Intro to SSH for relative newbies

10 Nov 2015 I have an app running on an Amazon EC2 instance, and it requires an SSH key to access it. Previously, I had to access it by navigating to the folder containing my private key pem file, then running ssh -p 2222 -i private_key.pem -A ubuntu@www.example.com.

Let’s break this down a bit.

-p 2222 - the port that my server runs on
-i private_key.pem - use an Identity File (SSH key) and specify the name
-A - use ForwardAgent to allow my public keys to pass through to the AWS server (important if I want to be able to access Github or some other service while SSH-ed into the server)
ubuntu@www.example.com - username (ubuntu) and server HostName (www.example.com)

This is all fine and dandy, but it’s a pain to remember. So, my next step to simplify this was setting up a terminal alias in ~/.bash_aliases

alias my-server-ssh="cd ~ && ssh -p 2222 -i private_key.pem -A ubuntu@www.example.com"

This lets me simply run my-server-ssh from whatever directory I’m in on the terminal and automatically login to my server. However, once I have a couple more servers to juggle, it starts to get troublesome keeping track of these things. It’s also problematic if I want to use a tool like Capistrano for deployment.

Here’s where setting up the ~/.ssh/config file comes in handy. I opened this file in my text editor, and entered this info:

Host my-server
    HostName www.example.com
    Port 2222
    User ubuntu
    IdentityFile "~/.ssh/private_key.pem"
    ForwardAgent yes

Once I save, I can now use my computer’s built in SSH manager to access my server by running the command ssh my-server. Then, in a tool like Capistrano, I can plug this line into my config file:

server 'my-server', roles: %w{app web}

It will read my ~/.ssh/config file, find the configuration for host my-server and SSH in.

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Big ups to Nerderati for the helpful explanation on SSH config.