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Simplifying SSH connections with a 
config file
Before we leave the topic of OpenSSH, there's another trick that benefits convenience, 
and that 
is the creation of a local configuration file for SSH. This file must be stored 
in the 
.ssh
 directory of your home directory, and be named 
config
. The full path for 
this file in my case looks like this:
/home/jay/.ssh/config

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This file 
doesn't exist by default, but if it's found, SSH will parse it whenever you use 
the client and you'll be able to benefit from it. Go ahead and open this file in your 
text editor, such as 
nano
:
nano /home/your_username/.ssh/config
This 
config
 file allows you to type configuration for servers that you connect 
to often, which can simplify the 
ssh
 command automatically. The following are 
example contents from such a file that will help me illustrate what it does:
host myserver 
    Hostname 192.168.1.23 
    Port 22 
    User jdoe 
 
Host nagios 
    Hostname nagios.mynetwork.org 
    Port 2222 
    User nagiosuser 
In the example contents, I have two hosts outlined, 
myserver
 and 
nagios
. For each, 
I've identified a way to reach it by name or IP address (the 
Hostname
 line), as well as 
the 
Port
 and 
User
 account to use for the connection. If I use 
ssh
 to connect to either 
Host
 by the name I outlined in this file, it will use the values I have stored there, for 
example:
ssh nagios 
That command is a lot shorter than if I set all the options manually. Considering I 
have a 
config
 file for SSH, that command is essentially the same as if I identified the 
connection details manually, which would've been the following:
ssh -p 2222 [e-mail] 
I'm sure you can see how much simpler it is to type the first command than the 
second. With the 
config
 file for SSH, I can have some of those details automatically 
applied. Since I've outlined that my 
nagios
 server is located at 
nagios.mynetwork.
org
, its SSH user is 
nagiosuser
, and it's listening on port 
2222
, it will automatically 
use those values even though I only typed 
ssh nagios
. Furthermore, you can also 
override this entry as well. If you provide a different username when you use the 
ssh
 
command, it will use that instead of what you have written in the 
config
 file.

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Connecting to Networks