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kext_logging(8)           BSD System Manager's Manual          kext_logging(8)


     kext logging -- verbose/logging flags for kernel extensions (kexts) in
     the kernel and command-line utilities


     The kext management facilities of Mac OS X allow for logging of kext
     activity at all system levels, from the kernel to the user-space kext
     daemon and most command-line kext tools.  The -verbose (-v) flag of the
     tools provides a simple system of levels that apply a set of lower level
     binary logging flags appropriate to each tool, for maximally useful ver-
     bose output.  The binary log specification is used for kernel logging and
     is also available for use with the -verbose option when you need precise
     control over logging.


     For command-line tools the -verbose (-v) and -quiet (-q) flags control
     verbose output.  The -verbose flag accepts a decimal level from 0-6 or a
     hexadecimal log specification, both described below.  The -verbose flag
     temporarily sets the log spec within the kernel, and captures any log
     messages from the kernel to print along with the tool's own log messages.

     If you wish to alter the logging behavior of kextd(8), you will need to
     edit its launchd.plist(5) file in

     To enable kernel kext logging (in /var/log/kernel.log) on a long-term
     basis, use the kextlog boot arg or sysctl(8) parameter.  You can set it
     as root using nvram(8) like so:

           nvram boot-args="kextlog=0xlogspec other_boot_args"

     where logspec is a hexadecimal log specification, as described below

     Caution: Enabling logging at a high level via boot arg can greatly slow
     down system startup time.

     To change the kextlog setting at any time use sysctl(8):

           sysctl -w debug.kextlog=0xlogspec


     As mentioned, for the command-line kext tools you use the -verbose (-v)
     flag, which takes an optional argument that is either a decimal level
     from 0-6, or a hexadecimal log specification (described under ``BINARY
     LOG SPECIFICATION''). The details of each level vary by tool, but in gen-
     eral they are:

     0            Errors only (that is, suppress warnings).  Tools with a
                  -verbose flag also support a -quiet flag to suppress all

     1 (or none)  Basic information about program operation.

     2            Basic information about program progress, including files

     3            Information about individual kexts, link/load operation, and
                  processing of I/O Kit personalities.

     4            Detailed information about kext operations, including C++
                  class construction/destruction, and for archives, about com-
                  pression and architectures processed.

     5            Debug-level information about internal operations.

     6            Identical to level 5 but with bit 0x8 turned on (see the
                  hecadecimal log specification for details).


     The binary log specification is a 32-bit value comprising a log level
     with a bitmask divided into several regions from the least-significant
     nibble (corresponding to digits from right to left in a hexadecimal rep-
     resentation).  This table describes the regions and bits used; unlisted
     regions and bits are reserved for future use:

     Nibble 0     The log level, from 0-7.  Each level includes all levels
                  below it.  This is generally two higher than the decimal
                  level specified with -verbose.

                  Log level 0 - Silent.

                  Log level 1 - Errors.

                  Log level 2 - Warnings.

                  Log level 3 - Basic outcome/result.

                  Log level 4 - Operation progress.

                  Log level 5 - Steps in a given operation.

                  Log level 6 - Detailed logging.

                  Log level 7 - Debug level logging.

                  In addition, bit 0x8 of this nibble controls whether kext-
                  specific log messages are always printed.  kextcache(8) and
                  kextunload(8) turn this bit on with their -verbose flag.
                  See ``PER-KEXT LOGGING'' for more information.

     Nibbles 1-2  Activity flags relevant to general tool use, as in develop-
                  ment scenarios.  The -verbose flag always includes these.  8
                  bits total.

                  Nibble 1, Bit 0 (0x10) - General activity.

                  Nibble 1, Bit 1 (0x20) - Load activity.

                  Nibble 1, Bit 2 (0x40) - IPC and load settings.

                  Nibble 1, Bit 3 (0x80) - Archive processing.

                  Nibble 2 - Reserved.

     Nibbles 3-7  Activity flags for internal operations, for debugging the
                  kext management system itself.  These are available only
                  when using a hexadecimal log specification; the -verbose
                  flag never includes these.  20 bits total.

                  Nibble 3, Bit 0 (0x1000) - Kext validation.

                  Nibble 3, Bit 1 (0x2000) - Kext authentication.

                  Nibble 3, Bit 2 (0x4000) - Kext dependency resolution.

                  Nibble 4, Bit 0 (0x10000) - Directory scan (booter data scan
                  in the kernel).

                  Nibble 4, Bit 1 (0x20000) - File I/O.

                  Nibble 4, Bit 2 (0x40000) - Kext bookkeeping.

                  Nibble 5, Bit 0 (0x100000) - Link activity.

                  Nibble 5, Bit 1 (0x200000) - C++ patching activity.

                  Nibbles 6-7 - Reserved.


     Many log messages apply to the kext being processed.  The kernel and most
     of the command-line kext tools do not log these messages by default.  You
     can enable these messages for an individual kext by specifying an
     OSBundleEnableKextLogging property in its Info.plist file with a boolean
     value of true.  For convenience, kextutil(8) automatically sets this
     property for the kexts it is loading.

     You can activate all per-kext log messages using level 6 with the
     -verbose flag or by turning on bit 0x8 in a hexadecimal log specifica-
     tion.  For convenience, kextcache(8) and kextunload(8) do this for all
     verbose levels of their -verbose flag.


     Here is a list of the exact hecadecimal log specifications applied by
     each of the -verbose levels:

     0            equivalent to 0x0 for all tools.

     (default level)
                  equivalent to 0xff2, 0xff9 for kextcache(8) and
                  kextunload(8), 0xff3 for kextd(8) and for kextcache(8)
                  spawned by kextd(8).

     1 (or none)  equivalent to 0xff3, or 0xffa for kextcache(8) and

     2            equivalent to 0xff4, or 0xffb for kextcache(8) and

     3            equivalent to 0xff5, or 0xffc for kextcache(8) and

     4            equivalent to 0xff6, or 0xffd for kextcache(8) and

     5            equivalent to 0xff7, or 0xffe for kextcache(8) and

     6            equivalent to 0xfff for all tools.


     /var/log/kernel.log  The kernel log file, where kernel kext activity is

     /var/log/system.log  The system log file, where kextd(8) activity is

                          Edit this launchd.plist(5) file to specify verbose
                          logging for kextd(8).


     syslog(1), kextcache(8), kextd(8), kextlibs(8), kextload(8),
     kextunload(8), kextutil(8)

Darwin                           March 6, 2009                          Darwin

Mac OS X 10.6 - Generated Thu Sep 17 20:25:59 CDT 2009
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