Give file permissions back to root

Question

I accidentally typed out this command, not knowing exactly what it did:

sudo chown -R user:user /

Now when I type ls -la /, it shows that user has permission to all directories (before it showed root only).

How do I revert it back to root?

Answer 1

This is messed up very badly.

For starters:

cd /
chown root:root -R bin boot cdrom etc initrd.img* lib lib64 lost+found mnt opt root  run sbin srv tmp usr var vmlinuz*  
# essentially everything except home and media
chown root:root home media # we don't want to recursively chown here.

I assume you have a root shell open somewhere. If not, try pkexec chown, since sudo won't work when /etc/sudoers has incorrect permissions/owners.

Then there are various folders in /var whose correct owners you'll have to set, but that depends on which programs you have installed and which services you need to run.

If you're not able to run a command, or some other errors happen, try this from a bootable live USB (after mounting the root partition somewhere and replacing cd / with the path of the mount point).

Note that I have skipped a few directories, such as sys, proc, as these are directories populated by the kernel.