Not keeping a server up to date is like a house left with its door open. Most software updates are patches that close discovered security vulnerabilities. Regular and methodical updating — that is, patch management — is the most fundamental and most neglected part of server security. This guide covers server updates.
Related reading: Linux package management · Server backup with rsync
Why Are Updates Critical?
When a security vulnerability is discovered in software, the vendor releases a patch — but that vulnerability is also announced publicly. So every day you do not apply the patch, you stay online with a publicly known hole. Automated scanners constantly look for such vulnerabilities; an out-of-date server sooner or later becomes a target.
Types of Updates
| Type | Priority | Approach |
|---|---|---|
| Security patches | Very high | Apply quickly, do not delay |
| Bug fixes | Medium | Apply at regular intervals |
| Version upgrades | Planned | Test first, then apply |
| Kernel updates | High | Usually require a reboot |
A Safe Update Process
On a production server, updating should be done methodically:
- Back up first: Before updating, prepare critical data and, where possible, a server snapshot.
- See what will change: Inspect the packages to be upgraded with
apt list --upgradable. - Test first where possible: On critical systems, try the update in a test environment first.
- Choose the right time: Update at a low-traffic hour.
- Verify afterward: After the update, check that services and the site work.
Automatic Security Updates
Tracking security patches by hand is hard and prone to delay. On Debian/Ubuntu, the unattended-upgrades package applies only security updates automatically — this is a strong default for server security:
# Install and enable automatic security updates
sudo apt install unattended-upgrades
sudo dpkg-reconfigure unattended-upgradesKernel Updates and Reboots
Most updates do not require a reboot; however, kernel updates are the exception — the server needs to be rebooted for the new kernel to take effect. The presence of the /var/run/reboot-required file on the system indicates a reboot is needed. On live servers, do this reboot in a planned maintenance window.
Frequently Asked Questions
Will my site go down during an update?
Package updates usually cause only a very short interruption while the relevant service restarts. Kernel updates that require a reboot mean a few minutes of downtime — that is why they are done in a planned way.
Is staying on an old version safe?
No. An end-of-life (EOL) operating system version no longer receives security patches; no matter how careful you are with it, you live with holes that will not be closed. Upgrading to a supported version is essential.
What do I do if an update breaks something?
This is exactly why you back up first. If an update causes a problem, you can roll back from a backup or server snapshot. Updating without a backup is the riskiest approach.
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