View source for How to unpack and pack a debian archive

[[Category:tutorial]]

The primary command to manipulate deb packages is <code>dpkg-deb</code>.

To unpack the package, create an empty directory and switch to it, then run <code>dpkg-deb</code> to extract its control information and the package files. Use <code>dpkg-deb -b</code> to rebuild the package.
 <code>mkdir tmp
 dpkg-deb -R original.deb tmp
 # edit DEBIAN/postinst
 dpkg-deb -b tmp fixed.deb</code>
Beware that unless your script is running as root, the files' permissions and ownership will be corrupted at the extraction stage. One way to avoid this is to run your script under <code>fakeroot</code>. Note that you need to run the whole sequence under <code>fakeroot</code>, not each <code>dpkg-deb</code> individually, since it's the <code>fakeroot</code> process that keeps the memory of the permissions of the files that can't be created as they are.
 <code>fakeroot sh -c '
   mkdir tmp
   dpkg-deb -R original.deb tmp
   # edit DEBIAN/postinst
   dpkg-deb -b tmp fixed.deb
 '</code>
Rather than mess with permissions, you can keep the data archive intact and modify only the control archive. <code>dpkg-deb</code> doesn't provide a way to do that. Fortunately, deb packges are in a standard format: they're <code>ar</code> archives. So you can use <code>ar</code> to extract the control archive, modify its files, and use <code>ar</code> again to replace the control archive by a new version.
 <code>mkdir tmp
 cd tmp
 ar p ../original.deb control.tar.gz | tar -xz
 # edit postinst
 cp ../original.deb ../fixed.deb
 tar czf control.tar.gz *[!z]
 ar r ../fixed.deb control.tar.gz</code>
You should '''add a changelog entry and change the version number''' if you modify anything in the package. The infrastructure to manipulate Debian packages assumes that if two packages have the same name and version, they're the same package. Add a suffix to the ''debian_revision'' part at the end of the version number; for sorting reasons the suffix should start with <code>~</code>, e.g. <code>1.2.3-4.1</code> becomes <code>1.2.3-4.1~johnjumper1</code>.

Instead of using shell tools, you can use Emacs. The <code>dpkg-dev-el</code> package (which is its own upstream as this is a native Debian package) contains modes to edit <code>.deb</code> files and to edit Debian changelogs. Emacs can be used interactively or scripted.


Attribution: https://unix.stackexchange.com/questions/138188/easily-unpack-deb-edit-postinst-and-repack-deb