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update_dyld_shared_cac... BSD General Commands Manualupdate_dyld_shared_cac...


     update_dyld_shared_cache -- Updates dyld's shared cache


     update_dyld_shared_cache [-root directory] [-overlay directory]
                              [-arch arch] [-force] [-debug] [-sort_by_name]
                              [-universal_boot] [-verify] [-dylib_list file]
                              [-iPhone] [-cache_dir dir]


     update_dyld_shared_cache ensures that dyld's shared cache is up-to-date.
     This tool is normally only run by Apple's Installer and Software Update,
     as they are the only official ways for OS dylibs to be updated.  But if
     for some reason you used another mechanism to alter an OS dylib, you
     should manually run update_dyld_shared_cache.

     Note that the new cache does not take effect until the OS is rebooted.

     If a safe-boot is done (booting with shift key held down) the cache is

     The dyld shared cache is mapped by dyld into a process at launch time.
     Later, when loading any mach-o image, dyld will first check if is in the
     share cache, and if it is will use that pre-bound version instead of
     opening, mapping, and binding the original file.  This results in signif-
     icant performance improvements to launch time.

     update_dyld_shared_cache scans the directory
     /var/db/dyld/shared_region_roots for text files containing paths to mach-
     o executables.  The full dependencies of all dylibs required by those
     executables is used to determine which libraries are commonly used and
     should be placed in the shared cache. If one of the text files contains a
     path to a dylib, that dylib and its dependents will be forced into the

     update_dyld_shared_cache builds a separate cache file for each architec-
     ture.  The cache files and a readable text map of the cached are gener-
     ated to /var/db/dyld.

     You must be root to run this tool.

     The options are as follows:

     -root directory
                 This option specifies the root of an OS installation for
                 which dyld's shared cache should be updated.  This is used by
                 the Installer to update the dyld shared cache in a partition
                 other than the one you into which you are currently booted.
                 The cache files are created in the var/db/dyld directory of
                 the specified directory.  Note: if you are manually doing
                 this, be sure to run the update_dyld_shared_cache tool that
                 is in the partition being updated.  This assures the cache
                 format created will match that expected when booting off that

     -overlay directory
                 This option specifies the root of a sparse directory tree.
                 When building the dyld shared cache, any corresponding mach-o
                 files in the sparse directory will override those in the boot
                 partition.  This is used by Software Update to build a dyld
                 shared cache for the update that is about to be installed.
                 The cache files are created in the var/db/dyld directory of
                 the specified directory.

     -arch arch  By default update_dyld_shared_cache generates cache files for
                 all architecture that the current machine can execute.  You
                 can override this behavior by specifying one or more -arch
                 options and list exactly which architectures should have
                 their shared caches updated.

     -force      This option will cause update_dyld_shared_cache to regener-
                 ated the shared cache files even if they appear to be already

     -debug      This option prints out additional information about the work
                 being done.

                 By default update_dyld_shared_cache assigns a random start
                 address to each mach-o image in the cache.  This option
                 causes the start addresses to be chosen in path order, thus
                 subsequent runs will produce the same address layout which
                 can help reproduce some bugs.

                 This option can only be used running on an machine with an
                 Intel processor.  It builds caches that can be used when
                 booting on both 32-bit and 64-bit machines.

     -dylib_list file
                 Instead of scanning /var/db/dyld/shared_region_roots/, this
                 option provides a file that contains a list of the dylibs to
                 use when building the shared cache file.

     -verify     Will regenerate a shared cache in-memory that matches the
                 randomization of the existing shared cache file.  Then
                 instead of writing the cache file, it compares the in-memory
                 cache file to the on disk version and reports any differ-

     -iPhone     indicates that cache is not for the current Mac OS X, but for
                 rather for an iPhone

     -cache_dir directory
                 This option specifies the directory in which to create the
                 cache file(s).  If not specified, the cache file(s) are cre-
                 ated in the standard location (e.g. var/db/dyld/) of the root


     /var/db/dyld/shared_region_roots directory of text files with paths to
     mach-o images used to determine what should be in shared cache.



Darwin                           Oct 10, 2008                           Darwin

Mac OS X 10.7 - Generated Wed Aug 10 18:39:55 CDT 2011
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