Generating SSH keys (OSX)

This guide will step you through the process of generating a keypair on Mac OSX and uploading it to GitHub

Generating an SSH key on OSX is a fairly straightforward process. First and foremost, open up Terminal.app. You can usually find it at /Applications/Utilities.

Backup and remove existing keys

Unless this is your first time setting up ssh or git on your computer, you should double check that keys do not already exist. If they do you can either use the existing key(s) or remove them. In either case, you should make a backup of the keys.

$ cd ~/.ssh
$ ls
config  id_rsa  id_rsa.pub  known_hosts
$ cd ..
$ mkdir ssh_key_backup
$ cp .ssh/id_rsa* ssh_key_backup
$ rm .ssh/id_rsa*

Here we have an existing keypair, id_rsa and id_rsa.pub, which we’ve copied into ~/ssh_key_backup before removing. By default, ssh will use keys in ~/.ssh that are named id_rsa, id_dsa or identity.

Generating a key

If you have an existing keypair you wish to use, you can skip this step.

Now that we’re certain ssh won’t use an existing key, it’s time to generate a new keypair. Lets make an RSA keypair:

$ ssh-keygen -t rsa -C "tekkub@gmail.com"
Generating public/private rsa key pair.
Enter file in which to save the key (/Users/tekkub/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /Users/tekkub/.ssh/id_rsa.
Your public key has been saved in /Users/tekkub/.ssh/id_rsa.pub.
The key fingerprint is:
01:0f:f4:3b:ca:85:d6:17:a1:7d:f0:68:9d:f0:a2:db tekkub@gmail.com
The key's randomart image is:
+--[ RSA 2048]----+
|     .+   +      |
|       = o O .   |
|        = * *    |
|       o = +     |
|      o S .      |
|     o o =       |
|      o . E      |
|                 |
|                 |
+-----------------+

At the first prompt you can just hit enter to generate the key with the default name. You should use a good passphrase with your key. See Working with SSH key passphrases for more details on why you should use a passphrase and how to avoid re-entering it every time you use your key.

Note: If you don’t use the default key names, or store your keys in a different path, you will need to run ssh-add path/to/my_key so that ssh knows where to find your key.

Adding the key to your GitHub account

Now launch your browser and open the account page. In the “SSH Public Keys” section click “add another public key”, then paste your public key into the “key” field. If you leave the title blank the key comment (your email) will be used for the title.

Make sure you use the public key (id_rsa.pub in our example), and do not add any newlines or whitespace inside the key. To ensure you copy the key correctly, you can copy the key directly into the clipboard from Terminal.app:

$ cat ~/id_rsa.pub | pbcopy

Testing things out

Testing if our new key works is simple:

$ ssh git@github.com
Hi tekkub! You've successfully authenticated, but GitHub does not provide shell access.
Connection to github.com closed.

If you do not get the “successfully authenticated” message, check out the troubleshooting guide.