sudo: unknown user: root - please help!

I was using terminal, and vim, to edit my /etc/passwd file and got a ‘broken pipe’ message in the window. I have CentOS

When I logged back onto the server I tried to access the file again using sudo.

I got the following: sudo: unknown user: root sudo: unable to initialize policy plugin

I can open the file without sudo, and notice there are a couple of lines that were at beginning of the list that have disappeared - Luckily I’ve been keeping a ‘diary’ of what I’ve been doing over the past couple of months so have a print-out of the contents of passwd.

The missing lines are: root:x:0:0:root:/root:/bin/bashing bin:x:1:1:bin:/bin:/sbin/nologin:

I’m able to copy the missing lines back but the file won’t save.

At the bottom of the window I see: “/etc/passwd” [readonly] 29L, 1454C

When I hit ‘ESC :wq’ I see: E45: ‘readonly’ option is set (add ! to override)

I’ve tried all manner of ways including ‘:w !sudo tee %’ to try to get this file to save but to no avail.

I also discovered another warning that momentarily displayed then disappeared. I managed to get a screen shot of it.

E325: ATTENTION Found a swap file by the name “var/tmp/passwd.swp” … While opening file “/etc/passwd”

(1) Another program may be editing the same file. …

(2) An edit session for this file crashed. If this is the case, use “:recover” or “vim -r /etc/passwd” to recover the changes (see “:help recovery”). If you did this already, delete the swap file “/var/tmp/passwd.swp” to avoid this message.

Can anyone give me any suggestions please? I’ve spent all day trying to figure it out but I’m fairly new to all this.