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Debian Cross Build

How to cross build

We often use dpkg-buildpackage and sbuild to cross build a Debian package.

Cross build with dpkg-buildpackage

  • Install a Debian Unstable system.

  • Enable the foreign architecture and install cross toolchain.

    For example "armhf":

    sudo dpkg --add-architecture armhf
sudo apt-get update
sudo apt-get install build-essential crossbuild-essential-armhf

  • Download source code, which we want to cross build, and install its dependencies.

    apt-get source <package>
sudo apt-get build-dep -aarmhf <package>

  • Cross build with dpkg-buildpackage.

    cd <package>-<version>
DEB_BUILD_OPTIONS=nocheck dpkg-buildpackage -aarmhf

Cross build with sbuild

  • Set up a sbuild chroot for Debian Unstable.

    # Configure user
sudo mkdir /root/.gnupg # To work around #792100; not needed on post-Jessie
sudo sbuild-update --keygen # Not needed since sbuild 0.67.0 (postJessie, see #801798)
sudo sbuild-adduser $LOGNAME

# logout and re-login or use `newgrp sbuild` in your current shell

# Create chroot
sudo sbuild-createchroot unstable ./chroot-sbuild http://ftp.debian.org/debian

    Note: On Debian Jessie, sbuild needs to be installed from jessie-backports (Bug #827315)

  • Cross build with sbuild.

    cd <source code dir>
sbuild --host=armhf -d unstable

How to create patch

Create patch for upstream source

A Debian source package has structure like this:

package
├── Makefile
├── file.c
├── file.h
├── debian
│   ├── control
│   ├── rules
│   ├── patches
│   │   ├── patch1.patch
│   │   ├── patch2.patch
│   │   └── ...
│   └── ...
└── ...

If we change the files outside of debian subdir, we need create patches for those changes and put them into debian/patches first.

  • Create patch for the changes in upstream source.

    diff -Nuar old_source_dir new_source_dir > patchname.patch

  • Put the patch into debian/patches, and add it to patch list in debian/patches/series.

  • Clean the changes in upstream source.

Create the final patch

After successful build with dpkg-buildpackage or sbuild, files *.debian.tar.xz and *.dsc will be updated automatically with modified codes.

Example:

.
├── coreutils-8.28/
├── coreutils_8.28-1_armhf.buildinfo
├── coreutils_8.28-1_armhf.changes
├── coreutils_8.28-1_armhf.deb
├── coreutils_8.28-1.debian.tar.xz # this file contains new codes of 'debian' subdir
├── coreutils_8.28-1.dsc # dsc has been updated with new checksum
├── coreutils_8.28.orig.tar.xz
└── ...

We can compare the new with the old source code by debdiff 2 files *.dsc.

mkdir orig
cd orig
# Download the original source code from Debian
# (*.orig.tar.*, *.debian.tar.*, *.dsc, etc.)

cd ..
debdiff orig/filename.dsc filename.dsc > patchname.debdiff

How to apply patch

All patches in this repository should be applied at level 1 of source code.

cd <source code dir>
patch -p1 < path/to/patch/file

Submit patch

A patch can be submited by sending it to [email protected] or <number>@bugs.debian.org if the bug report has already been filed.
When submit a patch, the below information should be described at the first part of report:

Source: <name of source package>
Version: <version of package>
Tags: patch
Severity: <critical|grave|serious|important|normal|minor|wishlist>

Also, for easy tracking of cross build bugs, some Usertags may be added. Use one of these tags:

  • For general cross/bootstrap bugs:

    User: [email protected]
Usertags: rebootstrap

  • For bugs where Build-Depends are cross-installable, but the cross-build fails:

    User: [email protected]
Usertags: ftcbfs

  • For bugs about packages that fail to satisfy their cross Build-Depends or that cause other packages to fail dependency satisfaction:

    User: [email protected]
Usertags: cross-satisfiability

Example:

Source: coreutils
Version: 8.28-1
Severity: normal
Tags: patch
User: [email protected]
Usertags: rebootstrap

You can see the discussion about these tags at https://lists.debian.org/debian-cross/2018/07/msg00001.html

References

https://wiki.debian.org/sbuild

https://wiki.debian.org/CrossCompiling

https://www.debian.org/Bugs/Reporting