The package management system manipulates data represented in a common format, known as control data, stored in control files. Control files are used for source packages, binary packages and the .changes files which control the installation of uploaded files (dpkg's internal databases are in a similar format).
A control file consists of one or more paragraphs of fields (the paragraphs are also sometimes referred to as stanzas). The paragraphs are separated by empty lines. Parsers may accept lines consisting solely of U+0020 SPACE and U+0009 TAB as paragraph separators, but control files should use empty lines. Some control files allow only one paragraph; others allow several, in which case each paragraph usually refers to a different package. (For example, in source packages, the first paragraph refers to the source package, and later paragraphs refer to binary packages generated from the source.) The ordering of the paragraphs in control files is significant.
Each paragraph consists of a series of data fields. Each field consists of the field name followed by a colon (U+003A ‘:’), and then the data/value associated with that field. The field name is composed of US-ASCII characters excluding control characters, space, and colon (i.e., characters in the ranges U+0021 ‘!’ through U+0039 ‘9’, and U+003B ‘;’ through U+007E ‘~’, inclusive). Field names must not begin with the comment character (U+0023 ‘#’), nor with the hyphen character (U+002D ‘-’).
The field ends at the end of the line or at the end of the last continuation line (see below). Horizontal whitespace (U+0020 SPACE and U+0009 TAB) may occur immediately before or after the value and is ignored there; it is conventional to put a single space after the colon. For example, a field might be:
the field name is Package and the field value dpkg.
Empty field values are only permitted in source package control files (debian/control). Such fields are ignored.
A paragraph must not contain more than one instance of a particular field name.
There are three types of fields:
The field, including its value, must be a single line. Folding of the field is not permitted. This is the default field type if the definition of the field does not specify a different type.
The value of a folded field is a logical line that may span several lines. The lines after the first are called continuation lines and must start with a U+0020 SPACE or a U+0009 TAB. Whitespace, including any newlines, is not significant in the field values of folded fields.
This folding method is similar to RFC5322, allowing control files that contain only one paragraph and no multiline fields to be read by parsers written for RFC5322.
The value of a multiline field may comprise multiple continuation lines. The first line of the value, the part on the same line as the field name, often has special significance or may have to be empty. Other lines are added following the same syntax as the continuation lines of the folded fields. Whitespace, including newlines, is significant in the values of multiline fields.
Whitespace must not appear inside names (of packages, architectures, files or anything else) or version numbers, or between the characters of multi-character version relationships.
The presence and purpose of a field, and the syntax of its value may differ between types of control files.
Field names are not case-sensitive, but it is usual to capitalize the field names using mixed case as shown below. Field values are case-sensitive unless the description of the field says otherwise.
Paragraph separators (empty lines) and lines consisting only of U+0020 SPACE and U+0009 TAB, are not allowed within field values or between fields. Empty lines in field values are usually escaped by representing them by a U+0020 SPACE followed by a dot (U+002E ‘.’).
Lines starting with U+0023 ‘#’, without any preceding whitespace are comments lines that are only permitted in source package control files (debian/control) and in deb-origin(5) files. These comment lines are ignored, even between two continuation lines. They do not end logical lines.
All control files must be encoded in UTF-8.