Sorry, sudo must be setuid root.

Problem:

$ sudo su –

Sorry, sudo must be setuid root.

Solution:

Login to the server as root and do the following:

# chown root:root /usr/bin/sudo

# chmod 4111 /usr/bin/sudo

# ls -ld /usr/bin/sudo

---s--x--x 2 root root 174436 Sep 15  2010 /usr/bin/sudo

To kill / delete remote login session in Linux

Solution:            

Check login user list:

# users

# last

# who

# w

Or,

First locate the process, for example, user logged in using ssh.

# ps -ef | grep ssh

Or,

Check process ID of users

              # ps -fu username

Kill the process    

# kill -HUP parent_processid

Or,

# skill -STOP -u username

# skill -CONT -u username

# skill -KILL -u username

Command to kill and logout all users as below

# skill -KILL -v /dev/pts/*

Or,

# pkill -STOP -u username
# pkill -CONT -u username
# pkill -KILL -u username