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Linux man pages : (8)			

NAME,* - dynamic linker/loader

DESCRIPTION loads the shared libraries needed by a program, prepares the pro- gram to run, and then runs it. Unless explicitly specified via the -static option to ld during compilation, all Linux programs are incom- plete and require further linking at run time. The necessary shared libraries needed by the program are searched for in the following order o Using the DT_RPATH dynamic section attribute of the binary if present and DT_RUNPATH attribute does not exist. o Using the environment variable LD_LIBRARY_PATH . Except if the executable is a setuid/setgid binary, in which case it is ignored. o Using the DT_RUNPATH dynamic section attribute of the binary if present. o From the cache file /etc/ which contains a compiled list of candidate libraries previously found in the augmented library path. If, however, the binary was linked with -z node- flib linker option, libraries in the default library paths are skipped. o In the default path /lib, and then /usr/lib. If the binary was linked with -z nodeflib linker option, this step is skipped.


The dynamic linker can be run either indirectly through running some dynamically linked program or library (in which case no command line options to the dynamic linker can be passed and the dynamic linker which is stored in the .interp section of the program is executed) or directly by running: /lib/* [OPTIONS] [PROGRAM [ARGUMENTS]]


--list List all dependencies and how they are resolved. --verify Verify that program is dynamically linked and this dynamic linker can handle it. --library-path PATH Override LD_LIBRARY_PATH environment variable setting (see below). --ignore-rpath LIST Ignore RPATH and RUNPATH information in object names in LIST.


LD_LIBRARY_PATH A colon-separated list of directories in which to search for ELF libraries at execution-time. Similar to the PATH environment variable. LD_PRELOAD A whitespace-separated list of additional, user-specified, ELF shared libraries to be loaded before all others. This can be used to selectively override functions in other shared libraries. For setuid/setgid ELF binaries, only libraries in the standard search directories that are also setuid will be loaded. LD_TRACE_LOADED_OBJECTS If set to non-empty string, causes the program to list its dynamic library dependencies, as if run by ldd, instead of run- ning normally. LD_BIND_NOW If set to non-empty string, causes the dynamic linker to resolve all symbols at program startup instead of deferring function call resolval to the point when they are first referenced. LD_WARN If set to non-empty string, warn about unresolved symbols. LD_DEBUG Output verbose debugging information about the dynamic linker. If set to all prints all debugging information it has, if set to help prints a help message about which categories can be speci- fied in this environment variable. LD_DEBUG_OUTPUT File where LD_DEBUG output should be fed into, default is stan- dard output. LD_DEBUG_OUTPUT is ignored for setuid/setgid bina- ries. LD_VERBOSE If set to non-empty string, output symbol versioning information about the program if querying information about the program (ie. either LD_TRACE_LOADED_OBJECTS has been set, or --list or --ver- ify options have been given to the dynamic linker).


/lib/* ELF dynamic linker/loader /etc/ File containing a compiled list of directories in which to search for libraries and an ordered list of candidate libraries. /etc/ File containing a whitespace separated list of ELF shared libraries to be loaded before the program. libraries and an ordered list of candidate libraries. lib*.so* shared libraries


ldd(1), ldconfig(8).


Roland McGrath, Ulrich Drepper and others. This man page is derived from libc 5 manual page. 30 October 2000