Installing and Updating Software

Objectives
Learn how to install software
Learn how package managers work
Learn about dependencies

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Installing Software
Historically in order to install software:
We would download the source code
Then depending on the type of code we would either:
C Code - Use a compiler like GCC (GNU C Compiler) to
compile the software into a usable application
BASH Script - store the file as an executable script
Now we usually use some kind of package manager or package
management system

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Compiling
Source code has a manifest definition in the compiling
instructions which lists all dependencies and versions
If the compiler cannot find these dependencies then it cannot
continue to compile the software
In this case the operation will be aborted and stderr displays an
error message with what dependencies haven't been met

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Dependencies
A dependency is a software library used by the program
Why should we use dependencies?
Instead of everyone creating the same software over and over,
on developer creates a library and everyone can rely on it
This allows for software to be developed quicker and more
modularly so pieces and be replaced as needed
Example: MD5 hashing function can be quickly implemented using
an MD5 hashing library

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Dependencies - Scenario - Multiple Versions
App1 needs libfoo v1.2
App2 needs libfoo v1.3
When you have 2 different applications requiring the same library
but different versions there is an issue
You can either store 2 libraries, which can get messy
Upgrade the older application to the new library if you are the
developer

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Dependencies - Scenario - Nested Dependencies
Libfoo1.3 requires libgc1.33 and libC++1.67
libgc1.33 requires libBar1.99 and libLubar2.37
libLubar2.37 requires libnet1.2
Just imagine this could be nested hundreds of times with
thousands of dependencies especially when dealing with complex
applications
Imagine doing that manually?

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Dependencies - Scenario - Circular Dependencies
AppX v1 depends on app2
which depends on app3
which depends on app4
which depends on AppX v0
This is called circular dependencies
In order to solve this problem all versions have to be installed
simultaneously

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So how do we fix this?
We could keep track of version numbers and install versions side
by side as required

OR

We could use a package management system!

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What is a Package?
Software Package is a collection of:
Scripts
Programs
Files
Directories
List of Dependencies
Programs are:
Executable files
Source code to be compiled
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Package Management Systems
A Package Management System is a set of utilities that allow for
package
Installation
Upgrading
Removal
Searching
All these procedures are done based on a local database
The local database is synced with remote repositories

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Repositories
A repository is a server that holds packages and package
information
They can be located on the internet
Hosted internally
Stored on the installation DVD
Each distribution has at least one centralized repository, with
packages tested and compiled for that specific distribution
Each distribution has different package delivery standards

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Repository Configuration FIles
A Repository configuration file will contain information about the
repository including:
Name
Location (URL)
Alternate locations (Mirror)
In debian the repository configuration files are in
/etc/apt/sources.list

Example:
deb.debian.org/debian/ bullseye-updates main
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Distribution Package Formats
*.deb for Debian Based Distros
Ex. Debian, Ubuntu, MX Linux
Also may contain Source or Pre-Compiled Binaries
*.rpm for Redhat Based Distros
Including CentOS
May Contain Source or Pre-Compiled Binaries
*.tgz/.tar.gz for Source Code compilation
Contains compressed version of the source code to be installed

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Debian Package Manager (dpkg)
dpkg can
Install
Uninstall
Upgrade
Query and Verify deb packages
Maintain a record of installed packages
Cannot automatically install dependencies
Does not communicate with the repository

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Command: dpkg/dpkg-query
dpkg [options] action
dpkg-query [options] action

Command Description
dpkg-query --list tmux Query for the tmux package
dpkg-query --list Query every package
dpkg -i tmux-2.4.2.e17_x86_64.deb Install tmux from file
dpkg -r tmux Removes the package tmux

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apt
apt (advanced package tool)
The front end manager for dpkg packages
Installs package and dependencies when required
Manages software upgrades from a repository
Deals with managing all potential software from repositories

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Command: apt

Command Description
apt list --installed List installed packages
apt list --upgradeable List upgradeable packages
List all versions of installed
apt list --all-version
paackages
apt list --installed tmux List installed version of tmux
apt list --upgradeable
tmux
List upgradeable versions of tmux
apt list --all-version
tmux
List all versions of tmux
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Command: apt

Command Description
apt install tmux Install tmux package
apt search tmux Search for tmux package
apt-file search
bin/tmux
Find packages that provide the tmux file

apt info tmux Provide info on the tmux package

apt update Update the package listing
This command will upgrade your installed
apt upgrade
packages
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Why ever use dpkg?
Software packages maintained in server repositories are generally
old and thoroughly tested, therefore considered stable
Sometimes you'll want a newer version of software for the latest
features
In that case you'll have to download the latest version manually
and install it using dpkg
Keep in mind this means you are dealing with dependencies

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dpkg Package Information
nano-2.2.6-1.i386.deb
This states that the package name is nano
It is version 2.2.6
-1 is the release
A release is backports of security fixes
It has been compiled for the i386 platform
What is i386?
i386,i486,i586,i686 are the codenames for 32 Bit processors
amd64 is the codename for 64 Bit processors
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Additional Repos
It is possible to add additional repositories
However keep in mind you have to make sure you trust the
repository as they are sending you software
Imagine your repositories could have data miners or other
malicious software in them
Many software providers have their own repositories for example
Node.js
https://github.com/nodesource/distributions/blob/master/READ
ME.md
Docker https://docs.docker.com/engine/install/debian/ 22
Other Package Types
FlatPak - Developed by Redhat
https://flatpak.org/
Snap Packages - Developed by Canonical (Ubuntu)
https://snapcraft.io/
AppImage - Community Created
https://appimage.org/

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