[CMake] cpack, debian and python virtualenvs:

Thu Feb 10 16:44:43 EST 2011

What I'm trying to do: use cpack to turn a directory of python and shell
files into a debian package.  The wrinkle: I want the package to install the
python files into /usr/lib/python2.6/dist-packages/thingy and the shell
scripts into /etc/sv/thingy, and I want to be able to run the entire build
process without requiring superuser privileges.  In order to do this, I'm
using a python virtualenv (http://pypi.python.org/pypi/virtualenv) as the
build destination.

The problem: cpack keeps prepending '/usr' to the install paths in
install_manifest.txt, and hence in the generated deb package.

The cmake file, slightly edited for clarity:

PROJECT(thingy)

SET(VIRTUAL_ENV $ENV{VIRTUAL_ENV})
IF(VIRTUAL_ENV)
  MESSAGE(STATUS "Detected a python virtualenv in use, setting install
prefix to ${VIRTUAL_ENV}")
  SET(CMAKE_INSTALL_PREFIX ${VIRTUAL_ENV} )
ELSE(VIRTUAL_ENV)
  SET(CMAKE_INSTALL_PREFIX / )
ENDIF(VIRTUAL_ENV)

EXEC_PROGRAM("python -c 'from sys import version; print version[:3]'"
OUTPUT_VARIABLE PYTHON_VERSION)
SET(thingy_python_install_DIR
usr/lib/python${PYTHON_VERSION}/dist-packages/herd)

SET(thingy_python_SOURCES __init__.py main.py)
SET(thingy_service_DIR rc )

INSTALL(FILES ${thingy_python_SOURCES} DESTINATION
${thingy_python_install_DIR})
INSTALL(DIRECTORY ${thingy_service_DIR} DESTINATION etc
        FILE_PERMISSIONS WORLD_EXECUTE WORLD_READ
        PATTERN "supervise" EXCLUDE )

# cpack comes at the end
SET(CPACK_GENERATOR "DEB")
SET(CPACK_INCLUDE_TOPLEVEL_DIRECTORY 0)
SET(CPACK_PACKAGE_NAME "thingy")
SET(CPACK_PACKAGE_CONTACT "memory at blank.org")
SET(CPACK_PACKAGE_VENDOR "blank.org")
SET(CPACK_PACKAGE_DESCRIPTION_SUMMARY "Thingy Runner")
SET(CPACK_PACKAGE_VERSION_MAJOR "0")
SET(CPACK_PACKAGE_VERSION_MINOR "2")
SET(CPACK_PACKAGE_INSTALL_DIRECTORY "/")
SET(CPACK_TOPLEVEL_TAG "/")
SET(CPACK_DEBIAN_PACKAGE_NAME "thingy")
SET(CPACK_DEBIAN_PACKAGE_ARCHITECTURE "amd64")
SET(CPACK_DEBIAN_PACKAGE_DEPENDS "python")
SET(CPACK_DEBIAN_PACKAGE_MAINTAINER "memory at blank.org")
SET(CPACK_DEBIAN_PACKAGE_CONTROL_EXTRA

"${CMAKE_CURRENT_SOURCE_DIR}/debian/postinst;${CMAKE_CURRENT_SOURCE_DIR}/debian/postrm;"

)
include(CPack)

What this produces is a correct direct installation (the files end up in
$VIRTUAL_ENV/usr/lib/python2.6), but a broken package:

$ VIRTUAL_ENV=/home/memory/sandbox cmake ..
[standard output elided]
-- Detected a python virtualenv in use, setting install prefix to
/home/memory/sandbox
-- Configuring done
-- Generating done
-- Build files have been written to: /home/memory/thingy/build

$ make install
Install the project...
-- Install configuration: ""
-- Installing:
/home/memory/sandbox/usr/lib/python2.6/dist-packages/thingy/__init__.py
-- Installing:
/home/memory/sandbox/usr/lib/python2.6/dist-packages/thingy/main.py
-- Installing: /home/memory/sandbox/etc/rc
-- Installing: /home/memory/sandbox/etc/rc/run

$ make package
Run CPack packaging tool...
CPack: Create package using DEB
CPack: Install projects
CPack: - Run preinstall target for: thingy
CPack: - Install project: thingy
CPack: Compress package
CPack: Finalize package
CPack: Package /home/memory/thingy/build/thingy-0.2-Linux.deb generated.

$ dpkg-deb -c thingy-0.2.0-Linux.deb
drwxr-xr-x memory/memory     0 2011-02-10 21:23 ./usr/
drwxr-xr-x memory/memory     0 2011-02-10 21:23 ./usr/usr/
drwxr-xr-x memory/memory     0 2011-02-10 21:23 ./usr/usr/lib/
drwxr-xr-x memory/memory     0 2011-02-10 21:23 ./usr/usr/lib/python2.6/
drwxr-xr-x memory/memory     0 2011-02-10 21:23
./usr/usr/lib/python2.6/dist-packages/
drwxr-xr-x memory/memory     0 2011-02-10 21:23
./usr/usr/lib/python2.6/dist-packages/thingy/
-rw-r--r-- memory/memory 13054 2011-02-03 20:52
./usr/usr/lib/python2.6/dist-packages/thingy/job.py
-rw-r--r-- memory/memory    22 2011-02-03 20:52
./usr/usr/lib/python2.6/dist-packages/thingy/__init__.py
-rw-r--r-- memory/memory  1063 2011-02-03 20:52
./usr/usr/lib/python2.6/dist-packages/thingy/control.py
-rw-r--r-- memory/memory  5347 2011-02-03 20:52
./usr/usr/lib/python2.6/dist-packages/thingy/main.py
-rw-r--r-- memory/memory  2971 2011-02-03 20:52
./usr/usr/lib/python2.6/dist-packages/thingy/util.py
drwxr-xr-x memory/memory     0 2011-02-10 21:23 ./usr/etc/
drwxr-xr-x memory/memory     0 2011-02-10 21:23 ./usr/etc/rc/
-r-xr-xr-x memory/memory   595 2011-02-10 01:15 ./usr/etc/rc/run

Note the extra /usr prepended to all of the paths inside the debian
package.  If I build the package *without* $VIRTUAL_ENV being set, the same
thing happens.

I've trawled a bit through the various CPack module files, but can't see
where that /usr is coming from.

A helpful person on the cmake IRC channel suggested setting
CPACK_SET_DESTDIR to ON: this solves the problem only in the case of
$VIRTUAL_ENV being unset; if it's set, the package ends up being installed
into a duplicate of the install directory, ie:

$ dpkg-deb -c herd-0.2.0-Linux.deb
drwxr-xr-x memory/memory     0 2011-02-10 21:32 ./home/
drwxr-xr-x memory/memory     0 2011-02-10 21:32 ./home/memory/
drwxr-xr-x memory/memory     0 2011-02-10 21:32 ./home/memory/sandbox/
drwxr-xr-x memory/memory     0 2011-02-10 21:32 ./home/memory/sandbox/usr/
drwxr-xr-x memory/memory     0 2011-02-10 21:32
./home/memory/sandbox/usr/lib/
drwxr-xr-x memory/memory     0 2011-02-10 21:32
./home/memory/sandbox/usr/lib/python2.6/
drwxr-xr-x memory/memory     0 2011-02-10 21:32
./home/memory/sandbox/usr/lib/python2.6/dist-packages/
drwxr-xr-x memory/memory     0 2011-02-10 21:32
./home/memory/sandbox/usr/lib/python2.6/dist-packages/herd/
-rw-r--r-- memory/memory    22 2011-02-03 20:52
./home/memory/sandbox/usr/lib/python2.6/dist-packages/herd/__init__.py

So... where the heck is cpack picking up that /usr from?

-- 
Everyone knows history moves in circles;
the surprise is how big the circles are.
  (--Greil Marcus)
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