doc/man/man1/update_dyld_shared_cache.1

   1 .Dd Oct 10, 2008
   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 overlay Ar directory
  11 .Op Fl arch Ar arch
  12 .Op Fl force
  13 .Op Fl debug
  14 .Op Fl sort_by_name
  15 .Op Fl universal_boot
  16 .Op Fl verify
  17 .Op Fl dylib_list Ar file
  18 .Op Fl iPhone
  19 .Op Fl cache_dir Ar dir
  20 .Sh DESCRIPTION
  21 .Nm update_dyld_shared_cache
  22 ensures that dyld's shared cache is up-to-date.  This tool is normally
  23 only run by Apple's Installer and Software Update, as they are the only
  24 official ways for OS dylibs to be updated.  But if for some reason you
  25 used another mechanism to alter an OS dylib, you should manually run
  26 .Nm update_dyld_shared_cache .
  27 .Pp
  28 Note that the new cache does not take effect until the OS is rebooted.
  29 .Pp
  30 If a safe-boot is
  31 done (booting with shift key held down) the cache is deleted.
  32 .Pp
  33 The dyld shared cache
  34 is mapped by dyld into a process at launch time. Later, when loading
  35 any mach-o image, dyld will first check if is in the share cache, and if
  36 it is will use that pre-bound version instead of opening, mapping, and binding
  37 the original file.  This results in significant performance improvements to
  38 launch time.
  39 .Pp
  40 .Nm update_dyld_shared_cache
  41 scans the directory /var/db/dyld/shared_region_roots for text files containing paths to
  42 mach-o executables.  The full dependencies of all dylibs required by those executables is
  43 used to determine which libraries are commonly used and should be placed in the
  44 shared cache. If one of the text files contains a path to a dylib, that dylib and its
  45 dependents will be forced into the cache.
  46 .Pp
  47 .Nm update_dyld_shared_cache
  48 builds a separate cache file for each architecture.  The cache files and a readable text
  49 map of the cached are generated to /var/db/dyld.
  50 .Pp
  51 You must be root to run this tool.
  52 .Pp
  53 The options are as follows:
  54 .Bl -tag
  55 .It Fl root Ar directory
  56 This option specifies the root of an OS installation for which dyld's
  57 shared cache should be updated.  This is used by the Installer to update the
  58 dyld shared cache in a partition other than the one you into which you are currently
  59 booted.  The cache files are created in the var/db/dyld directory of the specified directory.
  60 Note: if you are manually doing this, be sure to run the update_dyld_shared_cache tool
  61 that is in the partition being updated.  This assures the cache format created will
  62 match that expected when booting off that partition.
  63 .It Fl overlay Ar directory
  64 This option specifies the root of a sparse directory tree.  When building
  65 the dyld shared cache, any corresponding mach-o files in the sparse directory
  66 will override those in the boot partition.  This is used by Software
  67 Update to build a dyld shared cache for the update that is about to be
  68 installed.  The cache files
  69 are created in the var/db/dyld directory of the specified directory.
  70 .It Fl arch Ar arch
  71 By default
  72 .Nm update_dyld_shared_cache
  73 generates cache files for all architecture that the current machine
  74 can execute.  You can override this behavior by specifying one or more -arch options and list
  75 exactly which architectures should have their shared caches updated.
  76 .It Fl force
  77 This option will cause
  78 .Nm update_dyld_shared_cache
  79 to regenerated the shared cache files even if they appear to be already up-to-date.
  80 .It Fl debug
  81 This option prints out additional information about the work being done.
  82 .It Fl sort_by_name
  83 By default
  84 .Nm update_dyld_shared_cache
  85 assigns a random start address to each mach-o image in the cache.
  86 This option causes the start addresses to be chosen in path order, thus subsequent runs will
  87 produce the same address layout which can help reproduce some bugs.
  88 .It Fl universal_boot
  89 This option can only be used running on an machine with an Intel processor.  It builds caches
  90 that can be used when booting on both 32-bit and 64-bit machines.
  91 .It Fl dylib_list Ar file
  92 Instead of scanning /var/db/dyld/shared_region_roots/, this option provides a file that contains
  93 a list of the dylibs to use when building the shared cache file.
  94 .It Fl verify
  95 Will regenerate a shared cache in-memory that matches the randomization of the existing shared
  96 cache file.  Then instead of writing the cache file, it compares the in-memory cache file to
  97 the on disk version and reports any differences.
  98 .It Fl iPhone
  99 indicates that cache is not for the current Mac OS X, but for rather for an iPhone
 100 .It Fl cache_dir Ar directory
 101 This option specifies the directory in which to create the cache file(s).  If not specified,
 102 the cache file(s) are created in the standard location (e.g. var/db/dyld/) of the root partition.
 103 .El
 104 .Sh FILES
 105 .Tp
 106 /var/db/dyld/shared_region_roots
 107 directory of text files with paths to mach-o images used to determine what should be in shared cache.
 108 .Sh SEE ALSO
 109 .Xr dyld 1