How to force user to logout in Linux
You might need to forcefully let logged-in users in your system log out when doing some administrative work or when a rogue or unidentified user is acting maliciously.
If you have physical access to the server, you could unplug the network connection and reboot the system. That might not always be possible, such as when working on remotes servers via SSH. To forcefully log a user out of the system, you'll need to kill processes owned by the user to terminate whatever session the user currently has.
Steps to kick out user in Linux:
List currently logged in user in the system.
$ who user :0 2021-01-23 16:23 (:0) shakir pts/1 2021-01-23 16:31 (192.168.111.1)
List all processes owned by the user you want to kick out of the system.
$ ps -U shakir PID TTY TIME CMD 2086 ? 00:00:00 systemd 2087 ? 00:00:00 (sd-pam) 2093 ? 00:00:00 pulseaudio 2097 ? 00:00:00 tracker-miner-f 2106 ? 00:00:00 dbus-daemon 2126 ? 00:00:00 gvfsd 2135 ? 00:00:00 gvfsd-fuse 2136 ? 00:00:00 gvfs-udisks2-vo 2149 ? 00:00:00 gvfs-mtp-volume 2153 ? 00:00:00 gvfs-goa-volume 2157 ? 00:00:00 goa-daemon 2177 ? 00:00:00 goa-identity-se 2186 ? 00:00:00 gvfs-afc-volume 2194 ? 00:00:00 gvfs-gphoto2-vo 2248 ? 00:00:00 sshd 2249 pts/1 00:00:00 bash
Kill user's terminal or other session processes.
$ sudo kill 2249 [sudo] password for user:
bash is normally the process if the user is connected via SSH.
Alternatively, kill all processes owned by the user.
$ sudo pkill -u shakir
Check if user still logged in.
$ who user :0 2021-01-23 16:23 (:0)
Force process termination if the user is still logged in after a while.
$ sudo pkill -9 -u shakir