Log Out a Specific User (KILL)

carlosinfl · 08-28-2007, 02:32 PM

I created a test user simply with the "adduser" command and he is the only user on the machine except root obvioulsy but now I am trying to delete his account and it tells me that he is logged in so I can't delete him. I assumed my question was very basic so I did a Google search on how to log out a curently logged in user with out rebooting the box.

I found a page that referenced the "skill" command which I assumed was sig kill and I tried the following suggestions but it does not work. What am I doing wrong or is the problem the Linux box for some strange reason?

Code:

[root@lt2fs0 ~]# man skill
[root@lt2fs0 ~]# skill -KILL -u emery
[root@lt2fs0 ~]# users
emery root
[root@lt2fs0 ~]# skill -KILL -v /dev/pts/*
[root@lt2fs0 ~]# users
emery root

XavierP · 08-28-2007, 03:02 PM

http://www.cyberciti.biz/tips/howto-...out-users.html may be of help

carlosinfl · 08-29-2007, 07:15 AM

That was the exact page I pulled the commands from in my original thread for help. I don't understand why I get no response from this...

Perhaps I need to call Redhat support...?

colucix · 08-29-2007, 09:09 AM

In which way the user has looged in? If through ssh, you should be able to kill its login shell, e.g.

Code:

[root@linux ~]# who
colucix  :0           2007-08-27 09:58
colucix  pts/1        2007-08-29 12:26 (:0.0)
colucix  pts/2        2007-08-29 15:52 (name.domain.it)
[root@linux ~]# ps -u colucix | grep bash$
1420 pts/1    00:00:00 bash
7888 pts/2    00:00:00 bash
[root@linux ~]# kill -9 7888
[root@linux ~]#

Here the user I want to force logout has been allocated on pts/2 and the login shell is bash.
If the user logged in from a terminal, you can kill the X starting process, e.g.

Code:

[root@linux ~]# ps -u colucix
 7714 ?        00:00:00 gnome-session
 7774 ?        00:00:00 ssh-agent
 7777 ?        00:00:00 dbus-launch
 7778 ?        00:00:00 dbus-daemon-1
 7783 ?        00:00:00 gconfd-2
 ...
[root@linux ~]# kill -9 7714
[root@linux ~]#

A quite brutal approach, but it works for me!

carlosinfl · 08-29-2007, 09:14 AM

Thanks for lending some info!

Perhaps I am doing something wrong...

Code:

[root@lt2fs0 home]# who
root     pts/0        Aug 29 08:13 (10.1.1.204)
emery    pts/1        Aug 28 15:07
[root@lt2fs0 home]# ps -u emery | grep bash$
ERROR: User name does not exist.
********* simple selection *********  ********* selection by list *********
-A all processes                      -C by command name
-N negate selection                   -G by real group ID (supports names)
-a all w/ tty except session leaders  -U by real user ID (supports names)
-d all except session leaders         -g by session OR by effective group name
-e all processes                      -p by process ID
T  all processes on this terminal     -s processes in the sessions given
a  all w/ tty, including other users  -t by tty
g  OBSOLETE -- DO NOT USE             -u by effective user ID (supports names)
r  only running processes             U  processes for specified users
x  processes w/o controlling ttys     t  by tty
*********** output format **********  *********** long options ***********
-o,o user-defined  -f full            --Group --User --pid --cols --ppid
-j,j job control   s  signal          --group --user --sid --rows --info
-O,O preloaded -o  v  virtual memory  --cumulative --format --deselect
-l,l long          u  user-oriented   --sort --tty --forest --version
-F   extra full    X  registers       --heading --no-heading --context
                    ********* misc options *********
-V,V  show version      L  list format codes  f  ASCII art forest
-m,m,-L,-T,H  threads   S  children in sum    -y change -l format
-M,Z  security data     c  true command name  -c scheduling class
-w,w  wide output       n  numeric WCHAN,UID  -H process hierarchy

colucix · 08-29-2007, 09:50 AM

Hmmm... really strange! What about

Code:

ps -lft pts\/1

to see what processes (if any) are associated to the pseudo-terminal of the (supposed) logged user?

pwc101 · 08-29-2007, 10:02 AM

You could search for all processes not owned by root, and see if there's something still running from your test user:

Code:

ps -ef | grep -v root

Assuming it finds something, kill it and then try deleting the user again.

carlosinfl · 08-29-2007, 10:11 AM

Quote:

Originally Posted by colucix

Hmmm... really strange! What about

Code:

ps -lft pts\/1

to see what processes (if any) are associated to the pseudo-terminal of the (supposed) logged user?

Code:

[root@lt2fs0 ~]# ps -lft pts\/1
ERROR: TTY could not be found.

colucix · 08-29-2007, 10:53 AM

It sounds as - for some reason - the file /var/run/utmp has been not properly updated and all the applications that require a check for logged users are tricked (the who and users commands take info from this file). However it looks like the user emery has been deleted and pts/1 unallocated, since the ps command does not find them! You can easily verify these issues.
Furthermore, you can try the command last to see if emery is really still logged in, since in this case the file containing info is /var/log/wtmp. For example

Code:

[root@linux ~]# last
...
colucix  pts/5        :0.0             Wed Aug 29 15:43 - 15:50  (00:06)
colucix  pts/7        :0.0             Wed Aug 29 12:26   still logged in
...

Here, the first row tells about a closed session, the second one tells about a still open session. Also, the check suggested by pwc101 is worth a try.