Custom Debian package creation method

This blog explains how to create a custom package in Debian OS. We will see how to configure a customize Debian package and create customize command.

Debian package creation in Ubuntu/Debian:

We will create the helloworld package without any command and with command like e.g.- ipaddr (to get external ip)

Create a debian package:

Let’s start creating empty directory helloworld. This folder will contain both source code and the Debian build instructions.

1.1 Create the debian/ Directory

Here we will use dh_make command to create the debian/ Directory:

This created the debian/ folder. Explore them! Especially the example files (*.ex) as well as most importantly the files:

• debian/control
• debian/changelog
• debian/rules

1.2 Build the first (empty) Package

The dpkg-buildpackage command can be used to build  first package:

That’s it! This command build four files:

• .tar.gz: Source package, contains the contents of the helloworld/ folder
• .deb: Debian package, contains the installable package
• .dsc/.changes: Signature files, cryptographic signatures of all files

Let’s examine the contents with the dpkg -c command:

Nothing really in the package except the default changelog, copyright and README file.

1.3 Install the (empty) package

Let’s install it with dpkg -i command:

Done. That installed the package. Check out that it was actually installed by listing the installed packages with dpkg -l

The columns in the list are desired package state, actual package state, package name, package version, package architecture and a short package description. If all is well, the first column will contain ii, which means that the package is properly installed.

Now that the package is installed, you can list its contents with the dpkg -L

2.0 Adding files and updating the changelog

Let’s now add actual files in empty package. To do that, let’s create a folder file/usr/bin and add scripts to check IP address under ipaddr file.

For this demo, we’ll use a short script to grab the public IP address from a service called ipify. It provides an API to return the IP address in various formats. We’ll grab it with curl in JSON and then use jq to parse out the ‘ip’ field:

If we were to rebuild the package now, the dpkg-buildpackage command, we wouldn’t know which files to include in the package. So we’ll create the Debian/install file to list directories to include (e.g. vi Debian/install):

This basically means that everything in the files/usr/ folder will be installed at /usr/ on the target file system when the package is installed.

Once this is done, we can just rebuild and reinstall the package, but let’s go one step further and update the version of the package to 1.1.0. Versions are handled by the Debian/changelog file. You can update it manually, or use the dchscript (short for “Debian changelog”) to do so:

Let’s rebuild and reinstall the package:

Looks like it installed correctly. Let’s check if the ipaddr script is where it’s supposed to be. And then let’s try to run it:

2.1 Updating description and adding dependencies

Each Debian package can depend on other packages. In the case of our ipaddr script, we use the curl and jqcommands, so the ‘helloworld’ package depends on these commands.

To add the dependencies to the ‘helloworld’ package, edit the Depends: section in the debian/control file (e.g. via vi debian/control):

Again update the version and rebuild the package

unlike apt-get install, the dpkg -i command does not automatically resolve and install missing dependencies. It just highlights them. That is perfectly normal and expected. In fact, it gives us the perfect opportunity to check the package state (like we did above):

As you can see by the output, the desired state for the package is ‘i’ (= installed), but the actual state is ‘U’ (= Unpacked). That’s not good. Luckily though, dependencies can be automatically resolved by apt-get install -f

root@ip-172-31-19-221:/final_dpkg/helloworld-1.0# apt-get install -f
Reading package lists… Done
Building dependency tree
Reading state information… Done
Correcting dependencies… Done
The following additional packages will be installed:
jq libjq1 libonig4
The following NEW packages will be installed:
jq libjq1 libonig4
0 upgraded, 3 newly installed, 0 to remove and 28 not upgraded.
1 not fully installed or removed.
Need to get 327 kB of archives.
After this operation, 1,157 kB of additional disk space will be used.
Do you want to continue? [Y/n] y

Processing triggers for man-db (2.7.6.1-2) …

Setting up jq (1.5+dfsg-1.3) …

Setting up helloworld (1.0.3) …

Finally, its installed correctly. Now, let’s test it…

Conclusion:

This method makes it easy to install dependencies and multiple packages which we might require at bootup. It also installs a cluster of dependencies and customized packaged with the help of just one customized package.