dpkg-architecture - set and determine the architecture for package building

dpkg-architecture [options] [action]

Valid options: -aDebian-Architecture -tGnu-System-Type -f

Valid actions: -l, -qVariable-Name, -s, -u, -c Command, -L

dpkg-architecture does provide 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, and can not be set at the command line.

You can specify the host architecture by providing one or both of the options -a and -t. The default is determined by an external call to gcc, or the same as the build architecture if CC or gcc are both not available. One out of -a and -t 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 doesn't match the default.

The default action is -l, which prints the environment variables, one each line, in the format VARIABLE=value. If you are only interested in the value of a single variable, you can use -q. If you specify -s, it will output an export command. This can be used to set the environment variables using eval. -u does return a similar command to unset all variables. -c does execute a command in an environment which has all variables set to the determined value.

A list of valid architecture names can be printed with the -L action.

Existing environment variables with the same name as used by the scripts are not overwritten, except if the -f 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).

build machine

The machine the package is built on.

host machine

The machine the package is built for.

Debian Architecture

The Debian architecture string, which specifies the binary tree in the FTP archive. Examples: i386, sparc, hurd-i386.

GNU System Type

An architecture specification string consisting of two parts, cpu-system. Examples: i386-linux-gnu, sparc-linux-gnu, i386-gnu, x86_64-netbsd.

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

CC=i386-gnu-gcc dpkg-architecture CW-c debian/rules build

eval `dpkg-architecture CW-u`

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.

DEB_BUILD_ARCH_CPU

The Debian cpu name of the build machine.

DEB_BUILD_GNU_TYPE

The GNU system type of the build machine.

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_HOST_ARCH

The Debian architecture of the host machine.

DEB_HOST_ARCH_OS

The Debian system name of the host machine.

DEB_HOST_ARCH_CPU

The Debian cpu name of the host machine.

DEB_HOST_GNU_TYPE

The GNU system type of the host machine.

DEB_HOST_GNU_CPU

The CPU part of DEB_HOST_GNU_TYPE

DEB_HOST_GNU_SYSTEM

The System part of DEB_HOST_GNU_TYPE

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:

Instead of:

ARCH=`dpkg --print-architecture`
configure $(ARCH)-linux

please use the following:

DEB_BUILD_GNU_TYPE := $(shell dpkg-architecture -qDEB_BUILD_GNU_TYPE)
DEB_HOST_GNU_TYPE := $(shell dpkg-architecture -qDEB_HOST_GNU_TYPE)

configure --build=$(DEB_BUILD_GNU_TYPE) --host=$(DEB_HOST_GNU_TYPE)

Instead of:

ARCH=`dpkg --print-architecture`
ifeq ($(ARCH),alpha)
  ...
endif

please use:

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.

In general, calling dpkg in the rules file to get architecture information is deprecated (until you want to provide backward compatibility, see below). Especially the --print-architecture option is unreliable since we have Debian architectures which don't equal a processor name.

The DEB_HOST_ARCH_CPU and DEB_HOST_ARCH_OS variables were only introduced in relatively recent versions of dpkg-architecture (since dpkg 1.13.2), before this debian/rules files tended to check the values of the DEB_HOST_GNU_CPU or DEB_HOST_GNU_TYPE variables which have been subject to change.

Where debian/rules files check these variables to decide how or what to compile, this should be updated to use the new variables and values. You may wish to retain backwards compatibility with older version of dpkg-dev by using the following code:

DEB_HOST_ARCH_CPU := $(shell dpkg-architecture -qDEB_HOST_ARCH_CPU 2>/dev/null)
DEB_HOST_ARCH_OS := $(shell dpkg-architecture -qDEB_HOST_ARCH_OS 2>/dev/null)

# Take account of old dpkg-architecture output. ifeq ($(DEB_HOST_ARCH_CPU),) DEB_HOST_ARCH_CPU := $(shell dpkg-architecture -qDEB_HOST_GNU_CPU) ifeq ($(DEB_HOST_ARCH_CPU),x86_64) DEB_HOST_ARCH_CPU := amd64 endif endif ifeq ($(DEB_HOST_ARCH_OS),) DEB_HOST_ARCH_OS := $(subst -gnu,,$(shell dpkg-architecture -qDEB_HOST_GNU_SYSTEM)) ifeq ($(DEB_HOST_ARCH_OS),gnu) DEB_HOST_ARCH_OS := hurd endif endif

And similarly for DEB_BUILD_ARCH_CPU and DEB_BUILD_ARCH_OS.

If you still wish to support versions of dpkg-dev that did not include dpkg-architetcure, the following does the job:

DEB_BUILD_ARCH := $(shell dpkg --print-architecture)
DEB_BUILD_GNU_CPU := $(patsubst hurd-%,%,$(DEB_BUILD_ARCH))
ifeq ($(filter-out hurd-%,$(DEB_BUILD_ARCH)),)
  DEB_BUILD_GNU_SYSTEM := gnu
else
  DEB_BUILD_GNU_SYSTEM := linux-gnu
endif
DEB_BUILD_GNU_TYPE=$(DEB_BUILD_GNU_CPU)-$(DEB_BUILD_GNU_SYSTEM)

DEB_HOST_ARCH := $(DEB_BUILD_ARCH) DEB_HOST_GNU_CPU := $(DEB_BUILD_GNU_CPU) DEB_HOST_GNU_SYSTEM := $(DEB_BUILD_GNU_SYSTEM) DEB_HOST_GNU_TYPE := $(DEB_BUILD_GNU_TYPE)

Put a subset of these lines at the top of your debian/rules file; these default values will be overwritten if dpkg-architecture is used.

You don't need the full set. Choose a consistent set which contains the values you use in the rules file. For example, if you only need the host Debian architecture, `DEB_HOST_ARCH=`dpkg --print-architecture` is sufficient (this is indeed the Debian architecture of the build machine, but remember that we are only trying to be backward compatible with native compilation).

dpkg-buildpackage dpkg-cross

If you have questions about the usage of the make variables in your rules files, or about cross compilation support in your packages, please email me. The address is Marcus Brinkmann <brinkmd@debian.org>.