Debian 13 (Trixie) Guides: Server Setup, Security and Troubleshooting

This page collects every LiberianGeek guide written or updated for Debian 13 “Trixie”, the current Debian stable release, grouped by the job you are trying to do. Most guides also cover Debian 12 “Bookworm” where the steps differ. If you are setting up a new server, follow the order in the next section; if you have a specific problem, jump to the table that matches it.

Debian 13 at a glance

	Debian 13 (Trixie)	Debian 12 (Bookworm)
Status	Current stable	Oldstable
Released	9 August 2025	10 June 2023
End of regular security support	9 August 2028	11 July 2026 (already ended)
End of LTS	30 June 2030	30 June 2028
APT source format	deb822 .sources files	One-line sources.list (deb822 optional)

Because Debian 12 left regular security support on 11 July 2026 and is now covered only by the volunteer LTS team, servers still on Bookworm should plan the move. Start with how to upgrade Debian 12 to Debian 13 without breaking your server.

Setting up a new Debian 13 server: a sensible order

1. Create a normal admin account and give it sudo rights, so you stop working as root.
2. Set up SSH key authentication and confirm you can log in with the key in a second terminal.
3. Only then harden sshd_config (no root login, no password login).
4. Turn on the UFW firewall, allowing SSH before you enable it.
5. Enable automatic security updates.
6. Set the hostname and time zone, and add a swap file on small VPS plans.
7. Add Fail2Ban if SSH is reachable from the internet.

Steps 2 to 4 are where lockouts happen. Keep your current SSH session open until a new login works, and on a VPS make sure you know how to reach the provider’s web console before you change SSH or firewall settings. The Debian server security checklist goes through the security part in more depth.

Install, upgrade and package management

Task	Guide
Move a server from Bookworm to Trixie	Upgrade Debian 12 to Debian 13
Understand or fix APT repository files (debian.sources)	Debian 13 sources.list and the deb822 format
Install security updates automatically	Automatic security updates with unattended-upgrades
Install a newer kernel or boot an older one	Update the kernel on Debian 13 and 12

Users, system settings and SSH access

Task	Guide
Give a user sudo rights	Enable sudo for a user
Change a user or root password, or reset a forgotten one	Change password in Debian 13 and 12
Log in with an SSH key instead of a password	SSH key authentication
Rename the machine	Change the hostname
Fix the time zone or clock sync	Set the time zone and time sync
Add swap on a low-memory server	Create a swap file
Run your own program as a service that restarts on failure	Create a systemd service

Security

Task	Guide
Firewall with simple allow/deny rules	UFW firewall setup
Lock down the SSH server	Harden SSH (sshd_config)
Ban IPs that keep failing to log in	Fail2Ban setup
See which ports are listening and which program owns them	Check open ports
HTTPS certificate for a website	Let’s Encrypt with Certbot and nginx

Monitoring and troubleshooting

Symptom or question	Guide
Disk is full, or you need to find what uses the space	Check disk space (df, du, ncdu)
Server is slow or swapping; did the OOM killer run?	Check memory usage
High load average or a process eating CPU	Check CPU usage and info
A service failed and you need its logs	View logs with journalctl
Back up folders to another disk or server	rsync backups

Networking and DNS tools

Task	Guide
Find the private and public IP address	Get IP address
Give the server a fixed address	Set a static IP address
Query DNS records	dig or nslookup
Test reachability and find where packets stop	ping and traceroute
Use netstat, or its modern replacement ss	Install netstat (net-tools or ss)

To check a domain’s records from the browser instead of the server, use the DNS lookup and email records checker.

Web server, databases and applications

Task	Guide
PHP for WordPress or other PHP apps (PHP-FPM with nginx or Apache)	Install PHP 8.4
Database server	Install MariaDB
Put nginx in front of an app running on a local port	nginx reverse proxy with proxy_pass
Free TLS certificate and HTTP to HTTPS redirect	Certbot with nginx
Run containers	Install Docker
Java development kit	Install JDK on Ubuntu and Debian 13

Which Debian version am I running?

Before following any guide, check the release, because some package names and file locations differ between Debian 12 and 13:

cat /etc/debian_version
grep VERSION_CODENAME /etc/os-release

A 13.x version and VERSION_CODENAME=trixie mean Debian 13; 12.x and bookworm mean Debian 12. If something in a guide does not match what you see, or you would rather have someone do the work for you, tell us what is broken.