Using multiple ssh keys in different git projects and accounts

SSH besides standard configuration where we define what host uses which key and user can have advanced features. Let’s check the feature that allows to specify different ssh keys for the same host (github.com) but for different projects and users.

Generate SSH keys add them to you local machine and to remote git server

This is standard flow, check this post for full details: Sign git commits with GPG key

Update ~/.ssh/config:

Let’s say we have 2 users, that have different github accounts:

• superhacker
• admin

For both of them we need to create 2 section in ssh config, the difference is that after defining the hostname we also define a username.

Based on this username configure at github repo, appropriate ssh key will be used for ssh protocol when working with git

Host github.com-superhacker
User git
Hostname github.com
PreferredAuthentications publickey
IdentityFile ~/.ssh/github_superhacker_rsa

Host github.com-admin
User git
Hostname github.com
PreferredAuthentications publickey
IdentityFile ~/.ssh/github_admin_rsa

Add ssh keys to local agent

$ ssh-add ~/.ssh/github_superhacker_rsa
$ ssh-add ~/.ssh/github_admin_rsa

Test connection

$ ssh-keyscan github.com
$ ssh-keyscan github.com >> ~/.ssh/known_hosts
$ ssh -T git@github.com-superhacker
$ ssh -T git@github.com-admin

Working with 1st repo:

$ git clone git@github.com:superhacker/project1.git
$ git config user.name "superhacker"
$ git config user.email "superhacker@gmail.com"

Other option:

[remote "origin"]
        url = git@github.com-superhacker:superhacker/project1.git

Same content is shown in .git/config in project folder

[core]
        repositoryformatversion = 0
        filemode = true
        bare = false
        logallrefupdates = true
        ignorecase = true
        precomposeunicode = true
[remote "origin"]
        url = git@github.com:superhacker/project1.git
        fetch = +refs/heads/*:refs/remotes/origin/*
[branch "main"]
        remote = origin
        merge = refs/heads/main
[user]
        name = superhacker
        email = superhacker@gmail.com

All commits of this repo will be done under user superhacker and signed with key github_superhacker_rsa

Workings with 2nd repo:

$ git clone git@github.com:admin/project1.git
$ git config user.name "admin"
$ git config user.email "admin@gmail.com"

Same content is shown in .git/config in project folder

[core]
        repositoryformatversion = 0
        filemode = true
        bare = false
        logallrefupdates = true
        ignorecase = true
        precomposeunicode = true
[remote "origin"]
        url = git@github.com:admin/project1.git
        fetch = +refs/heads/*:refs/remotes/origin/*
[branch "main"]
        remote = origin
        merge = refs/heads/main
[user]
        name = admin
        email = admin@gmail.com

All commits of this repo will be done under user admin and signed with key github_admin_rsa