.\" Copyright 1999 SuSE GmbH Nuernberg, Germany
.\" Author: Thorsten Kukuk <kukuk@suse.de>
.\"
.\" SPDX-License-Identifier: GPL-2.0-or-later
.\"
.\" Modified, 6 May 2002, Michael Kerrisk, <mtk.manpages@gmail.com>
.\"   Change listed order of /usr/lib and /lib
.TH LDCONFIG 8 (date) "Linux man-pages (unreleased)"
.SH NAME
ldconfig \- configure dynamic linker run-time bindings
.SH SYNOPSIS
.PD 0
.BR /sbin/ldconfig " [" \-nNvXV "] [" \-f " \fIconf\fP] [" \-C " \fIcache\fP] [" \-r " \fIroot\fP]"
.IR directory ...
.PP
.B /sbin/ldconfig
.B \-l
.RB [ \-v ]
.IR library ...
.PP
.B /sbin/ldconfig
.B \-p
.PD
.SH DESCRIPTION
.B \%ldconfig
creates the necessary links and cache to the most recent shared
libraries found in the directories specified on the command line,
in the file
.IR /etc/ld.so.conf ,
and in the trusted directories,
.I /lib
and
.I /usr/lib
(on some 64-bit architectures such as x86-64,
.I /lib
and
.I /usr/lib
are the trusted directories for 32-bit libraries,
while
.I /lib64
and
.I /usr/lib64
are used for 64-bit libraries).
.PP
The cache is used by the run-time linker,
.I ld.so
or
.IR ld\-linux.so .
.B \%ldconfig
checks the header and filenames of the libraries it encounters when
determining which versions should have their links updated.
.PP
.B \%ldconfig
will attempt to deduce the type of ELF libraries
(i.e.,
libc5 or libc6/glibc)
based on what C libraries,
if any,
the library was linked against.
.\" The following sentence looks suspect
.\" (perhaps historical cruft) -- MTK, Jul 2005
.\" Therefore, when making dynamic libraries,
.\" it is wise to explicitly link against libc (use \-lc).
.PP
Some existing libraries do not contain enough information
to allow the deduction of their type.
Therefore,
the
.I /etc/ld.so.conf
file format allows the specification of an expected type.
This is used
.I only
for those ELF libraries which we can not work out.
The format
is "dirname=TYPE",
where TYPE can be libc4,
libc5,
or libc6.
(This syntax also works on the command line.)
Spaces are
.I not
allowed.
Also see the
.B \-p
option.
.B \%ldconfig
should normally be run by the superuser as it may require write
permission on some root owned directories and files.
.PP
Note that
.B \%ldconfig
will only look at files that are named
.I lib*.so*
(for regular shared objects) or
.I ld\-*.so*
(for the dynamic loader itself).
Other files will be ignored.
Also,
.B \%ldconfig
expects a certain pattern to how the symlinks are set up,
like this example,
where the middle file
.RB ( libfoo.so.1
here) is the SONAME for the library:
.PP
.in +4n
.EX
libfoo.so \-> libfoo.so.1 \-> libfoo.so.1.12
.EE
.in
.PP
Failure to follow this pattern may result in compatibility issues
after an upgrade.
.SH OPTIONS
.TP
.BR \-c " \fIfmt\fP, " \-\-format=\fIfmt\fP
(Since glibc 2.2)
.\" commit 45eca4d141c047950db48c69c8941163d0a61fcd
Cache format to use:
.IR old ,
.IR new ,
or
.IR \%compat .
Since glibc 2.32,
the default is
.IR new .
.\" commit cad64f778aced84efdaa04ae64f8737b86f063ab
Before that,
it was
.IR \%compat .
.TP
.BI "\-C " cache
Use
.I cache
instead of
.IR /etc/ld.so.cache .
.TP
.BI "\-f " conf
Use
.I conf
instead of
.IR /etc/ld.so.conf .
.TP
.BR \-i ", " \-\-ignore\-aux\-cache
(Since glibc 2.7)
.\" commit 27d9ffda17df4d2388687afd12897774fde39bcc
Ignore auxiliary cache file.
.TP
.B \-l
(Since glibc 2.2)
Library mode.
Manually link individual libraries.
Intended for use by experts only.
.TP
.B \-n
Process only the directories specified on the command line.
Don't process the trusted directories,
nor those specified in
.IR /etc/ld.so.conf .
Implies
.BR \-N .
.TP
.B \-N
Don't rebuild the cache.
Unless
.B \-X
is also specified,
links are still updated.
.TP
.BR \-p ", " \-\-print\-cache
Print the lists of directories and candidate libraries stored in
the current cache.
.TP
.BI "\-r " root
Change to and use
.I root
as the root directory.
.TP
.BR \-v ", " \-\-verbose
Verbose mode.
Print current version number,
the name of each directory as it is scanned,
and any links that are created.
Overrides quiet mode.
.TP
.BR \-V ", " \-\-version
Print program version.
.TP
.B \-X
Don't update links.
Unless
.B \-N
is also specified,
the cache is still rebuilt.
.SH FILES
.\" FIXME Since glibc-2.3.4, "include" directives are supported in ld.so.conf
.\"
.\" FIXME Since glibc-2.4, "hwcap" directives are supported in ld.so.conf
.PD 0
.TP
.I /lib/ld.so
Run-time linker/loader.
.TP
.I /etc/ld.so.conf
File containing a list of directories,
one per line,
in which to search for libraries.
.TP
.I /etc/ld.so.cache
File containing an ordered list of libraries found in the directories
specified in
.IR /etc/ld.so.conf ,
as well as those found in the trusted directories.
.PD
.SH SEE ALSO
.BR ldd (1),
.BR ld.so (8)