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CAMCONTROL(8)           FreeBSD System Manager's Manual          CAMCONTROL(8)

     camcontrol -- CAM control program

     camcontrol <command> [device id] [generic args] [command args]
     camcontrol devlist [-v]
     camcontrol periphlist [device id] [-n dev_name] [-u unit_number]
     camcontrol tur [device id] [generic args]
     camcontrol inquiry [device id] [generic args] [-D] [-S] [-R]
     camcontrol reportluns [device id] [generic args] [-c] [-l]
                [-r reporttype]
     camcontrol start [device id] [generic args]
     camcontrol stop [device id] [generic args]
     camcontrol load [device id] [generic args]
     camcontrol eject [device id] [generic args]
     camcontrol rescan <all | bus[:target:lun]>
     camcontrol reset <all | bus[:target:lun]>
     camcontrol defects [device id] [generic args] <-f format> [-P] [-G]
     camcontrol modepage [device id] [generic args] <-m page | -l> [-P pgctl]
                [-b | -e] [-d]
     camcontrol cmd [device id] [generic args] <-c cmd [args]> [-i len fmt]
                [-o len fmt [args]]
     camcontrol debug [-I] [-P] [-T] [-S] [-X] [-c]
     camcontrol tags [device id] [generic args] [-N tags] [-q] [-v]
     camcontrol negotiate [device id] [generic args] [-c] [-D enable|disable]
                [-O offset] [-q] [-R syncrate] [-T enable|disable] [-U]
                [-W bus_width] [-v]
     camcontrol format [device id] [generic args] [-q] [-r] [-w] [-y]
     camcontrol help

     The camcontrol utility is designed to provide a way for users to access
     and control the FreeBSD CAM subsystem.

     The camcontrol utility can cause a loss of data and/or system crashes if
     used improperly.  Even expert users are encouraged to exercise caution
     when using this command.  Novice users should stay away from this util-

     The camcontrol utility has a number of primary functions, many of which
     support an optional device identifier.  A device identifier can take one
     of three forms:

     deviceUNIT      Specify a device name and unit number combination, like
                     "da5" or "cd3".  Note that character device node names
                     (e.g. /dev/da0) are not allowed here.

     bus:target      Specify a bus number and target id.  The bus number can
                     be determined from the output of ``camcontrol devlist''.
                     The lun defaults to 0.

     bus:target:lun  Specify the bus, target and lun for a device.  (e.g.

     The device identifier, if it is specified, must come immediately after
     the function name, and before any generic or function-specific arguments.
     Note that the -n and -u arguments described below will override any
     device name or unit number specified beforehand.  The -n and -u arguments
     will not override a specified bus:target or bus:target:lun, however.

     Most of the camcontrol primary functions support these generic arguments:

     -C count        SCSI command retry count.  In order for this to work,
                     error recovery (-E) must be turned on.

     -E              Instruct the kernel to perform generic SCSI error recov-
                     ery for the given command.  This is needed in order for
                     the retry count (-C) to be honored.  Other than retrying
                     commands, the generic error recovery in the code will
                     generally attempt to spin up drives that are not spin-
                     ning.  It may take some other actions, depending upon the
                     sense code returned from the command.

     -n dev_name     Specify the device type to operate on, e.g. "da", "cd".

     -t timeout      SCSI command timeout in seconds.  This overrides the
                     default timeout for any given command.

     -u unit_number  Specify the device unit number, e.g. "1", "5".

     -v              Be verbose, print out sense information for failed SCSI

     Primary command functions:

     devlist     List all physical devices (logical units) attached to the CAM
                 subsystem.  This also includes a list of peripheral drivers
                 attached to each device.  With the -v argument, SCSI bus num-
                 ber, adapter name and unit numbers are printed as well.

     periphlist  List all peripheral drivers attached to a given physical
                 device (logical unit).

     tur         Send the SCSI test unit ready (0x00) command to the given
                 device.  The camcontrol utility will report whether the
                 device is ready or not.

     inquiry     Send a SCSI inquiry command (0x12) to a device.  By default,
                 camcontrol will print out the standard inquiry data, device
                 serial number, and transfer rate information.  The user can
                 specify that only certain types of inquiry data be printed:

                 -D    Get the standard inquiry data.

                 -S    Print out the serial number.  If this flag is the only
                       one specified, camcontrol will not print out "Serial
                       Number" before the value returned by the drive.  This
                       is to aid in script writing.

                 -R    Print out transfer rate information.

     reportluns  Send the SCSI REPORT LUNS (0xA0) command to the given device.
                 By default, camcontrol will print out the list of logical
                 units (LUNs) supported by the target device.  There are a
                 couple of options to modify the output:

                 -c              Just print out a count of LUNs, not the
                                 actual LUN numbers.

                 -l              Just print out the LUNs, and don't print out
                                 the count.

                 -r reporttype   Specify the type of report to request from
                                 the target:

                                 default    Return the default report.  This
                                            is the camcontrol default.  Most
                                            targets will support this report
                                            if they support the REPORT LUNS

                                 wellknown  Return only well known LUNs.

                                 all        Return all available LUNs.

                 camcontrol will try to print out LUN numbers in a reasonable
                 format.  It can understand the peripheral, flat, LUN and
                 extended LUN formats.

     start       Send the SCSI Start/Stop Unit (0x1B) command to the given
                 device with the start bit set.

     stop        Send the SCSI Start/Stop Unit (0x1B) command to the given
                 device with the start bit cleared.

     load        Send the SCSI Start/Stop Unit (0x1B) command to the given
                 device with the start bit set and the load/eject bit set.

     eject       Send the SCSI Start/Stop Unit (0x1B) command to the given
                 device with the start bit cleared and the load/eject bit set.

     rescan      Tell the kernel to scan all busses in the system (with the
                 all argument), the given bus (XPT_SCAN_BUS), or bus:tar-
                 get:lun (XPT_SCAN_LUN) for new devices or devices that have
                 gone away.  The user may specify a scan of all busses, a sin-
                 gle bus, or a lun.  Scanning all luns on a target is not sup-

     reset       Tell the kernel to reset all busses in the system (with the
                 all argument) or the given bus (XPT_RESET_BUS) by issuing a
                 SCSI bus reset for that bus, or to reset the given bus:tar-
                 get:lun (XPT_RESET_DEV), typically by issuing a BUS DEVICE
                 RESET message after connecting to that device.  Note that
                 this can have a destructive impact on the system.

     defects     Send the SCSI READ DEFECT DATA (10) command (0x37) to the
                 given device, and print out any combination of: the total
                 number of defects, the primary defect list (PLIST), and the
                 grown defect list (GLIST).

                 -f format    The three format options are: block, to print
                              out the list as logical blocks, bfi, to print
                              out the list in bytes from index format, and
                              phys, to print out the list in physical sector
                              format.  The format argument is required.  Most
                              drives support the physical sector format.  Some
                              drives support the logical block format.  Many
                              drives, if they do not support the requested
                              format, return the data in an alternate format,
                              along with sense information indicating that the
                              requested data format is not supported.  The
                              camcontrol utility attempts to detect this, and
                              print out whatever format the drive returns.  If
                              the drive uses a non-standard sense code to
                              report that it does not support the requested
                              format, camcontrol will probably see the error
                              as a failure to complete the request.

                 -G           Print out the grown defect list.  This is a list
                              of bad blocks that have been remapped since the
                              disk left the factory.

                 -P           Print out the primary defect list.

                 If neither -P nor -G is specified, camcontrol will print out
                 the number of defects given in the READ DEFECT DATA header
                 returned from the drive.

     modepage    Allows the user to display and optionally edit a SCSI mode
                 page.  The mode page formats are located in
                 /usr/share/misc/scsi_modes.  This can be overridden by speci-
                 fying a different file in the SCSI_MODES environment vari-
                 able.  The modepage command takes several arguments:

                 -d            Disable block descriptors for mode sense.

                 -b            Displays mode page data in binary format.

                 -e            This flag allows the user to edit values in the
                               mode page.  The user may either edit mode page
                               values with the text editor pointed to by his
                               EDITOR environment variable, or supply mode
                               page values via standard input, using the same
                               format that camcontrol uses to display mode
                               page values.  The editor will be invoked if
                               camcontrol detects that standard input is ter-

                 -l            Lists all available mode pages.

                 -m mode_page  This specifies the number of the mode page the
                               user would like to view and/or edit.  This
                               argument is mandatory unless -l is specified.

                 -P pgctl      This allows the user to specify the page con-
                               trol field.  Possible values are:
                               0    Current values
                               1    Changeable values
                               2    Default values
                               3    Saved values

     cmd         Allows the user to send an arbitrary SCSI CDB to any device.
                 The cmd function requires the -c argument to specify the CDB.
                 Other arguments are optional, depending on the command type.
                 The command and data specification syntax is documented in
                 cam_cdbparse(3).  NOTE: If the CDB specified causes data to
                 be transfered to or from the SCSI device in question, you
                 MUST specify either -i or -o.

                 -c cmd [args]      This specifies the SCSI CDB.  CDBs may be
                                    6, 10, 12 or 16 bytes.

                 -i len fmt         This specifies the amount of data to read,
                                    and how it should be displayed.  If the
                                    format is `-', len bytes of data will be
                                    read from the device and written to stan-
                                    dard output.

                 -o len fmt [args]  This specifies the amount of data to be
                                    written to a device, and the data that is
                                    to be written.  If the format is `-', len
                                    bytes of data will be read from standard
                                    input and written to the device.

     debug       Turn on CAM debugging printfs in the kernel.  This requires
                 options CAMDEBUG in your kernel config file.  WARNING:
                 enabling debugging printfs currently causes an EXTREME number
                 of kernel printfs.  You may have difficulty turning off the
                 debugging printfs once they start, since the kernel will be
                 busy printing messages and unable to service other requests
                 quickly.  The debug function takes a number of arguments:

                 -I                  Enable CAM_DEBUG_INFO printfs.

                 -P                  Enable CAM_DEBUG_PERIPH printfs.

                 -T                  Enable CAM_DEBUG_TRACE printfs.

                 -S                  Enable CAM_DEBUG_SUBTRACE printfs.

                 -X                  Enable CAM_DEBUG_XPT printfs.

                 -c                  Enable CAM_DEBUG_CDB printfs.  This will
                                     cause the kernel to print out the SCSI
                                     CDBs sent to the specified device(s).

                 all                 Enable debugging for all devices.

                 off                 Turn off debugging for all devices

                 bus[:target[:lun]]  Turn on debugging for the given bus, tar-
                                     get or lun.  If the lun or target and lun
                                     are not specified, they are wildcarded.
                                     (i.e., just specifying a bus turns on
                                     debugging printfs for all devices on that

     tags        Show or set the number of "tagged openings" or simultaneous
                 transactions we attempt to queue to a particular device.  By
                 default, the tags command, with no command-specific arguments
                 (i.e., only generic arguments) prints out the "soft" maximum
                 number of transactions that can be queued to the device in
                 question.  For more detailed information, use the -v argument
                 described below.

                 -N tags  Set the number of tags for the given device.  This
                          must be between the minimum and maximum number set
                          in the kernel quirk table.  The default for most
                          devices that support tagged queueing is a minimum of
                          2 and a maximum of 255.  The minimum and maximum
                          values for a given device may be determined by using
                          the -v switch.  The meaning of the -v switch for
                          this camcontrol subcommand is described below.

                 -q       Be quiet, and do not report the number of tags.
                          This is generally used when setting the number of

                 -v       The verbose flag has special functionality for the
                          tags argument.  It causes camcontrol to print out
                          the tagged queueing related fields of the
                          XPT_GDEV_TYPE CCB:

                          dev_openings   This is the amount of capacity for
                                         transactions queued to a given

                          dev_active     This is the number of transactions
                                         currently queued to a device.

                          devq_openings  This is the kernel queue space for
                                         transactions.  This count usually
                                         mirrors dev_openings except during
                                         error recovery operations when the
                                         device queue is frozen (device is not
                                         allowed to receive commands), the
                                         number of dev_openings is reduced, or
                                         transaction replay is occurring.

                          devq_queued    This is the number of transactions
                                         waiting in the kernel queue for
                                         capacity on the device.  This number
                                         is usually zero unless error recovery
                                         is in progress.

                          held           The held count is the number of CCBs
                                         held by peripheral drivers that have
                                         either just been completed or are
                                         about to be released to the transport
                                         layer for service by a device.  Held
                                         CCBs reserve capacity on a given

                          mintags        This is the current "hard" minimum
                                         number of transactions that can be
                                         queued to a device at once.  The
                                         dev_openings value above cannot go
                                         below this number.  The default value
                                         for mintags is 2, although it may be
                                         set higher or lower for various

                          maxtags        This is the "hard" maximum number of
                                         transactions that can be queued to a
                                         device at one time.  The dev_openings
                                         value cannot go above this number.
                                         The default value for maxtags is 255,
                                         although it may be set higher or
                                         lower for various devices.

     negotiate   Show or negotiate various communication parameters.  Some
                 controllers may not support setting or changing some of these
                 values.  For instance, the Adaptec 174x controllers do not
                 support changing a device's sync rate or offset.  The
                 camcontrol utility will not attempt to set the parameter if
                 the controller indicates that it does not support setting the
                 parameter.  To find out what the controller supports, use the
                 -v flag.  The meaning of the -v flag for the negotiate com-
                 mand is described below.  Also, some controller drivers do
                 not support setting negotiation parameters, even if the
                 underlying controller supports negotiation changes.  Some
                 controllers, such as the Advansys wide controllers, support
                 enabling and disabling synchronous negotiation for a device,
                 but do not support setting the synchronous negotiation rate.

                 -a                 Attempt to make the negotiation settings
                                    take effect immediately by sending a Test
                                    Unit Ready command to the device.

                 -c                 Show or set current negotiation settings.
                                    This is the default.

                 -D enable|disable  Enable or disable disconnection.

                 -O offset          Set the command delay offset.

                 -q                 Be quiet, do not print anything.  This is
                                    generally useful when you want to set a
                                    parameter, but do not want any status

                 -R syncrate        Change the synchronization rate for a
                                    device.  The sync rate is a floating point
                                    value specified in MHz.  So, for instance,
                                    `20.000' is a legal value, as is `20'.

                 -T enable|disable  Enable or disable tagged queueing for a

                 -U                 Show or set user negotiation settings.
                                    The default is to show or set current
                                    negotiation settings.

                 -v                 The verbose switch has special meaning for
                                    the negotiate subcommand.  It causes
                                    camcontrol to print out the contents of a
                                    Path Inquiry (XPT_PATH_INQ) CCB sent to
                                    the controller driver.

                 -W bus_width       Specify the bus width to negotiate with a
                                    device.  The bus width is specified in
                                    bits.  The only useful values to specify
                                    are 8, 16, and 32 bits.  The controller
                                    must support the bus width in question in
                                    order for the setting to take effect.

                 In general, sync rate and offset settings will not take
                 effect for a device until a command has been sent to the
                 device.  The -a switch above will automatically send a Test
                 Unit Ready to the device so negotiation parameters will take

     format      Issue the SCSI FORMAT UNIT command to the named device.

                 WARNING! WARNING! WARNING!

                 Low level formatting a disk will destroy ALL data on the
                 disk.  Use extreme caution when issuing this command.  Many
                 users low-level format disks that do not really need to be
                 low-level formatted.  There are relatively few scenarios that
                 call for low-level formatting a disk.  One reason for low-
                 level formatting a disk is to initialize the disk after
                 changing its physical sector size.  Another reason for low-
                 level formatting a disk is to revive the disk if you are get-
                 ting "medium format corrupted" errors from the disk in
                 response to read and write requests.

                 Some disks take longer than others to format.  Users should
                 specify a timeout long enough to allow the format to com-
                 plete.  The default format timeout is 3 hours, which should
                 be long enough for most disks.  Some hard disks will complete
                 a format operation in a very short period of time (on the
                 order of 5 minutes or less).  This is often because the drive
                 does not really support the FORMAT UNIT command -- it just
                 accepts the command, waits a few minutes and then returns it.

                 The `format' subcommand takes several arguments that modify
                 its default behavior.  The -q and -y arguments can be useful
                 for scripts.

                 -q      Be quiet, do not print any status messages.  This
                         option will not disable the questions, however.  To
                         disable questions, use the -y argument, below.

                 -r      Run in ``report only'' mode.  This will report status
                         on a format that is already running on the drive.

                 -w      Issue a non-immediate format command.  By default,
                         camcontrol issues the FORMAT UNIT command with the
                         immediate bit set.  This tells the device to immedi-
                         ately return the format command, before the format
                         has actually completed.  Then, camcontrol gathers
                         SCSI sense information from the device every second
                         to determine how far along in the format process it
                         is.  If the -w argument is specified, camcontrol will
                         issue a non-immediate format command, and will be
                         unable to print any information to let the user know
                         what percentage of the disk has been formatted.

                 -y      Do not ask any questions.  By default, camcontrol
                         will ask the user if he/she really wants to format
                         the disk in question, and also if the default format
                         command timeout is acceptable.  The user will not be
                         asked about the timeout if a timeout is specified on
                         the command line.

     help        Print out verbose usage information.

     The SCSI_MODES variable allows the user to specify an alternate mode page
     format file.

     The EDITOR variable determines which text editor camcontrol starts when
     editing mode pages.

     /usr/share/misc/scsi_modes  is the SCSI mode format database.
     /dev/xpt0                   is the transport layer device.
     /dev/pass*                  are the CAM application passthrough devices.

           camcontrol eject -n cd -u 1 -v

     Eject the CD from cd1, and print SCSI sense information if the command

           camcontrol tur da0

     Send the SCSI test unit ready command to da0.  The camcontrol utility
     will report whether the disk is ready, but will not display sense infor-
     mation if the command fails since the -v switch was not specified.

           camcontrol tur da1 -E -C 4 -t 50 -v

     Send a test unit ready command to da1.  Enable kernel error recovery.
     Specify a retry count of 4, and a timeout of 50 seconds.  Enable sense
     printing (with the -v flag) if the command fails.  Since error recovery
     is turned on, the disk will be spun up if it is not currently spinning.
     The camcontrol utility will report whether the disk is ready.

           camcontrol cmd -n cd -u 1 -v -c "3C 00 00 00 00 00 00 00 0e 00" \
                   -i 0xe "s1 i3 i1 i1 i1 i1 i1 i1 i1 i1 i1 i1"

     Issue a READ BUFFER command (0x3C) to cd1.  Display the buffer size of
     cd1, and display the first 10 bytes from the cache on cd1.  Display SCSI
     sense information if the command fails.

           camcontrol cmd -n cd -u 1 -v -c "3B 00 00 00 00 00 00 00 0e 00" \
                   -o 14 "00 00 00 00 1 2 3 4 5 6 v v v v" 7 8 9 8

     Issue a WRITE BUFFER (0x3B) command to cd1.  Write out 10 bytes of data,
     not including the (reserved) 4 byte header.  Print out sense information
     if the command fails.  Be very careful with this command, improper use
     may cause data corruption.

           camcontrol modepage da3 -m 1 -e -P 3

     Edit mode page 1 (the Read-Write Error Recover page) for da3, and save
     the settings on the drive.  Mode page 1 contains a disk drive's auto read
     and write reallocation settings, among other things.

           camcontrol rescan all

     Rescan all SCSI busses in the system for devices that have been added,
     removed or changed.

           camcontrol rescan 0

     Rescan SCSI bus 0 for devices that have been added, removed or changed.

           camcontrol rescan 0:1:0

     Rescan SCSI bus 0, target 1, lun 0 to see if it has been added, removed,
     or changed.

           camcontrol tags da5 -N 24

     Set the number of concurrent transactions for da5 to 24.

           camcontrol negotiate -n da -u 4 -T disable

     Disable tagged queueing for da4.

           camcontrol negotiate -n da -u 3 -R 20.000 -O 15 -a

     Negotiate a sync rate of 20MHz and an offset of 15 with da3.  Then send a
     Test Unit Ready command to make the settings take effect.

     cam(3), cam_cdbparse(3), cam(4), pass(4), xpt(4)

     The camcontrol utility first appeared in FreeBSD 3.0.

     The mode page editing code and arbitrary SCSI command code are based upon
     code in the old scsi(8) utility and scsi(3) library, written by Julian
     Elischer and Peter Dufault.  The scsi(8) program first appeared in 386BSD, and first appeared in FreeBSD in FreeBSD 2.0.5.

     Kenneth Merry <>

     The code that parses the generic command line arguments does not know
     that some of the subcommands take multiple arguments.  So if, for
     instance, you tried something like this:

           camcontrol cmd -n da -u 1 -c "00 00 00 00 00 v" 0x00 -v

     The sense information from the test unit ready command would not get
     printed out, since the first getopt(3) call in camcontrol bails out when
     it sees the second argument to -c (0x00), above.  Fixing this behavior
     would take some gross code, or changes to the getopt(3) interface.  The
     best way to circumvent this problem is to always make sure to specify
     generic camcontrol arguments before any command-specific arguments.

FreeBSD 6.2                   September 14, 1998                   FreeBSD 6.2


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