apt-cacher-ng is a nice little software to create a local cache of the Debian mirrors (but it can also operate on other distribution mirrors). The full documentation is available on the project's homepage (see in particular the excellent user manual).

Here are some quick instructions to get started.


Please make sure to use classic mirror server URLs such as http://ftp.us.debian.org in your /etc/apt/sources.list instead of its modern default http://deb.debian.org to avoid 986356 before installing apt-cacher-ng.

apt install apt-cacher-ng

To announce the service on the network, you may also want to install Avahi:

apt install avahi-daemon


Now of course, clients need to know about this proxy. You have two options:

apt install squid-deb-proxy-client

apt install auto-apt-proxy

echo 'Acquire::http { Proxy "http://proxy:3142"; }' | sudo tee -a /etc/apt/apt.conf.d/proxy

This assumes the server's hostname is proxy, change to its IP address or another hostname as convenient.

Acquire::http::ProxyAutoDetect "/usr/local/bin/apt-proxy-checker";

And creating a script at /usr/local/bin/apt-proxy-checker (or whatever location you configured) that will print out the address:port of AptCacherNg, or print “DIRECT” to use no proxy. This permits falling back to alternative AptCacherNg locations if one is down.

Using “DIRECT” as the final fallback value also prevents Apt from hanging and not updating packages.

There are several ways to check for listening addresses, such as using netcat with  nc -w1 -z $ADDR $PORT.

HTTPS repositories

apt-cacher-ng will obviously fail to serve HTTPS repositories. There are many solutions upstream but I have found the simplest solution to be to simply tunnel HTTPS connections directly on the proxy, by putting this in /etc/apt-cacher-ng/acng.conf:

PassThroughPattern: ^(.*):443$

This is, as far as I can tell, the only way to avoid doing a special configuration on the clients for HTTPS repositories. The downside is that HTTPS content is not cached.

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