Chapter 5. Control files and their fields
into a Debian package, and so there is only one debianization of it and therefore no
revision indication is required.
It is conventional to restart the debian_revision at
each time the upstream_version is in
The package management system 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 sys
tem 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.
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
), or with silly orderings (the author of this
manual has heard of a package whose versions went
In a source or binary control file, the
field contains a description of the binary
package, consisting of two parts, the synopsis or the short description, and the long descrip
tion. The field's format is as follows:
The lines in the extended description can have these formats:
Those starting with a single space are part of a paragraph. Successive lines of this form
will be word wrapped when displayed. The leading space will usually be stripped off.