Add custom ssh key for github

The recommended way of accessing (cloning/fetching/pushing code) github repos via command line is to generate ssh key pair (private key and public key) and setting the public key content in the Github’s settings.

Generating key pair

ssh-keygen -t ed25519 -C "Your EMail"

Provide the file name this time.

Enter file in which to save the key (/Users/sabyasachi.ghosh/.ssh/id_ed25519): github

Once can use the default key generated (without any file name specified) globally for all git hosts, however there is a chance you are using two different git servers and want to keep the keys separate. This becomes really important in cases you are using the same machine for work and personal git repos.

laptop % ls -ltr ~/.ssh/
total 56
-rw-------@ 1 sabyasachi.ghosh  staff   432 Oct 27 13:20 id_ed25519
-rw-r--r--@ 1 sabyasachi.ghosh  staff   113 Oct 27 13:20 id_ed25519.pub
-rw-------@ 1 sabyasachi.ghosh  staff   411 Nov  9 10:16 github
-rw-r--r--@ 1 sabyasachi.ghosh  staff   102 Nov  9 10:16 github.pub
-rw-r--r--@ 1 sabyasachi.ghosh  staff    84 Nov  9 10:38 config
-rw-------@ 1 sabyasachi.ghosh  staff  1523 Nov  9 10:39 known_hosts

In this case you have to explicitly provide the key generated specifically for a git server in ~/.ssh/config file. For example

Host github.com
  AddKeysToAgent yes
  UseKeychain yes
  IdentityFile ~/.ssh/github

Now you can test the connection (even before attempting to clone)

ssh -T [email protected]

Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added 'github.com' (ED25519) to the list of known hosts.
Hi neilghosh! You've successfully authenticated, but GitHub does not provide shell access.

Now we can go ahead and go all git operation.