Command-line tools for the HPC administrator

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The HPC world has some amazing "big" tools that help administrators monitor their systems and keep them running, such as the Ganglia and Nagios cluster monitoring systems. Although they are extremely useful, sometimes it is the small tools that can help debug a user problem or find system issues. Here are a few favorites.

ldd

The introduction of sharable objects [1], or "dynamic libraries," has allowed for smaller binaries, less "skew" across binaries, and a reduction in memory usage, among other things. Users, myself included, tend to forget that when code compiles, we only see the size of the binary itself, not the "shared" objects.

For example, the following simple Hello World program, test1, uses PGI compilers (16.10):

PROGRAM HELLOWORLD
write(*,*) "hello world"
END

Running the ldd command against the compiled program produces the output in Listing 1. If you look at the binary, which is very small, you might think it is the complete story, but after looking at the list of libraries linked to it, you can begin to appreciate what compilers and linkers do for users today.

Listing 1

Show Linked Libraries (ldd)

$ pgf90 test1.f90 -o test1
$ ldd test1
    linux-vdso.so.1 =>  (0x00007fff11dc8000)
    libpgf90rtl.so => /opt/pgi/linux86-64/16.10/lib/libpgf90rtl.so (0x00007f5bc6516000)
    libpgf90.so => /opt/pgi/linux86-64/16.10/lib/libpgf90.so (0x00007f5bc5f5f000)
    libpgf90_rpm1.so => /opt/pgi/linux86-64/16.10/lib/libpgf90_rpm1.so (0x00007f5bc5d5d000)
    libpgf902.so => /opt/pgi/linux86-64/16.10/lib/libpgf902.so

...

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