This is a text-only version of the following page on https://raymii.org: --- Title : Building opkg .ipk packages by hand (for OpenEmbedded/Yocto/OpenWRT) Author : Remy van Elst Date : 05-04-2019 URL : https://raymii.org/s/tutorials/Building_IPK_packages_by_hand.html Format : Markdown/HTML --- ![VAR-SOM-MX6][1] > Variscite VAR-SOM-MX6 - a high-performance ARM System on Module that can run Yocto `.ipk` packages are used by a variety of embedded linux systems, like routers running OpenWRT and appliances running on OpenEmbedded (Yocto). The `opkg` command installs these packages and OpenEmbedded comes with a set of tools to build `.ipk` packages. Recently I had to create ipk packages in a scripted fashion for a few hundred systems, all unique per system. The `.ipk` packages includes a few software changes for debugging, a systemd service and one precompiled binary. The yocto build tools were not available on the machine where these packages would be made so I had to figure out how to make them by hand, which means, automatically. The packages are actually just compressed files containing a few control files and the data to be extracted on the filesystem. This article will walk you through the steps of creating these packages by hand.

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All steps are executed as the root user. The system the packages are built on is running Ubuntu 18.04. If you haven't got `ar` installed, make sure to apt-get install binutils ### IPK packages An IPK package is very simple. It's like a `.deb` debian package, as in that is has both data and control files packaged up into an archive. The data will be extracted onto the filesystem where the package is installed, the control files are used for dependency management and to execute pre and post install actions. In my case, the `postinst` script is used to start the service (the binary we're packaging up). The `prerm` script is used to stop the service and disable it before uninstalling the package. The `postinst` script is used to check if the serial number matches the machine. An `ipk` is an archive (either `tar` or `ar` or `gzip`) containing two archives (`control.tar.gz` & `data.tar.gz`) and a `debian-binary` file with the contents `2.0`: tar -tzf example_package_1.3.3.7.varam335x.ipk Output: ./debian-binary ./data.tar.gz ./control.tar.gz ### Folder structure & Data The following folder structure is used for the package build. There is a `main` folder named `packages`, which has a subfolder for each machine based on the machines serial number. Under the machine folder there is a folder named after the package we're building (`examplepackage`), which has a `control` and `data` folder. The `data` folder contains the files that will be extracted on the filesystem and the `control` folder contains the pre and post scripts and some package information. packages/serialnumber/ |-- ipkbuild | `-- example_package | |-- control | | |-- control | | |-- postinst | | |-- preinst | | `-- prerm | |-- data | | |-- usr | | | `-- bin | | | `-- my_binary | | `-- lib | | `-- systemd | | `-- system | | `-- example_package.service | `-- debian-binary `-- example_package_1.3.3.7_varam335x.ipk To create the folder structure listed above, use this command: mkdir -p packages/serial/ipkbuild/example_package/{control,data} Then copy all the files you need installed (including folder structure and permissions) into the `data` folder. As you can see in the above listing, my `data` folder contains one binary and a systemd script (to start that binary). Make sure that your binaries have executable permissions and are for the correct architecture. A binary for a `mipsel` machine will not run on an `armv7l`, even if it's in that `ipk` package. ### Control & Postint, preinst, postrm and prerm scripts The `control` folder must contain at least a file named `control`. This has information on the package, like name, version, dependencies, etc. My control file is simple and contains just the bare minimum: cat packages/serial/ipkbuild/example_package/control/control Output: Package: example_package Version: 1.3.3.7 Architecture: varam335x Maintainer: user@domain.tld Description: This is an example IPK package Priority: optional Depends: systemd other_package The `debian-binary` file must contain just `2.0`: echo 2.0 > packages/serial/ipkbuild/example_package/debian-binary Some systems use this to check the MIME type of the package. The `postinst`, `postrm`, `preinst` and `prerm` are executed in their respective phases during installation or removal. Exit code 0 means all is well and the action will continue. Other exit codes (>1) mean that something went wrong and the action will stop. By default these scripts are executed with `sh`, but that depends entirely on your embedded system. In my case I know `bash` is available, but make sure to hold back onto `bash` specifics. My `preinst` file contains a check on the machine serial number. Since I build the packages for a specific machine, I know this beforehand. I want to make sure that packages can only run on the machine they're built for: cat packages/serial/ipkbuild/example_package/control/preinst Ouput: #!/bin/bash confserial=123456789 machineserial=`cat /example/serial.txt` if [ $confserial -ne $machineserial ]; then echo "Configured serial does not match machine serial" exit 1 fi Make sure this file is executable. It will not run otherwise, `opkg` will fail with a `Permission Denied` error. chmod +x packages/serial/ipkbuild/example_package/control/preinst The `postinst` file is executed after successfull installation. I use it to start the service we just installed: cat packages/serial/ipkbuild/example_package/control/postinst Output: #!/bin/bash systemctl --system daemon-reload systemctl enable example_service systemctl start example_service This file must be executable as well: chmod +x packages/serial/ipkbuild/example_package/control/postinst The `prerm` file is used to stop the service and remove it from systemd: cat packages/serial/ipkbuild/example_package/control/prerm Output: #!/bin/bash systemctl stop example_service systemctl disable example_service systemctl --system daemon-reload This one has to be executable as like all the others: chmod +x packages/serial/ipkbuild/example_package/control/prerm If you have all your data files and your control files in the correct folder you can continue to package it all up. ### Packing it all up The archive files must not contain any paths, therefore we create them in the folder structure we've created. I use `pushd` and `popd` because it's all scripted, but `cd` might work just as well. The paths and archive structure were a bit of a try, fail and retry experiment for me. pushd packages/serial/ipkbuild/example_package/control/ tar --numeric-owner --group=0 --owner=0 -czf ../control.tar.gz ./* popd pushd packages/serial/ipkbuild/example_package/data tar --numeric-owner --group=0 --owner=0 -czf ../data.tar.gz ./* popd pushd packages/serial/ipkbuild/example_package tar --numeric-owner --group=0 --owner=0 -cf ../../example_package_1.3.3.7.varam335x.ipk ./debian-binary ./data.tar.gz ./control.tar.gz popd You will now have an `ipk` package built: packages/serial/example_package_1.3.3.7_varam335x.ipk #### gzip vs debian binary package (mime type) If you have a system that does specific MIME type checks, you might want to use `ar` to create the package. If you use `tar` to create a package, the mimetype will be that of a tar or gzip file. Using `ar`, it will be a Debian Binary package format. `tar` packaged package: example_package_1.3.3.7.varam335x.ipk: gzip compressed data, last modified: Thu Apr 4 07:51:34 2019, from Unix (application/gzip) `ar` packaged package: example_package_1.3.3.7.varam335x.ipk: Debian binary package (format 2.0) (application/vnd.debian.binary-package) To create the package with `ar`, use the following command: pushd packages/serial/ipkbuild/example_package ar rv ../../example_package_1.3.3.7.varam335x.ipk debian-binary ./data.tar.gz ./control.tar.gz popd Output: ar: creating example_package_1.3.3.7.varam335x.ipk a - ./debian-binary a - ./data.tar.gz a - ./control.tar.gz [1]: https://raymii.org/s/inc/img/var-som-mx6.png [2]: https://www.digitalocean.com/?refcode=7435ae6b8212 --- License: All the text on this website is free as in freedom unless stated otherwise. 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