man dpkg-architecture (1): set and determine the architecture for package building

SYNOPSIS

dpkg-architecture [option...] [command]

DESCRIPTION

dpkg-architecture provides a facility to determine and set the build and host architecture for package building.

The build architecture is always determined by an external call to dpkg(1), and can not be set at the command line.

You can specify the host architecture by providing one or both of the options --host-arch and --host-type. The default is determined by an external call to gcc(1), or the same as the build architecture if CC or gcc are both not available. One out of --host-arch and --host-type is sufficient, the value of the other will be set to a usable default. Indeed, it is often better to only specify one, because dpkg-architecture will warn you if your choice does not match the default.

COMMANDS

-l, --list: Print the environment variables, one each line, in the format VARIABLE=value. This is the default action.
-e, --equal architecture: Check for equality of architecture (since dpkg 1.13.13). It compares the current or specified Debian host architecture against architecture, to check if they are equal. This action will not expand the architecture wildcards. Command finishes with an exit status of 0 if matched, 1 if not matched.
-i, --is architecture-wildcard: Check for identity of architecture (since dpkg 1.13.13). It compares the current or specified Debian host architecture against architecture-wildcard after having expanded it as an architecture wildcard, to check if they match. Command finishes with an exit status of 0 if matched, 1 if not matched.
-q, --query variable-name: Print the value of a single variable.
-s, --print-set: Print an export command. This can be used to set the environment variables using eval.
-u, --print-unset: Print a similar command to --print-unset but to unset all variables.
-c, --command command: Execute a command in an environment which has all variables set to the determined value.
-L, --list-known: Print a list of valid architecture names. Possibly restricted by one or more of the matching options --match-wildcard, --match-bits or --match-endian (since dpkg 1.17.14).
-?, --help: Show the usage message and exit.
--version: Show the version and exit.

OPTIONS

-a, --host-arch architecture: Set the host Debian architecture.
-t, --host-type gnu-system-type: Set the host GNU system type.
-A, --target-arch architecture: Set the target Debian architecture (since dpkg 1.17.14).
-T, --target-type gnu-system-type: Set the target GNU system type (since dpkg 1.17.14).
-W, --match-wildcard architecture-wildcard: Restrict the architectures listed by --list-known to ones matching the specified architecture wildcard (since dpkg 1.17.14).
-B, --match-bits architecture-bits: Restrict the architectures listed by --list-known to ones with the specified CPU bits (since dpkg 1.17.14). Either 32 or 64.
-E, --match-endian architecture-endianness: Restrict the architectures listed by --list-known to ones with the specified endianness (since dpkg 1.17.14). Either little or big.
-f, --force: Values set by existing environment variables with the same name as used by the scripts are honored (i.e. used by dpkg-architecture), except if this force flag is present. This allows the user to override a value even when the call to dpkg-architecture is buried in some other script (for example dpkg-buildpackage(1)).

TERMS

build machine: The machine the package is built on.
host machine: The machine the package is built for.
target machine: The machine the compiler is building for. This is only needed when building a cross-toolchain, one that will be built on the build architecture, to be run on the host architecture, and to build code for the target architecture.
Debian architecture: The Debian architecture string, which specifies the binary tree in the FTP archive. Examples: i386, sparc, hurd-i386.
Debian architecture wildcard: A Debian architecture wildcard is a special architecture string that will match any real architecture being part of it. The general form is <kernel>-<cpu>. Examples: linux-any, any-i386, hurd-any.
GNU system type: An architecture specification string consisting of two parts separated by a hyphen: cpu and system. Examples: i586-linux-gnu, sparc-linux-gnu, i686-gnu, x86_64-netbsd.
multiarch triplet: The clarified GNU system type, used for filesystem paths. This triplet does not change even when the baseline ISA gets bumped, so that the resulting paths are stable over time. The only current difference with the GNU system type is that the CPU part for i386 based systems is always i386. Examples: i386-linux-gnu, x86_64-linux-gnu. Example paths: /lib/powerpc64le-linux-gnu/, /usr/lib/i386-kfreebsd-gnu/.

VARIABLES

The following variables are set by dpkg-architecture:

DEB_BUILD_ARCH: The Debian architecture of the build machine.
DEB_BUILD_ARCH_OS: The Debian system name of the build machine (since dpkg 1.13.2).
DEB_BUILD_ARCH_CPU: The Debian cpu name of the build machine (since dpkg 1.13.2).
DEB_BUILD_ARCH_BITS: The pointer size of the build machine (in bits; since dpkg 1.15.4).
DEB_BUILD_ARCH_ENDIAN: The endianness of the build machine (little / big; since dpkg 1.15.4).
DEB_BUILD_GNU_CPU: The CPU part of DEB_BUILD_GNU_TYPE.
DEB_BUILD_GNU_SYSTEM: The System part of DEB_BUILD_GNU_TYPE.
DEB_BUILD_GNU_TYPE: The GNU system type of the build machine.
DEB_BUILD_MULTIARCH: The clarified GNU system type of the build machine, used for filesystem paths (since dpkg 1.16.0).
DEB_HOST_ARCH: The Debian architecture of the host machine.
DEB_HOST_ARCH_OS: The Debian system name of the host machine (since dpkg 1.13.2).
DEB_HOST_ARCH_CPU: The Debian cpu name of the host machine (since dpkg 1.13.2).
DEB_HOST_ARCH_BITS: The pointer size of the host machine (in bits; since dpkg 1.15.4).
DEB_HOST_ARCH_ENDIAN: The endianness of the host machine (little / big; since dpkg 1.15.4).
DEB_HOST_GNU_CPU: The CPU part of DEB_HOST_GNU_TYPE.
DEB_HOST_GNU_SYSTEM: The System part of DEB_HOST_GNU_TYPE.
DEB_HOST_GNU_TYPE: The GNU system type of the host machine.
DEB_HOST_MULTIARCH: The clarified GNU system type of the host machine, used for filesystem paths (since dpkg 1.16.0).
DEB_TARGET_ARCH: The Debian architecture of the target machine (since dpkg 1.17.14).
DEB_TARGET_ARCH_OS: The Debian system name of the target machine (since dpkg 1.17.14).
DEB_TARGET_ARCH_CPU: The Debian cpu name of the target machine (since dpkg 1.17.14).
DEB_TARGET_ARCH_BITS: The pointer size of the target machine (in bits; since dpkg 1.17.14).
DEB_TARGET_ARCH_ENDIAN: The endianness of the target machine (little / big; since dpkg 1.17.14).
DEB_TARGET_GNU_CPU: The CPU part of DEB_TARGET_GNU_TYPE (since dpkg 1.17.14).
DEB_TARGET_GNU_SYSTEM: The System part of DEB_TARGET_GNU_TYPE (since dpkg 1.17.14).
DEB_TARGET_GNU_TYPE: The GNU system type of the target machine (since dpkg 1.17.14).
DEB_TARGET_MULTIARCH: The clarified GNU system type of the target machine, used for filesystem paths (since dpkg 1.17.14).

FILES

Architecture tables

All these files have to be present for dpkg-architecture to work. Their location can be overridden at runtime with the environment variable DPKG_DATADIR.

/usr/share/dpkg/cputable: Table of known CPU names and mapping to their GNU name.
/usr/share/dpkg/ostable: Table of known operating system names and mapping to their GNU name.
/usr/share/dpkg/triplettable: Mapping between Debian architecture triplets and Debian architecture names.
/usr/share/dpkg/abitable: Table of Debian architecture ABI attribute overrides.

Packaging support

/usr/share/dpkg/architecture.mk: Makefile snippet that properly sets and exports all the variables that dpkg-architecture outputs (since dpkg 1.16.1).

EXAMPLES

dpkg-buildpackage accepts the -a option and passes it to dpkg-architecture. Other examples:

: CC=i386-gnu-gcc dpkg-architecture -c debian/rules build
: eval `dpkg-architecture -u`

Check if the current or specified host architecture is equal to an architecture:

: dpkg-architecture -elinux-alpha
: dpkg-architecture -amips -elinux-mips

Check if the current or specified host architecture is a Linux system:

: dpkg-architecture -ilinux-any
: dpkg-architecture -ai386 -ilinux-any

Usage in debian/rules

The environment variables set by dpkg-architecture are passed to debian/rules as make variables (see make documentation). However, you should not rely on them, as this breaks manual invocation of the script. Instead, you should always initialize them using dpkg-architecture with the -q option. Here are some examples, which also show how you can improve the cross compilation support in your package:

Retrieving the GNU system type and forwarding it to ./configure:

DEB_BUILD_GNU_TYPE ?= $(shell dpkg-architecture -qDEB_BUILD_GNU_TYPE)
DEB_HOST_GNU_TYPE ?= $(shell dpkg-architecture -qDEB_HOST_GNU_TYPE)
[...]
ifeq ($(DEB_BUILD_GNU_TYPE), $(DEB_HOST_GNU_TYPE))
  confflags += --build=$(DEB_HOST_GNU_TYPE)
else
  confflags += --build=$(DEB_BUILD_GNU_TYPE) \
               --host=$(DEB_HOST_GNU_TYPE)
endif
[...]
./configure $(confflags)

Doing something only for a specific architecture:

DEB_HOST_ARCH ?= $(shell dpkg-architecture -qDEB_HOST_ARCH)
ifeq ($(DEB_HOST_ARCH),alpha)
  [...]
endif

or if you only need to check the CPU or OS type, use the DEB_HOST_ARCH_CPU or DEB_HOST_ARCH_OS variables.

Note that you can also rely on an external Makefile snippet to properly set all the variables that dpkg-architecture can provide:

include /usr/share/dpkg/architecture.mk
ifeq ($(DEB_HOST_ARCH),alpha)
  [...]
endif

In any case, you should never use dpkg --print-architecture to get architecture information during a package build.

NOTES

All long command and option names available only since dpkg 1.17.17.