NAME¶
sg_start - send SCSI START STOP UNIT command to start, stop, load or eject
medium
SYNOPSIS¶
sg_start [
0] [
1] [
--eject] [
--help]
[
--fl=FL] [
--immed] [
--load] [
--loej]
[
--mod=PC_MOD] [
--noflush] [
--pc=PC] [
--readonly]
[
--start] [
--stop] [
--verbose] [
--version]
DEVICE
sg_start [
--eject] [
--fl=FL] [
-i]
[
--imm=0|1] [
--load] [
--loej] [
--mod=PC_MOD]
[
--noflush] [
--pc=PC] [
-r] [
--start]
[
--stop] [
-v] [
-V] [
0|1]
DEVICE
DESCRIPTION¶
sg_start sends a SCSI START STOP UNIT command to the
DEVICE with the
selected options. The most used options are
--stop to spin down a disk
and
--start to spin up a disk. Using
--start on a disk that is
already spinning is harmless. There is also finer grain control with
"power condition": active, idle or standby. This is set with the
--pc=PC option. In some contexts the "stop" state can be
considered an additional power condition.
Devices that contain removable media such as cd/dvds can use the
--loej
option to load the medium when used in conjunction with
--start (i.e.
load medium then spin up). Alternatively
--loej may be used to eject
the medium when used in conjunction with
--stop (i.e. spin down then
eject medium). More simply, the loading or ejecting of a removable medium can
be requested with the
--load or
--eject' option.
If no option or argument is given then a
--start is assumed; as the
utility's name suggests.
This utility supports two command line syntaxes, the preferred one is shown
first in the synopsis and explained in this section. A later section on the
old command line syntax outlines the second group of options.
OPTIONS¶
Arguments to long options are mandatory for short options as well.
- 0
- same action as --stop.
- 1
- same action as --start.
- -e, --eject
- stop the medium and eject it from the drive. Only
appropriate for a device with removable medium. Might be ignored
(prevented), see below.
- -h, --help
- print out the usage message then exit.
- -f, --fl=FL
- sets the format layer number for the disc to
"jump" to (defined in MMC-5). Values of FL can be 0 to 3.
When this option is chosen, the FL, LoEj and Start bits are set in the cdb
as required by MMC-5; thus the user does not need to set the
--start and/or --load options.
- -i, --immed
- sets the IMM bit on the START STOP UNIT command so this
utility will return immediately and not wait for the media to complete the
requested action. The default is to wait until the media to complete the
requested action before returning.
- -l, --load
- load the medium in the drive and start it. Only appropriate
for a removable medium.
- -L, --loej
- sets the LOEJ bit on the START STOP UNIT command. This
loads the media when the unit is started or eject it when the unit is
stopped (i.e. works in conjunction with START bit in cdb). This option is
ignored if 'pc > 0'. Default is off (i.e. don't attempt to load or
eject media). If a start/start indication is not given (i.e. neither
--start nor --stop) and this option is given then a load and
start action is assumed.
- -m, --mod=PC_MOD
- where PC_MOD is the 'power condition modifier'
value. 0 to 15 (inclusive) are valid and 0 is the default. This 'power
condition modifier' field in the cdb was added after sbc3r13.
- -n, --noflush
- do not perform a flush to media (e.g. like SYNCHRONIZE
CACHE does) before a variant of this utility that limits access to the
media. Using the --stop option is an example of something that
limits access to the media. This 'noflush' field in the cdb was added
after sbc3r13.
- -O, --old
- switch to older style options.
- -p, --pc=PC
- where PC is the 'power conditions' value. 0 to 15
(inclusive) are valid. Default value is 0. When '--pc=0' then
--eject, --load, --loej, --start and
--stop are active. Some common values are 1 for the
"active" power condition (SBC); 2 for the idle power condition;
3 for the standby power condition; 5 for sleep power condition (MMC); 7
for LU_CONTROL (SBC), 0xa (decimal 10) for FORCE_IDLE_0 (SBC) and 0xb
(decimal 11) for FORCE_STANDBY_0 (SBC). See recent SBC-3, MMC-5 and SAS
drafts at www.t10.org for more information.
- -r, --readonly
- open the DEVICE in read-only mode. Maybe required in
Linux to stop a nuisance spin-up if the DEVICE is an ATA disk. The
nuisance spin-up may occur at the end of this command negating the effect
of the --stop option.
- -s, --start
- start (spin-up) the DEVICE. This sets the START bit
in the cdb. Using this option on an already started device is harmless. In
the absence of other options, this option defaults (i.e. set the START cdb
bit).
- -S, --stop
- stop (spin-down) the DEVICE. This clears the START
bit in the cdb.
- -v, --verbose
- increase the level of verbosity. Can be used multiple
times.
- -V, --version
- print out version string then exit.
NOTES¶
To avoid confusion, only one of
0,
1 --eject,
--load,
--start and
--stop should be given.
There is an associated "power condition" mode page (0x1a) in which
timer values can be set for transitioning to either idle or standby state
after a period of inactivity. The sdparm utility can be used to view the power
condition mode page and if required change it. If a
DEVICE is in either
idle or standby power condition state then a REQUEST SENSE command (see the
sg_requests utility) should yield a sense key of "no sense" and an
additional sense code of "Low power condition on" on recent SCSI
devices.
Ejection of removable media (e.g. 'sg_start --eject /dev/hdd' where the
DEVICE is an ATAPI cd/dvd drive) may be prevented by a prior SCSI
PREVENT ALLOW MEDIUM REMOVAL command (see sg_prevent). In this case this
utility should fail with an error generated by the device: illegal request /
medium removal prevented. This can be overridden using sg_prevent or, for
example, 'sdparm --command=unlock /dev/hdd'.
The SCSI TEST UNIT READY command can be used to find out whether a
DEVICE
is ready to transfer data. If rotating media is stopped or still coming up to
speed, then the TEST UNIT READY command will yield a "not ready"
sense key and an more informative additional sense code. See the sg_turs
utility.
In the 2.4 series of Linux kernels the
DEVICE must be a SCSI generic (sg)
device. In the 2.6 series block devices (e.g. SCSI disks and DVD drives) can
also be specified. For example "sg_start 0 /dev/sda" will work in
the 2.6 series kernels.
In the Linux 2.6 series, especially with ATA disks, using this utility to stop
(spin down) a disk may not be sufficient and other mechanisms will start the
disk again some time later. The user might additionally mark the disk as
"offline" with 'echo offline > /sys/block/sda/device/state' where
sda is the block name of the disk. To restart the disk "offline" can
be replaced with "running". Note that once the 'state' is set to
offline, no SCSI commands can be sent to the device until it is set back to
running. Also stopping a disk via a pass-through interface (e.g. /dev/sg1 or
/dev/bsg/1:0:0:0) may reduce unwanted side effects (such as restarting it
again when this utility completes).
EXIT STATUS¶
The exit status of sg_start is 0 when it is successful. Otherwise see the
sg3_utils(8) man page.
OLDER COMMAND LINE OPTIONS¶
The options in this section were the only ones available prior to sg3_utils
version 1.23 . In sg3_utils version 1.23 and later these older options can be
selected by either setting the SG3_UTILS_OLD_OPTS environment variable or
using '--old' (or '-O) as the first option.
Note that the action of
--loej is slightly different in the older
interface: when neither
--start nor
--stop (nor proxies for
them) are given,
--loej performs an eject operation. In the same
situation the newer interface will perform a load operation.
Earlier versions of sg_start had a '-s' option to perform a SYNCHRONIZE CACHE
command before the START STOP UNIT command was issued. According to recent
SBC-2 drafts this is done implicitly if required. Hence the '-s' option has
been dropped.
All options, other than '-v' and '-V', can be given with a single "-".
For example: "sg_start -stop /dev/sda" and "sg_start --stop
/dev/sda" are equivalent. The single "-" form is for backward
compatibility.
- 0
- stop (spin-down) DEVICE.
- 1
- start (spin-up) DEVICE.
- --eject
- stop the medium and eject it from the drive.
- --fl=FL
- sets the format layer number for the disc to
"jump" to (defined in MMC-5).
- -i
- sets the IMM bit on the START STOP UNIT command so this
utility will return immediately and not wait for the media to spin down.
Same effect as '--imm=1'. The default action (without this option or a
'--imm=1' option) is to wait until the media spins down before
returning.
- --imm=0|1
- when the immediate bit is 1 then this utility returns
immediately after the DEVICE has received the command. When this
option is 0 (the default) then the utility returns once the command has
completed its action (i.e. it waits until the device is started or
stopped).
- --load
- load the medium in the drive and start it.
- --loej
- sets the LOEJ bit in the START STOP UNIT cdb. When a
"start" operation is indicated, then a load and start is
performed. When a "stop" operation is indicated, then a stop and
eject is performed. When neither a "start" or "stop"
operation is indicated does a stop and eject. [Note that the last action
differs from the new interface in which the option of this name defaults
to load and start.]
- -N
- switch to the newer style options.
- --mod=PC_MOD
- where PC_MOD is the 'power condition modifier'
value. 0 to 15 (inclusive) are valid and 0 is the default. This field was
added after sbc3r13.
- --noflush
- do not perform a flush to media (e.g. like SYNCHRONIZE
CACHE does) before a variant of this utility that limits access to the
media. Using the --stop option is an example of something that
limits access to the media. This field was added after sbc3r13.
- --pc=PC
- where PC is the 'power condition' value (in hex). 0
to f (inclusive) are valid. Default value is 0.
- -r
- see the --readonly option above. May be useful for
ATA disks.
- --start
- start (spin-up) DEVICE.
- --stop
- stop (spin-down) DEVICE. Same meaning as
"0" argument.
- -v
- verbose: outputs SCSI command in hex to console before with
executing it. '-vv' and '-vvv' are also accepted yielding greater
verbosity.
- -V
- print out version string then exit.
AUTHOR¶
Written by K. Garloff and D. Gilbert
REPORTING BUGS¶
Report bugs to <dgilbert at interlog dot com>.
COPYRIGHT¶
Copyright © 2002-2011 Kurt Garloff, Douglas Gilbert
This software is distributed under the GPL version 2. There is NO warranty; not
even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
SEE ALSO¶
sg_prevent(sg3_utils), sg_requests(sg3_utils), sg_turs(sg3_utils)
sdparm(sdparm)