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camcontrol - CAM control program


See Also


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 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]
.Bk -words [-o len fmt [args]]
.Ek camcontrol debug [-I] [-P] [-T] [-S] [-X] [-c] <all|off|bus [:target [:lun]]> 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
.Fx 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 utility.

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:

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.
Specify a bus number and target id. The bus number can be determined from the output of "camcontrol devlist". The lun defaults to 0.
Specify the bus, target and lun for a device. (e.g. 1:2:0)

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 recovery 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 spinning. 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 commands.

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 number, adapter name and unit numbers are printed as well.
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.
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.
Tell the kernel to scan all busses in the system (with the all argument), the given bus (XPT_SCAN_BUS), or bus:target:lun (XPT_SCAN_LUN) for new devices or devices that have gone away. The user may specify a scan of all busses, a single bus, or a lun. Scanning all luns on a target is not supported.
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:target: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.
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.

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 specifying a different file in the SCSI_MODES environment variable. 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 terminal.
-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 control 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 standard 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, target 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 bus.)
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 tags.
-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:
This is the amount of capacity for transactions queued to a given device.
This is the number of transactions currently queued to a device.
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.
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 device.
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 devices.
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.
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 command 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 information.
-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 device.
-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 effect.

Issue the SCSI FORMAT UNIT command to the named device.


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 getting "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 complete. 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 immediately 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.


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 fails.

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 information 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)


scsi(8) scsi(3) scsi(8)



getopt(3) getopt(3)

Created by Blin Media, 2008-2013