ssh has the -i option to tell which private key file to use when authenticating:

-i identity_file

    Selects a file from which the identity (private key) for RSA or DSA authentication is read.  The default is ~/.ssh/identity for protocol version 1, and ~/.ssh/id_rsa and ~/.ssh/id_dsa for protocol version 2.  Identity files may also be specified on a per-host basis in the configuration file.  It is possible to have multiple -i options (and multiple identities specified in configuration files).

Is there a similar way to tell git which private key file to use on a system with multiple private keys in the ~/.ssh directory?

15 Answers 15

up vote 558 down vote accepted

In ~/.ssh/config, add:

host github.com
 HostName github.com
 IdentityFile ~/.ssh/id_rsa_github
 User git

Now you can do git clone git@github.com:username/repo.git.

NOTE: Verify that the permissions on IdentityFile are 400.SSH will reject, in a not clearly explicit manner, SSH keys that are too readable. It will just look like a credential rejection. The solution, in this case, is:

chmod 400 ~/.ssh/id_rsa_github
  • 76
    What if you need to connect to the same host with different keys? – Valentin Klinghammer Nov 30 '12 at 11:24
  • 6
    @Quelltextfabrik - you can add another section with a different Host: nerderati.com/2011/03/… – Ben Challenor Dec 4 '12 at 14:17
  • 1
    @Cliff Nop, in my manpage: "HostName: Specifies the real host name to log into. This can be used to specify nicknames or abbreviations for hosts." My ssh version is openssh-6.7p1. – Grissiom Jan 7 '15 at 2:17
  • 1
    @Grissiom That's exactly what it says. But you seem to understand the meaning backwards. Host (or Match) is required. To create a host nickname you place the nickname in the Host line and the real hostname in the HostName line. Examples: saltycrane.com/blog/2008/11/… – Cliff Jan 8 '15 at 3:55
  • 7
    If the config file is new, don't forget to do chmod 600 ~/.ssh/config – elysch Mar 15 '16 at 23:02

Environment variable GIT_SSH_COMMAND:

From Git version 2.3.0, you can use the environment variable GIT_SSH_COMMAND like this:

GIT_SSH_COMMAND="ssh -i ~/.ssh/id_rsa_example" git clone example

Note that -i can sometimes be overridden by your config file, in which case, you should give SSH an empty config file, like this:

GIT_SSH_COMMAND="ssh -i ~/.ssh/id_rsa_example -F /dev/null" git clone example

Configuration core.sshCommand:

From Git version 2.10.0, you can configure this per repo or globally, so you don't have to set the environment variable any more!

git config core.sshCommand "ssh -i ~/.ssh/id_rsa_example -F /dev/null"
git pull
git push
  • 1
    I had to export the shell variable to an environment variable to make this work, i.e. export GIT_SSH_COMMAND="ssh -i ~/.ssh/id_rsa_example", then git clone example – Abdull Dec 1 '15 at 13:46
  • 6
    @Abdull In Bash, doing the assignment on the same line as the command exports the environment variable for just that command. Try it: example=hello /usr/bin/env | grep example. – Flimm Jan 8 '16 at 9:50
  • 3
    things have become even better: as of Git 2.10, you can store the command in your Git configuration: stackoverflow.com/a/38474220/520162 – eckes Oct 21 '16 at 7:57
  • 1
    @Noitidart /dev/null is only a valid filename in UNIX-like operating systems, it doesn't work on Windows. – Flimm Mar 7 '17 at 8:19
  • 1
    If you need multiple keys, the -i parameter can be repeated, and ssh will try each key in turn. git config core.sshcommand "ssh -i /path/to/keyA -i /path/to/keyB". This lets git use different keys with different remote hosts. – Mark Jun 23 '17 at 3:44

There is no direct way to tell git which private key to use, because it relies on ssh for repository authentication. However, there are still a few ways to achieve your goal:

Option 1: ssh-agent

You can use ssh-agent to temporarily authorize your private key.

For example:

$ ssh-agent sh -c 'ssh-add ~/.ssh/id_rsa; git fetch user@host'

Option 2: GIT_SSH_COMMAND

Pass the ssh arguments by using the GIT_SSH_COMMAND environment variable (Git 2.3.0+).

For example:

$ GIT_SSH_COMMAND='ssh -i ~/.ssh/id_rsa -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no' \
  git clone user@host

You can type this all on one line — ignore $ and leave out the \.

Option 3: GIT_SSH

Pass the ssh arguments by using the GIT_SSH environment variable to specify alternate ssh binary.

For example:

$ echo 'ssh -i ~/.ssh/id_rsa -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no $*' > ssh
$ chmod +x ssh
$ GIT_TRACE=1 GIT_SSH='./ssh' git clone user@host

Note: The above lines are shell (terminal) command lines which you should paste into your terminal. They will create a file named ssh, make it executable, and (indirectly) execute it.

Note: GIT_SSH is available since v0.99.4 (2005).

Option 4: ~/.ssh/config

Use the ~/.ssh/config file as suggested in other answers in order to specify the location of your private key, e.g.

Host github.com
  User git
  Hostname github.com
  IdentityFile ~/.ssh/id_rsa
  • 1
    // , What if your identity in ssh-agent is forwarded, though, as in this question? superuser.com/questions/971732/… – Nathan Basanese Sep 11 '15 at 18:06
  • 1
    I've allowed me to reformat this post: IMO this is by far the most comprehensive answer. In its original design, a quick scan suggested the post where describing a single complicated solution to the problem, so I missed it. – Alberto Jan 21 '16 at 10:01
  • 2
    $ ssh-agent sh -c 'ssh-add ~/.ssh/id_rsa; git fetch user@host' worked for me when nothing else would. Kudos. – Daniel Dewhurst Sep 11 '17 at 15:24
  • I had to use ~/.ssh/config method, env vars didn't work for me... – Greg Dubicki Sep 22 '17 at 7:53
  • 1
    GIT_SSH is available since v0.99.4 (August 2005), so basically since Git exists (April 2005). – Dominik Nov 17 '17 at 8:10

Write a script that calls ssh with the arguments you want, and put the filename of the script in $GIT_SSH. Or just put your configuration in ~/.ssh/config.

  • 1
    Another explanation of how to do this. – Sithsu May 12 '14 at 19:44
  • 1
    ~/.ssh/config Is the way to go. – hek2mgl May 8 '15 at 13:56
  • I work on a machine (A) from which I git push to a server (B) that only accepts ssh key authentication. While my ~/.ssh/config setup on (A) works perfectly fine when I work directly on that machine, it does not when I login from some other location (C). Using $GIT_SSH and a script solved this problem. Thanks! – bsumirak Dec 3 '15 at 17:28

If you do not want to have to specify environment variables every time you run git, do not want another wrapper script, do not/can not run ssh-agent(1), nor want to download another package just for this, use the git-remote-ext(1) external transport:

$ git clone 'ext::ssh -i $HOME/.ssh/alternate_id git.example.com %S /path/to/repository.git'
Cloning into 'repository'
(...)
$ cd repository
$ git remote -v
origin  ext::ssh -i $HOME/.ssh/alternate_id git.example.com %S /path/to/repository.git (fetch)
origin  ext::ssh -i $HOME/.ssh/alternate_id git.example.com %S /path/to/repository.git (push)

I consider this solution superior because:

  • It is repository/remote specific
  • Avoid wrapper script bloat
  • Do not need the SSH agent -- useful if you want unattended clones/push/pulls (e.g. in cron)
  • Definitely, no external tool needed
  • // , Excellent solution. I wonder, though, if this would allow one to specify an identity passed through using agent forwarding. Most of my keys are not local to the servers I am using them on. I asked about this here: superuser.com/questions/971732/… – Nathan Basanese Sep 11 '15 at 18:09
  • The answer deals only with a way of specifying arbitrary command lines to be used as git repositories. IMHO, you should try to sort out your issue using ssh alone first (e.g. "ssh host" should connect using the right key). I will try to provide more info on your other question, though. – flaviovs Sep 14 '15 at 16:34
  • 1
    This answer was exactly what I needed to force Chef's git resource to use repository-specific deployment keys to clone/fetch from private Github repositories. The additional advantage of this method over the environment/script based ones is that since the key-path is encoded in the working-repo's config, it will use the same key on both initial clone and subsequent fetches/pushes. – Adam Franco Nov 19 '15 at 16:20
  • 1
    WOW! This is just great, didn't know about this. Thanks for the answer, quite helpful as well in puppet environments, to prevent the extra hassle to manage .ssh/config etc. +1! – gf_ Jun 10 '16 at 18:36
  • 2
    If you encounter the following error fatal: transport 'ext' not allowed, you have to whitelist the ext protocol via the export GIT_ALLOW_PROTOCOL=ext. Basically, the git-remote-ext remote helper (which supports "ext::ssh example.com %S foo/repo" URLs) allows arbitrary command execution. This normally isn't ever a concern because user always sees and trusts the URL they pass to git. However git submodules, through the .gitmodules file, allow an attacker to request the client to fetch arbitrary git URLs. hackerone.com/reports/104465 – Gomino May 13 at 17:21

After my struggle with $GIT_SSH I would like to share what worked for me.

Through my examples I will assume you have your private key located at/home/user/.ssh/jenkins

Error to avoid: GIT_SSH value includes options

$ export GIT_SSH="ssh -i /home/user/.ssh/jenkins"

or whatever similar will fails, as git will try to execute the value as a file. For that reason, you have to create a script.

Working example of $GIT_SSH script /home/user/gssh.sh

The script will be invoked as follows:

$ $GIT_SSH [username@]host [-p <port>] <command>

Sample script working could look like:

#!/bin/sh
ssh -i /home/user/.ssh/jenkins $*

Note the $* at the end, it is important part of it.

Even safer alternative, which would prevent any possible conflict with anything in your default config file (plus explicitly mentioning the port to use) would be:

#!/bin/sh
ssh -i /home/user/.ssh/jenkins -F /dev/null -p 22 $*

Assuming the script is in /home/user/gssh.sh, you shall then:

$ export GIT_SSH=/home/user/gssh.sh

and all shall work.

  • Thanks. Just note: use "$@" instead of $* for pass-thru arguments, as the former behaves correctly when arguments contain whitespace. – Piotr Findeisen Mar 31 '16 at 7:39
  • @PiotrFindeisen Thanks for your note. However, I do not understand it completely - in zsh it helps me to keep strings with space in one piece, but in bash not. Can you tell me more or point to some explanation? I do not want to add some modification blindly. – Jan Vlcinsky Mar 31 '16 at 10:33
  • You should remove the first half of your answer. No one's interested in a solution that doesn't work, and it's wasted reading that obfuscates the correct answer at the bottom, which works wonderfully. – Cerin Aug 3 at 16:47
  • @Cerin If you mean removing the "Error to avoid" I am going to keep it there. It shares common pitfall to avoid and it is very short. I am sure, someone would try optimizing the solution by providing all the things into variable (this happened to me), so I tried to shorten the path to success. – Jan Vlcinsky Aug 4 at 20:14

Use custom host config in ~/.ssh/config, like this:

Host gitlab-as-thuc  
    HostName github.com
    User git
    IdentityFile ~/.ssh/id_rsa.thuc
    IdentitiesOnly yes

then use your custom hostname like this:

git remote add thuc git@gitlab-as-thuc:your-repo.git  
  • 1
    This is the answer I was looking for, as I have separate GitHub accounts for home and work. I just had to set Host work.github.com HostName github.com IdentityFile ~/.ssh/work, and then replace "github.com" by "work.github.com" whenever I clone a work repository. It still connects to "github.com", but using a non-default key pair. – Mikkel May 25 '16 at 17:06
  • 1
    The URL for details ("itblog.study.land/...") doesn't work any more :( – Carl Smotricz Sep 15 '17 at 8:10
  • @CarlSmotricz the original one was moved here: medium.com/@thucnc/… – thucnguyen Nov 27 at 7:13
  • 1
    FINALLY!!! This answer actually shows how you can utilize what you put in the ~/.ssh/config file. Every other answer misses how you can set the host when you add the origin, which automatically allows git to use the correct key file. THANK YOU!! – BrianVPS Dec 4 at 15:17

You can just use ssh-ident instead of creating your own wrapper.

You can read more at: https://github.com/ccontavalli/ssh-ident

It loads ssh keys on demand when first needed, once, even with multiple login sessions, xterms or NFS shared homes.

With a tiny config file, it can automatically load different keys and keep them separated in different agents (for agent forwarding) depending on what you need to do.

I had a client that needed a separate github account. So I needed to use a separate key just for this one project.

My solution was to add this to my .zshrc / .bashrc:

alias infogit="GIT_SSH_COMMAND=\"ssh -i ~/.ssh/id_specialkey\" git $@"

Whenever I want to use git for that project I replace "infogit" with git:

infogit commit -am "Some message" && infogit push

For me, it's easier to remember.

My solution was this:

create a script:

#!/bin/bash
KEY=dafault_key_to_be_used
PORT=10022 #default port...
for i in $@;do
   case $i in
    --port=*)
        PORT="${i:7}";;
    --key=*)KEY="${i:6}";;
   esac
done
export GIT_SSH_COMMAND="ssh -i $HOME/.ssh/${KEY} -p ${PORT}"
echo Command: $GIT_SSH_COMMAND

then when you have to change the var run:

. ./thescript.sh [--port=] [--key=]

Don't forget the extra dot!! this makes the script set the environments vars!! --key and --port are optional.

So I set the GIT_SSH env variable to $HOME/bin/git-ssh.

In order to support having my repo configuration dictate which ssh identity to use, my ~/bin/git-ssh file is this:

#!/bin/sh
ssh -i $(git config --get ssh.identity) -F /dev/null -p 22 $*

Then I have a global git config setting:

$ git config --global ssh.identity ~/.ssh/default_id_rsa

And within any git repository I can just set a local ssh.identity git config value:

$ git config --local ssh.identity ~/.ssh/any_other_id_rsa

Voila!

If you can have a different email address for each identity, it gets even simpler, because you can just name your keys after your email addresses and then have the git config's user.email drive the key selection in a ~/bin/git-ssh like this:

#!/bin/sh
ssh -i $HOME/.ssh/$(git config --get user.email) -F /dev/null -p 22 $*

Generally, you want to use ~/.ssh/config for this. Simply pair server addresses with the keys you want to use for them as follows:

Host github.com
  IdentityFile ~/.ssh/id_rsa.github
Host heroku.com
  IdentityFile ~/.ssh/id_rsa.heroku
Host *
  IdentityFile ~/.ssh/id_rsa

Host * denotes any server, so I use it to set ~/.ssh/id_rsa as the default key to use.

I build on @shellholic and this SO thread with a few teaks. I use GitHub as an example and assume that you have a private key in ~/.ssh/github (otherwise, see this SO thread) and that you added the public key to your GitHub profile (otherwise see GitHub's help).

If needed, create a new SSH config file at ~/.ssh/config and change permissions to 400

touch ~/.ssh/config
chmod 600 ~/.ssh/config

Add this to the ~/.ssh/config file:

Host github.com
    IdentityFile ~/.ssh/github
    IdentitiesOnly yes

If you already have a remote set up, you may want to delete it, otherwise you may still be prompted for username and password:

git remote rm origin

Then add a remote to the git repository, and notice the colon before the user name:

git remote add origin git@github.com:user_name/repo_name.git

And then git commands work normally, e.g.:

git push origin master
git pull origin 

@HeyWatchThis on this SO thread suggested adding IdentitiesOnly yes to prevent the SSH default behavior of sending the identity file matching the default filename for each protocol. See that thread for more information and references.

  • This was my mistake: "If you already have a remote set up...". Thanks a lot!!! – Allan Andrade Oct 4 at 17:43

I'm using git version 2.16 and I don't need a single piece of script not even a config or modified commands.

  • Just copied my private key to .ssh/id_rsa
  • set permissions to 600

And git reads to key automatically. I doesn't ask anything and it doesn't throw an error. Just works fine.

  • Did you notice that the question is about “a system with multiple private keys in the ~/.ssh directory”? – Scott Jun 6 at 5:16

Just use ssh-agent and ssh-add commands.

# create a agent
ssh-agent

# add your default key
ssh-add ~/.ssh/id_rsa

# add your second key
ssh-add ~/.ssh/<your key name>

After execute above commands, you can use both key as same time. Just type

git clone git@github.com:<yourname>/<your-repo>.git

to connect your repository.

You need to execute above command after you reboot your machine.

English is not my native language; please excuse typing errors.

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