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lonix
Asked: 2018-05-11 00:41:17 +0800 CST

Mount device as RW for root and RO for everyone else

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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?

fstab permissions mount read-only

1 Answers

  1. 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

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