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_toolon macOS and patchelf on Linux.
Any text file without NULL bytes that contains the build prefix or the placeholder prefix
/opt/anaconda1anaconda2anaconda3is registered in the
info/has_prefixfile in the package metadata. When conda installs the package, any files in
info/has_prefixhave 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
meta.yaml. Alternatively, individual binary files can be registered by listing them in
meta.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
_placeholds to the end of the build directory name.
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