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update_dyld_shared_cac... BSD General Commands Manualupdate_dyld_shared_cac...

NAME
     update_dyld_shared_cache -- Updates dyld's shared cache

SYNOPSIS
     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]

DESCRIPTION
     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 deleted.

     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 significant 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 cache.

     update_dyld_shared_cache builds a separate cache file for each architecture.  The cache files and a
     readable text map of the cached are generated 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 partition.

     -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 regenerated the shared cache files even
                 if they appear to be already up-to-date.

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

     -sort_by_name
                 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 subse-quent subsequent
                 quent runs will produce the same address layout which can help reproduce some bugs.

     -universal_boot
                 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 differences.

     -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 speci-fied, specified,
                 fied, the cache file(s) are created in the standard location (e.g. var/db/dyld/) of the
                 root partition.

FILES
     /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.

SEE ALSO
     dyld(1)

Darwin                           Oct 10, 2008                           Darwin