Debian APT Package Download Cache Configuration

Debian's Advanced Package Tool (APT) stores downloaded .deb packages in a local cache before installing them. By modifying or creating configuration snippets in /etc/apt/apt.conf.d/, administrators can control whether packages are retained after installation, adjust the cache directory location, or enforce size and age limits on stored archives.

The Primary Retention Setting: APT::Keep-Downloaded-Packages

The primary directive controlling whether downloaded .deb files remain on the system after installation is APT::Keep-Downloaded-Packages.

• To retain packages in the cache:

  APT::Keep-Downloaded-Packages "true";

• To automatically delete packages after installation:

  APT::Keep-Downloaded-Packages "false";

In modern Debian releases, the command-line utility apt defaults to deleting packages (false), whereas apt-get historically defaults to keeping them (true). To enforce a uniform policy across all package management tools, create a dedicated file such as /etc/apt/apt.conf.d/01cache containing your preferred directive.

Changing the Download Directory: Dir::Cache::Archives

By default, APT stores packages in /var/cache/apt/archives/ and incomplete downloads in /var/cache/apt/archives/partial/. You can redirect this storage path to an alternative filesystem or mount point using the following configuration:

Dir::Cache::Archives "/path/to/custom/cache/";

Ensure the destination directory exists and has appropriate read and write permissions for the _apt and root users.

Controlling Automatic Cache Cleanup

For systems using background maintenance scripts (such as apt-daily.service or unattended upgrades), APT supports parameters that limit cache expansion based on time and disk consumption:

• APT::Archives::MaxAge: Sets the maximum number of days a package file can stay in the cache. Files older than this value are removed during automated cleanup runs.

  APT::Archives::MaxAge "30";

• APT::Archives::MinAge: Prevents the deletion of packages that were downloaded more recently than the specified number of days, regardless of cache size limits.

  APT::Archives::MinAge "2";

• APT::Archives::MaxSize: Sets a target maximum size (in megabytes) for the cache. If the directory exceeds this limit, older packages are purged until the size falls back beneath it.

  APT::Archives::MaxSize "500";

Completely Disabling Disk Caching

In containerized environments (like Docker) or environments with extreme storage constraints, you can prevent APT from using disk storage for archives entirely by directing the archive storage to an empty string:

Dir::Cache::Archives "";
APT::Keep-Downloaded-Packages "false";

This prevents APT from committing .deb files to permanent storage, saving disk space at the expense of needing to redownload files if a package reinstallation is required.