man/man8/ldconfig.8

.\" 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
.SY /sbin/ldconfig
.\" TODO?: -c, --format, -i, --ignore-aux-cache, --print-cache,
.\" --verbose, -V, --version, -?, --help, --usage
.RB [ \-nNvVX ]
.RB [ \-C\~\c
.IR cache ]
.RB [ \-f\~\c
.IR conf ]
.RB [ \-r\~\c
.IR root ]
.IR directory \~.\|.\|.
.YS
.SY /sbin/ldconfig
.B \-l
.RB [ \-v ]
.IR library \~.\|.\|.
.YS
.SY /sbin/ldconfig
.B \-p
.YS
.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
.IR /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.
.P
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.
.\" Support for libc4 and libc5 dropped in
.\" 8ee878592c4a642937152c8308b8faef86bcfc40 (2022-07-14) as "obsolete
.\" for over twenty years".
.B \%ldconfig
should normally be run by the superuser as it may require write
permission on some root owned directories and files.
.P
.B \%ldconfig
will look only 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 symbolic links are set up,
like this example,
where the middle file
.RB ( libfoo.so.1
here) is the SONAME for the library:
.P
.in +4n
.EX
libfoo.so \-> libfoo.so.1 \-> libfoo.so.1.12
.EE
.in
.P
Failure to follow this pattern may result in compatibility issues
after an upgrade.
.SH OPTIONS
.TP
.BI \-\-format= fmt
.TQ
.BI \-c\~ fmt
(Since glibc 2.2)
.\" commit 45eca4d141c047950db48c69c8941163d0a61fcd
Use cache format
.IR fmt ,
which is one of
.BR old ,
.BR new ,
or
.BR \%compat .
Since glibc 2.32,
the default is
.BR new .
.\" commit cad64f778aced84efdaa04ae64f8737b86f063ab
Before that,
it was
.BR \%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
.B \-\-ignore\-aux\-cache
.TQ
.B \-i
(Since glibc 2.7)
.\" commit 27d9ffda17df4d2388687afd12897774fde39bcc
Ignore auxiliary cache file.
.TP
.B \-l
(Since glibc 2.2)
Interpret each operand as a library name and configure its links.
Intended for use only by experts.
.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
.B \-\-print\-cache
.TQ
.B \-p
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
.B \-\-verbose
.TQ
.B \-v
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
.B \-\-version
.TQ
.B \-V
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
is the run-time linker/loader.
.TP
.I /etc/ld.so.conf
contains a list of directories,
one per line,
in which to search for libraries.
.TP
.I /etc/ld.so.cache
contains 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)