APT-CACHER-NG - Base Config

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Installation

Debian / Ubuntu

Install the package from the official repositories: 

sudo apt update
sudo apt install apt-cacher-ng

The service is automatically started after installation.

Check service status: 

systemctl status apt-cacher-ng

Enable it at boot: 

sudo systemctl enable apt-cacher-ng

RHEL / Rocky / AlmaLinux

Enable EPEL and install: 

sudo dnf install epel-release
sudo dnf install apt-cacher-ng

Start and enable the service: 

sudo systemctl start apt-cacher-ng
sudo systemctl enable apt-cacher-ng

Directory Layout

Default paths (may vary by distribution):

  • Configuration: /etc/apt-cacher-ng/
  • Main configuration file: /etc/apt-cacher-ng/acng.conf
  • Cache storage: /var/cache/apt-cacher-ng/
  • Logs: /var/log/apt-cacher-ng/

Cache directory structure example:

  • deb/ – cached Debian/Ubuntu packages
  • ubuntu/ – Ubuntu repositories
  • security.ubuntu.com/
  • partial/ – incomplete downloads

Core Configuration

Edit the main configuration file: 

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

Cache Directory

CacheDir: /var/cache/apt-cacher-ng

Listening Port

Default port is 3142: 

Port:3142

Bind Address

Restrict listening interface: 

BindAddress: 0.0.0.0

For localhost only: 

BindAddress: 127.0.0.1

Client Configuration

Using APT Proxy Configuration

Create a proxy configuration file on the client: 

sudo nano /etc/apt/apt.conf.d/02proxy

Content: 

Acquire::http::Proxy "http://APT_CACHER_IP:3142";
Acquire::https::Proxy "http://APT_CACHER_IP:3142";

Example: 

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

Test: 

sudo apt update

HTTPS and SSL Handling

apt-cacher-ng does not decrypt HTTPS, but tunnels it.

Ensure HTTPS support is enabled (default): 

PassThroughPattern: .*

HTTPS repositories benefit from metadata caching but not from package-level deduplication.

Supported Repositories

apt-cacher-ng supports:

  • Debian
  • Ubuntu
  • Linux Mint
  • Kali Linux
  • Proxmox
  • Docker APT repositories
  • Custom APT repositories

Example custom repository rewrite: 

Remap-myrepo: file:custom_mirror /myrepo

Pre-Fetching Packages

Pre-download packages to warm the cache: 

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

Or from a client: 

sudo apt install --download-only linux-image-generic

Cache Maintenance

Check Cache Usage

du -sh /var/cache/apt-cacher-ng

Expire Old Packages

Manual expiration: 

sudo apt-cacher-ng -c /etc/apt-cacher-ng/acng.conf -e

Clear Cache Completely

sudo systemctl stop apt-cacher-ng
sudo rm -rf /var/cache/apt-cacher-ng/*
sudo systemctl start apt-cacher-ng

Logging and Monitoring

Log files:

  • apt-cacher.log
  • apt-cacher.err
  • apt-cacher.debug

Tail logs in real time: 

tail -f /var/log/apt-cacher-ng/apt-cacher.log

Web interface (read-only): 

http://APT_CACHER_IP:3142/acng-report.html

Security Hardening

Restrict Access

Firewall example: 

sudo ufw allow from 192.168.1.0/24 to any port 3142

Bind only to internal IP: 

BindAddress: 192.168.1.10

Protect Administrative Pages

AdminAuth: admin:strongpassword

Performance Tuning

Increase file descriptor limit: 

ulimit -n 65535

Adjust worker threads: 

MaxConThreads: 50

Using SSD-backed storage for the cache significantly improves performance.

Integration with Containers

Example Docker run: 

docker run -d \
  -p 3142:3142 \
  -v /var/cache/apt-cacher-ng:/var/cache/apt-cacher-ng \
  apt-cacher-ng

Dockerfile APT proxy usage: 

RUN echo 'Acquire::http::Proxy "http://host.docker.internal:3142";' \
    > /etc/apt/apt.conf.d/02proxy

Troubleshooting

Clients Do Not Use Cache

  • Verify proxy configuration on client
  • Inspect logs:
grep CONNECT /var/log/apt-cacher-ng/apt-cacher.log

Permission Errors

Fix ownership: 

sudo chown -R apt-cacher-ng:apt-cacher-ng /var/cache/apt-cacher-ng

Restart service: 

sudo systemctl restart apt-cacher-ng

Port Already in Use

Check port usage: 

sudo ss -tulpn | grep 3142

Change port if required: 

Port:3143

Corrupted Cache

Clean and rebuild partial cache: 

sudo systemctl stop apt-cacher-ng
sudo rm -rf /var/cache/apt-cacher-ng/partial/*
sudo systemctl start apt-cacher-ng
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