Root Directory ‘/’ Locked After Using Chmod – Permissions Issue

chmodpermissionsroot

I accidentally used

sudo chmod 3 /

which gives a execute and write permission to the root directory, while deleting the read permission. How can I recover from this, I cannot even use sudo now.

Best Answer

First, try other suggestions while still logged in, because mine requires a reboot. If you see that no other attempt works, you should reboot and start a live DVD/USB session.

Mount the root partition and edit the /etc/fstab as root. You will need to run a command similar to this:

gksu gedit /media/ubuntu/sda1/etc/fstab

Please adjust the path to the correct mount point you used.

In the file, locate the line belonging to the root partition, it should look similar to the following:

UUID=[...] /               ext4    errors=remount-ro 0       1

Try to enforce "universal" permissions by adding the proper parameter:

UUID=[...] /               ext4    umask=000,errors=remount-ro 0       1

Reboot and try to log in again. You should be able to fix the permissions with:

sudo chmod 755 /

Warning

After the fix, remember to revert the changes made to /etc/fstab, otherwise anyone will be able to access and modify every system file.

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