Re-Packaging Debian Packages

Introduction

There are times when the metadata on a Debian package needs to be modified to allow a package to be installed. For example, several QNAP packages require Ubuntu 18.04. The way this is implemented in the package is by a preinst script that parses the version. To allow installation on a Debian system only the preinst script needs to be modified. This document describes a process for updating package metadata without otherwise modifying the package contents.

Re-Packaging

Optain a copy of the raw Debian package file, i.e. the .deb.
Create a work directory and cd into it.
```
 $ mkdir tmp
 $ cd tmp
```
List the archive contents of the package to obtain the name of the control tar ball. This name changes depending on the compression used.
```
 $ ar t ../QNAPQfinderProUbuntux64-7.9.0.0627.deb
 debian-binary
 control.tar.xz
 data.tar.xz
```

Extract the control files for editing.

 $ ar p ../QNAPQfinderProUbuntux64-7.9.0.0627.deb control.tar.xz | tar -x --xz

Edit the metadata files as required. It makes sense to update the version as well as any files by adding ~1 to the version number. Adding ~1 treats the modification as a backport.

Tar the control files and replace the files in a new copy of the .deb file. Note, the new .deb file should follow the Debian Policy format, i.e. package-nameversionarch.deb.

 $ cp ../QNAPQfinderProUbuntux64-7.9.0.0627.deb ../QNAPQfinderProUbuntux64-7.9.0.0627~1.deb
 $ tar --xz -cf control.tar.xz *[!z]
 $ ar r ../QNAPQfinderProUbuntux64-7.9.0.0627~1.deb control.tar.xz

The package QNAPQfinderProUbuntux64-7.9.0.0627~1.deb is ready to be installed using dpkg.