Linux – w command not showing users when not root

linuxpermissionsshellssh

I have multiple users logged on my server (ubuntu 12.10), with ssh. None of them has root privileges.

If I log in with my admin account and type

w

the resulting output is:

17:21:05 up 10 days, 18:47,  3 users,  load average: 0,09, 0,09, 0,08
USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT

Now if I type

sudo w

the resulting output is:

17:22:00 up 10 days, 18:48,  3 users,  load average: 0,04, 0,07, 0,07
USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT
admin    pts/0    XX.XX.XX.XX      16:15    4.00s  0.34s  0.06s sshd: admin [priv]
user1    pts/1    XX.XX.XX.XX      17:04   17:40   0.17s  0.17s -sh
user2    pts/2    XX.XX.XX.XX      14:31    2:50m  0.16s  0.16s -sh

Why is that?

Unrelated question: what does the first line, last column (sshd: admin [priv]) mean in this case? I read it's relative to sshd privilege separation threads, but that's not clear to me what the line precisely means.

Best Answer

You have a security mechanism that doesn't allow w to iterate over /proc/$pid/ and get the information necessary for this. I think the grsecurity kernel hardening does this by default.

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