How to specify the private SSH-key to use when executing shell command on Git?

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 [email protected]: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 [email protected]: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

None of these solutions worked for me.

Instead, I elaborate on @Martin v. Löwis 's mention of setting a config file for SSH.

SSH will look for the user's ~/.ssh/config file. I have mine setup as:

Host gitserv     Hostname remote.server.com     IdentityFile ~/.ssh/id_rsa.github     IdentitiesOnly yes # see NOTES below 

And I add a remote git repository:

git remote add origin git@gitserv:myrepo.git 

And then git commands work normally for me.

git push -v origin master 

NOTES

• The IdentitiesOnly yes is required to prevent the SSH default behavior of sending the identity file matching the default filename for each protocol. If you have a file named ~/.ssh/id_rsa that will get tried BEFORE your ~/.ssh/id_rsa.github without this option.

References

• Best way to use multiple SSH private keys on one client
• How could I stop ssh offering a wrong key

Answer 2

Something like this should work (suggested by orip):

ssh-agent bash -c 'ssh-add /somewhere/yourkey; git clone [email protected]: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 [email protected]: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.