Maintaining multiple Ubuntu desktops in an office, school, or lab environment can become bandwidth-intensive if each machine downloads updates from the internet individually. A more efficient solution is to set up a local update server, which caches packages and distributes them to all local machines.

In this guide, we walk through how to set up a local Ubuntu package mirror using apt-cacher-ng, a lightweight and efficient caching proxy for Debian-based systems.

🧰 Prerequisites

• A dedicated Ubuntu server (or one of your desktops) that will act as the cache server.
• Internet access on the server.
• Static IP or reserved DHCP IP for the cache server.
• Ubuntu desktops configured to use the cache.

🖥️ Step 1: Install apt-cacher-ng on the Server

sudo apt update
sudo apt install apt-cacher-ng

Once installed, the service starts automatically. You can check its status with:

sudo systemctl status apt-cacher-ng

⚙️ Step 2: Configure apt-cacher-ng (Optional)

The default settings are usually fine for most use cases. But if you want to review or tweak the settings:

sudo nano /etc/apt-cacher-ng/acng.conf

Ensure this line is set (it usually is):

PassThroughPattern: .*ubuntu.com/.* 

To allow web access to the stats page, find and set:

ReportPage: acng-report.html

Then restart the service:

sudo systemctl restart apt-cacher-ng

🌐 Step 3: Allow Access Through Firewall (If Enabled)

If UFW is enabled:

sudo ufw allow 3142/tcp

Port 3142 is the default port used by apt-cacher-ng.

🧪 Step 4: Test the Server Locally

You can test the server by accessing this URL in a browser on another machine:

http://<cache-server-ip>:3142/acng-report.html

You should see the Apt-Cacher NG status page.

🧑‍💻 Step 5: Configure Ubuntu Clients

On each Ubuntu desktop, edit or create the file:

sudo nano /etc/apt/apt.conf.d/01proxy

Add this line (replace <cache-server-ip> with your server’s IP address):

Acquire::http::Proxy "http://<cache-server-ip>:3142";

Example:

Acquire::http::Proxy "http://192.168.1.10:3142";

Now, whenever you run:

sudo apt update && sudo apt upgrade

The desktop will fetch packages from your local cache server, downloading from the internet only if they’re not already cached.

🧹 Optional: Exclude Certain Packages or Repositories

You can fine-tune what gets cached in /etc/apt-cacher-ng/acng.conf. Look for directives like:

ExThreshold: 10

Or define blacklist patterns. See the man page for more advanced options:

man acng.conf

📊 Monitor Usage

Check the cache statistics and logs via:

• Web UI: http://<cache-server-ip>:3142/acng-report.html
• Log file: /var/log/apt-cacher-ng/apt-cacher.log

✅ Final Tips

• Regularly monitor disk space. Cache can grow over time.
• Use cron or logrotate to manage logs and old cached files.
• Works seamlessly for Ubuntu, Debian, and derivatives (Linux Mint, Pop!_OS).

Setting up a local update server is a smart move for environments with multiple machines. It reduces internet usage, speeds up updates, and improves reliability during high-traffic times. Once configured, it’s mostly maintenance-free.