Sharing SSH keys

Question

I use a private SSH key and passwordless entry for a number of user accounts on a server that hosts a number of websites.

I use the same private key for each user account. (because I'm lazy? or is that the "right" way).

I now want to authorise another trusted computer in a different part of the country. If I copy the contents of my ~/.ssh onto that machine will that work without any other set up?

Will both machines be able to maintain a connection at the same time?

Answer 1

Update: as an additional security recommendation, you should generate a new set of keys for a new machine and send your new public key out to the various hosts you use it on, rather than copying your private keys. If you're just moving everything to a new computer however, you can take your keys with you, but remember to destroy them securely on the old computer.

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The correct answer is to copy your .ssh directory from the old machine to the new. This part is easy (scp -r .ssh user@newmachinehost:~ will do fine—or you can type the keys in character-by-character, up to you).

BUT—I think the missing link to answer this question is what you have to do after you copy your private keys to the new machine.

I had to run the following for each key (I have 3 separate keys for various organizations)

ssh-add .ssh/[key-filename] 

If the filename argument is omitted, id_rsa is assumed.

Once you do this to each key (and enter they key's passphrase if required; it will prompt you), ssh will be able to use those keys to authenticate.

Otherwise, no amount of copying will do much. SSH will ignore the keys in .ssh until they are explicitly used (via ssh -i [keyfilename] ...).

Answer 2

This should work, and both machines should be able to maintain a connection at the same time - I've had to copy my ~/.ssh directory a few times before when hard drives have crashed.