How To Set Up SSH Keys
This mini-tutorial assumes that you have the knowledge of SSH, remote servers (CS and Cluster worlds at Earlham, to be specific) and basic Unix environment. Let's begin.
- Step One - Create the RSA key pair
user$ ssh-keygen -t rsa -b 4096
-t specifies the type of key to create. You can check the possible options in the help. Since we are creating an RSA key, we will use -t rsa. -b flag specifies the number of bits for the key. It is common to use 2048 or 4096 as possible values for this flag. Press enter for all questions, you may change the defaults, but it is preferred not to. Also, it is common to leave the passphrase empty. The entire point of ssh keys is to make login easier and faster, and passphrase defeats the purpose, I believe. So, your public key will be saved in ~/.ssh/id_rsa.pub and private key will be saved in ~/.ssh/id_rsa.
- Step Two - Copy the public id to remote host.
user$ ssh-copy-id user@remote.host
You can install ssh-copy-id if it doesn't exist already. OR, manually copy it as follows
user$ cat ~/.ssh/id_rsa.pub | ssh user@remote.host "mkdir -p ~/.ssh && chmod 700 ~/.ssh && cat >> ~/.ssh/authorized_keys"
Note that, user@remote.host should be replaced with appropriate terms.
- Step Three - Create a config file (Optional)
Now that you have the key setup, and know how to use vi editor, let's create a config file. Personally, I enjoy the ability to type `ssh tools` and let ssh config take over, instead of typing `ssh user@tools.cs.earlham.edu`. For that,
user$ vi ~/.ssh/config
Enter the insert mode
Host $hostname_you_want_to_use HostName $complete_hostname User $username
$ sign indicates variable, so you should replace your username with $username, and you can use tools in place of $hostname_you_want_to_use, tools.cs.earlham.edu in place of $complete_hostname.
Similarly, you can add more hosts to this config file with a line space between each. For e.g., a file with multiple configs might look like:
Host host1 HostName remote.host.1 User username Host host2 HostName remote.host.2 User username Host host3 HostName remote.host.3 User username
