scu - SCSI CAM Utility Program
/sbin/scu [-options ...] [command [keywords...]]
Specifies the user agent path.
Specify the raw device pathname. You must specify a character device
special file, for example, /dev/rdisk/dsk10c.
If the device name is not specified on the command line, the program
checks the environment variable SCU_DEVICE to define the device name.
-n Do not execute a startup script.
-p Enable pipe operation mode.
Specify a script startup file name.
The SCSI utility program, scu, interfaces with the CAM I/O subsystem and
the peripherals attached to the SCSI buses. Use this program to maintain
and diagnose problems with SCSI peripherals and the CAM I/O subsystem.
Data corruption can occur when the write back cache is enabled using
scu. Compaq recommends that you do not enable the write back cache.
The scu utility program has an extensive help feature. Log in as root and
enter /sbin/scu help at the command prompt to view the help overview and
enter a ? at the topic>> prompt to view a list of the utility's commands and
The file /sbin/scu.hlp contains the help information used in the help
The following table summarizes the scu commands and their functions. Refer
to the help command for complete syntax and examples of use.
allow Allows media removal from a device
change Changes mode pages for a device
download Downloads microcode to a device
dump Dumps data from a device
eject Stops a CD-ROM and then ejects its caddy
erase Performs erase operations on a device
Exit the scu program. Ctrl/d can be used in interac-
tive operation. An alias for exit is quit.
evaluate Evaluates an expression
format Formats disk media
Displays help on scu command elements
mbad Produces hard and soft errors on disks
mt Issues one of the supported magnetic tape commands
onerror Controls program actions when an error occurs
pause Pauses playing a CD-ROM audio disk
play Plays tracks on a CD-ROM audio disk
prevent Prevents removal of media from a device
read Performs read operations on a device
reassign Reassigns a defective block on a disk device
release Releases a reserved device or a frozen SIM queue
repeat Defines a repeat count for a series of commands
reserve Reserves a device for exclusive use
resume Resumes playing a paused CD-ROM audio disk
reset Resets a bus or device
rezero Issues a CAM Bus Reset CCB command
Scans device media or the CAM Equipment Device Table
seek Seeks a logical block address
Sets parameters for a device or the scu program
shell Exits to shell program until you exit the shell
Displays parameters for a device or the scu program
Specifies the time the scu program is to sleep
source Sources input from an external command file
start Starts a unit that is stopped
stop Stops a unit
switch Switches to another device
system Passes one system command to the shell program
test Performs tests on a controller
time Times command sequences
tur Issues a Test Unit Ready command to a device
Specifies the time the scu program is to sleep (in
verify Performs verify operations on a device
write Performs write operations on a device
xza Performs operations on the KZMSA controller
Zeros device or scu program parameters
Commands that modify device data or device parameters require write access
to the device entry. Applications that change the volume level of the
CD-ROM must open the device for write access since a SCSI Mode Select com-
mand is used to modify the volume level.
When a SCSI device error occurs, both the sense key and the addition sense
code or qualifier are decoded and displayed as follows:
scu: Sense Key = 0x5 = ILLEGAL REQUEST - Illegal request or CDB parameter,
Sense Code/Qualifier = (0x20, 0) = Invalid command operation code
This error indicates that you have issued a command that is not supported
by the selected device. This can happen for optional commands that are not
supported by all devices.
1. To format an RX26 diskette at extra density, enter:
scu>> format density ED
2. To verify 1024 blocks starting at block 1000, enter:
scu>> verify media starting 1000 length 1024
3. To display all changeable mode pages for a device, enter:
scu>> show page pcf changeable
4. To display inquiry information for all devices on the first SCSI bus
at lun 0 in the Equipment Device Table (EDT), enter:
scu>> show edt bus 0 lun 0 full
The SCSI Utility executable file.
The device entry for the CAM User Agent driver.
Contains the scu help information.
Is the location of the raw device special files for hard disk devices.
Commands: file(1), more(1)
Functions: open(2), close(2), ioctl(2), fopen(3), fgets(3), fputs(3),
popen(3), pclose(3), malloc(3), printf(3), fprintf(3)
American National Standard for Information Systems, Small Computer Systems
Interface - 2 (SCSI - 2), X3.131-199X
American National Standard for Information Systems, SCSI-2 Common Access
Method: Transport and SCSI Interface Module, working draft, X3T9.2/90-186