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====== How to setup a Password Free Linux Remote Log In ======

This is helpful when you **remote log in to a Linux machine frequently**. It stores your account password safely on the remote machine so that only your local account on your current machine can log in to the remote machine without needing to enter a password.

**__Warning: Before setting this up, make sure you understand the concept of SSH and working remotely on another Linux computer!__**

**YOU are responsible for the security of your account on the remote machine!**

Here are the steps:
  - On your local Linux computer (for example aircraft.atmos.und.edu), open a terminal, and type: ssh-keygen -t ed25519 -C "delene@aero.und.edu" to generated two key in ~/.ssh. Where you need to replace "delene@aero.und.edu" with your email address.
  - You will get a prompt asking you where to save the key. The default is given within (). Press enter key to use the default.
  - You will get another prompt to enter a pass phrase, leave it blank by hitting "Enter"
  - The passkey is generated, you should have two files in /home/username/.ssh/
  - Use a text editor (e.g. vi) to open the public key file, *pub*
  - opy the entire string, starting with "ssh- ..."
  - Now log in to your remote Linux machine. To navigate to your "~/.ssh/" directory, type: .ssh
  - You should see a file named "authorized_keys", change the file's permission by entering: chmod 600 authorized_keys. If you don't have a file named "authorized_keys", type: gvim authorized_keys. This will create the file for you. This assumes that when you ssh-ed into the remote location, you typed "ssh -Y remoteLocation". The -Y allows you to use graphical interfaces.
  - Make sure your .ssh directory has the correct permissions. Type: chmod 700 ~/.ssh
  - Now only you have the permission to read/write to this file (for security purpose), use a text editor to open this file and paste the string you copy from your "id_rsa.pub"
  - Save and exit the file "authorized_keys"

**At this point, the setup is complete!**

**You should be able to SSH in the remote Linux machine without getting a prompt to enter your password.**


===== How to Handle Multiple Usernames between Local and Remote Machines =====

If your local machine has a different username than the remote machine, an ssh configuration file can be setup so a username will not have to be entered to connect to the remote machine.

  * Navigate to the ~/.ssh directory
  * Create a config file and set user-only read/write permissions by typing:

  touch config && chmod 600 config

  * Within the config file, type something like below (explanation of each line follows):

  host aircraft
  hostname aircraft.atmos.und.edu
  user username_on_aircraft
  user default_username

  * The first line ("host") is the nickname of the remote computer to be connected to.  To access aircraft.atmos.und.edu as written above without needing a preceding username, all that needs to be typed is 'ssh aircraft'.
  * The second line ("hostname") is the full hostname of the remote computer.
  * The third line ("user") is the username used to login to the remote computer
  * The fourth line ("user") is the default username to use for all other ssh connections.
  * More connection configurations can be added between the third and fourth lines by repeating lines 1-3.