Provided by: libc-bin_2.15-0ubuntu10_amd64 bug

NAME

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

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

       o      Using the environment  variable  LD_LIBRARY_PATH  (LD_AOUT_LIBRARY_PATH  for  a.out
              programs).  Except if the executable is a setuid/setgid binary, in which case it is
              ignored.

       o      From the cache file /etc/ld.so.cache which contains a compiled  list  of  candidate
              libraries  previously  found  in the augmented library path. Libraries installed in
              hardware capabilities directories (see below) are prefered to other libraries.

       o      In the default path /lib, and then /usr/lib.

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
              Override LD_LIBRARY_PATH environment variable setting (see below).

       --ignore-rpath LIST
              Ignore RPATH and RUNPATH information in object names in LIST.  This option has been
              supported by glibc2 for about one hour.  Then it was renamed into:

       --inhibit-rpath 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 setgid will be loaded.

       LD_TRACE_LOADED_OBJECTS
              If  present, causes the program to list its dynamic library dependencies, as if run
              by ldd, instead of running normally.

       LD_BIND_NOW
              If present, causes the dynamic linker to resolve all  symbols  at  program  startup
              instead of when they are first referenced.

       LD_BIND_NOT
              Do not update the GOT (global offset table) and PLT (procedure linkage table) after
              resolving a symbol.

       LD_AOUT_LIBRARY_PATH
              A colon-separated list of directories in which to search  for  a.out  libraries  at
              execution-time.  Similar to the PATH environment variable.

       LD_AOUT_PRELOAD
              The  name of an additional, user-specified, a.out shared library to be loaded after
              all others.  This can be used to selectively override  functions  in  other  shared
              libraries.

       LD_NOWARN
              Suppress warnings about a.out libraries with incompatible minor version numbers.

       LD_WARN
              If set to non-empty string, warn about unresolved symbols.

       LD_KEEPDIR
              Don't  ignore  the  directory in the names of a.out libraries to be loaded.  Use of
              this option is strongly discouraged.

       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).

       LD_PROFILE
              Shared object to be profiled.

       LD_PROFILE_OUTPUT
              File  where  LD_PROFILE  output  should  be  stored,  default  is  standard output.
              LD_PROFILE_OUTPUT is ignored for setuid/setgid binaries.

       LD_ASSUME_KERNEL
              Every DSO (Dynamic Shared Object, aka shared library) can tell the  dynamic  linker
              in  glibc which minimum OS ABI version is needed. The information about the minimum
              OS ABI version is encoded in a ELF note section usually named  .note.ABI-tag.  This
              is  used  to  determine  which  library  to  load when multiple version of the same
              library is installed on the  system.   The  LD_ASSUME_KERNEL  environment  variable
              overrides  the kernel version used by the dynamic linker to determine which library
              to load.

RPATH TOKEN EXPANSION

       The runtime linker provides a number of tokens that can be used in an rpath  specification
       (DT_RPATH or DT_RUNPATH).

       $ORIGIN
              ld.so  understands  the  string  $ORIGIN  (or  equivalently  ${ORIGIN}) in an rpath
              specification to mean the directory containing the application executable. Thus, an
              application    located    in    somedir/app    could    be    compiled   with   gcc
              -Wl,-rpath,'$ORIGIN/../lib' so that  it  finds  an  associated  shared  library  in
              somedir/lib no matter where somedir is located in the directory hierarchy.

       $PLATFORM
              The string $PLATFORM (or equivalently ${PLATFORM}) in an rpath specifcation expands
              to  the  processor  type  of  the  current  machine.  Please  note  that  on   some
              architectures  the  Linux  kernel  doesn't provide a platform string to the dynamic
              linker.

       $LIB   The string $LIB (or equivalently ${LIB}) in an  rpath  corresponds  to  the  system
              libraries  directory,  which  is  /lib for the native architecture on FHS compliant
              GNU/Linux systems.

HARDWARE CAPABILITIES

       Libraries might be compiled using hardware-specific instructions which do not exist on all
       CPU.  Such  libraries  should  be installed in directories whose name defines the hardware
       capabilities such as /usr/lib/sse2/. The dynamic linker checks these  directories  against
       the  hardware  of  the  machine  and selects the best suitable version of a given library.
       Hardware capabilities directories could be cascaded  to  combine  CPU  features.  Hardware
       capabilities depends on the CPU. The following names are currently recognized:

       Alpha  ev4, ev5, ev56, ev6, ev67

       MIPS   loongson2e, loongson2f, octeon, octeon2

       PowerPC
              4xxmac,  altivec,  arch_2_05,  arch_2_06, booke, cellbe, dfp, efpdouble, efpsingle,
              fpu, ic_snoop, mmu, notb, pa6t, power4, power5, power5+,  power6x,  ppc32,  ppc601,
              ppc64, smt, spe, ucache, vsx

       SPARC  flush, muldiv, stbar, swap, ultra3, v9, v9v, v9v2

       s390   dfp,  eimm,  esan3,  etf3enh,  g5,  highgprs, hpage, ldisp, msa, stfle, z900, z990,
              z9-109, z10, zarch

       x86 (32-bit only)
              acpi, apic, clflush, cmov, cx8, dts, fxsr, ht, i386, i486, i586,  i686,  mca,  mmx,
              mtrr, pat, pbe, pge, pn, pse36, sep, ss, sse, sse2, tm

FILES

       /lib/ld.so          a.out dynamic linker/loader
       /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.
       /etc/ld.so.nohwcap  When this file is present  the  dynamic  linker  will  load  the  non-
                           optimized version of a library, even if the CPU supports the optimized
                           version.
       lib*.so*            shared libraries

SEE ALSO

       ldd(1), ldconfig(8).

BUGS

       Currently ld.so has no means of unloading and searching for compatible or newer version of
       libraries.

       ld.so functionality is only available for executables compiled using libc version 4.4.3 or
       greater.

AUTHORS

       David Engel, Eric Youngdale, Peter MacDonald, Hongjiu Lu, Linus Torvalds,  Lars  Wirzenius
       and Mitch D'Souza (not necessarily in that order).

                                           26 May 2007                                   LD.SO(8)