Thursday, January 14, 2010

ssh keys

This guide will give you everything you need to create and start using an ssh key to bypass password authentication. Before you begin, please understand that ssh keys need to be maintained with a high level of security. If your keys were to become compromised for some reason, whomever inherited your keys could potentially break your pass phrase and gain access to your data.

In a safe location, run the following command to generate your key pair:
ssh-keygen -b 4096 -t rsa

You'll immediately be prompted to choose a file name for the key pair. Most commonly, the string 'identity' is used and I suggest using that. Following that, you'll need to enter a pass phrase twice. The end result of running the above command will leave you with two files: 'identity', and '' One is private, you should just keep this file on your home machine, laptop, or flash drive and the other is public.

Next, back up your current '~/.ssh' folder and create a new one to house your fresh keys.
mv ~/.ssh ~/.ssh-old
mkdir ~/.ssh
mv identity* ~/.ssh/

Once your keys are in place you can run the following command to 'add' your keys and ensure that everything has gone according to plan. Running this will prompt you for your pass phrase.

Now, we need to set up the public part of your key on any remote hosts you want to access without typing your password. If you have an NFS mount on those hosts (like CSEE) you just need to do this in your home directory. ssh into the server or machine in question and if '~/.ssh' does not exist create it. Once created, go to '~/.ssh' and create the file 'authorized_keys'.
cd ~/.ssh && touch authorized_keys

Finally, copy the contents of your '' file into 'authorized_keys' on the remote host. The next time you authenticate (ensuring that you've used 'ssh-add' in advance) you won't need to enter your password.

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