[git] Multiple github accounts on the same computer?

Trying to work on both my actual "work" repos, and my personal repos on git hub, from my computer.

The work account was set up first, and everything works flawlessly.

My personal account, however cannot seem to push to my personal repo, which is set up under a different account/email.

I've tried copying my work key up to my personal account, but that throws an error, because of course a key can be only attached to one account.

How can I push/pull to and from both accounts from their respective github credentials?

Got my private repo working using SSH key pairs. This was tested on git for Windows.

Source: https://docs.github.com/en/free-pro-team@latest/github/authenticating-to-github/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent

A. Generate public and private key pairs

1. Start git bash
2. Run ssh-keygen -t ed25519 -C "[email protected]"
3. When you're prompted to "Enter a file in which to save the key," press Enter to accept the default.
4. Press enter for a blank passphrase.
5. Start the ssh agent: eval $(ssh-agent)
6. Add private key to ssh agent and store the passphrase: ssh-add ~/.ssh/id_ed25519

B. Add SSH keys to GitHub account

1. Copy the public key to the clipboard: clip < ~/.ssh/id_ed25519.pub
2. On GitHub, go to Profile -> Settings -> SSH Keys -> New SSH Key
3. Give a title. E.g. "Windows on MacBook Pro"
4. Paste the key and hit "Add SSH Key".

C. Test SSH connection

1. Enter: ssh -T [email protected]
2. Hit "yes" for any warning message.
3. It should show: "Hi username!..." indicating a successful test.

D. Setup local repository to use SSH keys

1. Change email and user name:

git config user.email [email protected]
git config user.name github_username

2. Update remote links to use git. First list remote URI's:

git remote -v
git remote set-url origin [email protected]:github_username/your-repo-name.git

E. Test

git remote show origin

Getting into shape

To manage a git repo under a separate github/bitbucket/whatever account, you simply need to generate a new SSH key.

But before we can start pushing/pulling repos with your second identity, we gotta get you into shape – Let's assume your system is setup with a typical id_rsa and id_rsa.pub key pair. Right now your tree ~/.ssh looks like this

$ tree ~/.ssh
/Users/you/.ssh
+-- known_hosts
+-- id_rsa
+-- id_rsa.pub

First, name that key pair – adding a descriptive name will help you remember which key is used for which user/remote

# change to your ~/.ssh directory
$ cd ~/.ssh

# rename the private key
$ mv id_rsa github-mainuser

# rename the public key
$ mv id_rsa.pub github-mainuser.pub

Next, let's generate a new key pair – here I'll name the new key github-otheruser

$ ssh-keygen -t rsa -b 4096 -f ~/.ssh/github-otheruser

Now, when we look at tree ~/.ssh we see

$ tree ~/.ssh
/Users/you/.ssh
+-- known_hosts
+-- github-mainuser
+-- github-mainuser.pub
+-- github-otheruser
+-- github-otheruser.pub    

Next, we need to setup a ~/.ssh/config file that will define our key configurations. We'll create it with the proper owner-read/write-only permissions

$ (umask 077; touch ~/.ssh/config)

Open that with your favourite editor, and add the following contents

Host github.com
  User git
  IdentityFile ~/.ssh/github-mainuser

Host github.com-otheruser
  HostName github.com
  User git
  IdentityFile ~/.ssh/github-otheruser

Presumably, you'll have some existing repos associated with your primary github identity. For that reason, the "default" github.com Host is setup to use your mainuser key. If you don't want to favour one account over another, I'll show you how to update existing repos on your system to use an updated ssh configuration.

Add your new SSH key to github

Head over to github.com/settings/keys to add your new public key

You can get the public key contents using: copy/paste it to github

$ cat ~/.ssh/github-otheruser.pub
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAACAQDBVvWNQ2nO5...

Now your new user identity is all setup – below we'll show you how to use it.

Getting stuff done: cloning a repo

So how does this come together to work with git and github? Well because you can't have a chicken without and egg, we'll look at cloning an existing repo. This situation might apply to you if you have a new github account for your workplace and you were added to a company project.

Let's say github.com/someorg/somerepo already exists and you were added to it – cloning is as easy as

$ git clone github.com-otheruser:someorg/somerepo.git

That bolded portion must match the Host name we setup in your ~/.ssh/config file. That correctly connects git to the corresponding IdentityFile and properly authenticates you with github

Getting stuff done: creating a new repo

Well because you can't have a chicken without and egg, we'll look at publishing a new repo on your secondary account. This situation applies to users that are create new content using their secondary github account.

Let's assume you've already done a little work locally and you're now ready to push to github. You can follow along with me if you'd like

$ cd ~
$ mkdir somerepo
$ cd somerepo
$ git init

Now configure this repo to use your identity

$ git config user.name "Mister Manager"
$ git config user.email "[email protected]"

Now make your first commit

$ echo "hello world" > readme
$ git add .
$ git commit -m "first commit"

Check the commit to see your new identity was used using git log

$ git log --pretty="%H %an <%ae>"
f397a7cfbf55d44ffdf87aa24974f0a5001e1921 Mister Manager <[email protected]>

Alright, time to push to github! Since github doesn't know about our new repo yet, first go to github.com/new and create your new repo – name it somerepo

Now, to configure your repo to "talk" to github using the correct identity/credentials, we have add a remote. Assuming your github username for your new account is someuser ...

$ git remote add origin github.com-otheruser:someuser/somerepo.git

That bolded portion is absolutely critical and it must match the Host that we defined in your ~/.ssh/config file

Lastly, push the repo

$ git push origin master

Update an existing repo to use a new SSH configuration

Say you already have some repo cloned, but now you want to use a new SSH configuration. In the example above, we kept your existing repos in tact by assigning your previous id_rsa/id_rsa.pub key pair to Host github.com in your SSH config file. There's nothing wrong with this, but I have at least 5 github configurations now and I don't like thinking of one of them as the "default" configuration – I'd rather be explicit about each one.

Before we had this

Host github.com
  User git
  IdentityFile ~/.ssh/github-mainuser

Host github.com-otheruser
  HostName github.com
  User git
  IdentityFile ~/.ssh/github-otheruser

So we will now update that to this (changes in bold)

Host github.com-mainuser
  HostName github.com
  User git
  IdentityFile ~/.ssh/github-mainuser

Host github.com-otheruser
  HostName github.com
  User git
  IdentityFile ~/.ssh/github-otheruser

But now any existing repo with a github.com remote will not work with this identity file. But don't worry, it's a simple fix.

To update any existing repo to use your new SSH configuration, update the repo's remote origin field using set-url -

$ cd existingrepo
$ git remote set-url origin github.com-mainuser:someuser/existingrepo.git

That's it. Now you can push/pull to your heart's content

SSH key file permissions

If you're running into trouble with your public keys not working correctly, SSH is quite strict on the file permissions allowed on your ~/.ssh directory and corresponding key files

As a rule of thumb, any directories should be 700 and any files should be 600 - this means they are owner-read/write-only – no other group/user can read/write them

$ chmod 700 ~/.ssh
$ chmod 600 ~/.ssh/config
$ chmod 600 ~/.ssh/github-mainuser
$ chmod 600 ~/.ssh/github-mainuser.pub
$ chmod 600 ~/.ssh/github-otheruser
$ chmod 600 ~/.ssh/github-otheruser.pub

How I manage my SSH keys

I manage separate SSH keys for every host I connect to, such that if any one key is ever compromised, I don't have to update keys on every other place I've used that key. This is like when you get that notification from Adobe that 150 million of their users' information was stolen – now you have to cancel that credit card and update every service that depends on it – what a nuisance.

Here's what my ~/.ssh directory looks like: I have one .pem key for each user, in a folder for each domain I connect to. I use .pem keys to so I only need one file per key.

$ tree ~/.ssh
/Users/myuser/.ssh
+-- another.site
¦   +-- myuser.pem
+-- config
+-- github.com
¦   +-- myuser.pem
¦   +-- someusername.pem
+-- known_hosts
+-- somedomain.com
¦   +-- someuser.pem
+-- someotherdomain.org
     +-- root.pem

And here's my corresponding /.ssh/config file – obviously the github stuff is relevant to answering this question about github, but this answer aims to equip you with the knowledge to manage your ssh identities on any number of services/machines.

Host another.site
  User muyuser
  IdentityFile ~/.ssh/another.site/muyuser.pem

Host github.com-myuser
  HostName github.com
  User git
  IdentityFile ~/.ssh/github.com/myuser.pem

Host github.com-someuser
  HostName github.com
  User git
  IdentityFile ~/.ssh/github.com/someusername.pem

Host somedomain.com
  HostName 162.10.20.30
  User someuser
  IdentityFile ~/.ssh/somedomain.com/someuser.pem

Host someotherdomain.org
  User someuser
  IdentityFile ~/.ssh/someotherdomain.org/root.pem

Getting your SSH public key from a PEM key

Above you noticed that I only have one file for each key. When I need to provide a public key, I simply generate it as needed.

So when github asks for your ssh public key, run this command to output the public key to stdout – copy/paste where needed

$ ssh-keygen -y -f someuser.pem
ssh-rsa AAAAB3NzaC1yc2EAAAA...

Note, this is also the same process I use for adding my key to any remote machine. The ssh-rsa AAAA... value is copied to the remote's ~/.ssh/authorized_keys file

Converting your id_rsa/id_rsa.pub key pairs to PEM format

So you want to tame you key files and cut down on some file system cruft? Converting your key pair to a single PEM is easy

$ cd ~/.ssh
$ openssl rsa -in id_rsa -outform pem > id_rsa.pem

Or, following along with our examples above, we renamed id_rsa -> github-mainuser and id_rsa.pub -> github-mainuser.pub – so

$ cd ~/.ssh
$ openssl rsa -in github-mainuser -outform pem > github-mainuser.pem

Now just to make sure that we've converted this correct, you will want to verify that the generated public key matches your old public key

# display the public key
$ cat github-mainuser.pub
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAA ... R++Nu+wDj7tCQ==

# generate public key from your new PEM
$ ssh-keygen -y -f someuser.pem
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAA ... R++Nu+wDj7tCQ==

Now that you have your github-mainuser.pem file, you can safely delete your old github-mainuser and github-mainuser.pub files – only the PEM file is necessary; just generate the public key whenever you need it ^_^

Creating PEM keys from scratch

You don't need to create the private/public key pair and then convert to a single PEM key. You can create the PEM key directly.

Let's create a newuser.pem

$ openssl genrsa -out ~/.ssh/newuser.pem 4096

Getting the SSH public key is the same

$ ssh-keygen -y -f ~/.ssh/newuser.pem
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAACA ... FUNZvoKPRQ==

• Go to ~/.ssh
• Create a file named config(have no extension )

• Open config file & add below codes. (change according to your account)

  1. Account 1

     # account_1
     Host gitlab.com-account_1
     HostName gitlab.com
     User git
     PreferredAuthentications publickey
     IdentityFile ~/.ssh/id_rsa_account_1
     

  2. Account 2

     # Account2
     Host gitlab.com-Account2
     HostName gitlab.com
     User git
     PreferredAuthentications publickey
     IdentityFile ~/.ssh/id_rsa_Account2
     

  3. Account 3

     # Account_3
     Host github.com-Account3
     HostName github.com
     User git
     PreferredAuthentications publickey
     IdentityFile ~/.ssh/id_rsa_Account_3
     

• Add remote url as follows

  1. Account 1

     git remote add origin [email protected]_1:group_name/repo_name.git
     

  2. Account 2

     git remote add origin [email protected]:group_name/repo_name.git
     

  3. Account 3

     git remote add origin github.com-Account3:github_username/repo_name.git
     

Make sure that IdentityFile names are same as you created during ssh key generation.

Use HTTPS:

change remote url to https:

git remote set-url origin https://[email protected]/USERNAME/PROJECTNAME.git

and you are good to go:

git push

To ensure that the commits appear as performed by USERNAME, one can setup the user.name and user.email for this project, too:

git config user.name USERNAME
git config user.email [email protected]

Personal Directory .gitconfig using a personal access token

If you do not want to modify your host file, use SSH keys, or setup a .gitconfig for each repo, then you may use a personal .gitconfig that you basically include from the root level config. Given an OSX directory structure like

# root level git config
~/.gitconfig

# your personal repos under some folder like
../personal/
../home/
~/Dropbox/

Add a .gitconfig in your personal folder, such as ~/Dropbox/.gitconfig

[user]
    email = [email protected]
    name = First Last
[credential]
    username = PersonalGithubUsername
    helper = osxkeychain

In your root level .gitconfig add an includeIf section to source your personal config whenever you are in your personal directory. Any settings there will override the root config as long as the includeIf comes after the settings you want to override.

[user]
    email = [email protected]
    name = "First Last"
[credential]
    helper = osxkeychain
[includeIf "gitdir:~/Dropbox/**"]
    path = ~/Dropbox/.gitconfig

Try pushing to your personal repo or pulling from your private repo

git push
# prompts for password

When prompted enter either your personal password or, better yet, your personal access token that you have created in your account developer settings. Enter that token as your password.

Assuming you are already using git-credential-osxkeychain, your personal credentials should be stored in your keychain, so two github entries will show up, but with different accounts.

The details at http://net.tutsplus.com/tutorials/tools-and-tips/how-to-work-with-github-and-multiple-accounts/ linked to by mishaba work very well for me.

From that page:

$ touch ~/.ssh/config

Then edit that file to be something like this (one entry per account):

#Default GitHub
Host github.com
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_rsa

Host github-COMPANY
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_rsa_COMPANY

This answer is for beginners (none-git gurus). I recently had this problem and maybe its just me but most of the answers seemed to require rather advance understanding of git. After reading several stack overflow answers including this thread, here are the steps I needed to take in order to easily switch between GitHub accounts (e.g. assume two GitHub accounts, github.com/personal and gitHub.com/work):

1. Check for existing ssh keys: Open Terminal and run this command to see/list existing ssh keys ls -al ~/.ssh
   files with extension .pub are your ssh keys so you should have two for the personal and work accounts. If there is only one or none, its time to generate other wise skip this.
   
   - Generating ssh key: login to github (either the personal or work acc.), navigate to Settings and copy the associated email.
   now go back to Terminal and run ssh-keygen -t rsa -C "the copied email", you'll see:
   
   Generating public/private rsa key pair.
   Enter file in which to save the key (/.../.ssh/id_rsa):
   
   id_rsa is the default name for the soon to be generated ssh key so copy the path and rename the default, e.g. /.../.ssh/id_rsa_work if generating for work account. provide a password or just enter to ignore and, you'll read something like The key's randomart image is: and the image. done.
   Repeat this step once more for your second github account. Make sure you use the right email address and a different ssh key name (e.g. id_rsa_personal) to avoid overwriting.
   At this stage, you should see two ssh keys when running ls -al ~/.ssh again.
2. Associate ssh key with gitHub account: Next step is to copy one of the ssh keys, run this but replacing your own ssh key name: pbcopy < ~/.ssh/id_rsa_work.pub, replace id_rsa_work.pub with what you called yours.
   Now that our ssh key is copied to clipboard, go back to github account [Make sure you're logged in to work account if the ssh key you copied is id_rsa_work] and navigate to
   Settings - SSH and GPG Keys and click on New SSH key button (not New GPG key btw :D)
   give some title for this key, paste the key and click on Add SSH key. You've now either successfully added the ssh key or noticed it has been there all along which is fine (or you got an error because you selected New GPG key instead of New SSH key :D).
3. Associate ssh key with gitHub account: Repeat the above step for your second account.

4. Edit the global git configuration: Last step is to make sure the global configuration file is aware of all github accounts (so to say).
   Run git config --global --edit to edit this global file, if this opens vim and you don't know how to use it, press i to enter Insert mode, edit the file as below, and press esc followed by :wq to exit insert mode:

   [inside this square brackets give a name to the followed acc.] name = github_username email = github_emailaddress [any other name] name = github_username email = github_email [credential] helper = osxkeychain useHttpPath = true

Done!, now when trying to push or pull from a repo, you'll be asked which GitHub account should be linked with this repo and its asked only once, the local configuration will remember this link and not the global configuration so you can work on different repos that are linked with different accounts without having to edit global configuration each time.

You do not have to maintain two different accounts for personal and work. In fact, Github Recommends you maintain a single account and helps you merge both.

Follow the below link to merge if you decide there is no need to maintain multiple accounts.

https://help.github.com/articles/merging-multiple-user-accounts/

I found this gem to be very useful: sshwitch

https://github.com/agush22/sshwitch
http://rubygems.org/gems/sshwitch

It helps to switch out ssh keys. Remember to back up everything first!

Also to make sure that commits have the correct email address associated with them, I made sure that the ~/.gitconfig file had the proper email address.

Unlike other answers, where you need to follow few steps to use two different github account from same machine, for me it worked in two steps.

You just need to :

1) generate SSH public and private key pair for each of your account under ~/.ssh location with different names and

2) add the generated public keys to the respective account under Settings >> SSH and GPG keys >> New SSH Key.

To generate the SSH public and private key pairs use following command:

cd ~/.ssh
ssh-keygen -t rsa -C "[email protected]" -f "id_rsa_WORK"
ssh-keygen -t rsa -C "[email protected]" -f "id_rsa_PERSONAL"

As a result of above commands, id_rsa_WORK and id_rsa_WORK.pub files will be created for your work account (ex - git.work.com) and id_rsa_PERSONAL and id_rsa_PERSONAL.pub will be created for your personal account (ex - github.com).

Once created, copy the content from each public (*.pub) file and do Step 2 for the each account.

PS : Its not necessary to make an host entry for each git account under ~/.ssh/config file as mentioned in other answers, if hostname of your two accounts are different.

IntelliJ Idea has built-in support of that https://www.jetbrains.com/help/idea/github.html#da8d32ae

In case you don't want to mess with the ~/.ssh/config file mentioned here, you could instead run git config core.sshCommand "ssh -i ~/.ssh/custom_id_rsa" in the repo where you want to commit from a different account.

The rest of the setup is the same:

1. Create a new SSH key for the second account with ssh-keygen -t rsa -f ~/.ssh -f ~/.ssh/custom_id_rsa

2. Sign in to github with your other account, go to https://github.com/settings/keys , and paste the contents of ~/.ssh/custom_id_rsa.pub

3. Make sure you're using SSH instead of HTTPS as remote url: git remote set-url origin [email protected]:upstream_project_teamname/upstream_project.git

The easiest and straightforward approach (IMHO) - no config files not too much hassle

Just create another ssh key.

Let's say you have aa new work GitHub account, just create a new key for it:

sh-keygen -t rsa -C "email@work_mail.com" -f "id_rsa_work_user1"`

Now you should have the old one and the new one, to see them, run:

ls -al ~/.ssh

You need to run the above only once.

From now on, every time you want to switch between the two, just run:

ssh-add -D
ssh-add ~/.ssh/id_rsa_work_user1 #make to use this without the suffix .pub

In order the switch to the old one, run again:

 ssh-add -D
 ssh-add ~/.ssh/<previous id_rsa>

Option 0: you dont want to mess around with OS settings.. you just want to commit to a different github account with a different public key for one repo.

solution:

1. create the new key: ssh-keygen -t rsa -b 4096 -f ~/.ssh/alt_rsa

2. add the key to the keyset: ssh-add -K ~/.ssh/alt_rsa

3. copy and add the pub key to the github account: (see github instructions)

4. test the key with github: ssh -i ~/.ssh/alt_rsa T [email protected]

5. clone the repo using the git protocol (not HTTP): git clone git@github:myaccount...

6. in the cloned repo:

   git config core.sshCommand "ssh -i ~/.ssh/alt_rsa -F /dev/null"
   git config user.name [myaccount]
   git config user.email [myaccount email]

7. now you should be able to git push correctly without interferring with your everyday git account

If you happen to have WSL installed you can have two seperate git accounts - one on WSL and one in windows.

1. Navigate to the directory in which you want to push your changes to a different GitHub account.

2. Create a new SSH key in your terminal/command line.

   ssh-keygen -t rsa -C “your-email-address”

3. The following will then show:

   Generating public/private rsa key pair. Enter file in which to save the key (/home/your_username/.ssh/id_rsa):

Copy and paste the path followed by an identifiable name for the file:

/home/your_username/.ssh/id_rsa_personal

4) It will then ask you for the following:

Enter passphrase (empty for no passphrase):
Enter same passphrase again:

5) You can now type in the following command to see all the SSH keys you have on your local machine:

ls -al ~/.ssh

You should be able to see your new SSH key file. As you can see in my one I have both id_rsa_test and id_rsa_personal.pub.

drwx------  2 gmadmin gmadmin 4096 Nov 16 22:20 .
drwxr-xr-x 42 gmadmin gmadmin 4096 Nov 16 21:03 ..
-rw-------  1 gmadmin gmadmin 1766 Nov 16 22:20 id_rsa_personal
-rw-r--r--  1 gmadmin gmadmin  414 Nov 16 22:20 id_rsa_personal.pub
-rw-r--r--  1 gmadmin gmadmin  444 Nov  6 11:32 known_hosts

6) Next you need to copy the SSH key which is stored in id_rsa_personal.pub file. You can open this in text editor of your choice. I am currently using atom so I opened the file using the following command:

atom ~/.ssh/id_rsa_personal.pub

You will then get something similar to this:

ssh-rsa AAB3HKJLKC1yc2EAAAADAQABAAABAQCgU5+ELtwsKkmcoeF3hNd7d6CjW+dWut83R/Dc01E/YzLc5ZFri18doOwuQoeTPpmIRVDGuQQsZshjDrTkFy8rwKWMlXl7va5olnGICcpg4qydEtsW+MELDmayW1HHsi2xHMMGHlNv

7) Copy this and navigate to your GitHub account ? Settings ? SSH and GPG keys 8) Click on New SSH key. Copy the key, give it a title and add it. 9) Add key from terminal

ssh-add ~/.ssh/id_rsa_personal
Enter passphrase for /home/your_username/.ssh/id_rsa_personal: 

10) Configure user and password.

git config --global user.name "gitusername"
git config --global user.email "gitemail"

11) We are ready to commit and push now.

git init
git add .
git commit 
git push

Simpler and Easy fix to avoid confusions..

For Windows users to use multiple or different git accounts for different projects.

Following steps: Go Control Panel and Search for Credential Manager. Then Go to Credential Manager -> Windows Credentials

Now remove the git:https//github.com node under Generic Credentials Heading

This will remove the current credentials. Now you can add any project through git pull it will ask for username and password.

When you face any issue with other account do the same process.

Thanks

refer to image

Beside of creating multiple SSH Keys for multiple accounts you can also consider to add collaborators on each project using the same account emails and store the password permanently.

#this store the password permanently
$ git config --global credential.helper wincred

I have setup multiple accounts with different emails then put the same user and email on each account as one of the collaborators. By this way I can access to all account without adding SSH Key, or switching to another username, and email for the authentication.

If you have created or cloned another repository and you were not able to pull from origin or upstream adding the ssh key at that directory using the following command worked.

This is the error I was getting here:

Warning: Permanently added the RSA host key for IP address '61:fd9b::8c52:7203' to the list of known hosts.
Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

I used the following command, this works:

ssh-add ~/.ssh/id_rsa_YOUR_COMPANY_NAME

Manage multiple GitHub accounts on one Windows machine (HTTPS)

Let's say you previously use git on your machine and configure git global config file. To check it open the terminal and :

git config --global -e

It opens your editor, and you may see something like this:

[user]
    email = [email protected]
    name = Your_Name
...

And this is great because you can push your code to GitHub account without entering credentials every time. But what if it needs to push to repo from another account? In this case, git will reject with 403 err, and you must change your global git credentials. To make this comfortable lat set storing a repo name in a credential manager:

git config --global credential.github.com.useHttpPath true

to check it open config one more time git config --global -e you will see new config lines

[credential]
    useHttpPath = true
...

The is it. Now when you first time push to any account you will see a pop-up Screenshot_1

Enter specific for this repo account credentials, and this will "bind" this account for the repo. And so in your machine, you can specify as many accounts/repos as you want.

For a more expanded explanation you can see this cool video that I found on youtube: https://youtu.be/2MGGJtTH0bQ

another easier way is using multiple desktop apps, like what i am doing, using account A on Github desktop, while using account B on Github Kraken

You should and must not push to the project with some common credentials. Once starting on a new machine use the following steps to setup and use correctly your gitlab credentials:

• create the pubic / private ssh keys on the machine
• copy paste the public key to the gitlab/github ui interface ( anyone hinting how-to do via the cmd line gets a free beer ... )
• make sure you clone the repo via the git and not http url
• set the git alias to avoid constant typing of the same prefix to the git command
• during git commit ALWAYS use the author and e-mail flags
• use git as normal you would do it

All this as follows:

 # create the public / private key credentials on that specific machine
 ssh-keygen -t rsa -b 4096 -C "<<you>>@org.net" -f ~/.ssh/id_rsa.<<you>>.`hostname -s`

 # setup your public key in the gitlab ui 
 cat ~/.ssh/id_rsa.<<you>>.`hostname -s`

 # make sure you clone the repo via the git and not http url
 git clone [email protected]:org/some-repo.git

 # set the git alias to avoid constant typing of the repeating prefix to the git cmd
 alias git='GIT_SSH_COMMAND="ssh -i ~/.ssh/id_rsa.<<you>>.`hostname -s`" git'

 # during git commit ALWAYS use the author and e-mail flags
 git add --all ; git commit -nm "$git_msg" --author "YourFirstName YourLastName <[email protected]>"

 # use git as normal
 git fetch --all; git pull --all 

just figured this out for Windows, using credentials for each repo:

cd c:\User1\SomeRepo
git config --local credential.https://github.com.user1 user1
git config --local credential.useHttpPath true
git config --local credential.helper manager
git remote set-url origin https://[email protected]/USERNAME/PROJECTNAME.git

The format of credential.https://github.com. tells the credential helper the URL for the credential. The 'useHttpPath' tells the credential manager to use the path for the credential. If useHttpPath is omitted then the credential manager will store one credential for https://github.com. If it is included then the credential manager will store multiple credentials, which is what I really wanted.

I use shell scripts to switch me to whatever account I want to be "active". Essentially you start from a fresh start, get one account configured properly and working, then move the these files to a name with the proper prefix. From then on you can use the command "github", or "gitxyz" to switch:

# my github script
cd ~/.ssh

if [ -f git_dhoerl -a -f git_dhoerl.pub -a -f config_dhoerl ]
then
    ; 
else 
    echo "Error: missing new files"
    exit 1
fi 

# Save a copy in /tmp, just in case
cp id_rsa /tmp
cp id_rsa.pub /tmp
cp config /tmp
echo "Saved old files in /tmp, just in case"

rm id_rsa
rm id_rsa.pub
rm config
echo "Removed current links/files"

ln git_dhoerl id_rsa
ln git_dhoerl.pub id_rsa.pub
ln config_dhoerl config

git config --global user.email "dhoerl@<company>.com"
git config --global github.user "dhoerl"        
git config --global github.token "whatever_it_is"

ssh-add -D

I've had great luck with this. I also created a run script in Xcode (for you Mac users) so it would not build my project unless I had the proper setting (since its using git):

Run Script placed after Dependencies (using /bin/ksh as the shell):

if [ "$(git config --global --get user.email)" != "dhoerl@<company>.com" ]
then
    exit 1
fi

EDIT: added tests for new files existence and copying old files to /tmp to address comment by @naomik below.

By creating different host aliases to github.com in your ~/.ssh/config, and giving each host alias its own ssh key, you can easily use multiple github accounts without confusion. That’s because github.com distinguishes not by user, which is always just git, but by the ssh key you used to connect. Just configure your remote origins using your own host aliases.”

The above summary is courtesy of comments on the blog post below.

I've found this explanation the clearest. And it works for me, at least as of April 2012.

http://net.tutsplus.com/tutorials/tools-and-tips/how-to-work-with-github-and-multiple-accounts/