Passwordless SSH

You can specify a file with the format

user1@host1 port1
user2@host2 port2
...

as the first argument to this script and run it to set up all SSH connection pairs and skip to step 3

1. Generate a key pair (You can skip this stage if you already have a key pair):
   ssh-keygen -t rsa -b 2048
   
   
2. Copy your public key to the remote machine
   cat ~/.ssh/id_dsa.pub | ssh user@remote.machine.com 'cat >> .ssh/authorized_keys'
   or
   ssh-copy-id user@remote.machine.com -p port
   
   
3. Set SSH agent so that you don't have to enter your passphrase every single time you log in:
   
   Create these aliases for convenience on your machine:
   alias agent='rm -f "$HOME"/.ssh/`hostname`.agent ; ssh-agent -t 86400 | grep -v echo > "$HOME"/.ssh/`hostname`.agent ; source "$HOME"/.ssh/`hostname`.agent ; ssh-add'

alias sshagent='if [ -e "$HOME"/.ssh/`hostname`.agent ]; then source "$HOME"/.ssh/`hostname`.agent ; fi'
   
   Run 'agent' once on your machine, and 'sshagent' for every shell instance
   
   You can modify the -t flag in ssh-agent -t 86400 to adjust the time needed to reenter your passphrase (in seconds)
   
   
4. To prevent password login to root, add the following to /etc/ssh/sshd_config on the server:
   PermitRootLogin prohibit-password
   
   
5. To prevent login to a user, add the following to /etc/ssh/sshd_config on the server:
   PasswordAuthentication no