Version numbers as used for Debian binary and source packages consist
of three components. These are:
epoch 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
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 upstream-version
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
It is conventional to restart the debian-revision at ‘1’ each
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 number).
The upstream-version and debian-revision 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 exhausted.
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.
This page is part of the dpkg (Debian Package Manager) project.
Information about the project can be found at
⟨https://wiki.debian.org/Teams/Dpkg/⟩. If you have a bug report for
this manual page, see
⟨http://bugs.debian.org/cgi-bin/pkgreport.cgi?src=dpkg⟩. This page
was obtained from the project's upstream Git repository
⟨git://git.debian.org/git/dpkg/dpkg.git⟩ on 2017-03-13. If you dis‐
cover any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page, or
you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a mail
1.18.15-3-ga2ef 1970-01-01 deb-version(5)