• Diff for "IntroDebianPackaging"

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Introduction to Debian Packaging

Debian Women IRC training session held by Lars Wirzenius on the 18th November 2010

• with a couple of small, clearly marked additions by Sebastian Tennant (following my crash course in Debian packaging by Daniel Baumann at DebCamp 2011, Banja Luka)

This is an introductory tutorial for making Debian packages: it doesn't get very deep into the more intricate bits of Debian packaging, but it will show how to make Debian packages for software that is simple to package.

For this purpose, we will use only the dh command from debhelper 9.

Requirements

In this tutorial it is assumed that:

• you understand installation of binary packages;

• you understand general command line use, and editing of text files using an editor of your choice (emacs, vim, gedit, kate, etc.);

Technical requirements:

• build-essential

• devscripts

• debhelper version 9 or higher

Three central concepts

The three central concepts are

• upstream tarball:

  • Usually, people package software that someone else, called the upstream developer, has written.

  • The upstream developers will make a release of their software in the "upstream source archive file" or tarball.

  • A tarball is the .tar.gz or .tgz file upstream makes (tarball is a bit of computer jargon), and it can also be compressed to .tar.bz2,.tb2 or .tar.xz. The tarball is exactly what Debian takes and builds a package out of.

• source package:

  • When you have the upstream tarball, the next step is to make the Debian source package.

• binary package:

  • From this source package you can then build the Debian binary package which is what actually get installed.

The source package consists, in its simplest form, of three files:

• The upstream tarball, renamed to follow a systematic pattern.

• A debian directory, with any changes made to upstream source, plus all the files created for the Debian package. This has a .debian.tar.gz ending.

• A description file (with .dsc ending), which lists the other two files.

This sounds a bit more complicated than is necessary, at first sight: It would be simpler to just have everything in one file.

• However, it turns out that it saves a lot of disk space and bandwidth to keep the upstream tarball separate from any Debian specific changes.
• It's also easier to keep track of what has been necessary to change for Debian.

The packaging work flow

The packaging work flow is usually like this:

• Step 1: Rename the upstream tarball
• Step 2: Unpack the upstream tarball
• Step 3: Add the Debian packaging files
• Step 4: Build the package
• Step 5: Install the package

Then you can test your package on your computer.

The source and binary packages can be uploaded to Debian.

For this tutorial Lars has used this tarball.

Step 1: Rename the upstream tarball

The Debian packaging tools assume the upstream tarball has a very specific name. It must follow a specific naming pattern.

The name consists of the source package name, an underscore, the upstream version number, followed by .orig.tar.gz. The source package name should be all in lower case, and can contain letters, digits, and dashes. Some other characters are also allowed.

If the upstream developers use a name that looks like a good Debian source package name, then you should use that. Otherwise, change the upstream name as little as possible to make it fit for Debian. In this case, upstream has wisely picked a suitable name, "hithere", so there's no need to worry about it.

We should end up with a file called hithere_1.0.orig.tar.gz.

Note that there is an underscore (_), not a dash (-), in the name. This is important, because the packaging tools are picky.

Step 2: Unpack the upstream tarball

In general, the sources should go into a directory named after the source package name and upstream version (with a hyphen, not an underscore, in between) so ideally the upstream tarball will unpack into a directory called "hithere-1.0".

This is again because the packaging tools are picky.

In this case, upstream has again been wise and made the tarball unpack into the right subdirectory.

Step 3: Add the Debian packaging files

All of these files go into the debian/ subdirectory inside the source tree.

There are a bunch of files we need to provide. Let's look at them in order.

debian/changelog

First file is debian/changelog. This is the log of changes to the Debian package.

It does not need to list everything that has changed in upstream code, though it can be helpful to users to summarize those changes, too. Since we are now making the first version, there is nothing to log. However, we still need to make a changelog entry, because the packaging tools read certain information from the changelog. Most importantly, they read the version of the package.

debian/changelog has a very particular format. The easiest way to create it is to use the dch tool.

This will result in a file like this:

hithere (1.0-1) UNRELEASED; urgency=low

  * Initial release. (Closes: #XXXXXX)

 -- Lars Wirzenius <liw@liw.fi>  Thu, 18 Nov 2010 17:25:32 +0000

A couple of notes:

• The hithere part MUST be the same as the source package name. 1.0-1 is the version. The 1.0 part is the upstream version. The -1 part is the Debian version: the first version of the Debian package of upstream version 1.0. If the Debian package has a bug, and it gets fixed, but the upstream version remains the same, then the next version of the package will be called 1.0-2. Then 1.0-3, and so on.

• UNRELEASED is called the upload target. It tells the upload tool where the binary package should be uploaded. UNRELEASED means the package is not yet ready to be uploaded. It's a good idea to keep the UNRELEASED there so you don't upload by mistake.

• Ignore urgency=low for now. Just keep it there.

• The (Closes: #XXXXXX) bit is for closing bugs when the package is uploaded. This is the usual way in which bugs are closed in Debian: when the package that fixes the bug is uploaded, the bug tracker notices this and marks the bug as closed. We can just remove the (Closes...) bit. Or not. It doesn't matter right now.

• The final line in the changelog tells who made this version of the package, and when. The dch tool tries to guess the name and e-mail address, but you can configure it with the right details. See the dch(1) manual page for details.

debian/compat

This file should contain the number 9. This is a magic number. Do not put any other number in there.

9

debian/compat specifies the "compatibility level" for the debhelper tool. We don't need to go into what that means, right now.

debian/control

The control file describes the source and binary package, and gives some information about them, such as their names, who the package maintainer is, and so on. Below an example of what it might look like.

Source: hithere
Maintainer: Lars Wirzenius <liw@liw.fi>
Section: misc
Priority: optional
Standards-Version: 3.9.2
Build-Depends: debhelper (>= 9)

Package: hithere
Architecture: any
Depends: ${shlibs:Depends}, ${misc:Depends}
Description: greet user
 hithere greets the user, or the world.

There are several required fields, but you can just treat them as magic, for now. So, in debian/control, there are two paragraphs.

The first paragraph describes the source package, with these fields:

Source

The source package name.

Maintainer

The name and e-mail address of the person responsible for the package.

Priority

The priority of the package (one of 'required', 'important', 'standard', 'optional' or 'extra'). In general a package is 'optional' unless it's 'essential' for a standard functioning system, i.e., booting or networking functionality. A package should be 'extra' rather than 'optional' if it conflicts with another 'optional' package, or if it's not intended to be used on a standard desktop installation. Notable example of 'extra' packages are debugging packages. (Added by Sebastian Tennant).

Build-Depends

The list of packages that need to be installed to build the package. They might or might not be needed to actually use the package.

All paragraphs after the first describe the binary packages built from this source. There can be many binary packages built from the same source; our example only has one. We use these fields:

Package

The name of the binary package. The name might be different from the source package name.

Architecture

Specifies which computer architectures the binary package is expected to work on: i386 for 32-bit Intel CPUs, amd64 for 64-bit, armel for ARM processors, and so on. Debian works on about a dozen computer architectures in total, so this architecture support is crucial. The "Architecture" field can contain names of particular architectures, but usually it contains one of two special values.

any

(which we see in the example) means that the package can be built for any architecture. In other words, the code has been written portably, so it does not make too many assumptions about the hardware. However, the binary package will still need to be built for each architecture separately.

all

means that the same binary package will work on all architectures, without having to be built separately for each. For example, a package consisting only of shell scripts would be "all". Shell scripts work the same everywhere and do not need to be compiled.

Depends

The list of packages that must be installed for the program in the binary package to work. Listing such dependencies manually is tedious, error-prone work. To make this work, the ${shlibs:Depends} magic bit needs to be in there. The other magic stuff is there for debhelper. The ${misc:Depends} bit. The shlibs magic is for shared library dependencies, the misc magic is for some stuff debhelper does. For other dependencies, you need to add them manually to Depends or Build-Depends and the ${...} magic bits only work in Depends

Description

The full description of the binary package. It is meant to be helpful to users. The first line is used as the short synopsis (summary) description, and the rest of the description must be an independent longer description of the package.

debian/copyright

It is quite an important file, but for now we will be happy enough with an empty file.

For Debian, this file is used to keep track of the legal, copyright-related information about a package. However, it is not important from a technical point of view. For now, we'll concentrate on the technical aspects. We can get back to debian/copyright later, if there's interest.

debian/rules

It should look like this:

#!/usr/bin/make -f
%:
        dh $@

• Note: The last line should be indented by one TAB character, not by spaces. The file is a makefile, and TAB is what the make command wants

debian/rules can actually be quite a complicated file. However, the dh command in debhelper version 7 has made it possible to keep it this simple in many cases.

debian/source/format

The final file we need is debian/source/format, and it should contain the version number for the format of the source package, which is "3.0 (quilt)".

3.0 (quilt)

Step 4: Build the package

First try

Now we can build the package.

There are many commands we could use for this, but this is the one we'll use. If you run the command, you'll get output similar to this:

make[1]: Entering directory `/home/liw/debian-packaging-tutorial/x/hithere-1.0'
install hithere /home/liw/debian-packaging-tutorial/x/hithere-1.0/debian/hithere/usr/local/bin
install: cannot create regular file `/home/liw/debian-packaging-tutorial/x/hithere-1.0/debian/hithere/usr/local/bin': No such file or directory
make[1]: *** [install] Error 1
make[1]: Leaving directory `/home/liw/debian-packaging-tutorial/x/hithere-1.0'
dh_auto_install: make -j1 install DESTDIR=/home/liw/debian-packaging-tutorial/x/hithere-1.0/debian/hithere returned exit code 2
make: *** [binary] Error 29
dpkg-buildpackage: error: fakeroot debian/rules binary gave error exit status 2
debuild: fatal error at line 1325:
dpkg-buildpackage -rfakeroot -D -us -uc failed

Something went wrong. This is what usually happens. You do your best creating debian/* files, but there's always something that you don't get right.

So, the thing that went wrong is this bit:

install hithere /home/liw/debian-packaging-tutorial/x/hithere-1.0/debian/hithere/usr/local/bin

The upstream Makefile is trying to install the compiled program into the wrong location.

There are a couple of things going on here: first is a bit about how Debian packaging works.

Correction

When the program has been built, and is "installed", it does not get installed into /usr or /usr/local, as usual, but somewhere under the debian/ subdirectory.

We create a subset of the whole file system under debian/hithere, and then we put that into the binary package. So the .../debian/hithere/usr/local/bin bit is fine, except that it should not be installing it under usr/local, but directly under usr.

We need to do something to make it install into the right location (debian/hithere/usr/bin).

The right way to fix this is to change debian/rules so that it tells the Makefile where to install things.

#!/usr/bin/make -f
%:
        dh $@

override_dh_auto_install:
        $(MAKE) DESTDIR=$$(pwd)/debian/hithere prefix=/usr install

It's again a bit of magic, and to understand it you'll need to know how Makefiles work, and the various stages of a debhelper run.

For now, I'll summarize by saying that there's a command debhelper runs that takes care of installing the upstream files, and this stage is called dh_auto_install.

We need to override this stage, and we do that with a rule in debian/rules called override_dh_auto_install.

The final line in the new debian/rules is a bit of 1970s technology to invoke the upstream Makefile from debian/rules with the right arguments.

Let's try again

It still fails!

• This time, this is the failing command:

install hithere /home/liw/debian-packaging-tutorial/x/hithere-1.0/debian/hithere/usr/bin

We are now trying to install into the right place, but it does not exist. To fix this, we need to tell the packaging tools to create the directory first.

Ideally, the upstream Makefile would create the directory itself, but in this case the upstream developer was too lazy to do so.

Another correction

The packaging tools (specifically, debhelper) provide a way to do that.

• Create a file called debian/hithere.dirs, and make it look like this:

usr/bin
usr/share/man/man1

The second line creates the directory for the manual page. We will need it later. You should be careful to maintain such *.dirs files because it can lead to empty directories in future versions of your package if the items listed in those files aren't valid any more.

Let's try once more

Now the build succeeds, but there's still some small problems.

debuild runs the lintian tool, which checks the package that has been built for some common errors. It reports several for this new package:

Now running lintian...
W: hithere source: out-of-date-standards-version 3.9.0 (current is 3.9.1)
W: hithere: copyright-without-copyright-notice
W: hithere: new-package-should-close-itp-bug
W: hithere: wrong-bug-number-in-closes l3:#XXXXXX
Finished running lintian.

These should eventually be fixed, but none of them look like they'll be a problem for trying the package. So let's ignore them for now.

Look in the parent directory to find the package that was built.

hithere-1.0                  hithere_1.0-1_amd64.deb  hithere_1.0.orig.tar.gz
hithere_1.0-1_amd64.build    hithere_1.0-1.debian.tar.gz
hithere_1.0-1_amd64.changes  hithere_1.0-1.dsc

Step 5: Install the package

The following command will install the package that you've just built.

Do NOT run it on a computer unless you don't mind breaking it.

• In general, it is best to do package development on a computer that is well backed up, and that you don't mind re-installing if everything goes really badly wrong.

Virtual machines are a good place to do development.

[sudo] password for liw:
Selecting previously deselected package hithere.
(Reading database ... 154793 files and directories currently installed.)
Unpacking hithere (from ../hithere_1.0-1_amd64.deb) ...
Setting up hithere (1.0-1) ...
Processing triggers for man-db ...
liw@havelock$

How do we test the package? We can run the command.

It works!

But, it's not perfect. Remember, lintian had things to say, and debian/copyright is empty, etc.

We have a package that works, but it isn't yet of the high quality that is expected of a Debian package.

Conclusion

Once you've built your own packages, you'll eventually want to learn how to set up your apt repository, so your package is easy to install. The best tool for that I know of is reprepro.

For more testing of your package, you may want to look at the tool called piuparts. (I wrote it originally so it is perfect and never has any bugs. er...)

And, finally, if you start making changes to the upstream source, you'll want to learn about the quilt tool.

Other things you might want to read are listed on the http://www.debian.org/devel/ web page.

Questions and Answers

QUESTION: Please clarify about packaging those packages that are already in binary form, i.e., nvidia blob or likewise

ANSWER: For binary blob packages, you treat the tarball with the blobs as the source package, and just avoid compiling them from source; I've never had to do this, though.

QUESTION: is there anything like PPA in Ubuntu?

ANSWER: Debian does not run a PPA service like Ubuntu, but all the tools to make apt repositories yourself are there, it's just a lot to configure by oneself.

QUESTION: do we need to repack the original tarball if it doesn't contains a properly named foo-1.0 folder?

ANSWER: I think that these days, you don't need to repack it. It used to be necessary, many many years ago, but now the "dpkg-source -x" command will name the directory the right way, if necessary.

QUESTION: I can see "official" DEB packages in /var/cache/apt/archives without changelog and compat files. Why?

ANSWER: the .deb packages in /var/cache/apt/archives are binary packages; the changelog is included in them (under a different name), the compat file is only in the source package

QUESTION: Liw said the the compat file should contain the magic number 9, I assume this just means as single char files as produced by 'echo 9 >debian/compat' ?

ANSWER: yes, a single character 9 is enough to have in debian/compat

QUESTION: I've heard of non-maintainer specific format for debian revision numbers

ANSWER: I think you mean either the "native package" format (in which the version number would be just 1.0, not 1.0-1); or the "non-maintainer upload" format, in which case that's too much detail for this session to get it right in all cases, but "1.0-1.1" would be an example

QUESTION: When is "dpkg-source -x" run? Is it done manually?

ANSWER: "dpkg-source -x" is the command to unpack a Debian source package after it has already been built (usually by someone else); it is not usually run when creating the package

QUESTION: how can one determine the needed packages to be used by Build-Depends?

ANSWER: I usually do that by a) trial and error and b) reading the source of the program. Both are usually necessary

QUESTION: can I build package for armel from my i386, and can i do it easy?

ANSWER: that would be cross-compilation, and I don't think there is an easy way to do it; there are tools for it, but I am not familiar with them, sorry.

QUESTION: what's the difference between Depends and Build Depends, in what case I have to use only Depends instead of Build-Depends?

ANSWER: Build-Depends are needed only during package build, while it is being compiled, and its test suite is being run. Depends is needed only when the package is actually being used, after being installed. Some things might be both build and runtime dependencies, and in that case you need to put them into both Build-Depends and Depends.

As an example, if a package contains a PHP script, but it does not get run while the package is built, then PHP would go into Depends only, not Build-Depends.

However, if the PHP script is only used to run a test, and does not get included in the binary package, it would only be in Build-Depends and not in Depends

QUESTION: may I have a Build-Depends that does not have a corresponding Depends? I'm thinking to statical linked libraries

ANSWER: Build-Depends and Depends are pretty much entirely separate, and it is perfectly ok (from a packaging tool point of view) to have dependencies only in one and not the other, or in both

QUESTION: If I want to do a NMU, should I write my name in the Uploader field, the Maintainer field, none ?

ANSWER: (by dapal) none, but the first line of the changelog should be "Non-maintainer upload"

QUESTION: When I build a package with "Architecture: all" field, some of the resulting file (b.build, .changes) still have the build architecture in the name. Is a right behavior?

ANSWER: yep, that is the right behavior, no need to worry about it

QUESTION: Is there another package for source package or its the same of binary package? I will generate and maintain two packages (binary and source)?

ANSWER: you edit the source package and then run a command (which I will get to in a bit) to build the binary package out of the source package

QUESTION: It's not clear to me if "Architecture" options will make effect over source package (building process) or binary package (install and run).

ANSWER: the "Architecture:" field tells whoever is building the package whether there is any point in building the package on a particular computer architecture so if it says i386 only, then there's no point in building it on AMD64

QUESTION: that example debian/rules contains only #!make -f , what to do with ./configure , or cmake or scons or .. anything else part?

ANSWER: dh has a lot of heuristic, so a package with a ./configure script, or one of the other common ways of building packages, will usually build without any additions

QUESTION: heuristics is good, but what if we need to pass --with-something-special to configure or cmake arguments, does heuristics handle those source packages that need ./waf and other tools to build ?

ANSWER: I like dapal's answer: <dapal> lilith: using dh7, if you want to pass something to ./configure, just do something like: override_dh_auto_configure <TAB>dh_auto_configure -- --your-params
dh has a nice extension/override mechanism that allows you to override particular parts; it is pretty easy to use, once you've read the docs
<aron> I had some bad experience with packaging software that uses waf as its build system. It usually contains binary blob that cannot be extract by standard tools (yes, it embedd a tgz in the script), and what's critical, it's hard to maintain your Debian package with a waf build system because it is not intended to help upstream to build their packages in a rather standard way, but only works for me. You should really suggest your upstream to consider another one (powerful ones like CMake, Autotools; or simpler ones like python-distutils-extra) if possible.

QUESTION: where can we find docs for override stuff of debhelper 9?

ANSWER: dh runs a specific sequence of commands to build a package; each command is called dh_something, and each such command can be overridden by having a debian/rules entry called override_dh_something.

Add the --no-act option to the dh command in debian/rules to see what commands it runs; you then have to read the manual page for that command to see if you can configure it (via a file such as debian/hithere.dirs), or if you need to override it. In practice, using --no-act option in combination with --verbose will let you know more details about what it would run.

QUESTION: from where do you usually run your commands? inside the dir hithere-1.0 or outside? should there be an outer dir called hithere (without number)

ANSWER: I always run the packaging commands in the hithere-1.0 directory, and i usually have a directory above that called hithere but the parent directory is not necessary, it is just neater, so files from different projects don't get mixed up

QUESTION: I have a upstream that needs a qmake (uses Qt) before make. Can I add it to debian/rules? How?

ANSWER: (by gregoa) debhelper supports qmake since 7.4.12 (so no additional things needed). before that you needed a override_dh_auto_configure :\n\tqmake

QUESTION: what is a good work flow to update a package to a new upstream version?

ANSWER: ah, I am not sure what is the best work flow for that, but basically: unpack the upstream source to a new directory, copy the debian/* directory from the old package, update debian/changelog ("dch -v 1.2.3-4") and try to build, and fix anything that is broken. That's not a really good work flow, but for that you will need to learn quilt, and possibly how to use version management with debian packaging, and that's too big a topic for this session, sorry

QUESTION: I have a made debian-package that depends on several other packages. The only thing my package does is actually configure the other packages in a certain way that it fits certain peoples needs. For this it also makes some system critical changes, like activating network routing in kernel and so on. Is there something like a rule what an official package is allowed to do or not? Can such a package get an official package?

ANSWER: http://www.debian.org/doc/debian-policy/ is the best written set of rules we have for what an official Debian package is allowed to do, or is required to do.

Debian packages are not allowed to change another package's configurations, unless that package provides a documented interface for it

See also

• http://www.debian.org/devel/

• http://www.debian.org/doc/debian-policy/

• http://liw.fi/manpages/

• Packaging is the page that gathers everything about packaging on this wiki

• Debian Women IRC log: making Debian packages

• Debian Women IRC log: taking an existing package, re-building it, applying changes to it, and preparing those changes so as to send them as a bug patch.

CategoryPackaging