Your First Server: Access and Orientation

System administration means keeping machines running, secure and recoverable. This track assumes you have finished Linux & the Command Line. Practise on a cheap cloud VPS (Hetzner, DigitalOcean, Linode, AWS Lightsail) or a local virtual machine, never first on a production server.

Connecting

ssh root@203.0.113.10                 # first login, often with a password or provider key
ssh -i ~/.ssh/id_ed25519 panda@203.0.113.10

Save hosts in ~/.ssh/config so you can type ssh web1:

Host web1
    HostName 203.0.113.10
    User panda
    IdentityFile ~/.ssh/id_ed25519

Orientation checklist

Run these on any machine you have not seen before:

cat /etc/os-release       # which distribution and version
uname -r                  # kernel version
hostnamectl               # hostname, OS, virtualisation
uptime                    # how long since reboot, load
nproc && free -h          # CPU cores and memory
df -h                     # disks and free space
ip -brief addr            # network interfaces and IPs
ss -tulpn                 # which programs listen on which ports
systemctl --failed        # services that crashed
last -n 10                # recent logins

Ten commands, and you know the machine's size, health, exposure and recent history.

Distributions

This track uses Ubuntu LTS commands. The concepts carry over to every distribution.

First tasks on a new server

1. Update everything: sudo apt update && sudo apt full-upgrade -y.
2. Set the timezone and hostname: sudo timedatectl set-timezone UTC, sudo hostnamectl set-hostname web1.
3. Create a personal admin user (next module).
4. Lock down SSH (module "Securing SSH and the Firewall").
5. Turn on automatic security updates.

Use UTC on servers. Logs from several machines and time zones are impossible to correlate otherwise.

Keep a runbook

Write down every change you make in a RUNBOOK.md: what, why, and how to undo it. When something breaks at 2 a.m., or when you hand the server to someone else, this file is worth more than your memory.

Check yourself

• Which command shows listening ports and the programs behind them?
• Why should servers use UTC?
• What are the five first tasks on a new server?