ldconfig -- configure the shared library cache
ldconfig [-aout | -elf] [-Rimrsv] [-f hints_file] [directory | file ...]
The ldconfig utility is used to prepare a set of ``hints'' for use by the
dynamic linker to facilitate quick lookup of shared libraries available
in multiple directories. It scans a set of built-in system directories
and any directories specified on the command line (in the given order)
looking for shared libraries and stores the results in a system file to
forestall the overhead that would otherwise result from the directory
search operations the dynamic linker would have to perform to load the
required shared libraries.
Files named on the command line are expected to contain directories to
scan for shared libraries. Each directory's pathname must start on a new
line. Blank lines and lines starting with the comment character `#' are
ignored. Filenames must conform to the lib*.so.[0-9] pattern in order to
be added to the hints file.
For security reasons, directories which are world or group-writable or
which are not owned by root produce warning messages and are skipped,
unless the -i option is present.
The shared libraries which are found will be automatically available for
loading if needed by the program being prepared for execution. This
obviates the need for storing search paths within the executable.
The LD_LIBRARY_PATH environment variable can be used to override the use
of directories (or the order thereof) from the cache or to specify additional
directories where shared libraries might be found.
LD_LIBRARY_PATH is a `:' separated list of directory paths which are
searched by the dynamic linker when it needs to load a shared library.
It can be viewed as the run-time equivalent of the -L switch of ld(1).
The ldconfig utility is typically run as part of the boot sequence.
The following options are recognized by ldconfig:
-aout Generate the hints for a.out format shared libraries.
-elf Generate the hints for ELF format shared libraries.
-R Rescan the previously configured directories. This opens the
previous hints file and fetches the directory list from the
header. Any additional pathnames on the command line are also
processed. This is the default action when no parameters are
Read and/or update the specified hints file, instead of the standard
file. This option is provided primarily for testing.
-i Run in insecure mode. The security checks will not be performed.
-m Instead of replacing the contents of the hints file with those
found in the directories specified, ``merge'' in new entries.
Directories recorded in the hints file by previous runs of
ldconfig are also rescanned for new shared libraries.
-r List the current contents of the hints file on the standard output.
The hints file is not modified. The list of directories
stored in the hints file is included.
-s Do not scan the built-in system directory (``/usr/lib'') for
-v Switch on verbose mode.
Special care must be taken when loading shared libraries into the address
space of set-user-Id programs. Whenever such a program is run by any
user except the owner of the program, the dynamic linker will only load
shared libraries from the hints file. In particular, the LD_LIBRARY_PATH
is not used to search for libraries. Thus, the role of ldconfig is dual.
In addition to building a set of hints for quick lookup, it also serves
to specify the trusted collection of directories from which shared
objects can be safely loaded.
OBJFORMAT Overrides /etc/objformat (see below) to determine whether
-aout or -elf is the default. If set, its value should be
either `aout' or `elf'.
/var/run/ld.so.hints Standard hints file for the a.out dynamic
/var/run/ld-elf.so.hints Standard hints file for the ELF dynamic
/etc/ld.so.conf Conventional configuration file containing
directory names for invocations with -aout.
/etc/ld-elf.so.conf Conventional configuration file containing
directory names for invocations with -elf.
/etc/objformat Determines whether -aout or -elf is the
default. If present, it must consist of a
single line containing either
`OBJFORMAT=aout' or `OBJFORMAT=elf'.
A ldconfig utility first appeared in SunOS 4.0, it appeared in its current
form in FreeBSD 1.1.
Some security checks (for example, verifying root ownership of added
directories) are not performed when -aout is specified.
FreeBSD 5.2.1 October 3, 1993 FreeBSD 5.2.1 [ Back ]