Limit concurrent session in linux

Check the file /etc/security/limits.conf. 

* hard maxlogins 4    (The asterisk means global. 4 is the number of concurrent logins.)


Eg.
         @users  hard  maxlogins  1

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Thanks
System Admin
TIST

Disconnect users in Linux....

who -u


kill [pid of user]

Change ownership of a directory in Linux

chown -R client1:users /home/client1

chown -R username somedir

chgrp -Rv usergroup somedir