APT Configuration Settings and Overrides

Ubuntu Tutorials - Herong's Tutorial Examples

∟APT Configuration Settings and Overrides

This section provides a quick introduction of APT (Advanced Package Tool) configuration settings and overriding configuration files.

If you use the "apt" command regularly, you may want to review and modify APT (Advanced Package Tool) configuration settings.

1. Review current settings using the "apt-config dump" command.

herong$ apt-config dump 

APT "";
APT::Architecture "amd64";
APT::Build-Essential "";
APT::Build-Essential:: "build-essential";
APT::Install-Recommends "1";
APT::Install-Suggests "0";
APT::Sandbox "";
APT::Sandbox::User "_apt";
APT::Authentication "";
APT::Authentication::TrustCDROM "true";
APT::NeverAutoRemove "";
APT::NeverAutoRemove:: "^firmware-linux.*";
APT::NeverAutoRemove:: "^linux-firmware$";
APT::NeverAutoRemove:: "^linux-image-[a-z0-9]*$";
APT::NeverAutoRemove:: "^linux-image-[a-z0-9]*-[a-z0-9]*$";
APT::VersionedKernelPackages "";
APT::VersionedKernelPackages:: "linux-image";
APT::VersionedKernelPackages:: "linux-headers";

...
Unattended-Upgrade::DevRelease "false";
CommandLine "";
CommandLine::AsString "apt-config dump";

To understand APT configuration settings, you should read apt.conf(5) man page.

herong$ man 5 apt.conf 

NAME
  apt.conf - Configuration file for APT

DESCRIPTION
  /etc/apt/apt.conf is the main configuration file shared by all the tools 
  in the APT suite of tools, though it is by no means the only place 
  options can be set. The suite also shares a common command line parser 
  to provide a uniform environment.

  When an APT tool starts up it will read the configuration files in the 
  following order:

   1. the file specified by the APT_CONFIG environment variable (if any)

  ...

APT uses configuration files in the /etc/apt/apt.conf.d directory to override default settings. I see the following files on my Ubuntu computer:

herong$ ls -l /etc/apt/apt.conf.d

total 72
-rw-r--r-- 1 root root   49 Sep 17  2019 00aptitude
-rw-r--r-- 1 root root   40 Sep 17  2019 00trustcdrom
-rw-r--r-- 1 root root 1018 Dec  7  2020 01autoremove
-rw-r--r-- 1 root root   42 Apr 20  2018 01-vendor-ubuntu
-rw-r--r-- 1 root root  129 Jun 27  2018 10periodic
-rw-r--r-- 1 root root  108 Jun 27  2018 15update-stamp
-rw-r--r-- 1 root root  392 Jun 24  2025 20apt-esm-hook.conf
-rw-r--r-- 1 root root   85 Jun 27  2018 20archive
-rw-r--r-- 1 root root   80 Dec 13  2018 20auto-upgrades
-rw-r--r-- 1 root root  243 Dec 16  2009 20dbus
-rw-r--r-- 1 root root 1040 Nov  8  2018 20packagekit
-rw-r--r-- 1 root root  127 Dec  1  2022 20snapd.conf
-rw-r--r-- 1 root root 2584 Apr  4  2018 50appstream
-rw-r--r-- 1 root root  625 Mar 16  2018 50command-not-found
-rw-r--r-- 1 root root 3800 Feb 17  2020 50unattended-upgrades
-rw-r--r-- 1 root root  435 Apr  4  2018 60icons
-rw-r--r-- 1 root root  182 Feb 28  2018 70debconf
-rw-r--r-- 1 root root  305 Jun 27  2018 99update-notifier

As you can see, settings are groupd into separate files for easier access. For example, "20archive" should hold lines to override APT::Archives::* settings.

herong$ cat /etc/apt/apt.conf.d/20archive 

APT::Archives::MaxAge "30";
APT::Archives::MinAge "2";
APT::Archives::MaxSize "500";

You can modify and add configuration files to update existing overrides or add new ones.

Here is what I did to override the Binary::apt::APT::Keep-Downloaded-Packages setting, to see downloaded packages after installation.

herong$ sudo vim /etc/apt/apt.conf.d/01keep-debs

binary::apt::APT::Keep-Downloaded-Packages "1";

Verify the setting.

herong$ apt-config dump | grep Keep-Downloaded 

binary::apt::APT::Keep-Downloaded-Packages "1";

Note APT configuration setting names are case sensitive. For example, Binary::apt::APT::Keep-Downloaded-Packages and binary::APT::APT::Keep-Downloaded-Packages will not be picked by the "apt" command.