.DEB File Format – Control files

Files in control.tar

The control file

A subset of the deb822 format: Field: value lines. Field names are not case-sensitive; values are, unless said otherwise. A value may continue on following lines; installation tools generally join them, except in Description, where line breaks matter. A binary package’s control file has one paragraph.

Package: hello
Version: 2.10-3
Architecture: amd64
Maintainer: Jane Doe <jane@example.org>
Installed-Size: 281
Depends: libc6 (>= 2.34)
Section: devel
Priority: optional
Homepage: https://www.gnu.org/software/hello/
Description: example package based on GNU hello
 The GNU hello program produces a familiar, friendly greeting.
 .
 Seriously, though: this is an example of how to do a Debian package.

Relationship syntax

Depends, Pre-Depends, Recommends, Suggests are comma-separated lists of groups, all of which must be met (AND); within a group, alternatives are separated by | (OR), which binds tighter. In Breaks, Conflicts and Replaces each comma-separated item stands alone.

Each item is name[:arch] [(op version)]:

Example: Depends: libc6 (>= 2.34), default-mta | mail-transport-agent.

Version numbers

[epoch:]upstream-version[-debian-revision]

Comparison: epochs numerically, then upstream versions, then revisions, each by repeatedly comparing a run of non-digits (character by character, letters before non-letters, and ~ before everything, even the end of the string) and then a run of digits as a number (empty = 0). So 1.0~rc1 < 1.0 < 1.0a < 1.0+b1, because the end of the string sorts after ~ but before anything else, and letters sort before other characters.

md5sums

One line per plain file: its MD5 as 32 hexadecimal digits (either case), two spaces, and its path, which the page’s examples write without a leading slash (usr/bin/dpkg). Trailing slashes are trimmed; trailing white space and empty lines are not accepted. Whether conffiles are listed is not stated.

conffiles

One absolute path per line, optionally preceded by a flag and white space. Empty lines are not allowed.

triggers

One directive trigger-name per line; everything after # is ignored, as are blank lines. An unknown directive stops the package installing.

shlibs

One line per shared library: [type:] library version dependencies, where library and version come from the library’s SONAME and dependencies, to the end of the line, use the Depends syntax; the dependency should name the latest package version that added symbols. The optional type is normally not needed. Lines starting with # are comments; blank lines are not allowed. Example: libcrunch 1 libcrunch1 (>= 1.2-1).

symbols

Finer-grained than shlibs: the minimum version needed for each exported symbol. For each library:

#MINVER# in a template becomes (>= min-version) or nothing.

libGL.so.1 libgl1
| libgl1-mesa-glx #MINVER#
* Build-Depends-Package: libgl1-mesa-dev
 publicGlSymbol@Base 6.3-1
 implementationSpecificSymbol@Base 6.5.2-7 1

Maintainer scripts

Executable files run by dpkg at fixed points, with arguments saying why. “new-” and “old-” name the script from the new or old version of the package. The new-version arguments marked † are passed since dpkg 1.18.5.

Sources

dpkg manual pages (dpkg 1.23): deb-control(5) (fields, relationship syntax), deb-version(7), deb-md5sums(5), deb-conffiles(5), deb-triggers(5), deb-shlibs(5), deb-symbols(5), deb-preinst(5), deb-postinst(5), deb-prerm(5) and deb-postrm(5); deb(5) for the list of control files.