$ skill -STOP -u user1

To resume already halted user1

$ skill -CONT -u user1

To kill and logout user1

$ skill -KILL -u user1

To kill and logout all users

$ skill -KILL -v /dev/pts/*

To stop 3 users user1, user2, user3
$ skill -STOP user1 user2 user3

regards,

T.Dhanasekar