Mount device as RW for root and RO for everyone else

I have a device I want to mount for root with full permissions and for everyone else as readonly. The man page tells me this is possible.

So:

• sudo mkdir /mnt/foo
• sudo mkdir /mnt/fooReadOnly
• sudo chmod 700 /mnt/foo (rw for root only)
• sudo chmod 444 /mnt/fooReadOnly (ro for everyone)
• ensure device /dev/sdaX is mounted as /mnt/foo

Then I did what the man page suggested:

• sudo mount --bind /mnt/foo /mnt/fooReadOnly
• sudo mount -o remount,bind,ro /mnt/foo /mnt/fooReadOnly

Now to test:

• ls /mnt/foo --> Permission denied ...CORRECT
• sudo ls /mnt/foo works ..CORRECT
• ls /mnt/fooReadOnly --> Permission denied ...INCORRECT?

How do I fix this?

Also, how do I add this to /etc/fstab so that it will automatically remount on boot?

1 Answer

First, unmount fooReadOnly with
sudo umount /mnt/fooReadOnly

Then, change the permission of fooReadOnly to 555
sudo chmod 555 /mnt/fooReadOnly
This is needed because entering a directory requires execute privilege.

Finally, remount fooReadOnly
sudo mount -o remount,bind,ro /mnt/foo /mnt/fooReadOnly