NAME
ldconfig
—
configure the shared library
cache
SYNOPSIS
ldconfig |
[-mRrsUv ] [path ...] |
DESCRIPTION
ldconfig
is used to prepare a set of
“hints” for use by the run-time linker
ld.so(1) 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 the file
/var/run/ld.so.hints to forestall the overhead that
would otherwise result from the directory search operations
ld.so(1) would have to
perform to load the required shared libraries.
The shared libraries so 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
ld.so(1) when it needs to
load a shared library. It can be viewed as the run-time equivalent of the
-L
switch of ld(1).
ldconfig
is typically run as part of the
boot sequence. In addition to the built-in system directories, directories
containing shared libraries may be specified via the
shlib_dirs
variable in
/etc/rc.conf.local. See
rc.conf(8) for further
information.
The following options are recognized by
ldconfig
:
-m
- Merge the result of the scan of the directories given as arguments into
the existing hints file. The default action is to build the hints file
afresh. This option cannot be used with
-U
. -R
- Rescan the previously configured directories. This opens the hints file and fetches the directory list from the header. Any additional pathnames on the command line are also processed.
-r
- List the current contents of ld.so.hints on the standard output. The hints file will not be modified.
-s
- Do not scan the built-in system directory (“/usr/lib”) for shared libraries.
-U
- Unconfigure directories specified on the command line or remove
inaccessible directories from search path if no directories specified.
This option cannot be used with
-m
. -v
- Switch on verbose mode.
SECURITY
Special care must be taken when loading shared libraries into the
address space of set-user-ID and set-group-ID programs. Whenever such a
program is run, ld.so(1)
will only load shared libraries from the ld.so.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. It is presumed that the set of directories
specified to ldconfig
are under control of the
system's administrator. ld.so(1) further assists set-user-ID and set-group-ID programs by
erasing the LD_LIBRARY_PATH
from the
environment.
ENVIRONMENT
LD_LIBRARY_PATH
- Additional directories containing shared libraries, settable in the user's environment.
shlib_dirs
- Additional directories containing shared libraries, settable in /etc/rc.conf.local.
FILES
- /etc/rc.conf
- /etc/rc.conf.local
- /var/run/ld.so.hints
SEE ALSO
HISTORY
An ldconfig
utility first appeared in
SunOS 4.0. It appeared in its current form in NetBSD
0.9A.