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ld.so (8) | | Unix Manual Pages | :man

NAME

ld.so, ld-linux.so* - dynamic linker/loader

CONTENTS

Description
Synopsis
Command Line Options
Environment
Files
See Also
Authors

DESCRIPTION

ld.so loads the shared libraries needed by a program, prepares the program to run, and then runs it. Unless explicitly specified via the -static option to ld during compilation, all Linux programs are incomplete and require further linking at run time.

The necessary shared libraries needed by the program are searched for in the following order

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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/ld.so.cache which contains a compiled list of candidate libraries previously found in the augmented library path. If, however, the binary was linked with -z nodeflib 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.

SYNOPSIS

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/ld-linux.so.* [OPTIONS] [PROGRAM [ARGUMENTS]]

COMMAND LINE OPTIONS

--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
use given PATH instead of content of the environment variable LD_LIBRARY_PATH
--inhibit-rpath LIST
ignore RUNPATH and RPATH information in object names in LIST

ENVIRONMENT

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 running 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 specified in this environment variable.
LD_DEBUG_OUTPUT
File where LD_DEBUG output should be fed into, default is standard output. LD_DEBUG_OUTPUT is ignored for setuid/setgid binaries.
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 --verify options have been given to the dynamic linker).

FILES

/lib/ld-linux.so.* ELF dynamic linker/loader
/etc/ld.so.cache
File containing a compiled list of directories in which to search for libraries and an ordered list of candidate libraries.
/etc/ld.so.preload
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

SEE ALSO

ldd(1), ldconfig(8).

AUTHORS

Roland McGrath, Ulrich Drepper and others. This man page is derived from libc 5 ld.so manual page.


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