Debian Package Management

Package management is one of the core features of a Linux system. It involves handling software packages, their installation, and dependency management. In this guide, we’ll look at package management in the Debian distribution and walk you through how to create, host, and deploy .deb packages. Setup First off, we need to create the folder structure and install the required packages to start building our Debian package. Create a folder that will contain all the code related to our project using the command ; mkdir deb-repo-example Then create two more folders within the main folder: One for our package, which we will name ; helloworld-package The second one is for our repository, called . helloworld-repo To have all the necessary packages installed, run the command . sudo apt-get install dpkg dpkg-dev Creating a .deb Package To start, let's create a simple .deb package locally and install it on our system. Navigate to folder that we created earlier; helloworld-package Next, we will create a file named that will represent our program: helloworld.sh Run the command echo "echo 'hello world'" > helloworld.sh Give executable permissions to the file by running . helloworld.sh chmod +x helloworld.sh Create a bash script that will generate our .deb package: Run the command touch create-deb.sh to create a new file; Set its permissions to executable by running . chmod +x create-deb.sh Finally, copy and paste the following code into the bash file to generate the Debian package. create-deb.sh #!/bin/bash VERSION=1 # remove any previously created package rm -r helloworld rm helloworld.deb # make a folder to create deb package mkdir -p helloworld/DEBIAN # we want our executable to be placed in /usr/local/bin after deb installation. mkdir -p helloworld/usr/local/bin cp helloworld.sh helloworld/usr/local/bin/ # create control file with information about the package touch helloworld/DEBIAN/control cat > helloworld/DEBIAN/control Package: helloworld Version: ${VERSION} Maintainer: John Doe Architecture: all Description: hello world program EOT # (optional) create script to run before installing begins touch helloworld/DEBIAN/preinst chmod +x helloworld/DEBIAN/preinst echo "echo 'helloworld: starting installation'" >> helloworld/DEBIAN/preinst # (optional) create script to run after installing completes touch helloworld/DEBIAN/postinst chmod +x helloworld/DEBIAN/postinst echo "echo 'helloworld: finish installation'" >> helloworld/DEBIAN/postinst # (optional) create script to run before removing touch helloworld/DEBIAN/prerm chmod +x helloworld/DEBIAN/prerm echo "echo 'helloworld: start removing'" >> helloworld/DEBIAN/prerm # (optional) create script to run after removing touch helloworld/DEBIAN/postrm chmod +x helloworld/DEBIAN/postrm echo "echo 'helloworld: finish removing'" >> helloworld/DEBIAN/postrm # build the package dpkg --build helloworld Now a package will be created with the name . helloworld.deb Managing Local Packages with DPKG We can use the command to install and remove a .deb package from our system. In this example, we will use the package that we just created to demonstrate these commands. dpkg helloworld.deb Let's start by managing our locally created package using dpkg: helloworld.deb Look up the package information by running . This will display metadata about the package, such as its name, version, and dependencies; dpkg --info helloworld.deb Check the contents of the package by running ; dpkg --contents helloworld.deb To install package, run : sudo dpkg --install helloworld.deb Note that the message from the post-install script appears at the end of the installation; Verify that the “helloworld” script is found in the system with ; which helloworld.sh Verify that the “helloworld” script runs by executing . helloworld.sh To remove the package run : sudo dpkg --remove helloworld Observe the pre- and post-removal scripts in action. Hosting a Debian Package in a Local APT Repository Now that we have created a deployable .deb package, we may want to distribute it to other users. In this section, we will look at how we can create an apt-repo to host our "helloworld" package. We’ll do this locally, but it can also be done by installing a web server to make it available online. To start, let's navigate to the previously created "helloworld-repo" folder by running ; cd ../helloworld-repo Copy the previously created .deb file to the repo folder by running ; cp ../helloworld-package/helloworld.deb helloworld_1.0-1_amd64.deb Note that we need to change the name to include the package name, version, and distribution: . {packageName}_{version}_{distribution}.deb Execute the following commands: ; dpkg-scanpackages . /dev/null | gzip -9c > Packages.gz . dpkg-scanpackages . /dev/null > Release This creates a valid repo that can now be used by apt to pull the “helloworld” binary. Let’s see how in the next section. Managing packages with APT As previously outlined, dpkg helps add and remove programs packaged as .deb files in our system. APT is a wrapper around dpkg that can do a lot more. It enables users to pull packages from repositories hosted online (or locally on a CD drive), install updates, remove packages, and manage their dependencies. In this section, we will explore the various commands and files associated with apt-get and demonstrate an example of using it to install the "helloworld" package that we created and hosted on our local file system. To install a package using APT, we first need to inform the system about the location of the repository that hosts the package. There are three ways to do this: Editing the file. By default the file contains the URLs of predefined repositories. You can add your source to this file. /etc/apt/sources.list sources.list Creating a new file in the directory and adding the URL to that file. This method is better because you can add all the sources that are related in a separate file that can be easily removed later. /etc/apt/sources.list.d Using the command. add-apt-repository The second step is to fetch all the available packages and their versions. This can be done by calling apt-get update Calling this command updates the files available in . /var/lib/apt/lists The files in list the available versions of the packages. /var/lib/apt/lists To install packages using APT, we have the following options: To update packages that are already installed on the system: Run ; apt-get upgrade This command only updates the package on the system and adds or removes dependencies as needed. To update packages that are already installed on the system with the possibility of adding or removing dependent packages: Run ; apt-get dist-upgrade This command upgrades all installed packages on the system but adds or removes additional dependencies if necessary. To install a package that does not exist on the current system: Run . apt-get install Installing packages results in the following: The .deb package is downloaded to ; /var/cache/apt/archives/partial The .deb file is moved to once the download is complete; /var/cache/apt/archives The package is installed in the system using dpkg. command can be used to clean up the .deb files to reclaim space. apt-get clean Now, let's see APT in action by installing our locally hosted package, helloworld, using apt-get. # add source (you will have to change the path to where your helloworld-repo is) sudo touch /etc/apt/sources.list.d/helloworld.list sudo echo "deb [trusted=yes] file:///home/my_user/deb-repo-example/helloworld-repo ./" > /etc/apt/sources.list.d/helloworld.list # fetch package versions sudo apt-get update # We can see that apt has downloaded the metadata of the package cat /var/lib/apt/lists/*helloworld* # install helloworld package on our system sudo apt-get install helloworld # see that the helloworld program is found in our system, and execute it. which helloworld helloworld.sh Now that we have installed the application, let's see how apt-get can also update packages installed on the system. # navigate back to helloworld-package # now lets create version 2 of helloworld package like we did before echo "echo 'hello world from version 2'" > helloworld.sh` # to create package for version 2 change the VERSION value in create-deb.sh then execute it ./create-deb.sh # examine the package and ensure that package is now version 2 dpkg --info helloworld.deb # copy package to helloworld-repo with cp helloworld.deb ../helloworld-repo/helloworld_2.0-1_amd64.deb # navigate to helloworld-repo and execute dpkg-scanpackages . /dev/null | gzip -9c > Packages.gz dpkg-scanpackages . /dev/null > Release # unfortunately dpkg only allows one version so we will replace our current repo with the new version. If you want to maintain multiple package you can use aptly # now that our repo has a new version of hello world we can update our system by. apt-get update apt-get upgrade # execute helloworld again and note that version is updated helloworld.sh # remove helloworld package from our system apt-get clean helloworld You have now successfully upgraded your package. References: "Debian Package Management Internals", Debian Project, https://www.debian.org/doc/manuals/debian-reference/ch02.en.html#_debian_package_management_internals "The Debian Maintainer's Guide", Debian Project, https://www.debian.org/doc/manuals/maint-guide/first.en.html "DebianRepository/Format", Debian Project, https://wiki.debian.org/DebianRepository/Format "Creating and Hosting Your Own Deb Packages and APT Repo", Alex Couture-Beil, 2021, https://earthly.dev/blog/creating-and-hosting-your-own-deb-packages-and-apt-repo/ "Creating Debian/Ubuntu .deb packages", Intracto Blog, https://www.iodigital.com/en/history/intracto/creating-debianubuntu-deb-packages