building a proper debian source package with dkms

How can one use DKMS to build a proper debian source package? The ‘mkdsc’ command will actually generate one automatically, but there are a few more steps to simplify it, and bring it up to date.

First follow the steps in [1] for setting up a DKMS package. Make sure you can build it using dkms. Then do the following:

#First pull in some dependencies as necessary
sudo apt-get install devscripts debhelper

# Create the debian source package
sudo dkms mkdsc -m hello -v 0.1

# Create a directory to work in, and let’s copy those files into it
mkdir ~/dsc && cd ~/dsc
cp /var/lib/dkms/hello/0.1/dsc/* .

# Extract the .dsc to be able to edit the directory
dpkg-source -x hello-dkms_0.1.dsc 
cd hello-dkms-0.1

If we run debuild -uc -us, we see a few lintian errors and warnings:

W: hello-dkms source: package-file-is-executable debian/changelog
W: hello-dkms source: package-file-is-executable debian/control
W: hello-dkms source: package-file-is-executable debian/copyright
W: hello-dkms source: package-file-is-executable debian/dirs
E: hello-dkms source: no-human-maintainers
W: hello-dkms source: debian-rules-ignores-make-clean-error line 28
W: hello-dkms source: debian-rules-missing-recommended-target build-arch
W: hello-dkms source: debian-rules-missing-recommended-target build-indep
W: hello-dkms source: ancient-standards-version 3.8.1 (current is 3.9.3)
E: hello-dkms: no-copyright-file
E: hello-dkms: extended-description-is-empty
W: hello-dkms: non-standard-dir-perm usr/src/hello-0.1/ 0655 != 0755

The errors are normal, and if this was a real package those will be taken care of since that information will need to be filled in anyway.

To address the executable issues, just chmod -x those files.

chmod -x debian/co* debian/dirs debian/ch*

To address some of the other issues, we can just completely modify and change the rules file. Because debhelper has a helper for DKMS specifically we should use it.

In addition, if we do something like dch -i you’ll notice some errors, since our source directory is hardcoded to hello-0.1. So we can modify it to be in a ‘src’ directory and get around this.

mv hello-0.1 src

Here is how I modified my debian/rules file:

#!/usr/bin/make -f
# -*- makefile -*-

# Uncomment this to turn on verbose mode.
#export DH_VERBOSE=1

NAME=hello
DEB_NAME=$(NAME)-dkms
VERSION=$(shell dpkg-parsechangelog |grep ^Version:|cut -d ' ' -f 2)

%:
        dh $@ --with dkms

override_dh_install:
        dh_install src/ usr/src/$(NAME)-$(VERSION)
        find "debian/$(DEB_NAME)/usr/src/$(NAME)-$(VERSION)" -type f -exec chmod 644 {} \;

override_dh_dkms:
        dh_dkms -V $(VERSION)

override_dh_auto_build:
override_dh_auto_install:

Now there are some things that can be removed from the package completely:

rm common.postinst Makefile

Now to update the control file to use modern versions, a proper description, and make yourself a maintainer!

Source: hello-dkms
Section: misc
Priority: optional
Maintainer: Dude Bodacious <dude@awesomeradical.com>
Build-Depends: debhelper (>= 8), dkms
Standards-Version: 3.9.3

Package: hello-dkms
Architecture: all
Depends: dkms, ${misc:Depends}
Description: hello driver in DKMS format.
A completely useful kernel module.

Now debuild -uc -us and fix remaining issues.

References

1. https://wiki.ubuntu.com/Kernel/Dev/DKMSPackaging
2. https://help.ubuntu.com/community/Kernel/DkmsDriverPackage
3. http://basilevsthecat.blogspot.com/2011/11/how-to-build-dkms-debian-package.html

building a binary debian kernel module package with dkms

DKMS packaging works great for building out of tree kernel modules. However, what do you do when you need to install to a machine without a compiler? You can accompish this by using DKMS's mkdriverdisk functionality.

First follow the steps in [0] for setting up a proper DKMS package.

After you've built the module successfully, you can use the following bash script to extract the .deb installer from the driverdisk. This way you can copy the deb file to the target machine and install. You must ensure that $(uname -rm) on the target machine matches the build machine.

The Script

NAME=hello
VERSION=0.1

# Build in a temp dir
TMPDIR=$(mktemp -d)
cd $TMPDIR
sudo dkms mkdriverdisk $NAME/$VERSION -d ubuntu --media tar | tee build.log
TARBALL_PATH=$(grep "Disk image location" build.log | cut -d':' -f2)
echo $TARBALL_PATH
tar -xf $TARBALL_PATH
cd -

# Extract the build
mv $TMPDIR/ubuntu-drivers/*/*.deb .

References

1. https://wiki.ubuntu.com/Kernel/Dev/DKMSPackaging