sed to change userid in /etc/passwd to zero

Question

I am trying to change user monitor uid in /etc/passwd , but below gives me an error:

sed -s /etc/passwd <<-"EOF" /^\(monitor:[^:]*:\)[0-9]*:[0-9]*:/s//\10:0:/ w q EOF

... This sounds like a tremendously bad idea if you accidentally succeed. What are you actually trying to accomplish? — Shadur-don't-feed-the-AI
– Shadur-don't-feed-the-AI, Commented Oct 10, 2017 at 14:11
Why do you "need" to change userid to 0? I bet if you explained the problem you are really trying to solve, somebody would come up with a better idea of how to solve it. — NickD
– NickD, Commented Oct 10, 2017 at 14:19
How have you added the user to the admin group? With groupmod? — Raman Sailopal
– Raman Sailopal, Commented Oct 10, 2017 at 14:43

hschou · Accepted Answer · 2017-10-10 15:53:34Z

If for some reason usermod -u can not be used:

sed -i -e 's/^\(monitor:[^:]\):[0-9]*:[0-9]*:/\1:0:0:/' /etc/passwd

Please note it is /\1:0 not /\10: as this would be parameter 10.

But having monitor to have uid 0 might not be a good idea at all.

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