:: [DNG] unstable ownership of mount p…
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Author: Haines Brown
To: dng
Subject: [DNG] unstable ownership of mount point
I want to add a mount point owned by user to /media

$ mkdir /media/working

  $ ls -la /media | grep working
    drwxr-xr-x  2 haines haines 4096 Mar  2 08:05 working

I mount a USB key on that mount point. I plug it in and do:

    # dmesg
    sdc: sdc1
    sd 7:0:0:0: [sdc] Attached SCSI removable disk
    FAT-fs (sdc1): Volume was not properly unmounted. Some data may
        be corrupt. Please run fsck.

    The error because I originally pulled the key without first
    unmounting it. Assume error irrelevant. 

I mount the key:

    $ sudo mount /dev/sdc1 /media/working

Now comes the trouble

    $ ls -la /media
    total 32
    drwxr-xr-x  6 haines haines 4096 Mar  2 08:14 .
    drwxr-xr-x 28 root   root   4096 Feb 16 14:29 ..
    drwxr-xr-x  2 haines haines 4096 Jan  8 09:22 cdrom
    drwxr-xr-x  2 root   root   4096 Dec 22 12:50 Elements
    drwxrwxr-x  2 root   users  8192 Dec 31  1969 usbhd-sdc1
    drwxrwxr-x  2 root   users  8192 Dec 31  1969 working

The mount command creates the strange usbhd-sdc1 mount point
and mounts /dev/sdc1 on it as well as on the working mount
point. /dev/sdc1 is mount twice:

  $ mount | grep sdc
  /dev/sdc1 on /media/usbhd-sdc1 type vfat
  /dev/sdc1 on /media/working type vfat

Also the owner of the working directory by mounting /dev/sdc1 becomes

In /etc/group are the lines:


I replace alt with haines.

I now umount the two directories. Doing causes the ownership of the
/media/working mount point to revert to owner haines:haines:
ownship of working reverts:

    $ ls -la /media | grep working
    drwxr-xr-x  2 haines haines 4096 Mar  2 08:05 working

I delete usbhd-sdc1 and remount /dev/sdc1 on /media/working
This time /usbhd-sdc1 mount point does not appear, but the
working mount point changes its ownership to root:root rather than to

I cannnot do

    $ sudo chown haines:haines working
    chown: changing ownership of 'working': Operation not permitted

I suppose this is because it is mounted, but if I unmount, haines
again becomes the owner.

Two questions. In group, should alt be member of users group or
should the member be user haines?

How can the mount command change ownership of a mount point? User owns
its parent directory:

    $ ls -la | grep media
    drwxr-xr-x   5 haines haines  4096 Mar  2 08:38 media


     Haines Brown