Best way to Manage SSH Hosts and Private Keys

As a system administrator, you deals regularly with multiple remote systems. You need to SSH systems multiple times during your work. Many of remote Linux server you have access through password a many of them you have access through private key. So this can be more typical to manage all of them.

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This article will help you to properly organize your ssh server details with key files.

Configuration File Syntax:

We can add multiple ssh hosts details to ~/.ssh/config file. Edit configuration file in your favorite editor like vi, vim or nano.

$ vi ~/.ssh/config  

The syntax will be like below.

Host <NICK_NAME>
     HostName <IP ADDRESS OF REMOTE>
     IdentityFile <PATH TO PRIVATE FILE>
     User <LOGIN AS USERNAME>
     Port <SSH PORT TO USE>
     LocalForward <LOCAL PORT>  <REMOTE_LOCATION:PORT>

1. Add First SSH Host

For example we have our first SSH host is running a PHP development web server with details nick name as php-web1, user root, port 22 and accessible through password. Add the following content in configuration file.

Host php-web1
     HostName 192.168.1.100
     User root

Now try SSH as following command.

$ ssh php-web1

2. Add Second SSH Host

Our second host server (php-web2) is accessible with ssh key-pair with user root on default port 22. Add the following content in configuration file.

Host php-web2
     HostName  192.168.1.101
     IdentityFile ~/.ssh/php-web2.pem
     User root

Now try SSH as following command.

$ ssh php-web2

3. Add Third SSH Host

Our third ssh host server (php-db1) is running on port 2222, accessible though key-pair with user ubuntu. Add the following content in configuration file.

Host php-db1
     HostName 192.168.1.110
     Port 2222
     IdentityFile ~/.ssh/php-db1.pem
     User ubuntu

Now try SSH as following command.

$ ssh php-db1

4. Setup Forwarding with SSH

In this setup we need to forward our local system port 3306 to remote servers (php-db1) hosts on port 3306 . Add the following content in configuration file.

Host php-db1-mysql-tunnel
     HostName 192.168.1.110
     Port 2222
     IdentityFile ~/.ssh/php-db1.pem
     LocalForward 3306 127.0.0.1:3306

Now try SSH as following command.

$ ssh php-db1-mysql-tunnel

Final Configuration File

Your final configuration file ~/.ssh/config will look like below.

Host php-web1
     HostName 192.168.1.100
     User root

Host php-web2
     HostName  192.168.1.101
     IdentityFile ~/.ssh/php-web2.pem
     User root

Host php-db1
     HostName 192.168.1.110
     Port 2222
     IdentityFile ~/.ssh/php-db1.pem
     User ubuntu

Host php-db1-mysql-tunnel
     HostName 192.168.1.110
     Port 2222
     IdentityFile ~/.ssh/php-db1.pem
     LocalForward 3306 127.0.0.1:3306