doc/man/man1/update_dyld_shared_cache.1

   1 .Dd March 23, 2007
   2 .Dt update_dyld_shared_cache 1
   3 .Os Darwin
   4 .Sh NAME
   5 .Nm update_dyld_shared_cache
   6 .Nd "Updates dyld's shared cache"
   7 .Sh SYNOPSIS
   8 .Nm
   9 .Op Fl root Ar directory
  10 .Op Fl arch Ar arch
  11 .Op Fl force
  12 .Op Fl debug
  13 .Op Fl sort_by_name
  14 .Op Fl universal_boot
  15 .Sh DESCRIPTION
  16 .Nm update_dyld_shared_cache
  17 ensures that dyld's shared cache is up-to-date.  Normally, this command
  18 never needs to be manually run.  Instead, it is automatically run by launchd
  19 when dyld notices the shared cache is out of date.  To prevent the cache
  20 from being regeneated during an install or during development of OS dylibs,
  21 dyld will not trigger a shared cache rebuild if the environment variable
  22 DYLD_NO_FIX_PREBINDING is set, or if the main executable is a setuid binary,
  23 or alternate dylibs are loaded via one of the DYLD_ environment variables.
  24 .Pp
  25 The dyld shared cache
  26 is mapped by dyld into a process at launch time. Later, when loading
  27 any mach-o image, dyld will first check if is in the share cache, and if
  28 it is will use that pre-bound version instead of opening, mapping, and binding
  29 the original file.  This results in significant performance improvements to
  30 launch time.
  31 .Pp
  32 .Nm update_dyld_shared_cache
  33 scans the directory /var/db/dyld/shared_region_roots for text files containing paths to
  34 mach-o executables.  The full dependencies of all dylibs required by those executables is
  35 used to determine which libraries are commonly used and should be placed in the
  36 shared cache. If one of the text files contains a path to a dylib, that dylib and its
  37 depenents will be forced into the cache.
  38 .Pp
  39 .Nm update_dyld_shared_cache
  40 builds a separate cache file for each architecture.  The cache files and a readable text
  41 map of the cached are generated to /var/db/dyld.
  42 .Pp
  43 You must be root to run this tool.
  44 .Pp
  45 The options are as follows:
  46 .Bl -tag
  47 .It Fl root Ar directory
  48 This option specifies the root of an OS installation for which dyld's
  49 shared cache should be updated.  This allosw you to update the
  50 shared cache on a non-running version of the OS.  The cache files
  51 are created in the var/db/dyld directory of the specified directory.
  52 .It Fl arch Ar arch
  53 By default
  54 .Nm update_dyld_shared_cache
  55 generates cache files for all architecture that the current machine
  56 can execute.  You can override this behavior by specifying one or more -arch options and list
  57 exactly which architectures should have their shared caches updated.
  58 .It Fl force
  59 This option will cause
  60 .Nm update_dyld_shared_cache
  61 to regenerated the shared cache files even if they appear to be already up-to-date.
  62 .It Fl debug
  63 This option prints out additional information about the work being done.
  64 .It Fl sort_by_name
  65 By default
  66 .Nm update_dyld_shared_cache
  67 assignes a random start address to each mach-o image in the cache.
  68 This option causes the start addresses to be choosen in path order, thus subsequent runs will
  69 produce the same address layout which can help reproduce some bugs.
  70 .It Fl universal_boot
  71 This option can only be used running on an machine with an Intel processor.  It builds caches
  72 that can be used when booting on an Intel or a PowerPC based machine.
  73 .El
  74 .Sh FILES
  75 .Tp
  76 /var/db/dyld/shared_region_roots
  77 directory of text files with paths to mach-o images used to determine what should be in shared cache.
  78 .Sh SEE ALSO
  79 .Xr dyld 1