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Abhishek Gowda
Abhishek Gowda

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Maintaining multiple ssh keys for git

#git #ssh #programming #beginners

I like to maintain multiple git accounts, one for Github and other for gitlab. I use gitlab to host my much private data in it. And only try to host that I feel safe to be online on with Github.
I will walk you through how to maintain multiple ssh key that could be used for different git accounts.
This is more specific on using ssh for git authentication.

Generation of SSH keys.

For windows install git-bash, to get working with git on windows. Once this is done. We generate keys using ssh-keygen

ssh-keygen -t ed25519 -C "personal_email@gitlab.com" -f ~/.ssh/id_ed25519_gitlab

ssh-keygen -t ed25519 -C "personal_email@github.com" -f ~/.ssh/id_ed25519_github
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This generates public and private keys. This keys are generally present in home directory (even in windows) under .ssh directory

Adding keys to ssh-agent 

eval "$(ssh-agent -s)"
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Add the keys to

ssh-add ~/.ssh/id_ed25519_gitlab
ssh-add ~/.ssh/id_ed25519_github
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Why I need to add these? For 1, you do not want to enter your phase key again, every time you start a new session. It would be wise to add these to rc (Run Command) files, like .bashrc and .zshrc.

Update .ssh/config file

This is the important step. Now we need to tell which keys to use when we connect to the remote host.
This is a property file, be careful with the spacings. Use # for adding comments

# Github
Host github.com
    HostName github.com
    User git
    IdentityFile ~/.ssh/id_ed25519_github

# Gitlab
Host gitlab.com
    HostName gitlab.com
    User git
    IdentityFile ~/.ssh/id_ed25519_gitlab
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There is other way of seeing as well, adding context to the Host itself. Let say you are working on a machine provided by an organization and want to just check your own repository now and then, but don't want to use keys and user-names of the organization. We can do the following

# Work
Host github.com-work
    HostName github.com
    User git
    IdentityFile ~/.ssh/id_ed25519_github_work

# Personal
Host github.com-personal
    HostName github.com
    User git
    IdentityFile ~/.ssh/id_ed25519_github_personal
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Now when we access the repository we provide context.

Update public keys to services

Now we have created our keys, we need to publish the public key to the service, so it used used when authenticating.
Copy the public key of github, you will see .pub at the end of the keys.

cat ~/.ssh/id_ed25519_github
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Now go to Github -> Settings -> SSH and GPG keys

Now copy the public key of gitlab

cat ~/.ssh/id_ed25519_gitlab
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Now go to Gitlab -> Preferences -> SSH Keys

Verify connection

Once the keys are added, it is good practice to check the connections.

ssh -T git@github.com 
ssh -T git@gitlab.com
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Make sure to use right Host, if you have setup with "-work" and "-personal", use them

ssh -T git@github.com-personal
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This should display the username, the keys were added to.

Using correct host names

Now when I use gitlab I will do something like

git clone git@gitlab.com:my-name/repo.git
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But when we have multiple github accounts, we could use the context I mentioned before to identify which ssh-key to use, like

git clone git@github.com-work:yourcompany/repo.git
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Updating git config

With the above steps, we are complete with setting up ssh. Which is used for authentication.
Now we would want to update gitconfig. Run

git config user.name
git config user.email
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commands. This will give the global name and email used. We would need to update our local name and local email, as they would want to reflect in the git logs.
Make sure you are in the repository where you want the name to be updated.

git config --local user.name "<USER_NAME>"
git config --local user.email "<private_email@example.com>"
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Leave any questions or suggestions you want to answer or improve on.

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