deb-version - Debian package version number format
Version numbers as used for Debian binary and source packages consist of three
components. These are:
- This is a single (generally small) unsigned integer. It may
be omitted, in which case zero is assumed. If it is omitted then the
upstream-version may not contain any colons.
- It is provided to allow mistakes in the version numbers of
older versions of a package, and also a package's previous version
numbering schemes, to be left behind.
- This is the main part of the version number. It is usually
the version number of the original ("upstream") package from
which the .deb file has been made, if this is applicable. Usually
this will be in the same format as that specified by the upstream
author(s); however, it may need to be reformatted to fit into the package
management system's format and comparison scheme.
- The comparison behavior of the package management system
with respect to the upstream-version is described below. The
upstream-version portion of the version number is mandatory.
- The upstream-version may contain only alphanumerics
("A-Za-z0-9") and the characters . + -
: ~ (full stop, plus, hyphen, colon, tilde) and should start
with a digit. If there is no debian-revision then hyphens are not
allowed; if there is no epoch then colons are not allowed.
- This part of the version number specifies the version of
the Debian package based on the upstream version. It may contain only
alphanumerics and the characters + . ~ (plus, full
stop, tilde) and is compared in the same way as the
- It is optional; if it isn't present then the
upstream-version may not contain a hyphen. This format represents
the case where a piece of software was written specifically to be turned
into a Debian package, and so there is only one "debianisation"
of it and therefore no revision indication is required.
- It is conventional to restart the debian-revision at
'1' each time time the upstream-version is increased.
- Dpkg will break the version number apart at the last hyphen
in the string (if there is one) to determine the upstream-version
and debian-revision. The absence of a debian-revision
compares earlier than the presence of one (but note that the
debian-revision is the least significant part of the version
parts are compared by the
package management system using the same algorithm:
The strings are compared from left to right.
First the initial part of each string consisting entirely of non-digit
characters is determined. These two parts (one of which may be empty) are
compared lexically. If a difference is found it is returned. The lexical
comparison is a comparison of ASCII values modified so that all the letters
sort earlier than all the non-letters and so that a tilde sorts before
anything, even the end of a part. For example, the following parts are in
sorted order: '~~', '~~a', '~', the empty part, 'a'.
Then the initial part of the remainder of each string which consists entirely of
digit characters is determined. The numerical values of these two parts are
compared, and any difference found is returned as the result of the
comparison. For these purposes an empty string (which can only occur at the
end of one or both version strings being compared) counts as zero.
These two steps (comparing and removing initial non-digit strings and initial
digit strings) are repeated until a difference is found or both strings are
Note that the purpose of epochs is to allow us to leave behind mistakes in
version numbering, and to cope with situations where the version numbering
scheme changes. It is not
intended to cope with version numbers
containing strings of letters which the package management system cannot
interpret (such as 'ALPHA' or 'pre-'), or with silly orderings.
The tilde character and its special sorting properties were introduced in dpkg,
version 1.10 and some parts of dpkg-dev only gained support for it later in
the 1.10.x series.