dh(1) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OVERRIDE AND HOOK TARGETS | OPTIONS | EXAMPLES | INTERNALS | SEE ALSO | AUTHOR | COLOPHON

DH(1)                           Debhelper                          DH(1)

NAME         top

       dh - debhelper command sequencer

SYNOPSIS         top

       dh sequence [--with addon[,addon ...]] [--list]
       [debhelper options]

DESCRIPTION         top

       dh runs a sequence of debhelper commands. The supported sequences
       correspond to the targets of a debian/rules file: build-arch,
       build-indep, build, clean, install-indep, install-arch, install,
       binary-arch, binary-indep, and binary.

OVERRIDE AND HOOK TARGETS         top

       A debian/rules file using dh can override the command that is run
       at any step in a sequence, by defining an override target.  It is
       also possible to inject a command before or after any step
       without affecting the step itself.

   Injecting commands before or after a step
       Note: This feature requires debhelper 12.8 or later plus the
       package must use compatibility mode 10 or later.

       To inject commands before dh_command, add a target named
       execute_before_dh_command to the rules files.  Similarly, if you
       want to inject commands after dh_command, add the target
       execute_after_dh_command.  Both targets can be used for the same
       dh_command and also even if the command is overridden (as
       described in "Overriding a command" below).

       When these targets are defined, dh will call the targets
       respectively before or after it would invoke dh_command (or its
       override target).

   Overriding a command
       To override dh_command, add a target named override_dh_command to
       the rules file. When it would normally run dh_command, dh will
       instead call that target. The override target can then run the
       command with additional options, or run entirely different
       commands instead. See examples below.

   Architecture dependent/independent override and hook targets
       The override and hook targets can also be defined to run only
       when building architecture dependent or architecture independent
       packages. Use targets with names like override_dh_command-arch
       and execute_afterdh_command-indep.

       This feature is available since debhelper 8.9.7 (for override
       targets) and 12.8 (for hook targets).

   Completely empty targets
       As a special optimization, dh will skip a target if it is
       completely empty.  This is mostly useful for override targets,
       where the command will simply be skipped without the overhead of
       invoking a dummy target.

       Note that the target has to be completely empty for this to work:

            # Skip dh_bar - the good and optimized way
            # Some rationale for skipping dh_bar goes here
            override_dh_bar:

            # Skip dh_foo - the slow way
            override_dh_foo:
               # Some rationale for skipping dh_foo goes here
               # (these comments causes a dummy target to be run)

   Verifying targets are picked up by dh
       If you want to confirm that dh has seen an override or a hook
       target, you can use the following command as an example:

           $ dh binary --no-act | grep dh_install | head -n5
                dh_installdirs
                dh_install
                debian/rules execute_after_dh_install
                dh_installdocs
                dh_installchangelogs

       The debian/rules execute_after_dh_install in the output, which
       signals that dh registered a execute_after_dh_install target and
       would run it directly after dh_install(1).

       Note that "Completely empty targets" will be omitted in the
       listing above.  This makes it a bit harder to spot as you are
       looking for the omission of a command name.  But otherwise, the
       principle remains the same.

   Caveats with hook targets and makefile conditionals
       If you choose to wrap a hook target in makefile conditionals,
       please be aware that dh computes all the hook targets a head of
       time and caches the result for that run.  Furthermore, the
       conditionals will be invoked again when dh calls the hook target
       later and will assume the answer did not change.

       The parsing and caching often happens before dh knows whether it
       will build arch:any (-a) or/and arch:all (-i) packages, which can
       produce confusing results - especially when dh_listpackages(1) is
       part of the conditional.

       Most of the problems can be avoided by making the hook target
       unconditional and then have the "body" be partially or completely
       conditional.  As an example:

             # SIMPLE: It is well-defined what happens.  The hook target
             # is always considered.  The "maybe run this" bit is
             # conditional but dh_foo is definitely skipped.
             #
             # Note: The conditional is evaluated "twice" where its
             # influences what happens.  Once when dh check which hook
             # targets exist and once when the override_dh_foo hook target
             # is run.  If *either* times return false, "maybe run this"
             # is skipped.
             override_dh_foo:
             ifneq (...)
                 maybe run this
             endif

             # SIMPLE: This is also well-defined.  The hook target is always
             # run and dh_bar is skipped.  The "maybe run this" bit is
             # conditional as one might expect.
             #
             # Note: The conditional is still evaluated multiple times (in
             # different process each time).  However, only the evaluation
             # that happens when the hook target is run influences what
             # happens.
             override_dh_bar:
                 : # Dummy command to force the target to always be run
             ifneq (...)
                 maybe run this
             endif

             # COMPLICATED: This case can be non-trivial and have sharp edges.
             # Use at your own peril if dh_listpackages in the conditional.
             #
             # Here, either dh_baz is run normally OR "maybe run this" is run
             # instead.
             #
             # And it gets even more complicated to reason about if dh needs to
             # recurse into debian/rules because you have an "explicit"
             # standard target (e.g. a "build-arch:" target separate from "%:").
             ifneq (...)
             override_dh_baz:
                 maybe run this
             endif

       These recipes are also relevant for conditional dependency
       targets, which are often seen in a variant of the following
       example:

             COND_TASKS =
             ifneq (...)
             COND_TASKS += maybe-run-this
             endif
             ...

             maybe-run-this:
                 ...

             # SIMPLE: It is well-defined what happens.  Either the
             # $(COND_TASKS) are skipped or run.
             #
             # Note: The conditional is evaluated "twice" where its
             # influences what happens.  Once when dh check which hook
             # targets exist and once when the override_dh_foo hook target
             # is run.  If *either* times return false, $(COND_TASKS)
             # is skipped.
             override_dh_foo: $(COND_TASKS)

             # SIMPLE: This is also well-defined.  The hook target is always
             # run and dh_bar is skipped.  The $(COND_TASKS) bit is
             # conditional as one might expect.
             #
             # Note: The conditional is still evaluated multiple times (in
             # different process each time).  However, only the evaluation
             # that happens when the hook target is run influences what
             # happens.
             override_dh_bar: $(COND_TASKS)
                 : # Dummy command to force the target to always be run

             # COMPLICATED: This case can be non-trivial and have sharp edges.
             # Use at your own peril if dh_listpackages in the conditional.
             #
             ifneq (...)
             override_dh_baz: $(COND_TASKS)
             endif

       When in doubt, pick the relevant SIMPLE case in the examples
       above that match your need.

OPTIONS         top

       --with addon[,addon ...]
           Add the debhelper commands specified by the given addon to
           appropriate places in the sequence of commands that is run.
           This option can be repeated more than once, or multiple
           addons can be listed, separated by commas.  This is used when
           there is a third-party package that provides debhelper
           commands. See the PROGRAMMING file for documentation about
           the sequence addon interface.

           A Build-Depends relation on the package dh-sequence-addon
           implies a --with addon. This avoids the need for an explicit
           --with in debian/rules that only duplicates what is already
           declared via the build dependencies in debian/control.  The
           relation can (since 12.5) be made optional via e.g.  build-
           profiles.  This enables you to easily disable an addon that
           is only useful with certain profiles (e.g. to facilitate
           bootstrapping).

           Since debhelper 12.5, addons can also be activated in
           indep-only mode (via Build-Depends-Indep) or arch-only mode
           (via Build-Depends-Arch). Such addons are only active in the
           particular sequence (e.g. binary-indep) which simplifies
           dependency management for cross-builds.

           Please note that addons activated via Build-Depends-Indep or
           Build-Depends-Arch are subject to additional limitations to
           ensure the result is deterministic even when the addon is
           unavailable (e.g. during clean).  This implies that some
           addons are incompatible with these restrictions and can only
           be used via Build-Depends (or manually via debian/rules).
           Currently, such addons can only add commands to sequences.

       --without addon
           The inverse of --with, disables using the given addon. This
           option can be repeated more than once, or multiple addons to
           disable can be listed, separated by commas.

       --list, -l
           List all available addons.

           When called only with this option, dh can be called from any
           directory (i.e. it does not need access to files from a
           source package).

       --no-act
           Prints commands that would run for a given sequence, but does
           not run them.

           Note that dh normally skips running commands that it knows
           will do nothing.  With --no-act, the full list of commands in
           a sequence is printed.

       Other options passed to dh are passed on to each command it runs.
       This can be used to set an option like -v or -X or -N, as well as
       for more specialised options.

EXAMPLES         top

       To see what commands are included in a sequence, without actually
       doing anything:

               dh binary-arch --no-act

       This is a very simple rules file, for packages where the default
       sequences of commands work with no additional options.

               #!/usr/bin/make -f
               %:
                       dh $@

       Often you'll want to pass an option to a specific debhelper
       command. The easy way to do with is by adding an override target
       for that command.

               #!/usr/bin/make -f
               %:
                       dh $@

               override_dh_strip:
                       dh_strip -Xfoo

               override_dh_auto_configure:
                       dh_auto_configure -- --with-foo --disable-bar

       Sometimes the automated dh_auto_configure(1) and dh_auto_build(1)
       can't guess what to do for a strange package. Here's how to avoid
       running either and instead run your own commands.

               #!/usr/bin/make -f
               %:
                       dh $@

               override_dh_auto_configure:
                       ./mondoconfig

               override_dh_auto_build:
                       make universe-explode-in-delight

       Another common case is wanting to do something manually before or
       after a particular debhelper command is run.

               #!/usr/bin/make -f
               %:
                       dh $@

               # Example assumes debhelper/12.8 and compat 10+
               execute_after_dh_fixperms:
                       chmod 4755 debian/foo/usr/bin/foo

       If you are on an older debhelper or compatibility level, the
       above example would have to be written as.

               #!/usr/bin/make -f
               %:
                       dh $@

               # Older debhelper versions or using compat 9 or lower.
               override_dh_fixperms:
                       dh_fixperms
                       chmod 4755 debian/foo/usr/bin/foo

       Python tools are not run by dh by default, due to the continual
       change in that area. Here is how to use dh_python2.

               #!/usr/bin/make -f
               %:
                       dh $@ --with python2

       Here is how to force use of Perl's Module::Build build system,
       which can be necessary if debhelper wrongly detects that the
       package uses MakeMaker.

               #!/usr/bin/make -f
               %:
                       dh $@ --buildsystem=perl_build

       Here is an example of overriding where the dh_auto_* commands
       find the package's source, for a package where the source is
       located in a subdirectory.

               #!/usr/bin/make -f
               %:
                       dh $@ --sourcedirectory=src

       And here is an example of how to tell the dh_auto_* commands to
       build in a subdirectory, which will be removed on clean.

               #!/usr/bin/make -f
               %:
                       dh $@ --builddirectory=build

       If your package can be built in parallel, please either use
       compat 10 or pass --parallel to dh. Then dpkg-buildpackage -j
       will work.

               #!/usr/bin/make -f
               %:
                       dh $@ --parallel

       If your package cannot be built reliably while using multiple
       threads, please pass --no-parallel to dh (or the relevant
       dh_auto_* command):

               #!/usr/bin/make -f
               %:
                       dh $@ --no-parallel

       Here is a way to prevent dh from running several commands that
       you don't want it to run, by defining empty override targets for
       each command.

               #!/usr/bin/make -f
               %:
                       dh $@

               # Commands not to run:
               override_dh_auto_test override_dh_compress override_dh_fixperms:

       A long build process for a separate documentation package can be
       separated out using architecture independent overrides.  These
       will be skipped when running build-arch and binary-arch
       sequences.

               #!/usr/bin/make -f
               %:
                       dh $@

               override_dh_auto_build-indep:
                       $(MAKE) -C docs

               # No tests needed for docs
               override_dh_auto_test-indep:

               override_dh_auto_install-indep:
                       $(MAKE) -C docs install

       Adding to the example above, suppose you need to chmod a file,
       but only when building the architecture dependent package, as
       it's not present when building only documentation.

               # Example assumes debhelper/12.8 and compat 10+
               execute_after_dh_fixperms-arch:
                       chmod 4755 debian/foo/usr/bin/foo

INTERNALS         top

       If you're curious about dh's internals, here's how it works under
       the hood.

       In compat 10 (or later), dh creates a stamp file
       debian/debhelper-build-stamp after the build step(s) are complete
       to avoid re-running them.  It is possible to avoid the stamp file
       by passing --without=build-stamp to dh.  This makes "no clean"
       builds behave more like what some people expect at the expense of
       possibly running the build and test twice (the second time as
       root or under fakeroot(1)).

       Inside an override target, dh_* commands will create a log file
       debian/package.debhelper.log to keep track of which packages the
       command(s) have been run for.  These log files are then removed
       once the override target is complete.

       In compat 9 or earlier, each debhelper command will record when
       it's successfully run in debian/package.debhelper.log. (Which
       dh_clean deletes.) So dh can tell which commands have already
       been run, for which packages, and skip running those commands
       again.

       Each time dh is run (in compat 9 or earlier), it examines the
       log, and finds the last logged command that is in the specified
       sequence. It then continues with the next command in the
       sequence.

       A sequence can also run dependent targets in debian/rules.  For
       example, the "binary" sequence runs the "install" target.

       dh uses the DH_INTERNAL_OPTIONS environment variable to pass
       information through to debhelper commands that are run inside
       override targets. The contents (and indeed, existence) of this
       environment variable, as the name might suggest, is subject to
       change at any time.

       Commands in the build-indep, install-indep and binary-indep
       sequences are passed the -i option to ensure they only work on
       architecture independent packages, and commands in the build-
       arch, install-arch and binary-arch sequences are passed the -a
       option to ensure they only work on architecture dependent
       packages.

SEE ALSO         top

       debhelper(7)

       This program is a part of debhelper.

AUTHOR         top

       Joey Hess <joeyh@debian.org>

COLOPHON         top

       This page is part of the debhelper (helper programs for
       debian/rules) project.  Information about the project can be
       found at [unknown -- if you know, please contact man-
       pages@man7.org] If you have a bug report for this manual page,
       send it to submit@bugs.debian.org.  This page was obtained from
       the project's upstream Git repository
       ⟨https://salsa.debian.org/debian/debhelper.git⟩ on 2021-06-20.
       (At that time, the date of the most recent commit that was found
       in the repository was 2021-03-06.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

13.2.2                         2020-10-25                          DH(1)

Pages that refer to this page: debhelper(7)