man8/ldconfig.8

   1 .\" Copyright 1999 SuSE GmbH Nuernberg, Germany
   2 .\" Author: Thorsten Kukuk <kukuk@suse.de>
   3 .\"
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  19 .\"
  20 .\" Modified, 6 May 2002, Michael Kerrisk, <mtk.manpages@gmail.com>
  21 .\"   Change listed order of /usr/lib and /lib
  22 .TH LDCONFIG 8 2020-06-09 "GNU" "Linux Programmer's Manual"
  23 .SH NAME
  24 ldconfig \- configure dynamic linker run-time bindings
  25 .SH SYNOPSIS
  26 .BR /sbin/ldconfig " [" \-nNvXV "] [" \-f " \fIconf\fP] [" \-C " \fIcache\fP] [" \-r " \fIroot\fP]"
  27 .IR directory \...
  28 .PD 0
  29 .PP
  30 .PD
  31 .B /sbin/ldconfig
  32 .B \-l
  33 .RB [ \-v ]
  34 .IR library \...
  35 .PD 0
  36 .PP
  37 .PD
  38 .B /sbin/ldconfig
  39 .B \-p
  40 .SH DESCRIPTION
  41 .B ldconfig
  42 creates the necessary links and cache to the most recent shared
  43 libraries found in the directories specified on the command line,
  44 in the file
  45 .IR /etc/ld.so.conf ,
  46 and in the trusted directories,
  47 .I /lib
  48 and
  49 .IR /usr/lib
  50 (on some 64-bit architectures such as x86-64,
  51 .I /lib
  52 and
  53 .IR /usr/lib
  54 are the trusted directories for 32-bit libraries, while
  55 .I /lib64
  56 and
  57 .IR /usr/lib64
  58 are used for 64-bit libraries).
  59 .PP
  60 The cache is used by the run-time linker,
  61 .I ld.so
  62 or
  63 .IR ld-linux.so .
  64 .B ldconfig
  65 checks the header and filenames of the libraries it encounters when
  66 determining which versions should have their links updated.
  67 .PP
  68 .B ldconfig
  69 will attempt to deduce the type of ELF libraries (i.e., libc5 or libc6/glibc)
  70 based on what C libraries, if any, the library was linked against.
  71 .\" The following sentence looks suspect
  72 .\" (perhaps historical cruft) -- MTK, Jul 2005
  73 .\" Therefore, when making dynamic libraries,
  74 .\" it is wise to explicitly link against libc (use \-lc).
  75 .PP
  76 Some existing libraries do not contain enough information
  77 to allow the deduction of their type.
  78 Therefore, the
  79 .I /etc/ld.so.conf
  80 file format allows the specification of an expected type.
  81 This is used
  82 .I only
  83 for those ELF libraries which we can not work out.
  84 The format
  85 is "dirname=TYPE", where TYPE can be libc4, libc5, or libc6.
  86 (This syntax also works on the command line.)
  87 Spaces are
  88 .I not
  89 allowed.
  90 Also see the
  91 .B \-p
  92 option.
  93 .B ldconfig
  94 should normally be run by the superuser as it may require write
  95 permission on some root owned directories and files.
  96 .PP
  97 Note that
  98 .B ldconfig
  99 will only look at files that are named
 100 .I lib*.so*
 101 (for regular shared objects) or
 102 .I ld-*.so*
 103 (for the dynamic loader itself).
 104 Other files will be ignored.
 105 Also,
 106 .B ldconfig
 107 expects a certain pattern to how the symlinks are set up, like this
 108 example, where the middle file
 109 .RB ( libfoo.so.1
 110 here) is the SONAME for the library:
 111 .PP
 112 .in +4n
 113 .EX
 114 libfoo.so -> libfoo.so.1 -> libfoo.so.1.12
 115 .EE
 116 .in
 117 .PP
 118 Failure to follow this pattern may result in compatibility issues
 119 after an upgrade.
 120 .SH OPTIONS
 121 .TP
 122 .BR \-c " \fIfmt\fP, " \-\-format=\fIfmt\fP
 123 (Since glibc 2.2)
 124 Cache format to use:
 125 .IR old ,
 126 .IR new ,
 127 or
 128 .IR compat .
 129 Since glibc 2.32, the default is
 130 .IR new .
 131 .\" commit cad64f778aced84efdaa04ae64f8737b86f063ab
 132 Before that, it was
 133 .IR compat .
 134 .TP
 135 .BI "\-C " cache
 136 Use
 137 .I cache
 138 instead of
 139 .IR /etc/ld.so.cache .
 140 .TP
 141 .BI "\-f " conf
 142 Use
 143 .I conf
 144 instead of
 145 .IR /etc/ld.so.conf .
 146 .\" FIXME glibc 2.7 added -i
 147 .TP
 148 .BR \-i ", " \-\-ignore\-aux\-cache
 149 (Since glibc 2.7)
 150 .\"             commit 27d9ffda17df4d2388687afd12897774fde39bcc
 151 Ignore auxiliary cache file.
 152 .TP
 153 .B \-l
 154 (Since glibc 2.2)
 155 Library mode.
 156 Manually link individual libraries.
 157 Intended for use by experts only.
 158 .TP
 159 .B \-n
 160 Process only the directories specified on the command line.
 161 Don't process the trusted directories,
 162 nor those specified in
 163 .IR /etc/ld.so.conf .
 164 Implies
 165 .BR \-N .
 166 .TP
 167 .B \-N
 168 Don't rebuild the cache.
 169 Unless
 170 .B \-X
 171 is also specified, links are still updated.
 172 .TP
 173 .BR \-p ", " \-\-print\-cache
 174 Print the lists of directories and candidate libraries stored in
 175 the current cache.
 176 .TP
 177 .BI "\-r " root
 178 Change to and use
 179 .I root
 180 as the root directory.
 181 .TP
 182 .BR \-v ", " \-\-verbose
 183 Verbose mode.
 184 Print current version number, the name of each directory as it
 185 is scanned, and any links that are created.
 186 Overrides quiet mode.
 187 .TP
 188 .BR \-V ", " \-\-version
 189 Print program version.
 190 .TP
 191 .B \-X
 192 Don't update links.
 193 Unless
 194 .B \-N
 195 is also specified, the cache is still rebuilt.
 196 .SH FILES
 197 .\" FIXME Since glibc-2.3.4, "include" directives are supported in ld.so.conf
 198 .\"
 199 .\" FIXME Since glibc-2.4, "hwcap" directives are supported in ld.so.conf
 200 .PD 0
 201 .TP
 202 .I /lib/ld.so
 203 Run-time linker/loader.
 204 .TP
 205 .I /etc/ld.so.conf
 206 File containing a list of directories, one per line,
 207 in which to search for libraries.
 208 .TP
 209 .I /etc/ld.so.cache
 210 File containing an ordered list of libraries found in the directories
 211 specified in
 212 .IR /etc/ld.so.conf ,
 213 as well as those found in the trusted directories.
 214 .PD
 215 .SH SEE ALSO
 216 .BR ldd (1),
 217 .BR ld.so (8)