Messed up /usr/bin permissions

General system Newbie
1

While installing Ruby/Jekyll and following ‘advice on internet’ I messed up the permissions on /usr/bin/, so now can not use sudo command.

sudo: /usr/bin/sudo must be owned by uid 0 and have the setuid bit set

StackExchange topics suggest a system reinstall to fix the permission issues.

Would a reinstall, with keeping (not formatting) the root ‘/’ and ‘home’ partitions solve the issue, or do I need to format the partitions?

I really do not want to lose the system settings and all, as I reinstalled the system just a couple of weeks ago (and switched to KDE).

Thanks in advance!

2

You should be able to fix this without reinstalling the system.

Please share the output of “ls -l /usr/bin/*”

Can you login with root user and root password, like with “su -” ? If not, you would need to boot with a live iso and mount your “/” filesystem there to fix it.

3

Here’s an extract of the log:

-rwxr-xr-x 1 reinis root     51K aug  4 14:32  /usr/bin/su*
-rwxr-xr-x 1 reinis root    5,0K nov 15 18:45  /usr/bin/substrings.pl*
-rwxr-xr-x 1 reinis root    2,0K dec 24 23:04  /usr/bin/su-c_wrapper*
-rwsr-xr-x 1 reinis root    243K nov  5 12:08  /usr/bin/sudo*
lrwxrwxrwx 1 reinis root       4 nov  5 12:08  /usr/bin/sudoedit -> sudo*
-rwxr-xr-x 1 reinis root    237K nov  5 12:08  /usr/bin/sudo_logsrvd*
-rwxr-xr-x 1 reinis root     84K nov  5 12:08  /usr/bin/sudoreplay*
-rwxr-xr-x 1 reinis root    119K nov  5 12:08  /usr/bin/sudo_sendlog*
-rwxr-xr-x 1 reinis root     39K aug  4 14:32  /usr/bin/sulogin*

I don’t have a ‘root’ user, thus the su root command gives an su: Authentication failure error.

4

If all you did was change the ownership, switch to a TTY, login as root and run:

chown -R root /usr/bin

That isn’t a particularly good idea in general but given the state of your system it shouldn’t make things worse. In my system, everything inside /bin is owned by root.

In general, if you have a tutorial/guide/person telling you to change permissions in /bin, find a different one. You should never need to do that.

1 Like
5

OK, will try that. How do I switch to TTY? I’m running KDE and systemd-boot (no grub), if that is relevant.

Yeah, will definitely remember this lesson on changing permissions, based on some online tutorial, without deeper research.

6

Press ctrl+alt+f3 after the system has booted.

7

Thanks for your help! Now the sudo command works. Though not sure if something else has not been messed up still.

I also had to do chmod u+s /usr/bin/sudo to apply the setuid bit to the file.

8

Don’t change permissions and owners on files installed by the package manager, not even on aur packages. It could make your system vulnerable, not a big deal on personal computers, but on servers it can be really bad. Most of the times you need to add your user to a group that owns the files in the package to use it.

2 Likes
9

That is probably what I should have done to begin with. Will now better the next time.

10

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