KEXTCACHE(8)

NAME
kextcache - create kext cache files

SYNOPSIS
kextcache -prelinked-kernel filename [options] [--] [kext_or_directory ...]
kextcache -system-prelinked-kernel [options] [--] [kext_or_directory ...]
kextcache -system-caches [options]
kextcache -update-volume os_volume [options]

DESCRIPTION
The kextcache program creates kext caches, which speed up kext loading operations. It is invoked automatically as needed to rebuild system caches.

Caution: Incorrect use of kextcache can render a volume incapable of startup. Installers and administrators should not use this program to update system kext caches. Instead they should run touch(1) on the /System/Library/Extensions/ directory of the installation target volume after they have finished, which invalidates the existing caches and causes the system to update all necessary kext caches. kextcache -update-volume can be used to wait for this process to complete. See “Apple Developer Technical Q&A QA1319: Installing an I/O Kit Kext Without Rebooting” for information on updating kext caches on prior releases of Mac OS X.

kextcache creates several kinds of kext caches. The first is the prelinked kernel (also known as a prelinkedkernel), which contains the kernel code and the essential files (info dictionary and executable) for an arbitrary set of kexts, with kext executables linked for their run-time locations. A prelinked kernel speeds early system startup by collecting these many files in one place for the booter to locate, and by having each kext linked in place and ready to start as needed. To create or update a prelinked kernel, use the -prelinked-kernel or -system-prelinked-kernel option.

Other kext caches collect specific data from the info dictionaries of kexts. There are many individual caches for specific subsets of data; they care collectively called system info caches. These caches are used to optimize disk I/O when working with kexts during late system startup and beyond. To update the system kext info caches for the root volume, use the -system-caches option.

PRIMARY OPTIONS
You must specify one of these options to have kextcache do anything:

-c [filename], -prelinked-kernel [filename]
    Create a prelinked kernel. filename is required unless this option is the last argument. If this option is the last argument and no filename is given, the startup prelinked kernel for the system is created. See -all-loaded.

-system-prelinked-kernel
    This option is a convenience to update the prelinked kernel used for startup on the root volume, with all kexts in /System/Library/Extensions and /Library/Extensions that have been loaded to date. This option implies -all-loaded.

-system-caches
    Rebuild the info caches for system kexts on the root volume.

-i os_volume, -invalidate os_volume
    Rebuild out-of-date caches and update any helper partitions associated with os_volume.

    This option mimics sudo touch /System/Library/Extensions on os_volume. If kextcache cannot find or make sense of os_volume/usr/standalone/bootcaches.plist, the volume is treated as if no caches need updating: success is returned.

-u os_volume, -update-volume os_volume
    Rebuild out-of-date caches and update any helper partitions associated with os_volume. os_volume/System/Library/Caches/com.apple.bootstamps/ is used as a cache of metadata from any helper partitions. See -caches-only and -force.

    Which caches are rebuilt depends on the Mac OS X release installed on os_volume. If kextcache cannot find or make sense of os_volume/usr/standalone/bootcaches.plist the volume is treated as if no caches need updating: success is returned.

-U os_volume
    Exit EX_OSFILE (72) if any updates were needed and were successfully made. -U is used during system startup to check whether the cache from which the currently-running kernel was loaded is out of date. System startup interprets an EX_OSFILE exit code to mean that the system should be immediately rebooted off the newer kernel cache.

-Boot
    Used with -U to enable early boot behaviors such as limiting which caches must be updated.

-e, -system-mkext
    This option is provided for legacy compatibility, and is simply an alias to -system-prelinked-kernel.

PRELINKED KERNEL FILTERING OPTIONS
These options restrict which kexts are included in a prelinked kernel. The options -arch and -bundle-id select kexts by supported architecture and bundle identifier; the remaining filtering options select kexts based on the value of their OSBundleRequired property. If these options are specified, the cache will contain only kexts whose OSBundleRequired property matches any of these options, or whose OSBundleRequired property is “Root” or “Console”.

A prelinked kernel cache intended for a startup from a local disk should be created with the -local-root option, while a cache intended for startup from the network should be created with the -network-root option. When creating a prelinked kernel, if the -all-loaded option is specified, kexts requested by the kernel are always included regardless of these filtering options.

-a arch, -arch arch
    Include in a prelinked kernel only kexts loadable on arch, thinning executables to that architecture before inclusion. Multiple architectures are allowed; in this case a multi-architecture file is created containing an embedded cache for each of the specified architectures. If no architectures are specified, a default set of architectures supported by the current Mac OS X version is used (Mac OS X 10.6 and later).

-b identifier, -bundle-id identifier
    Find the kext whose CFBundleIdentifier is identifier amongst known kexts and repository directories and include it in the prelinked kernel. The kext of the highest CFBundleVersion with the given identifier is used; in the case of version ties, the last such kext specified on the command line is used. This option may be specified multiple times; if so, the specified bundle identifiers select a subset from all named repositories and kexts, to which the remaining filters described in this section are then applied.

-l, -local-root
    Specifies that for directory arguments, only extensions required for local disk boot be included in a cache. Kexts explicitly indicated by name or identifier are included unconditionally; to apply this filter to all kexts, use the -local-root-all option.

-L, -local-root-all
    Specifies that only extensions required for local disk boot be included in a cache, regardless of whether they are from a repository directory or are explicitly indicated by name or identifier. To apply this restriction only to kexts from repository directories, use the -local-root option.

-n, -network-root
    Specifies that for directory arguments, only extensions required for network disk boot be included in a cache. Kexts explicitly indicated by name or identifier are included unconditionally; to apply this filter to all kexts, use the -network-root-all option.

-N, -network-root-all
    Specifies that only extensions required for network disk boot be included in a cache, regardless of whether they are from a repository directory or are explicitly indicated by name or identifier. To apply this restriction only to kexts from repository directories, use the -network-root option.

-s, -safe-boot
    Specifies that for directory arguments, only extensions required for safe boot be included in a cache. Kexts explicitly indicated by name or identifier are included unconditionally; to apply this filter to all kexts, use the -safe-boot-all option.

-S, -safe-boot-all
    Specifies that only extensions required for safe boot be included in a cache, regardless of whether they are from a repository directory or are explicitly indicated by name or identifier. To apply this restriction only to kexts from repository directories, use the -safe-boot option.

OTHER OPTIONS AND ARGUMENTS

kext_or_directory
    A kext bundle or a repository directory containing kexts to consider for inclusion in a prelinked kernel. The filtering options described under “PRELINKED KERNEL FILTERING OPTIONS” select the individual kexts to be included in the archive. If no filtering options are specified, then all kexts named as arguments are included (this is probably not what you want).

-caches-only
    With -update-volume, skips updating any helper partitions even if they appear out of to date.

-f, -force
    With -update-volume, rebuilds any helper partitions even if they appear up to date. If this version of kextcache does not understand bootcaches.plist well enough to be able to update the helpers, exit with EX_OSFILE (72).

-Installer
    With -update-volume, implies -force while making helper partition updates optional.

-F  Run in low-priority mode, as when forked and executed by kextd(8). (This used to actually fork, but no longer does, as kextd(8) handles the forking.)

-h, -help
    Print a help message describing each option flag and exit with a success result, regardless of any other options on the command line.

-K kernel_filename, -kernel kernel_filename
    The name of the kernel file to use as the base of a prelinked kernel file (the default is /System/Library/Kernels/kernel).

-q, -quiet
    Quiet mode; print no informational or error messages.

-r, -all-loaded
    When creating a prelinked kernel, include all kexts in /System/Library/Extensions and /Library/Extensions that have been loaded by the machine running this command during this startup session. This include kexts loaded and later unloaded.

-compressed
    Compress the prelinked kernel (enabled by default).

-uncompressed
    Do not compress the prelinked kernel. If specified as the only other argument with -c, uncompresses an existing prelinked kernel file in place.

-symbols symbol_directory
    Generate symbols for every kext in the prelinked kernel and save them in symbol_directory. The directory must already exist. Symbol files are named after the CFBundleIdentifier of each kext with a .sym suffix attached.

-t, -print-diagnostics
    If a kext has validation, authentication, or dependency resolution problems, print them. Note that tests are performed in three stages: validation, authentication, and dependency resolution; a failure at any stage can make tests in further stages impossible. Thus, a kext with validation failures may have unreported authentication problems or missing dependencies.

-v [0-6 | 0x####], -verbose [0-6 | 0x####]
    Verbose mode; print information about program operation. Higher levels of verbosity include all lower levels. By default kextcache prints only warnings and errors. You can specify a level from 0-6, or a hexadecimal log specification (as described in kext_logging(8)). The levels of verbose output are:

    0   Print only errors (that is, suppress warnings); see also -quiet.

    1 (or none)
        Print basic information about program operation.

    2   Print basic information about program progress and files created.

    3   Print information about individual kexts; for example, when a kext is added to or omitted from an archive.

    4   Print information about compression and architectures processed.

    5   Print debug-level information about internal operations.

    6   Identical to level 5 for kextcache.

    Unlike in other kext tools, the -verbose flag in kextcache applies to all kexts (that is, it turns on hexadecimal bit 0x8 by default). See kext_logging(8) for more information on verbose logging.

-volume-root path
    When creating caches for a volume other than the root volume, remove path from the beginning of absolute kext paths stored in the cache file. This ensures that the kext paths stored in the kernel are accurate when the caches are used for startup with that volume.

-z, -no-authentication
    Don't authenticate kexts. This option is for convenience in building cache files. Caches used for startup must have proper ownership (root:wheel) and permissions (0644) in order to be used by the system.

--  End of all options. Only kext or directory names follow.

FILES

/System/Library/Extensions/
    The standard system repository of kernel extensions.

/Library/Extensions/
    The standard repository of non Apple kernel extensions.

/System/Library/Caches/com.apple.kext.caches/
    Contains system kext info caches for a Mac OS X system.

/System/Library/PrelinkedKernels/
    Contains prelinked kernel for a Mac OS X system.

/System/Library/Kernels/kernel
    The default kernel file.

/usr/standalone/bootcaches.plist
    Describes specific kext cache files for a Mac OS X volume.

/System/Library/Caches/com.apple.bootstamps/
    Contains timestamp information about kext caches.

DIAGNOSTICS
kextcache exits with a zero status upon success. Upon failure, it prints an error message and exits with a nonzero status.

BUGS
Many single-letter options are inconsistent in meaning with (or directly contradictory to) the same letter options in other kext tools.

SEE ALSO
kext_logging(8), kextd(8), kextload(8), kextutil(8), kextstat(8), kextunload(8)