Using SSH keys

Generate ssh keypair

Using windows

• Download PuttyGen;
• Generate RSA keypair;
• Don't use password if you don't want to enter it;
• Save public and private key;
• Copy public key from window 'Public key for pasting into OpenSSH authorized_keys file';

Using linux

• Run ssh-keygen;

root@raspi:~# ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):
Created directory '/root/.ssh'.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:UHqwV9123123123123123e28X07V1ODpIr5Vy+hpi1g
The key's randomart image is:
...

• Your public key - cat ~/.ssh/id_rsa.pub;
• Your private key - cat ~/.ssh/id_rsa;

Create user

root@raspi-3-3:~# adduser test
Adding user `test' ...
Adding new group `test' (1001) ...
Adding new user `test' (1001) with group `test' ...
Creating home directory `/home/test' ...
Copying files from `/etc/skel' ...
New password:
Retype new password:
passwd: password updated successfully
Changing the user information for test
Enter the new value, or press ENTER for the default
        Full Name []: Test
        Room Number []:
        Work Phone []:
        Home Phone []:
        Other []:
Is the information correct? [Y/n] Y

Adding sudo capability to user

usermod -aG sudo username

Sudo without password

Add line to /etc/sudoers:

username     ALL=(ALL:ALL) ALL

Create ssh directory

install -d -m 700 /home/test/.ssh
# copy authorized_keys or create it
sudo chmod 644 /home/test/.ssh/authorized_keys
sudo chown -R test:test /home/test/.ssh

Copy public key to authorized_keys file