Manage multiple SSH keys on one machine

Today I got a problem when adding SSH key to my new Gitlab account. I was trying to add a new key, but I got an error Fingerprint has already been taken. Gitlab doesn't allow you to add the same key for multiple accounts.

After a few searching, I found the solution quite simple.

Firstly, you need to generate a new ssh key and save it in a different file name. E.g ~/.ssh/id_rsa_company (Suppose you're using RSA).

Then, edit ~/.ssh/config and add the following configuration:

# Company account
Host gitlab.company
  HostName gitlab.com
  PreferredAuthentications publickey
  IdentityFile ~/.ssh/id_rsa_company
 
# Personal account
Host gitlab.personal
  HostName gitlab.com
  PreferredAuthentications publickey
  IdentityFile ~/.ssh/id_rsa_personal

Now, this is the important thing that you should keep in mind whenever cloning a repository.

For example, let's clone the repository named demo. The usual repository URL will be something like:

git@gitlab.com:username/demo.git

However, you've already configured the host name for gitlab.com, so you should modify the above repository URL as:

git@gitlab.company:username/demo.git

Similarly, you have to modify the clone URL of the repository in the personal account depending on the alias provided in the configuration file.