I can login as root user on Debian or Ubuntu/RHEL/CentOS Linux based system. I need to log everyone off (all ssh users) to install new kernel and/or hardware. How do I do this on Linux?

What is the best way to logout ALL USERS remotely over the ssh based session in Linux like operating systems?

 

You need to use the following commands:

a] who or w command – Show who is logging 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 bring 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)