ssh (secure shell)
ssh (SSH client) is a program for logging into a remote machine and for executing commands on a remote machine. It is intended to replace rlogin and rsh, and provide secure encrypted communications between two untrusted hosts over an insecure network. X11 connections and arbitrary TCP ports can also be forwarded over the secure channel.
ssh connects and logs into the specified hostname (with optional user name). The user must prove his/her identity to the remote machine using one of several methods depending on the protocol version used (see below).
Install ssh on Ubuntu/Debian
Run following command in terminal
# apt-get install openssh-server openssh-client
Start and stop the ssh service
# service ssh start & # service ssh stop
Automatically start the service at boot
# chkconfig ssh on
Check status of ssh
# service ssh status
Check port 22 is opened or not
Run following command
# netstat -tulnp | grep :22
Output should be like this
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 9657/sshd tcp 0 0 :::22 :::* LISTEN 9657/sshd
Install ssh on CentPS/RHEL/Fedora
click here