updatedyldsharedcac... BSD General Commands Manualupdatedyldsharedcac...

NAME
     uuppddaatteeddyyllddsshhaarreeddccaacchhee - Updates dyld's shared cache

SYNOPSIS
     uuppddaatteeddyyllddsshhaarreeddccaacchhee [-rroooott directory] [-aarrcchh arch] [-ffoorrccee] [-ddeebbuugg]
                              [-ssoorrttbbyynnaammee] [-uunniivveerrssaallbboooott]

DESCRIPTION
     uuppddaatteeddyyllddsshhaarreeddccaacchhee ensures that dyld's shared cache is up-to-date.
     Normally, this command never needs to be manually run.  Instead, it is
     automatically run by launchd when dyld notices the shared cache is out of
     date.  To prevent the cache from being regeneated during an install or
     during development of OS dylibs, dyld will not trigger a shared cache
     rebuild if the environment variable DYLDNOFIXPREBINDING is set, or if
     the main executable is a setuid binary, or alternate dylibs are loaded
     via one of the DYLD environment variables.

     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.

     uuppddaatteeddyyllddsshhaarreeddccaacchhee scans the directory
     /var/db/dyld/sharedregionroots 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 depenents will be forced into the
     cache.

     uuppddaatteeddyyllddsshhaarreeddccaacchhee 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:

     -rroooott directory
                 This option specifies the root of an OS installation for
                 which dyld's shared cache should be updated.  This allosw you
                 to update the shared cache on a non-running version of the
                 OS.  The cache files are created in the var/db/dyld directory
                 of the specified directory.

     -aarrcchh arch  By default uuppddaatteeddyyllddsshhaarreeddccaacchhee 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.

     -ffoorrccee      This option will cause uuppddaatteeddyyllddsshhaarreeddccaacchhee to regener-
                 ated the shared cache files even if they appear to be already
                 up-to-date.

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

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

     -uunniivveerrssaallbboooott
                 This option can only be used running on an machine with an
                 Intel processor.  It builds caches that can be used when
                 booting on an Intel or a PowerPC based machine.

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

SEE ALSO
     dyld(1)

Darwin                          March 23, 2007                          Darwin