Force logout a user

Question

I When I logged into the machine as root and typed who to see which users are logged in, I found somebody else too logged in as root

devuser   pts/0        2011-11-18 09:55 (xxx.xxx.xxx.xxx)
root      pts/1        2011-11-18 09:56 (xxx.xxx.xxx.xxx)
testuser  pts/2        2011-11-18 14:54 (xxx.xxx.xxx.xxx)
root      pts/3        2011-11-18 14:55 (xxx.xxx.xxx.xxx)

How can I force a root user at pts/3 to logout?

Solution 1

You terminate a session by killing its parent process, called the session leader. Find out which process it is with:

ps -dN|grep pts/3

Solution 2

To kill and logout a user, you can send KILL signal. Type the following command:

# skill -KILL -u vivek

Check these links for more information:

• http://www.cyberciti.biz/tips/howto-linux-kill-and-logout-users.html
• http://www.serverschool.com/server-security/how-to-kill-a-user-session-on-a-linux-server/

Comments

[Xenoactive]

You've got an even bigger issue to resolve. Disable direct root logins, and force your users to use sudo.

[Mithun Sreedharan]

what if I am logged in as the same user?

[Niranjan Singh]

these command works for super user.. you must log in as super user.. network operating systems follow this approach for security.. i think those links are also saying same to login as admin..

[Mithun Sreedharan]

And then kill that process using kill -9 <processid>

[SK23]

@Mithun You can use -t <terminal name> instead of -u.

[GnP]

@pjammer It's not that you "weren't root after all". Consider what you are doing. You are logging in as user joe, this creates a shell process, say it's bash with pid 123. Then you spawn the sudo process which spawns a su process, which spawns a login shell for user root. On that shell you are calling a command that kills all processes belonging to user joe, including PID 123 and all it's children: sudo, su, the login shell for root. Once you understand what it is you are doing you'll see it's not possible by definition. Of course, there are alternatives as Melebius pointed out.

[EM0]

The cyberciti link now says "WARNING! These tools are obsolete, unportable and it is here due to historical reasons. Consider using the killall, pkill, and pgrep commands instead as follows." pkill -KILL -u vivek works just as well.

[TheDudeAbides]

Just kill <pid> should be sufficient, right? Please save the kill -9s for badly misbehaving processes that don't respond to INT, HUP, or TERM; it's kind of like the difference between shutting down a computer using the OS's menu system vs. pulling the plug on the computer.

[Torrien]

@TheDudeAbides I would try to use -15 for the TERM signal. It works for me.