The NAS-built pkgsrc module contains nearly 1,000 packages. A few known conflicts are described below. It is a common problem that users load a long list of modules for their entire workflow in their system startup scripts, but are not aware that some of these modules contain commands and/or shared libraries that are in conflict with one another. If hdf5/1.8.18_serial is loaded before pkgsrc/2016Q4, the entries from pkgsrc will be listed first, as follows: /nasa/pkgsrc/sles12/2016Q4/bin:/nasa/pkgsrc/sles12/2016Q4/sbin:/nasa/hdf5/1.8.18_serial/bin For example, both the hdf5/1.8.18_serial and pkgsrc/2016Q4 modulefiles use prepend-path to add their corresponding bin directories to PATH. The order in which the modulefiles are loaded.Įntries are added to PATH and LD_LIBRARY_PATH in the order the modulefiles are loaded.To find out whether prepend-path or append-path is used by a given modulefile, run: module show modulefile_name Whether a modulefile uses prepend-path or append-path.įor example, the tecplot/2017r2 modulefile prepends the /nasa/tecplot/2017r2/360ex_2017r2/bin:/nasa/tecplot/2017r2/chorus_2017r2/bin entry to the beginning of the existing PATH, while the netcdf/4.4.1.1_serial modulefile appends the /nasa/netcdf/4.4.1.1_serial/bin entry to the end of the PATH.The placement of an entry depends on two factors: Software modules add entries to PATH and LD_LIBRARY_PATH when they are loaded.
For LD_LIBRARY_PATH, a system default is not defined users typically define LD_LIBRARY_PATH in their own scripts. Many users modify PATH in their system startup files (such as. Some default directories (such as /usr/local/bin and /usr/bin) are automatically included in PATH for every NAS user account. Therefore, it is very important to pay attention to which entries are included in PATH and LD_LIBRARY_PATH, and where they are placed.
Using the wrong command or shared library could cause your application to fail or provide incorrect results. The system searches the PATH or LD_LIBRARY_PATH entries from beginning to end, and always uses the first matching entry it finds-regardless of whether it is the correct one. If multiple entries in these variables contain commands or libraries with the same filename as the one needed, this can potentially lead to conflicts. When building or running an application, the environment variables PATH and LD_LIBRARY_PATH may be used to find the commands and/or runtime shared libraries needed for the operation.
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