Return root ownership to /usr

Question

I stupidly ran this command in Ubuntu 18.04:

sudo chown -R $USER:$USER /usr

Now I want to undo this but when I run:

chown -R root:root /usr

I get this error:

operation not permitted

And I can't run a sudo command and gives me this error:

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

How can I fix this?

@Kulfy The accepted answer to that question suggests to completely reinstall Ubuntu, which is overkill. — Jos, May 16 '19 at 08:30
Iam facing a deadline isn't any other way except reinstalling? — fjahan, May 16 '19 at 08:36
@Jos In what way is the accepted answer "overkill"? I checked and there are 13 different [UID,GID] pairs on my /usr. — waltinator, May 16 '19 at 13:33
@waltinator Hm. All four of my systems have only /usr/bin/at as the exception (daemon:daemon). But I realize I simply assumed that the whole of /usr was owned by root. — Jos, May 16 '19 at 14:44
@Jos It's difficult to determine and replicate the original schema, I think. — Kulfy, May 16 '19 at 15:33

score 2 · Answer 1 · answered May 16 '19 at 08:26

2

You have to boot in maintenance (recovery) mode or with live CD / USB and mount the root volume.

answered May 16 '19 at 08:26

FedKad

Can you give more details of how to fix this in recovery mode? – fjahan May 16 '19 at 08:30
See the link I provided. After step 9, enter your chown -R root:root /usr and reboot. – Jos May 16 '19 at 08:59
That won't fix the files owned by root, but in one of the cricket, crontab, dip, mail, messagebus, mlocate, postdrop, shadow, ssh, tty or utmp groups. Many strange failures are in your future. – waltinator May 16 '19 at 17:24

1 Answers1