Tips to use ssh effectively

Workstations at CAM

There are two workstations “euler” and “fourier”, see this page. To connect to them from inside CAM, do

ssh euler
ssh fourier

To login from outside CAM, please ask me for details. When you connect from outside CAM, display may not work, you have to do all work from the terminal.

On euler or fourier, check your $HOME/.bashrc file. It runs a script in my directory to set some paths to various softwares. You can examine this file using vi/vim

vi /home/praveen/.setenv

Everything you need should be installed already. If something is missing, tell me about it.

SSH keys

YOU SHOULD SETUP SSH KEYS so you can login without typing password everytime.

On your laptop/desktop, run the following ONCE

ssh-keygen

Then just enter for all questions. This creates a directory $HOME/.ssh which contains some files. The file $HOME/.ssh/id_rsa.pub is your public key which must be copied to the remote server. You can do this manually by logging into the remote server and copy the contents of $HOME/.ssh/id_rsa.pub from your local computer to $HOME/.ssh/authorized_keys on the remote computer. Alternately, you can use ssh-copy-id command.

You are inside cam

From your local computer, do

ssh-copy-id USERNAME@REMOTEHOST

where USERNAME is your username on the REMOTEHOST. Enter password for your REMOTEHOST to copy the ssh id.

You are outside cam

From your local computer, do

ssh-copy-id -p PORT USERNAME@158.144.181.10

“PORT” depends on which computer you are connecting to, euler, fourier, etc. USERNAME is your username on the remote computer, euler, fourier, etc.

SSH to github, bitbucket, etc.

Copy the contents of your $HOME/.ssh/id_rsa.pub file into your github or bitbucket account by logging in through your browser. This option should be available somewhere in the settings part of your github/bitbucket account. Once keys are setup, you can clone and do push/pull without entering your github/bitbucket password everytime. E.g., clone using git

git clone git@github.com:USERNAME/PROJECT.git

Here USERNAME is your github username and PROJECT is the name of the git repository you want to clone.

Disable password based login

Edit the file

sudo vi /etc/ssh/sshd_config

and add these lines

ChallengeResponseAuthentication no
PasswordAuthentication          no
UsePAM                          no
PermitRootLogin                 no
PermitEmptyPasswords            no

Restart sshd

sudo systemctl reload sshd

Check that password based login is not allowed

ssh HOSTNAME -o PubkeyAuthentication=no

which should say permission denied.