Package Management in Ubuntu/Debian

dpkg: Debian Package Manager

It is responsible for installing packages

dpkg -i package.deb

.deb file is a compressed archive (ar file format) it includes all files needed for the program to run,= and its installation on the system.

To get debian packages for ubuntu

Go to https://packages.ubuntu.com

Get Ubuntu code name: lsb_release -a

Reconfigure DPKG package

sudo dpkg-reconfigure <package>

Dependency Management with `apt`

apt or apt-get search packages in the packages repositories configured in /etc/apt/sources.list or /etc/apt/sources.list.d/*

Update Package Definitions

sudo apt update

This updates the list of available versions of all packages installed on the ubuntu system from the configured repositories.

Upgrade the packages

sudo apt upgrade

Managing full-upgrade / dist-upgrade

sudo apt full-upgrade

dist-upgrade is equivalent to full-upgrade , this can remove some important dependencies packages

Auto removing packages

sudo apt autoremove

Source List Management

Structure of line in /etc/apt/source.list

deb http://ports.ubuntu.com/ubuntu-ports/ jammy main restricted

Field one deb: conatins binary packages, deb-src: This contains source packages

Field 2: URI

Field 3 or Field 4 ... : Domains,

Domains: main and universe are free, restricted and multiverse are non-free, code-updates : major bug fixes, code-backports: new version of software

Other format of Sources file

Types: deb
URIs: http://
Suites: code
Components: main
Architecture: amd64 i386
Signed-By: /etc/apt/Keyrings/XXXXXX.key

Custom Repositories

Creating a new file in /etc/apt/sources.list.d/*
Adding GPG key to our system for this repository
Updating the system after adding is recommended

PPA on ubuntu

This works on ubuntu not on debian

Steps:

Goto https://launchpad.net/ubuntu+ppas
Search the repository
sudo apt-add-repository ppa:person/package
It will add a file in /etc/apt/source.list.d/
Update the defnitions of the system

To remove ppa repo

sudo apt-add-repository -remove ppa:person/package

Verifying installation: `debsums`

Check all packages

debsums -a

Check all packages that has changed

debsums -a -s

Check all packages that do not have md5

checksums -l

Debug dependencies

Find the dependencies of the packages

apt show package

Pre-Depends: Should be installed before the package is unpacked and installed

Depends: Should also be installed before the package is unpacked and installed

Recommends: Not required, but should be installed unless any special requirements arise

Suggest: not required, can be ignored

Replaces: Will remove any dependencies that are causing conflicts

Conflict resolution

sudo apt install -f

-f = --fix-broken

To overwrite by ignoring dependencies while installing package using dpkg

sudo dpkg -i package.deb --ignore-depends

If software is not launching due to dependency conflict

Remove unnecessary packages: sudo apt autoremove
Remove conflicting packages, and update and upgrade
Remove the software and install again from official repository