doc/man/man1/update_dyld_shared_cache.1

   1 .Dd June 1, 2017
   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 universal_boot
  15 .Sh DESCRIPTION
  16 .Nm update_dyld_shared_cache
  17 ensures that dyld's shared cache is up-to-date.  This tool is normally
  18 only run by Apple's Installer and Software Update, as they are the only
  19 official ways for OS dylibs to be updated.  But if for some reason you
  20 used another mechanism to alter an OS dylib, you should manually run
  21 .Nm update_dyld_shared_cache .
  22 .Pp
  23 Note that the new cache does not take effect until the OS is rebooted.
  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 /System/Library/Receipts/ for .bom files which list all files
  34 installed.  From that info it creates the set of OS dylibs to build into the dyld cache.
  35 .Pp
  36 .Nm update_dyld_shared_cache
  37 builds a separate cache file for each architecture.  The cache files and a readable text
  38 map of the cached are generated to /var/db/dyld.
  39 .Pp
  40 You must be root to run this tool.
  41 .Pp
  42 The options are as follows:
  43 .Bl -tag
  44 .It Fl root Ar directory
  45 This option specifies the root of an OS installation for which dyld's
  46 shared cache should be updated.  This is used by the Installer to update the
  47 dyld shared cache in a partition other than the one you into which you are currently
  48 booted.  The cache files are created in the var/db/dyld directory of the specified directory.
  49 Note: if you are manually doing this, be sure to run the update_dyld_shared_cache tool
  50 that is in the partition being updated.  This assures the cache format created will
  51 match that expected when booting off that partition.
  52 .It Fl overlay Ar directory
  53 This option specifies the root of a sparse directory tree.  When building
  54 the dyld shared cache, any corresponding mach-o files in the sparse directory
  55 will override those in the boot partition.  This is used by Software
  56 Update to build a dyld shared cache for the update that is about to be
  57 installed.  The cache files
  58 are created in the var/db/dyld directory of the specified directory.
  59 .It Fl arch Ar arch
  60 By default
  61 .Nm update_dyld_shared_cache
  62 generates cache files for all architecture that the current machine
  63 can execute.  You can override this behavior by specifying one or more -arch options and list
  64 exactly which architectures should have their shared caches updated.
  65 .It Fl force
  66 This option will cause
  67 .Nm update_dyld_shared_cache
  68 to regenerated the shared cache files even if they appear to be already up-to-date.
  69 .It Fl debug
  70 This option prints out additional information about the work being done.
  71 .It Fl universal_boot
  72 This option builds caches for all machines.
  73 .El
  74 .Sh SEE ALSO
  75 .Xr dyld 1