Someone I know needed an easy way to SSH into a Linux host from a Mac without having to remember the password. The "correct" answer is to set up an RSA public/private key pair and configure the remote host to accept it, but for someone whose primary responsibilities involve wrestling with Adobe software all day, that's just another hurdle to jum…

create-ssh-public-private-key-pair.sh

#!/bin/bash
# The above line tells the OS to run this file with the executable stored
# in /bin/bash; in this case GNU BASH.

keydir=$HOME/.ssh/
keyfile=id_rsa
keyloc=$keydir/$keyfile
ruser= # The username of the remote user
rhost= # The IP Address or DNS name of the remote host
rport=22 # Remote port to connect to; this will nearly always be TCP 22.

# Many operating systems (notably OS X) don't come with a .ssh/ directory by
# default, so we attempt to create it here. If mkdir fails due to an already
# existing directory, that's fine, we can continue on anyway.
mkdir $keydir
chmod 0700 $keydir

# Generate an RSA 2048-bit private/public keypair with no passphrase protecting
# it and store it in the location specified by $keyloc
ssh-keygen -t rsa -b 2048 -f $keyloc -N ''

# Install the public key in the ~/.ssh/authorized_keys file on the remote host.
# This allows SSH to authenticate based on the public key you've presented.
# Additionally, it sets all the file permissions in the obnoxious way SSH
# likes it (if we didn't do that, SSH would simply refuse to use the key).
ssh -p $rport $ruser@$rhost \
    "cat > /tmp/id_rsa_$ruser; mkdir ~/.ssh/; chmod 0700 ~/.ssh/;
     cat /tmp/id_rsa_$ruser >> ~/.ssh/authorized_keys; rm /tmp/id_rsa_$ruser
     chmod 0600 ~/.ssh/authorized_keys" < $keyloc.pub