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phoenix |
.TH ld.so 8 "14 March 1998"
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.SH NAME
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ld.so/ld-linux.so \- dynamic linker/loader
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.SH DESCRIPTION
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.B ld.so
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loads the shared libraries needed by a program, prepares the program
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to run, and then runs it.
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Unless explicitly specified via the
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.B \-static
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option to
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.B ld
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during compilation, all Linux programs are incomplete and require
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further linking at run time.
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.PP
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The necessary shared libraries needed by the program are searched for
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in the following order
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.IP o
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Using the environment variable
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.B LD_LIBRARY_PATH
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.RB ( LD_AOUT_LIBRARY_PATH
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for a.out programs).
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Except if the executable is a setuid/setgid binary, in which case it
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is ignored.
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.IP o
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From the cache file
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.BR /etc/ld.so.cache
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which contains a compiled list of candidate libraries previously found
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in the augmented library path.
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.IP o
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In the default path
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.BR /usr/lib ,
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and then
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.BR /lib .
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.SH ENVIRONMENT
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.TP
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.B LD_LIBRARY_PATH
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A colon-separated list of directories in which to search for
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ELF libraries at execution-time.
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Similar to the
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.B PATH
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environment variable.
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.TP
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.B LD_PRELOAD
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A whitespace-separated list of additional, user-specified, ELF shared
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libraries to be loaded before all others.
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This can be used to selectively override functions in other shared libraries.
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For setuid/setgid ELF binaries, only libraries in the standard search
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directories that are also setgid will be loaded.
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.TP
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.B LD_TRACE_LOADED_OBJECTS
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If present, causes the program to list its dynamic library dependencies,
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as if run by ldd, instead of running normally.
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.TP
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.B LD_BIND_NOW
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If present, causes the dynamic linker to resolve all symbols at program
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startup instead of when they are first referenced.
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.TP
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.B LD_AOUT_LIBRARY_PATH
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A colon-separated list of directories in which to search for
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a.out libraries at execution-time.
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Similar to the
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.B PATH
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environment variable.
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.TP
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.B LD_AOUT_PRELOAD
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The name of an additional, user-specified, a.out shared library to be loaded
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after all others.
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This can be used to selectively override functions in other shared libraries.
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.TP
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.B LD_NOWARN
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Suppress warnings about a.out libraries with incompatible minor
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version numbers.
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.TP
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.B LD_KEEPDIR
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Don't ignore the directory in the names of a.out libraries to be loaded.
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Use of this option is strongly discouraged.
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.SH FILES
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.PD 0
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.TP 20
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.B /lib/ld.so
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a.out dynamic linker/loader
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.TP 20
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.B /lib/ld-linux.so.*
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ELF dynamic linker/loader
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.TP
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.B /etc/ld.so.cache
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File containing a compiled list of directories in which to search for
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libraries and an ordered list of candidate libraries.
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.TP
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.B /etc/ld.so.preload
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File containing a whitespace separated list of ELF shared libraries to
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be loaded before the program.
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libraries and an ordered list of candidate libraries.
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.TP
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.B lib*.so*
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shared libraries
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.PD
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.SH SEE ALSO
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.BR ldd (1),
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.BR ldconfig (8).
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.SH BUGS
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.LP
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Currently
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.B ld.so
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has no means of unloading and searching for compatible or newer version of
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libraries.
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.PP
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.B ld.so
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functionality is only available for executables compiled using libc version
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4.4.3 or greater.
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.SH AUTHORS
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David Engel, Eric Youngdale, Peter MacDonald, Hongjiu Lu, Linus
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Torvalds, Lars Wirzenius and Mitch D'Souza (not necessarily in that order).
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