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Debian Policy Manual
Chapter 5 - Control files and their fields

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[31].


5.1 Syntax of control files

A control file consists of one or more paragraphs of fields[32]. The paragraphs are separated by empty lines. Parsers may accept lines consisting solely of spaces and tabs 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 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 33-57 and 59-126, inclusive). Field names must not begin with the comment character, #, nor with the hyphen character, -.

The field ends at the end of the line or at the end of the last continuation line (see below). Horizontal whitespace (spaces and tabs) 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:

     Package: libc6

the field name is Package and the field value libc6.

A paragraph must not contain more than one instance of a particular field name.

There are three types of fields:

simple

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.

folded

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 space or a tab. Whitespace, including any newlines, is not significant in the field values of folded fields.[33]

multiline

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 spaces and tabs are not allowed within field values or between fields. Empty lines in field values are usually escaped by representing them by a space followed by a dot.

Lines starting with # without any preceding whitespace are comments lines that are only permitted in source package control files (debian/control). 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.


5.2 Source package control files -- debian/control

The debian/control file contains the most vital (and version-independent) information about the source package and about the binary packages it creates.

The first paragraph of the control file contains information about the source package in general. The subsequent sets each describe a binary package that the source tree builds.

The fields in the general paragraph (the first one, for the source package) are:

The fields in the binary package paragraphs are:

The syntax and semantics of the fields are described below.

These fields are used by dpkg-gencontrol to generate control files for binary packages (see below), by dpkg-genchanges to generate the .changes file to accompany the upload, and by dpkg-source when it creates the .dsc source control file as part of a source archive. Some fields are folded in debian/control, but not in any other control file. These tools are responsible for removing the line breaks from such fields when using fields from debian/control to generate other control files.

The fields here may contain variable references - their values will be substituted by dpkg-gencontrol, dpkg-genchanges or dpkg-source when they generate output control files. See Variable substitutions: debian/substvars, Section 4.10 for details.


5.3 Binary package control files -- DEBIAN/control

The DEBIAN/control file contains the most vital (and version-dependent) information about a binary package. It consists of a single paragraph.

The fields in this file are:


5.4 Debian source control files -- .dsc

This file consists of a single paragraph, possibly surrounded by a PGP signature. The fields of that paragraph are listed below. Their syntax is described above, in Syntax of control files, Section 5.1.

The Debian source control file is generated by dpkg-source when it builds the source archive, from other files in the source package, described above. When unpacking, it is checked against the files and directories in the other parts of the source package.


5.5 Debian changes files -- .changes

The .changes files are used by the Debian archive maintenance software to process updates to packages. They consist of a single paragraph, possibly surrounded by a PGP signature. That paragraph contains information from the debian/control file and other data about the source package gathered via debian/changelog and debian/rules.

.changes files have a format version that is incremented whenever the documented fields or their meaning change. This document describes format 1.8.

The fields in this file are:


5.6 List of fields


5.6.1 Source

This field identifies the source package name.

In debian/control or a .dsc file, this field must contain only the name of the source package.

In a binary package control file or a .changes file, the source package name may be followed by a version number in parentheses[34]. This version number may be omitted (and is, by dpkg-gencontrol) if it has the same value as the Version field of the binary package in question. The field itself may be omitted from a binary package control file when the source package has the same name and version as the binary package.

Package names (both source and binary, see Package, Section 5.6.7) must consist only of lower case letters (a-z), digits (0-9), plus (+) and minus (-) signs, and periods (.). They must be at least two characters long and must start with an alphanumeric character.


5.6.2 Maintainer

The package maintainer's name and email address. The name must come first, then the email address inside angle brackets <> (in RFC822 format).

If the maintainer's name contains a full stop then the whole field will not work directly as an email address due to a misfeature in the syntax specified in RFC822; a program using this field as an address must check for this and correct the problem if necessary (for example by putting the name in round brackets and moving it to the end, and bringing the email address forward).

See The maintainer of a package, Section 3.3 for additional requirements and information about package maintainers.


5.6.3 Uploaders

List of the names and email addresses of co-maintainers of the package, if any. If the package has other maintainers besides the one named in the Maintainer field, their names and email addresses should be listed here. The format of each entry is the same as that of the Maintainer field, and multiple entries must be comma separated.

This is normally an optional field, but if the Maintainer control field names a group of people and a shared email address, the Uploaders field must be present and must contain at least one human with their personal email address.

The Uploaders field in debian/control can be folded.


5.6.4 Changed-By

The name and email address of the person who prepared this version of the package, usually a maintainer. The syntax is the same as for the Maintainer field.


5.6.5 Section

This field specifies an application area into which the package has been classified. See Sections, Section 2.4.

When it appears in the debian/control file, it gives the value for the subfield of the same name in the Files field of the .changes file. It also gives the default for the same field in the binary packages.


5.6.6 Priority

This field represents how important it is that the user have the package installed. See Priorities, Section 2.5.

When it appears in the debian/control file, it gives the value for the subfield of the same name in the Files field of the .changes file. It also gives the default for the same field in the binary packages.


5.6.7 Package

The name of the binary package.

Binary package names must follow the same syntax and restrictions as source package names. See Source, Section 5.6.1 for the details.


5.6.8 Architecture

Depending on context and the control file used, the Architecture field can include the following sets of values:

In the main debian/control file in the source package, this field may contain the special value all, the special architecture wildcard any, or a list of specific and wildcard architectures separated by spaces. If all or any appears, that value must be the entire contents of the field. Most packages will use either all or any.

Specifying a specific list of architectures indicates that the source will build an architecture-dependent package only on architectures included in the list. Specifying a list of architecture wildcards indicates that the source will build an architecture-dependent package on only those architectures that match any of the specified architecture wildcards. Specifying a list of architectures or architecture wildcards other than any is for the minority of cases where a program is not portable or is not useful on some architectures. Where possible, the program should be made portable instead.

In the Debian source control file .dsc, this field contains a list of architectures and architecture wildcards separated by spaces. When the list contains the architecture wildcard any, the only other value allowed in the list is all.

The list may include (or consist solely of) the special value all. In other words, in .dsc files unlike the debian/control, all may occur in combination with specific architectures. The Architecture field in the Debian source control file .dsc is generally constructed from the Architecture fields in the debian/control in the source package.

Specifying only any indicates that the source package isn't dependent on any particular architecture and should compile fine on any one. The produced binary package(s) will be specific to whatever the current build architecture is.

Specifying only all indicates that the source package will only build architecture-independent packages.

Specifying any all indicates that the source package isn't dependent on any particular architecture. The set of produced binary packages will include at least one architecture-dependant package and one architecture-independent package.

Specifying a list of architectures or architecture wildcards indicates that the source will build an architecture-dependent package, and will only work correctly on the listed or matching architectures. If the source package also builds at least one architecture-independent package, all will also be included in the list.

In a .changes file, the Architecture field lists the architecture(s) of the package(s) currently being uploaded. This will be a list; if the source for the package is also being uploaded, the special entry source is also present. all will be present if any architecture-independent packages are being uploaded. Architecture wildcards such as any must never occur in the Architecture field in the .changes file.

See Main building script: debian/rules, Section 4.9 for information on how to get the architecture for the build process.


5.6.9 Essential

This is a boolean field which may occur only in the control file of a binary package or in a per-package fields paragraph of a source package control file.

If set to yes then the package management system will refuse to remove the package (upgrading and replacing it is still possible). The other possible value is no, which is the same as not having the field at all.


5.6.10 Package interrelationship fields: Depends, Pre-Depends, Recommends, Suggests, Breaks, Conflicts, Provides, Replaces, Enhances

These fields describe the package's relationships with other packages. Their syntax and semantics are described in Declaring relationships between packages, Chapter 7.


5.6.11 Standards-Version

The most recent version of the standards (the policy manual and associated texts) with which the package complies.

The version number has four components: major and minor version number and major and minor patch level. When the standards change in a way that requires every package to change the major number will be changed. Significant changes that will require work in many packages will be signaled by a change to the minor number. The major patch level will be changed for any change to the meaning of the standards, however small; the minor patch level will be changed when only cosmetic, typographical or other edits are made which neither change the meaning of the document nor affect the contents of packages.

Thus only the first three components of the policy version are significant in the Standards-Version control field, and so either these three components or all four components may be specified.[35]


5.6.12 Version

The version number of a package. The format is: [epoch:]upstream_version[-debian_revision]

The three components here 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.

upstream_version

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[36] 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.

debian_revision

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 is.

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 a Debian package, where the Debian package source must always be identical to the pristine source and therefore no revision indication is required.

It is conventional to restart the debian_revision at 1 each time the upstream_version is increased.

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 is equivalent to a debian_revision of 0.

When comparing two version numbers, first the epoch of each are compared, then the upstream_version if epoch is equal, and then debian_revision if upstream_version is also equal. epoch is compared numerically. The upstream_version and debian_revision parts are compared by the package management system using the following 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 from earliest to latest: ~~, ~~a, ~, the empty part, a.[37]

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.[38]


5.6.13 Description

In a source or binary control file, the Description field contains a description of the binary package, consisting of two parts, the synopsis or the short description, and the long description. It is a multiline field with the following format:

     	Description: <single line synopsis>
     	 <extended description over several lines>

The lines in the extended description can have these formats:

Do not use tab characters. Their effect is not predictable.

See The description of a package, Section 3.4 for further information on this.

In a .changes file, the Description field contains a summary of the descriptions for the packages being uploaded. For this case, the first line of the field value (the part on the same line as Description:) is always empty. It is a multiline field, with one line per package. Each line is indented by one space and contains the name of a binary package, a space, a hyphen (-), a space, and the short description line from that package.


5.6.14 Distribution

In a .changes file or parsed changelog output this contains the (space-separated) name(s) of the distribution(s) where this version of the package should be installed. Valid distributions are determined by the archive maintainers.[40] The Debian archive software only supports listing a single distribution. Migration of packages to other distributions is handled outside of the upload process.


5.6.15 Date

This field includes the date the package was built or last edited. It must be in the same format as the date in a debian/changelog entry.

The value of this field is usually extracted from the debian/changelog file - see Debian changelog: debian/changelog, Section 4.4).


5.6.16 Format

In .changes files, this field declares the format version of that file. The syntax of the field value is the same as that of a package version number except that no epoch or Debian revision is allowed. The format described in this document is 1.8.

In .dsc Debian source control files, this field declares the format of the source package. The field value is used by programs acting on a source package to interpret the list of files in the source package and determine how to unpack it. The syntax of the field value is a numeric major revision, a period, a numeric minor revision, and then an optional subtype after whitespace, which if specified is an alphanumeric word in parentheses. The subtype is optional in the syntax but may be mandatory for particular source format revisions. [41]


5.6.17 Urgency

This is a description of how important it is to upgrade to this version from previous ones. It consists of a single keyword taking one of the values low, medium, high, emergency, or critical[42] (not case-sensitive) followed by an optional commentary (separated by a space) which is usually in parentheses. For example:

       Urgency: low (HIGH for users of diversions)

The value of this field is usually extracted from the debian/changelog file - see Debian changelog: debian/changelog, Section 4.4.


5.6.18 Changes

This multiline field contains the human-readable changes data, describing the differences between the last version and the current one.

The first line of the field value (the part on the same line as Changes:) is always empty. The content of the field is expressed as continuation lines, with each line indented by at least one space. Blank lines must be represented by a line consisting only of a space and a full stop (.).

The value of this field is usually extracted from the debian/changelog file - see Debian changelog: debian/changelog, Section 4.4).

Each version's change information should be preceded by a "title" line giving at least the version, distribution(s) and urgency, in a human-readable way.

If data from several versions is being returned the entry for the most recent version should be returned first, and entries should be separated by the representation of a blank line (the "title" line may also be followed by the representation of a blank line).


5.6.19 Binary

This folded field is a list of binary packages. Its syntax and meaning varies depending on the control file in which it appears.

When it appears in the .dsc file, it lists binary packages which a source package can produce, separated by commas[43]. The source package does not necessarily produce all of these binary packages for every architecture. The source control file doesn't contain details of which architectures are appropriate for which of the binary packages.

When it appears in a .changes file, it lists the names of the binary packages being uploaded, separated by whitespace (not commas).


5.6.20 Installed-Size

This field appears in the control files of binary packages, and in the Packages files. It gives an estimate of the total amount of disk space required to install the named package. Actual installed size may vary based on block size, file system properties, or actions taken by package maintainer scripts.

The disk space is given as the integer value of the estimated installed size in bytes, divided by 1024 and rounded up.


5.6.21 Files

This field contains a list of files with information about each one. The exact information and syntax varies with the context.

In all cases, Files is a multiline field. The first line of the field value (the part on the same line as Files:) is always empty. The content of the field is expressed as continuation lines, one line per file. Each line must be indented by one space and contain a number of sub-fields, separated by spaces, as described below.

In the .dsc file, each line contains the MD5 checksum, size and filename of the tar file and (if applicable) diff file which make up the remainder of the source package[44]. For example:

     Files:
      c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
      938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz

The exact forms of the filenames are described in Source packages as archives, Section C.3.

In the .changes file this contains one line per file being uploaded. Each line contains the MD5 checksum, size, section and priority and the filename. For example:

     Files:
      4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
      c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
      938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
      7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb

The section and priority are the values of the corresponding fields in the main source control file. If no section or priority is specified then - should be used, though section and priority values must be specified for new packages to be installed properly.

The special value byhand for the section in a .changes file indicates that the file in question is not an ordinary package file and must be installed by hand by the distribution maintainers. If the section is byhand the priority should be -.

If a new Debian revision of a package is being shipped and no new original source archive is being distributed the .dsc must still contain the Files field entry for the original source archive package_upstream-version.orig.tar.gz, but the .changes file should leave it out. In this case the original source archive on the distribution site must match exactly, byte-for-byte, the original source archive which was used to generate the .dsc file and diff which are being uploaded.


5.6.22 Closes

A space-separated list of bug report numbers that the upload governed by the .changes file closes.


5.6.23 Homepage

The URL of the web site for this package, preferably (when applicable) the site from which the original source can be obtained and any additional upstream documentation or information may be found. The content of this field is a simple URL without any surrounding characters such as <>.


5.6.24 Checksums-Sha1 and Checksums-Sha256

These multiline fields contain a list of files with a checksum and size for each one. Both Checksums-Sha1 and Checksums-Sha256 have the same syntax and differ only in the checksum algorithm used: SHA-1 for Checksums-Sha1 and SHA-256 for Checksums-Sha256.

Checksums-Sha1 and Checksums-Sha256 are multiline fields. The first line of the field value (the part on the same line as Checksums-Sha1: or Checksums-Sha256:) is always empty. The content of the field is expressed as continuation lines, one line per file. Each line consists of the checksum, a space, the file size, a space, and the file name. For example (from a .changes file):

     Checksums-Sha1:
      1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
      a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
      5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
      71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
     Checksums-Sha256:
      ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
      0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
      f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
      3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb

In the .dsc file, these fields list all files that make up the source package. In the .changes file, these fields list all files being uploaded. The list of files in these fields must match the list of files in the Files field.


5.6.25 DM-Upload-Allowed

Obsolete, see below.


5.6.26 Version Control System (VCS) fields

Debian source packages are increasingly developed using VCSs. The purpose of the following fields is to indicate a publicly accessible repository where the Debian source package is developed.

Vcs-Browser

URL of a web interface for browsing the repository.

Vcs-Arch, Vcs-Bzr (Bazaar), Vcs-Cvs, Vcs-Darcs, Vcs-Git, Vcs-Hg (Mercurial), Vcs-Mtn (Monotone), Vcs-Svn (Subversion)

The field name identifies the VCS. The field's value uses the version control system's conventional syntax for describing repository locations and should be sufficient to locate the repository used for packaging. Ideally, it also locates the branch used for development of new versions of the Debian package.

In the case of Git, the value consists of a URL, optionally followed by the word -b and the name of a branch in the indicated repository, following the syntax of the git clone command. If no branch is specified, the packaging should be on the default branch.

More than one different VCS may be specified for the same package.


5.6.27 Package-List

Multiline field listing all the packages that can be built from the source package, considering every architecture. The first line of the field value is empty. Each one of the next lines describes one binary package, by listing its name, type, section and priority separated by spaces. Fifth and subsequent space-separated items may be present and parsers must allow them. See the Package-Type field for a list of package types.


5.6.28 Package-Type

Simple field containing a word indicating the type of package: deb for binary packages and udeb for micro binary packages. Other types not defined here may be indicated. In source package control files, the Package-Type field should be omitted instead of giving it a value of deb, as this value is assumed for paragraphs lacking this field.


5.6.29 Dgit

Folded field containing a single git commit hash, presented in full, followed optionally by whitespace and other data to be defined in future extensions.

Declares that the source package corresponds exactly to a referenced commit in a Git repository available at the canonical location called dgit-repos, used by dgit, a bidirectional gateway between the Debian archive and Git. The commit is reachable from at least one reference whose name matches refs/dgit/*. See the manual page of dgit for further details.


5.7 User-defined fields

Additional user-defined fields may be added to the source package control file. Such fields will be ignored, and not copied to (for example) binary or Debian source control files or upload control files.

If you wish to add additional unsupported fields to these output files you should use the mechanism described here.

Fields in the main source control information file with names starting X, followed by one or more of the letters BCS and a hyphen -, will be copied to the output files. Only the part of the field name after the hyphen will be used in the output file. Where the letter B is used the field will appear in binary package control files, where the letter S is used in Debian source control files and where C is used in upload control (.changes) files.

For example, if the main source information control file contains the field

       XBS-Comment: I stand between the candle and the star.

then the binary and Debian source control files will contain the field

       Comment: I stand between the candle and the star.

5.8 Obsolete fields

The following fields have been obsoleted and may be found in packages conforming with previous versions of the Policy.


5.8.1 DM-Upload-Allowed

Indicates that Debian Maintainers may upload this package to the Debian archive. The only valid value is yes. This field was used to regulate uploads by Debian Maintainers, See the General Resolution Endorse the concept of Debian Maintainers for more details.


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Debian Policy Manual

version 3.9.6.0, 2014-09-17

The Debian Policy Mailing List