Setting up multiple account on git

You must have a default key for SSH connections between other hosts and can setup multiple SSH keys for each VCS account you have. You can use your personal key as a default key also.

In case you just to setup SSH connection and signing of commits for a single account skip to the bottom

Github

You can switch between two accounts on Github

Steps

1. Click on the profile icon

2. Click on Add Account to add your secondary account

Now you can switch between both profiles easily

Git

In order to use two profiles, you need to create two main directories. For example one personal and one work. Now keep in mind to clone/create repos accordingly. Personal repos must go into personal folder and similarly for work repos

Steps

1. Generate SSH keys

ssh-keygen -t ed25519 -C "your_personal_email@example.com" -f ~/.ssh/<personal_key>

ED25519 are recommended for security and performance, but RSA with a sufficient length is also a valid alternative:

ssh-keygen -t rsa -b 4096 -C "your_personal_email@example.com" -f ~/.ssh/<personal_key>

-C is for adding a comment, it can be anything but it will be helpful to know the email associated with your account
-f is to define a filename, and creating a key with a descriptive name will help you remember which key is used for which user/remote

Do this for you work mail

ssh-keygen -t rsa -b 4096 -C "your_personal_email@example.com" -f ~/.ssh/<work_key>

You can optionally add a parapharse

To update the passphrase for your SSH keys:

ssh-keygen -p -f ~/.ssh/<private_key>

1. Adding the SSH Keys

First start the SSH agent

eval "$(ssh-agent -s)"

and then

ssh-add -K ~/.ssh/<personal_key>

ssh-add -K ~/.ssh/<work_key>

The -K flag in ssh-add is specific to macOS, and it adds the passphrase of the private key to the keychain. This means that once you've added the key to the keychain, you won't be asked for the passphrase again when using the key.

1. Edit you SSH config

If you don't have a SSH config inside ~/.ssh, then create one using touch ~/.ssh/config

Edit it to the following

Host *
  AddKeysToAgent yes
  UseKeychain yes
  IdentityFile ~/.ssh/<personal_key>

Host *
  AddKeysToAgent yes
  UseKeychain yes
  IdentityFile ~/.ssh/<work_key>

Here we are setting Host to * for every key because we will use Git configs to select the appropriate SSH key based on profiles, which will give us a bit more flexibility (more on that later).

1. Add public keys to hosts To copy public key of the generated keys use this

 pbcopy < ~/.ssh/<personal_key>.pub

The public key has been now copied to clipboard, you can use it in your desired VCS.

You can add the same SSH public key as a signing key also, you just have to specify that this this key is also used as a signing key in you VCS. Incase, you want to create another ssh key, follow the same steps and edit the necessary config options

1. Updating your gitconfigs

This is how the the file structure should look like

/<some_folder>/
|__work/
    |_.gitconfig-work
|__personal/
    |_.gitconfig-personal

# ~/<path_to_personal_folder>/.gitconfig.pers

[user]
email = your_personal_email@example.com
name = Your Name
signingkey = ~/.ssh/<personal_key>.pub


[core]
sshCommand = "ssh -i ~/.ssh/<personal_key>"

# ~/<path_to_work_folder>/.gitconfig.work

[user]
    email = your_work_email@google.com
    name = Your Name
    signingkey = ~/.ssh/<work_key>.pub


[core]
    sshCommand = "ssh -i ~/.ssh/<work_key>"

Here we tell Git which key to use by making explicit the SSH command (the -i option is for specifying an identity file or key). This gives us more control, for instance, imagine you have multiple accounts on the same host (like github.com), if you were using the SSH config file to use different SSH keys, you would need to create and remember an arbitrary prefix like first.github.com and then remember to use that domain each time you want to clone a repository with this account. This can be too much trouble.

Updating your global gitconfig, which is present at ~/.gitconfig , i.e the home directory

[init]
    defaultBranch = main

[gpg]
    format = ssh

[commit]
    gpgsign = true

[includeIf "gitdir:~/<path_to_work_folder>/"]
    path = ~/<path_to_work_folder>/.gitconfig-work

[includeIf "gitdir:~/<path_to_personal_folder>/"]
    path = ~/<path_to_personal_folder>/.gitconfig-personal

[core]
    excludesfile = ~/.gitignore

If you just have one profile

Follow till Step 4, the update your global .gitconfig.

[init]
    defaultBranch = main

[gpg]
    format = ssh

[commit]
    gpgsign = true

[user]
    email = your_personal_email@google.com
    name = Your Name
    signingkey = ~/.ssh/<personal_key>.pub

[core]
    sshCommand = "ssh -i ~/.ssh/<personal_key>"
    excludesfile = ~/.gitignore

Notes

• These steps are macOS specific in some cases, and will also work for Linux system.

• For windows, the steps are same just commands are different.

• This are my preferred config settings