what is ssh?

What is ssh?

SSH, or Secure Shell, is a protocol used to securely log onto remote systems. It is the most common way to access remote Linux and Unix-like servers.

ssh commands:

If your username on the remote system is the same as your username on your local system:

                              #ssh remote_host

remote_host means ip address or domain name that you are trying to connect to.

If your username is different on the remote system, you can specify it by using this syntax:

                     #ssh remote_username@remote_host

How to Set Up SSH on Linux systems

Edit the configuration file of sshd

#vim /etc/ssh/sshd_config

It may be a good idea to change this to a non-standard port to help obscure your server from random port scans. If you do change your port, we will show you how to connect to the new port later on.

  HostKey /etc/ssh/ssh_host_rsa_key

 HostKey /etc/ssh/ssh_host_dsa_key
 HostKey /etc/ssh/ssh_host_ecdsa_key

If you are having difficulties with SSH, increasing the amount of logging may be a good way to discover what the issue is.

LoginGraceTime 120    (LoginGraceTime specifies how many seconds to keep the connection alive without successfully logging in.)

PermitRootLogin yes     (PermitRootLogin selects whether root is allowed to log in.)

StrictModes yes      (strictModes is a safety guard that will refuse a login attempt if the authentication files are readable by everyone.)

 

Determine if the SSH server service sshd is running.

                         #service sshd status

If the SSH server service sshd is not running, start this daemon.
                          #service sshd restart

If the service is running, no further action is required.