Joachim Breitner

Creating a Debian source package without unpacking the source

Published 2012-10-13 in sections English, Debian.

There may be a situation where you want to create a Debian source package without having to unpack the upstream source. One case is where you store your debian/ directory in a version control system of its own and to build your package, you pass the .dsc file to a tool like pbuilder or some remote builder. Now a modern debian source package is just a text file (the .dsc file) that references two tarballs, one being the upstream source and the other being the Debian directory. Thanks to Niels Thykier on #debian, I found the magic invocation of dpkg-source that allows you to create the .dsc directly from the two tarballs, the control file and the changelog:

> apt-get source --download-only -t experimental haskell-mtl
Reading package lists... Done
Building dependency tree       
Reading state information... Done
NOTICE: 'haskell-mtl' packaging is maintained in the 'Darcs' version control system at:
Need to get 18.8 kB of source archives.
Get:1 experimental/main haskell-mtl 2.1.2-1 (dsc) [1616 B]
Get:2 experimental/main haskell-mtl 2.1.2-1 (tar) [13.7 kB]
Get:3 experimental/main haskell-mtl 2.1.2-1 (diff) [3509 B]
Fetched 18.8 kB in 0s (22.3 kB/s)    
Download complete and in download only mode
> cp ./haskell-mtl_2.1.2-1.dsc ./haskell-mtl_2.1.2-1.dsc-orig
> tar xzf haskell-mtl_2.1.2-1.debian.tar.gz
> dpkg-source -cdebian/control -ldebian/changelog --format="3.0 (custom)" --target-format="3.0 (quilt)" -b / haskell-mtl_2.1.2.orig.tar.gz haskell-mtl_2.1.2-1.debian.tar.gz
dpkg-source: info: using source format `3.0 (custom)'
dpkg-source: info: building haskell-mtl in haskell-mtl_2.1.2-1.dsc
> diff  -u haskell-mtl_2.1.2-1.dsc haskell-mtl_2.1.2-1.dsc-orig
--- haskell-mtl_2.1.2-1.dsc	2012-10-13 15:09:00.031695856 +0200
+++ haskell-mtl_2.1.2-1.dsc-orig	2012-10-13 15:08:47.267696329 +0200
@@ -1,3 +1,6 @@
+Hash: SHA1
 Format: 3.0 (quilt)
 Source: haskell-mtl
 Binary: libghc-mtl-dev, libghc-mtl-prof, libghc-mtl-doc
@@ -23,3 +26,11 @@
  943c110524d96126bfa0e61f7df1ebcd 13723 haskell-mtl_2.1.2.orig.tar.gz
  dda5ded58a8d009ecddeed68058ca787 3509 haskell-mtl_2.1.2-1.debian.tar.gz
+Version: GnuPG v1.4.12 (GNU/Linux)

As you can see, the resulting .dsc file is identical to the original one, so this approach works. The parameter to -b does not matter as long as it is some existing directory. Of course you can easily shoot yourself and others in the foot, almost as easily as hand-editing the .dsc file... but if you know what you are doing, then this can be quite handy.

Next to do: Write a tool that takes an unpacked Debian directory as an argument, packs it, finds the original tarball using uscan and creates the .dsc file. Would this be something that people would want in the devscripts package?


> Write a tool that takes an unpacked Debian directory as an argument, packs it, finds the original tarball using uscan and creates the .dsc file.

People should review what is included in the upstream before they create/upload a source package. So I think having something like this in devscripts is not too useful.
#1 Anonymous am 2012-10-13
Well, in a team, that would be the responsibility of the developer that bumps the version number in debian/changelog, not necessarily that of the developer building. Or maybe the check goes by a different mean, e.g. checking upstream’s VCS (assuming a reasonable trustworthy infrastructure for retrieving the tarball).
#2 Joachim Breitner (Homepage) am 2012-10-13

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