How to specify the private SSH-key to use when exe

Question

A rather unusual situation perhaps, but I want to specify a private SSH-key to use when executing a shell (git) command from the local computer.

Basically like this:

git clone [e-mail]:TheUser/TheProject.git -key "/home/christoffer/ssh_keys/theuser"

Or even better (in Ruby):

with_key("/home/christoffer/ssh_keys/theuser") do
  sh("git clone [e-mail]:TheUser/TheProject.git")
end

I have seen examples of connecting to a remote server with Net::SSH that uses a specified private key, but this is a local command. Is it possible?

Answer 1

Way better idea to add that host or ip to the .ssh/config file like so:

Host (a space separated list of made up aliases you want to use for the host)
    User git
    Hostname (ip or hostname of git server)
    PreferredAuthentications publickey
    IdentityFile ~/.ssh/id_rsa_(the key you want for this repo)

Answer 2

To sum up answers and comments, the best way to set up git to use different key files and then forget about it, which also supports different users for the same host (e.g. a personal GitHub account and a work one), which works on Windows as well, is to edit ~/.ssh/config (or c:\Users\<your user>\.ssh\config) and specify multiple identities:

Host github.com
HostName github.com
IdentityFile /path/to/your/personal/github/private/key
User dandv

Host github-work
HostName github.com
IdentityFile /path/to/your/work/github/private/key
User workuser

Then, to clone a project as your personal user, just run the regular git clone command.

To clone the repo as the workuser, run git clone git@github-work:company/project.git.

Answer 3

Something like this should work (suggested by orip):

ssh-agent bash -c 'ssh-add /somewhere/yourkey; git clone [e-mail]:user/project.git'

if you prefer subshells, you could try the following (though it is more fragile):

ssh-agent $(ssh-add /somewhere/yourkey; git clone [e-mail]:user/project.git)

Git will invoke SSH which will find its agent by environment variable; this will, in turn, have the key loaded.

Alternatively, setting HOME may also do the trick, provided you are willing to setup a directory that contains only a .ssh directory as HOME; this may either contain an identity.pub, or a config file setting IdentityFile.

Answer 4

If you're like me, you can:

• Keep your ssh keys organized

• Keep your git clone commands simple

• Handle any number of keys for any number of repositories.

• Reduce your ssh key maintenance.

I keep my keys in my ~/.ssh/keys directory.

I prefer convention over configuration.

I think code is law; the simpler it is, the better.

STEP 1 - Create Alias

Add this alias to your shell: alias git-clone='GIT_SSH=ssh_wrapper git clone'

STEP 2 - Create Script

Add this ssh_wrapper script to your PATH:

#!/bin/bash
# Filename: ssh_wrapper

if [ -z ${SSH_KEY} ]; then
    SSH_KEY='github.com/l3x'  # <= Default key
fi
SSH_KEY="~/.ssh/keys/${SSH_KEY}/id_rsa"
ssh -i "${SSH_KEY}" "$@"

EXAMPLES

Use github.com/l3x key:

KEY=github.com/l3x git-clone https://github.com/l3x/learn-fp-go

The following example also uses the github.com/l3x key (by default):

git-clone https://github.com/l3x/learn-fp-go

Use bitbucket.org/lsheehan key:

KEY=bitbucket.org/lsheehan git-clone [e-mail]:dave_andersen/exchange.git

NOTES

Change the default SSH_KEY in the ssh_wrapper script to what you use most of the time. That way, you don't need to use the KEY variable most of the time.

You may think, "Hey! That's a lot going on with an alias, a script and some directory of keys," but for me it's convention. Nearly all my workstations (and servers for that matter) are configured similarly.

My goal here is to simplify the commands that I execute regularly.

My conventions, e.g., Bash scripts, aliases, etc., create a consistent environment and helps me keep things simple.

KISS and names matter.

For more design tips check out Chapter 4 SOLID Design in Go from my book: https://www.amazon.com/Learning-Functional-Programming-Lex-Sheehan-ebook/dp/B0725B8MYW

Hope that helps. - Lex

Answer 5

I use zsh and different keys are loaded to my zsh shell's ssh-agent automatically for other purposes (i.e. access to remote servers) on my laptop. I modified @Nick's answer and I'm using it for one of my repos that needs to be refreshed often. (In this case it's my dotfiles which I want same and latest version across my all machines, wherever I'm working.)

bash -c 'eval `ssh-agent`; ssh-add /home/myname/.dotfiles/gitread; ssh-add -L; cd /home/myname/.dotfiles && git pull; kill $SSH_AGENT_PID'

• Spawn an ssh-agent
• Add read-only key to agent
• Change directory to my git repo
• If cd to repo dir is successful, pull from remote repo
• Kill spawned ssh-agent. (I wouldn't want many of agents lingering around.)

Answer 6

With git 2.10+ (Q3 2016: released Sept. 2d, 2016), you have the possibility to set a config for GIT_SSH_COMMAND (and not just an environment variable as described in Rober Jack Will's answer)

See commit 3c8ede3 (26 Jun 2016) by Nguyễn Thái Ngọc Duy (pclouds).
^{(Merged by Junio C Hamano -- gitster -- in commit dc21164, 19 Jul 2016)}

A new configuration variable core.sshCommand has been added to specify what value for GIT_SSH_COMMAND to use per repository.

core.sshCommand:

If this variable is set, git fetch and git push will use the specified command instead of ssh when they need to connect to a remote system.
The command is in the same form as the GIT_SSH_COMMAND environment variable and is overridden when the environment variable is set.

It means the git clone can be:

cd /path/to/my/repo
git config core.sshCommand 'ssh -i private_key_file' 
# later on
git clone host:repo.git