Setting up accounts on Linux servers

User Creation

Create a user:

useradd -m \
  --groups additional_groups \
  --shell login_shell username

or shorthand

useradd -m -G additional_groups -s login_shell username

For example, new user 'john' in group 'sudo'

useradd -m --groups sudo --shell /bin/bash john

This is assuming the sudo group is `sudo`, it can vary. It's usually `sudo` on ubuntu, sometimes `wheel`. You can check in /etc/sudoers:

# Allow members of group sudo to execute any command
%sudo   ALL=(ALL:ALL) ALL

You should also make sure the above line is uncommented in /etc/sudoers to allow users to elevate if they are the group.

Set the users password:

passwd username

User SSH Access

In order to allow users SSH access via public key authentication at their public key to the authorized_keys file in their $HOME.

First make sure they have the correct directory structure with the correct permissions:

user=john
mkdir -p /home/$user/.ssh 
chown $user:$user /home/$user/.ssh 
chmod 700 /home/$user/.ssh 

Create ~/.ssh/authorized_keys:

user=john
touch /home/$user/.ssh/authorized_keys

Add the users SSH public key(s) one on each line to ~/.ssh/authorized_keys. For testing purposes You may wish to add your own public key to their authorized keys file, confirm you can log in to their account, and then remove your public key after.

Make sure permissions are correct:

chown $user:$user /home/$user/.ssh/authorized_keys
chmod 644 /home/$user/.ssh/authorized_keys 

Example Setup

Create a user named 'john' With a public key:

ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIC6uS2pGu/Vg53skjc00jCqGbOGLihiiORjD5aOLw48d not a real key 

With sudo access

First elevate to root:

sudo -i

Then create user:

user=john
useradd -m --groups sudo --shell /bin/bash $user
mkdir -p /home/$user/.ssh 
chown $user:$user /home/$user/.ssh 
chmod 700 /home/$user/.ssh 
touch /home/$user/.ssh/authorized_keys
echo 'ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIC6uS2pGu/Vg53skjc00jCqGbOGLihiiORjD5aOLw48d not a real key' >> /home/$user/.ssh/authorized_keys
chown $user:$user /home/$user/.ssh/authorized_keys
chmod 644 /home/$user/.ssh/authorized_keys
passwd $user

Instructions For User

Provide the user with their username, and the host name of the server. Depending where the server lives on the UBC Network they may need to use a "jump server" such as ssh.ece.ubc.ca if they're not already on the UBC network.