First steps on a linux server

setup_linux_server.md

• First steps on a linux server
  • Update the system
  • Change the root password
  • Disable the default account
  • Make sudo require a password
  • Change the hostname
  • SSH
    • Prevent root login
    • Key-Based Authentication
    • Change the default port

First steps on a linux server

Update the system

Run sudo apt update and sudo apt full-upgrade to update the system.

Change the root password

1. Connect to the server with SSH. Change the user to root with the command sudo su -.
2. Run passwd to change the default password.

Disable the default account

1. Create a new user account with the command sudo adduser <username>.
2. Give the user the sudo privilege with the command sudo adduser <username> sudo.
3. Delete the default user account with the command sudo deluser -remove-home <default username>.

Make sudo require a password

1. In a terminal window, run sudo visudo.
2. Add the following line to the end of the file:

   YOUR_USERNAME_HERE ALL=(ALL) PASSWD: ALL
   

Change the hostname

1. Run this command: sudo hostname new-server-name-here.
2. Edit the /etc/hostname file and update hostname.
3. Edit the /etc/hosts file and update the lines that reads your old-host-name.

SSH

Prevent root login

1. Open the /etc/ssh/sshd_config file with a text editor.
2. Set the following line to no:

   PermitRootLogin no
   

3. Restart the SSH service with sudo service ssh restart.

Key-Based Authentication

⚠️ Important: Before that change is made, you must copy the SSH key from your computer to the server. For example, you can use the following command: ssh-copy-id -i ~/.ssh/id_rsa.pub YOUR_USERNAME_HERE@YOUR_SERVICE_HERE.

Change this line in the SSH configuration file we saw before:

PasswordAuthentication no

Change the default port

🗒️ NOTE: Note that the ports numbered 0-1023 are reserved for privileged services. Hence, it is best to use a port ranging from 49152 to 65535.

1. Open the /etc/ssh/sshd_config file with a text editor.
2. Insert the following line, if it already exists, replace it with the following line:

   Port 1111
   

3. Restart the SSH service with sudo service ssh restart.