man8/ldconfig.8

   1 .\" Copyright 1999 SuSE GmbH Nuernberg, Germany
   2 .\" Author: Thorsten Kukuk <kukuk@suse.de>
   3 .\"
   4 .\" SPDX-License-Identifier: GPL-2.0-or-later
   5 .\"
   6 .\" Modified, 6 May 2002, Michael Kerrisk, <mtk.manpages@gmail.com>
   7 .\"   Change listed order of /usr/lib and /lib
   8 .TH LDCONFIG 8 2021-03-22 "Linux man-pages (unreleased)"
   9 .SH NAME
  10 ldconfig \- configure dynamic linker run-time bindings
  11 .SH SYNOPSIS
  12 .BR /sbin/ldconfig " [" \-nNvXV "] [" \-f " \fIconf\fP] [" \-C " \fIcache\fP] [" \-r " \fIroot\fP]"
  13 .IR directory \...
  14 .PD 0
  15 .PP
  16 .PD
  17 .B /sbin/ldconfig
  18 .B \-l
  19 .RB [ \-v ]
  20 .IR library \...
  21 .PD 0
  22 .PP
  23 .PD
  24 .B /sbin/ldconfig
  25 .B \-p
  26 .SH DESCRIPTION
  27 .B ldconfig
  28 creates the necessary links and cache to the most recent shared
  29 libraries found in the directories specified on the command line,
  30 in the file
  31 .IR /etc/ld.so.conf ,
  32 and in the trusted directories,
  33 .I /lib
  34 and
  35 .I /usr/lib
  36 (on some 64-bit architectures such as x86-64,
  37 .I /lib
  38 and
  39 .I /usr/lib
  40 are the trusted directories for 32-bit libraries, while
  41 .I /lib64
  42 and
  43 .I /usr/lib64
  44 are used for 64-bit libraries).
  45 .PP
  46 The cache is used by the run-time linker,
  47 .I ld.so
  48 or
  49 .IR ld\-linux.so .
  50 .B ldconfig
  51 checks the header and filenames of the libraries it encounters when
  52 determining which versions should have their links updated.
  53 .PP
  54 .B ldconfig
  55 will attempt to deduce the type of ELF libraries (i.e., libc5 or libc6/glibc)
  56 based on what C libraries, if any, the library was linked against.
  57 .\" The following sentence looks suspect
  58 .\" (perhaps historical cruft) -- MTK, Jul 2005
  59 .\" Therefore, when making dynamic libraries,
  60 .\" it is wise to explicitly link against libc (use \-lc).
  61 .PP
  62 Some existing libraries do not contain enough information
  63 to allow the deduction of their type.
  64 Therefore, the
  65 .I /etc/ld.so.conf
  66 file format allows the specification of an expected type.
  67 This is used
  68 .I only
  69 for those ELF libraries which we can not work out.
  70 The format
  71 is "dirname=TYPE", where TYPE can be libc4, libc5, or libc6.
  72 (This syntax also works on the command line.)
  73 Spaces are
  74 .I not
  75 allowed.
  76 Also see the
  77 .B \-p
  78 option.
  79 .B ldconfig
  80 should normally be run by the superuser as it may require write
  81 permission on some root owned directories and files.
  82 .PP
  83 Note that
  84 .B ldconfig
  85 will only look at files that are named
  86 .I lib*.so*
  87 (for regular shared objects) or
  88 .I ld\-*.so*
  89 (for the dynamic loader itself).
  90 Other files will be ignored.
  91 Also,
  92 .B ldconfig
  93 expects a certain pattern to how the symlinks are set up, like this
  94 example, where the middle file
  95 .RB ( libfoo.so.1
  96 here) is the SONAME for the library:
  97 .PP
  98 .in +4n
  99 .EX
 100 libfoo.so \-> libfoo.so.1 \-> libfoo.so.1.12
 101 .EE
 102 .in
 103 .PP
 104 Failure to follow this pattern may result in compatibility issues
 105 after an upgrade.
 106 .SH OPTIONS
 107 .TP
 108 .BR \-c " \fIfmt\fP, " \-\-format=\fIfmt\fP
 109 (Since glibc 2.2)
 110 Cache format to use:
 111 .IR old ,
 112 .IR new ,
 113 or
 114 .IR compat .
 115 Since glibc 2.32, the default is
 116 .IR new .
 117 .\" commit cad64f778aced84efdaa04ae64f8737b86f063ab
 118 Before that, it was
 119 .IR compat .
 120 .TP
 121 .BI "\-C " cache
 122 Use
 123 .I cache
 124 instead of
 125 .IR /etc/ld.so.cache .
 126 .TP
 127 .BI "\-f " conf
 128 Use
 129 .I conf
 130 instead of
 131 .IR /etc/ld.so.conf .
 132 .\" FIXME glibc 2.7 added -i
 133 .TP
 134 .BR \-i ", " \-\-ignore\-aux\-cache
 135 (Since glibc 2.7)
 136 .\"             commit 27d9ffda17df4d2388687afd12897774fde39bcc
 137 Ignore auxiliary cache file.
 138 .TP
 139 .B \-l
 140 (Since glibc 2.2)
 141 Library mode.
 142 Manually link individual libraries.
 143 Intended for use by experts only.
 144 .TP
 145 .B \-n
 146 Process only the directories specified on the command line.
 147 Don't process the trusted directories,
 148 nor those specified in
 149 .IR /etc/ld.so.conf .
 150 Implies
 151 .BR \-N .
 152 .TP
 153 .B \-N
 154 Don't rebuild the cache.
 155 Unless
 156 .B \-X
 157 is also specified, links are still updated.
 158 .TP
 159 .BR \-p ", " \-\-print\-cache
 160 Print the lists of directories and candidate libraries stored in
 161 the current cache.
 162 .TP
 163 .BI "\-r " root
 164 Change to and use
 165 .I root
 166 as the root directory.
 167 .TP
 168 .BR \-v ", " \-\-verbose
 169 Verbose mode.
 170 Print current version number, the name of each directory as it
 171 is scanned, and any links that are created.
 172 Overrides quiet mode.
 173 .TP
 174 .BR \-V ", " \-\-version
 175 Print program version.
 176 .TP
 177 .B \-X
 178 Don't update links.
 179 Unless
 180 .B \-N
 181 is also specified, the cache is still rebuilt.
 182 .SH FILES
 183 .\" FIXME Since glibc-2.3.4, "include" directives are supported in ld.so.conf
 184 .\"
 185 .\" FIXME Since glibc-2.4, "hwcap" directives are supported in ld.so.conf
 186 .PD 0
 187 .TP
 188 .I /lib/ld.so
 189 Run-time linker/loader.
 190 .TP
 191 .I /etc/ld.so.conf
 192 File containing a list of directories, one per line,
 193 in which to search for libraries.
 194 .TP
 195 .I /etc/ld.so.cache
 196 File containing an ordered list of libraries found in the directories
 197 specified in
 198 .IR /etc/ld.so.conf ,
 199 as well as those found in the trusted directories.
 200 .PD
 201 .SH SEE ALSO
 202 .BR ldd (1),
 203 .BR ld.so (8)