You need to use the following commands:
a] who or w command – Show who is logged on and what they are doing.
b] pkill command – Kill user session and forcefully logout of the system.
c] shutdown command – Arranges for the system to be brought down in a safe way.
Examples
Use the who command to see list of logged in users as follows:
# w
OR
# who
Sample outputs:
root pts/0 Jul 29 13:53 (10.1.6.120) nixcraft pts/1 Jul 29 12:30 (10.1.6.121) sailee pts/2 Jul 29 12:33 (10.1.6.121)
To force and logout nixcraft and sailee user, enter:
# pkill -KILL -u nixcraft
# pkill -KILL -u sailee
Alternatively, just try bash and friends kung-fu and save time:
### warning must be run as root or via sudo ### who | awk '!/root/{ cmd="/sbin/pkill -KILL -u " $1; system(cmd)}' |
OR
### warning must be run as root or via sudo ### ### Safe version :) ### who | awk '$1 !~ /root/{ cmd="/sbin/pkill -KILL -u " $1; system(cmd)}' |
Finally, you can shutdown the system as follows:
# shutdown -h now
Instead of killing all users one by one you can type the following shutdown command with the warning message:
# shutdown -h +10 "Server is going down for maintenance in 10 minute. Please save ALL your work ASAP and logout of the system."
Please note that this method will not work with ftp/smtp/pop3 and all other user accounts on the server. I recommend that you set maintenance windows for your server when network traffic is at a minimum or when users/client computers were not engaged in other activities on the server. For example, week-end or the period between midnight and 3:00 a.m. can be set as maintenance windows for your system.
Recommended readings
- See man pages – who(1),w(1),pkill(1),shutdown(8)
Thank you….I enjoyed reading this article tonight :D….
Thanks. it’s useful.
Can someone explain what this kungfu method is doing. Specially system(cmd)}’ and why $1 is added in in the beginning of second Kungfu command
Couldn’t you just send out the message and change the runlevel?
I have done maintenance of UNIX systems for a long time and I have always done it after 6 PM during the week or on weekends; however, I always send a wall message which is advertised to every user letting them know about the system maintenance and to save everything they want and log out, say…30 minutes before the schedule shutdown. I also coordinate with the other departments; so they take proper action. Then, when the time comes to take action I use init 0 which does an orderly shutdown immediately.
All you need is a wall message an init 0.
That was, exactly, my thought. Glad to know it works in practice!