SSH Login Without Entering A Password

I tire of constantly entering my password everytime I need to login to a machine. Now that I have a system for keeping track of my passwords I no longer feel like I need to use them constantly for memory purposes. So here's the info that I use to log in to other machines through ssh without needing to enter a password each time. This is very handy for allowing scripts to access other machines to automate your tasks. Without futher ado here's how to allow an automatic login from host A / user a to Host B / user b.

How to do it

First log in on A as user a and generate a pair of authentication keys. Do not enter a passphrase:

a@A:~> ssh-keygen -t rsa Generating public/private rsa key pair. Enter file in which to save the key (/home/a/.ssh/id_rsa): Created directory '/home/a/.ssh'. Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /home/a/.ssh/id_rsa. Your public key has been saved in /home/a/.ssh/id_rsa.pub. The key fingerprint is: 3e:4f:05:79:3a:9f:96:7c:3b:ad:e9:58:37:bc:37:e4 a@A Now use ssh to create a directory ~/.ssh as user b on B. (The directory may already exist, which is fine):

a@A:~> ssh b@B mkdir -p .ssh b@B's password:

Finally append a's new public key to b@B:.ssh/authorized_keys and enter b's password one last time:

a@A:~> cat .ssh/id_rsa.pub | ssh b@B 'cat >> .ssh/authorized_keys' b@B's password:

From now on you can log into B as b from A as a without password:

a@A:~> ssh b@B hostname B

This post is a summarized version of a post on how to login through ssh without a password, copied here for long term memory purposes