How to manage multiple Git accounts

Set up SSH keys for multi git accounts

1. Generate SSH keys

Generate multiple SSH keys one for work and one for personal. You can have many multiple ssh key-pair for multiple git accounts as you want.

cd ~/.ssh
ssh-keygen -t ed25519 -C "[email protected]" -f "id_ed25519_git"
ssh-keygen -t ed25519 -C "[email protected]" -f "id_ed25519_git_opn"

-t: Specific key type ed25519 or rsa

-C: Specific comment

You will get 2 pairs of the SSH key-pair.

Private keys will name id_ed25519_git and id_ed25519_git_opn.

Public keys will name id_ed25519_git.pub and id_ed25519_git_opn.pub.

2. Add public keys to the Git Provider (Gihub/Gitlab/etc)

You have already generated the key pairs, Now let the Git provider know your SSH public key.

Copy the public key pbcopy < ~/.ssh/id_ed25519_git_opn.pub (avoid copy your private key)
Go to your git provider ssh setup panel https://github.com/settings/keys for Gihub https://gitlab.com/-/profile/keys for Gitlab
Paste the SSH public key and the Title you want
Generate a signature using the giving token from provider echo -n 'token' | ssh-keygen -Y sign -n <name-space> -f id_ed25519_git.pub you can replace the namespace
Apply the signature to the provider to verify

Next, do another one for the Github personal pbcopy < ~/.ssh/id_ed25519_git.pub to your personal git provider.

3. Creating the SSH Config

The SSH Config will help you choose the SSH key when you try to sign in to a different host.

touch config
vi config

Create and edit the ssh config file at ~/.ssh/config

# Personal Account
Host github.com
   HostName github.com
   User git
   IdentityFile ~/.ssh/id_ed25519_git

# Work Account
Host github.com-jirawat-opn
   HostName github.com
   User git
   IdentityFile ~/.ssh/id_ed25519_git_opn

4. Set remote url

The setup was done. Now you can clone or update your git URL.

git clone [email protected]:work_account/repo.git

# or the set origin url for the current repo

git remote set-url origin [email protected]:work_account/repo.git

For the personal git you can just do the normal way

git clone [email protected]:personal_account/repo.git

# or the set origin url for the current repo

git remote set-url origin [email protected]:personal_account/repo.git

Set up GPG keys for multi git accounts (optional)

1. Generate a new GPG key

gpg --default-new-key-algo ed25519 --gen-key

and follow the prompt dialog.

2. Generate public key

First, list all your GPG private keys

gpg --list-secret-keys --keyid-format=long

The key id will follow the key method ed25519/

for example

sec   ed25519/3AA5C34371567BD2 2021-11-23 [SC]
uid                 [ultimate] Jirawat Boonkumnerd <[email protected]>
ssb   cv25519/127C6D28828B3B8C 2021-11-23 [E]

in this case the key id is 3AA5C34371567BD2

3. Add a new uid and email to the key

3.1 gpg --edit-key 3AA5C34371567BD2 to edit the key

3.2 adduid to add a new uid then fill your uid info and the another email

3.3 uid to show uid list

3.4 uid 2 to choose uid 2

3.5 trust to trust the uid type 5 to ultimate trust then y

3.6 save the save edit

4. Add public keys to the Git Provider

export the public key

gpg --armor --export 3AA5C34371567BD2

Copy your GPG key and add to the Git provider. It may the same page as the SSH key.

If it ask to verify by a token, you can generate signature by using

echo "token" | gpg -a --default-key 3AA5C34371567BD2 --detach-sig

5. Set up git config to use the GPG key

git config --global user.signingkey 3AA5C34371567BD2

You can also edit the ~/.gitconfig

or for specific repo

git config user.signingkey 3AA5C34371567BD2

craete a sign commit

git commit -S -m 'test'

to make it automatically sign commits

git config --global commit.gpgsign true

Reference

https://docs.github.com/