SSH Public Key Authentication
If you find yourself logging into SSH servers a lot, you might find this tip useful – you’ll only need to type your password once per session. But first, let’s set the default username (so you don’t have to tell SSH what user you are every time):
$ cd ~ $ mkdir .ssh $ chmod 700 .ssh $ cat >> .ssh/config Host t2.technion.ac.il User slutzky Ctrl-D $
Now, create a public/private key pair for SSH, like so:
$ ssh-keygen -t rsa Generating public/private rsa key pair. Enter file in which to save the key (/home/tactless/.ssh/id_rsa): Enter passphrase (empty for no passphrase): use_a_password Enter same passphrase again: use_a_password Your identification has been saved in /home/tactless/.ssh/id_rsa. Your public key has been saved in /home/tactless/.ssh/id_rsa.pub. The key fingerprint is: 5a:3a:e3:f4:6e:91:fe:3f:27:4e:f4:46:0d:5e:50:4f tactless@dolphin
Now you have a public and private key: ~/.ssh/id_rsa is the private key (don’t give this to anyone!), and ~/.ssh/id_rsa.pub is the public key – give this to everyone. Specifically, put it on the SSH server you want to log into, making sure the permissions are correct. There’s a script which does this:
$ ssh-copy-id t2.technion.ac.il
It basically does the following for you:
$ scp ~/.ssh/id_rsa.pub t2.technion.ac.il: password: $ ssh t2.technion.ac.il > mkdir .ssh > cat id_rsa.pub >> .ssh/authorized_keys > chmod 700 .ssh .ssh/authorized_keys > chmod 755 . > logout
Now, when you log in to your local account, before using SSH for the first time, type the following command:
$ ssh-add Enter passphrase for /home/tactless/.ssh/id_rsa: your-password-here $ ssh t2.technion.ac.il > # notice, didn't type a password > logout $ ssh t2.technion.ac.il > # no password this time either
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