The who command is one of the first command we use when troubleshooting common Linux related issues to make sure how many users are logged in and what they are doing. In this post we will see on how to use this command to get more information about who logged into your machine at present and what they are doing.With this command we can get following basic information.
1)How many users logged into a machine
2)From which server they logged in
3)When is the system booted
4)Which run level the system is booted. see more.. http://www.linuxnix.com/8-who-command-examples-in-to-linuxsolarisaix/