[edit] What It Is

SSH is a secure protocol used for data exchange between computers. Oftentimes SSH is synonymous with logging into a remote computer. SSH is favored over telnet because communications are encrypted. See WikiPedia:SSH.

[edit] Log in Without Specifying Your Password

Users who go between multiple Linux and UNIX machines are often retarded by annoying password prompts.

Perform the following steps to eliminate a password prompt when logging in to a server from a client.

• On the client machine, run

ssh-keygen -t dsa

Take note where the output is stored. When prompted for a passphrase, just press ENTER.

• Copy the public key to the server machine:

scp ~/.ssh/id_dsa.pub user@server:/home/user/authorized.pub

• Log in to the server machine.
• If it doesn't exist, create the directory .ssh in your home directory and set permissions to 700.

mkdir ~/.ssh && chmod 700 ~/.ssh

• If it doesn't exist, create an authorized keys file:

touch ~/.ssh/authorized_keys

• Copy the contents of the public key to the authorized_keys file:

cat ~/authorized.pub >> ~/.ssh/authorized_keys

• Don't enter your password any more

There are some security concerns for this method. Any individual with access to your console can log into remote machines. To simplify matters, you can specify a simple passphrase during ssh-keygen. You can use this passphrase instead of your account password when doing an SSH. For example, if you UNIX account password is very long, you could substitute a shorter password for access to your public key.