I'm trying to set up a Raspberry Pi to run BitTorrent Sync to back up my files to an external hard drive, but I'm running into some frustrating issues.

First, I need to set up the USB hard drive to auto-mount on boot, because the power frequently goes out where I live. So, I added a line to /etc/fstab

/dev/sda1   /media/josiah    vfat    defaults   0   0

I rebooted, and it mounted the drive, but then btsync couldn't write to it. So, I did a little reading and found that you have to specify the user option, so I tried this;

/dev/sda1   /media/josiah    vfat    defaults,user   0   0

That didn't seem to work either, so I tried specifying all of the defaults manually

/dev/sda1   /media/josiah    vfat    rw,auto,user,async,suid,dev,exec    0   0

I thought it was working, but then btsync started complaining again that it couldn't write to the drive, and when I tried to unmount it as a normal user it said that only a super user can unmount the drive.

That's confusing to me, since I thought that's what the user option was for. What am I missing, or doing wrong?

4 Answers 4


You can do a chmod after you mounted the partition, but that wouldn't be persistent accross reboots.

You should try this fstab line:

/dev/sda1   /media/josiah    vfat    user,umask=0000   0   0

Or this mount options:

mount -t vfat -ouser,umask=0000 /dev/sda1 /media/josiah

That will make the mounted partition world readable and writable.

If you need a less permissive setup, you should create a new group and mount as follows:

mount -t vfat -ouser,gid=1010,umask=0007 /dev/sda1 /media/josiah

It assumes your new group's gid is 1010. All users that need access to the mountpoint will need to be added to the new group.


Edit the permissions for the mount directory.

In your case, chmod 777 /media/josiah ought to do the trick quite nicely.

  • Which line should I be using in /etc/fstab to auto mount the drive? Commented Jul 10, 2013 at 3:55
  • Also, that command still isn't allowing me to write to the drive. Commented Jul 10, 2013 at 3:58
  • have you tried mounting the directory manually and attempted a basic copy/write with a standard user?
    – Scandalist
    Commented Jul 10, 2013 at 4:02
  • Manually works fine. I'm trying to get it to work automatically on boot. Commented Jul 10, 2013 at 4:04
  • 2
    @JosiahSprague : Scandalists answer is not correct. You can't chmod a vfat mount. You can for NTFS if it's configured correctly. You will have to set the permission in the fstab. Refs: arstechnica.com/civis/viewtopic.php?f=16&t=724261 ... forums.justlinux.com/…
    – Michael M
    Commented Sep 29, 2013 at 5:39

The "user" option just let the user mount the device, it has no relation to access rights for the file.

As in gnp answer, see "uid"/"gid" and "umask" option.


FWIW: “when I tried to unmount it as a normal user it said that only a super user can unmount the drive. That's confusing to me, since I thought that's what the user option was for.”

User option means that only the user that mounted a filesystem can unmount it again. In your case, it seems that the drive was mounted during the startup, before you login – it means it was a super user mount. If any user should be able to unmount it, then use users instead of user in the fstab line. For more details, see man mount and/or man fstab.

(The solution of the problem itself was already explained – to make the drive all users writable, use umask/dmask/fmask options in fstab, eventually combined with uid/gid options. Again, man mount and/or man fstab will help. Chmod on vfat is really impossible, as a fat filesystem simply knows nothing about access rights.)

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