Making packages relocatable
Often, the most difficult thing about building a conda package is making it relocatable. Relocatable means that the package can be installed into any prefix. Otherwise, the package would be usable only in the environment in which it was built.
Conda-build does the following things automatically to make packages relocatable:
Binary object files are converted to use relative paths using
install_name_tool
on macOS and patchelf on Linux.Any text file without NULL bytes that contains the build prefix or the placeholder prefix
/opt/anaconda1anaconda2anaconda3
is registered in theinfo/has_prefix
file in the package metadata. When conda installs the package, any files ininfo/has_prefix
have the registered prefix replaced with the install prefix. For more information, see Package metadata.Any binary file containing the build prefix can automatically be registered in
info/has_prefix
usingbuild/detect_binary_files_with_prefix
inmeta.yaml
. Alternatively, individual binary files can be registered by listing them inbuild/binary_has_prefix_files
inmeta.yaml
. The registered files will have their build prefix replaced with the install prefix at install time. This works by padding the install prefix with null terminators, such that the length of the binary file remains the same. The build prefix must therefore be long enough to accommodate any reasonable installation prefix. On macOS and Linux, conda-build pads the build prefix to 255 characters by appending_placehold
s to the end of the build directory name.
Note
The prefix length was changed in conda-build 2.0 from 80 characters to 255 characters. Legacy packages with 80-character prefixes must be rebuilt to take advantage of the longer prefix.
There may be cases where conda identified a file as binary, but it needs to have the build prefix replaced as if it were text---no padding with null terminators. Such files can be listed in
build/has_prefix_files
inmeta.yaml
.