmount it again.

You want uid= and possibly gid=
Maybe fmask= and dmask= too.

The uid and gid for the same users/groups are not fixed across systems.
To make it work across systems the admin (that's you) needs to fix that.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

Tony0945 · Posted: Tue Oct 13, 2020 10:22 pm Post subject:

I just updated and tested my example: