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man page(1) manual page
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hdparm - get/set hard disk parameters
hdparm [ flags ] [device] ..
hdparm provides a command line interface to various hard disk ioctls
supported by the Linux SATA/PATA/SAS “libata” subsystem and the older
IDE driver subsystem. Some options may work correctly only with the
latest kernels.
When no flags are given, -acdgkmur is assumed.
- -a
- Get/set sector count for filesystem (software) read-ahead. This
is used to improve performance in sequential reads of large
files, by prefetching additional blocks in anticipation of them
being needed by the running task. Many IDE drives also have a
separate built-in read-ahead function, which augments this
filesystem (software) read-ahead function.
- -A
- Get/set the IDE drive´s read-lookahead feature (usually ON by
default). Usage: -A0 (disable) or -A1 (enable).
- -b
- Get/set bus state.
- -B
- Set Advanced Power Management feature, if the drive supports it.
A low value means aggressive power management and a high value
means better performance. A value of 255 will disable apm on the
drive.
- -c
- Query/enable (E)IDE 32-bit I/O support. A numeric parameter can
be used to enable/disable 32-bit I/O support: Currently supported
values include 0 to disable 32-bit I/O support, 1 to
enable 32-bit data transfers, and 3 to enable 32-bit data transfers
with a special sync sequence required by many chipsets.
The value 3 works with nearly all 32-bit IDE chipsets, but
incurs slightly more overhead. Note that “32-bit” refers to
data transfers across a PCI or VLB bus to the interface card
only; all (E)IDE drives still have only a 16-bit connection over
the ribbon cable from the interface card.
- -C
- Check the current IDE power mode status, which will always be
one of unknown (drive does not support this command),
active/idle (normal operation), standby (low power mode, drive
has spun down), or sleeping (lowest power mode, drive is completely
shut down). The -S, -y, -Y, and -Z flags can be used to
manipulate the IDE power modes.
- -d
- Disable/enable the “using_dma” flag for this drive. This option
now works with most combinations of drives and PCI interfaces
which support DMA and which are known to the kernel IDE driver.
It is also a good idea to use the appropriate -X option in combination
with -d1 to ensure that the drive itself is programmed
for the correct DMA mode, although most BIOSs should do this for
you at boot time. Using DMA nearly always gives the best performance,
with fast I/O throughput and low CPU usage. But there
are at least a few configurations of chipsets and drives for
which DMA does not make much of a difference, or may even slow
things down (on really messed up hardware!). Your mileage may
vary.
- --direct
-
Use the kernel O_DIRECT flag when performing a -t timing test.
This bypasses the page cache, causing the reads to go directly
from the drive into hdparm’s buffers, using so-called “raw” I/O.
In many cases, this can produce results that appear much faster
than the usual page cache method, giving a better indication of
raw device and driver performance.
- --drq-hsm-error
-
VERY DANGEROUS, DON’T EVEN THINK ABOUT USING IT. This flag
causes hdparm to issue an IDENTIFY command to the kernel, but
incorrectly marked as a “non-data” command. This results in the
drive being left with its DataReQust(DRQ) line “stuck” high.
This confuses the kernel drivers, and may crash the system immediately
with massive data loss. The option exists to help in
testing and fortifying the kernel against similar real-world
drive malfunctions. VERY DANGEROUS, DO NOT USE!!
- -D
- Enable/disable the on-drive defect management feature, whereby
the drive firmware tries to automatically manage defective sectors
by relocating them to “spare” sectors reserved by the factory
for such. Control of this feature via the -D flag is not
supported for most modern drives since ATA-4; thus this command
may fail.
- -E
- Set cdrom speed. This is NOT necessary for regular operation,
as the drive will automatically switch speeds on its own. But
if you want to play with it, just supply a speed number after
the option, usually a number like 2 or 4.
- -f
- Sync and flush the buffer cache for the device on exit. This
operation is also performed as part of the -t and -T timings.
- -F
- Flush the on-drive write cache buffer (older drives may not
implement this).
- -g
- Display the drive geometry (cylinders, heads, sectors), the size
(in sectors) of the device, and the starting offset (in sectors)
of the device from the beginning of the drive.
- -h
- Display terse usage information (help).
- -i
- Display the identification info that was obtained from the drive
at boot time, if available. This is a feature of modern IDE
drives, and may not be supported by older devices. The data
returned may or may not be current, depending on activity since
booting the system. However, the current multiple sector mode
count is always shown. For a more detailed interpretation of
the identification info, refer to AT Attachment Interface for
Disk Drives (ANSI ASC X3T9.2 working draft, revision 4a, April
19/93).
- -I
- Request identification info directly from the drive, which is
displayed in a new expanded format with considerably more detail
than with the older -i flag.
- --Istdin
-
This is a special variation on the -I option, which accepts a
drive identification block as standard input instead of using a
/dev/hd* parameter. The format of this block must be exactly
the same as that found in the /proc/ide/*/hd*/identify “files",
or that produced by the --Istdout option described below. This
variation is designed for use with collected “libraries” of
drive identification information, and can also be used on ATAPI
drives which may give media errors with the standard mechanism.
When --Istdin is used, it must be the *only* parameter given.
- --Istdout
-
This option dumps the drive’s identify data in hex to stdout, in
a format similar to that from /proc/ide/*/identify, and suitable
for later use with the --Istdin option.
- -k
- Get/set the keep_settings_over_reset flag for the drive. When
this flag is set, the driver will preserve the -dmu options over
a soft reset, (as done during the error recovery sequence).
This flag defaults to off, to prevent drive reset loops which
could be caused by combinations of -dmu settings. The -k flag
should therefore only be set after one has achieved confidence
in correct system operation with a chosen set of configuration
settings. In practice, all that is typically necessary to test
a configuration (prior to using -k) is to verify that the drive
can be read/written, and that no error logs (kernel messages)
are generated in the process (look in /var/adm/messages on most
systems).
- -K
- Set the drive´s keep_features_over_reset flag. Setting this
enables the drive to retain the settings for -APSWXZ over a soft
reset (as done during the error recovery sequence). Not all
drives support this feature.
- -L
- Set the drive´s doorlock flag. Setting this to 1 will lock the
door mechanism of some removable hard drives (eg. Syquest, ZIP,
Jazz..), and setting it to 0 will unlock the door mechanism.
Normally, Linux maintains the door locking mechanism automatically,
depending on drive usage (locked whenever a filesystem is
mounted). But on system shutdown, this can be a nuisance if the
root partition is on a removeable disk, since the root partition
is left mounted (read-only) after shutdown. So, by using this
command to unlock the door after the root filesystem is
remounted read-only, one can then remove the cartridge from the
drive after shutdown.
- -m
- Get/set sector count for multiple sector I/O on the drive. A
setting of 0 disables this feature. Multiple sector mode (aka
IDE Block Mode), is a feature of most modern IDE hard drives,
permitting the transfer of multiple sectors per I/O interrupt,
rather than the usual one sector per interrupt. When this feature
is enabled, it typically reduces operating system overhead
for disk I/O by 30-50%. On many systems, it also provides
increased data throughput of anywhere from 5% to 50%. Some
drives, however (most notably the WD Caviar series), seem to run
slower with multiple mode enabled. Your mileage may vary. Most
drives support the minimum settings of 2, 4, 8, or 16 (sectors).
Larger settings may also be possible, depending on the drive. A
setting of 16 or 32 seems optimal on many systems. Western Digital
recommends lower settings of 4 to 8 on many of their
drives, due tiny (32kB) drive buffers and non-optimized buffering
algorithms. The -i flag can be used to find the maximum
setting supported by an installed drive (look for MaxMultSect in
the output). Some drives claim to support multiple mode, but
lose data at some settings. Under rare circumstances, such
failures can result in massive filesystem corruption.
- -M
- Get/set Automatic Acoustic Management (AAM) setting. Most modern
harddisk drives have the ability to speed down the head movements
to reduce their noise output. The possible values are
between 0 and 254. 128 is the most quiet (and therefore slowest)
setting and 254 the fastest (and loudest). Some drives have only
two levels (quiet / fast), while others may have different levels
between 128 and 254. At the moment, most drives only support
3 options, off, quiet, and fast. These have been assigned
the values 0, 128, and 254 at present, respectively, but integer
space has been incorporated for future expansion, should this
change.
- -n
- Get or set the “ignore write errors” flag in the driver. Do NOT
play with this without grokking the driver source code first.
- -p
- Attempt to reprogram the IDE interface chipset for the specified
PIO mode, or attempt to auto-tune for the “best” PIO mode supported
by the drive. This feature is supported in the kernel
for only a few “known” chipsets, and even then the support is
iffy at best. Some IDE chipsets are unable to alter the PIO
mode for a single drive, in which case this flag may cause the
PIO mode for both drives to be set. Many IDE chipsets support
either fewer or more than the standard six (0 to 5) PIO modes,
so the exact speed setting that is actually implemented will
vary by chipset/driver sophistication. Use with extreme cau_tion!
This feature includes zero protection for the unwary, and
an unsuccessful outcome may result in severe filesystem corrup_tion!
- -P
- Set the maximum sector count for the drive´s internal prefetch
mechanism. Not all drives support this feature, and it was
dropped from the offical spec as of ATA-4.
- -q
- Handle the next flag quietly, suppressing normal output (but not
error messages). This is useful for reducing screen clutter
when running from system startup scripts. Not applicable to the
-i or -v or -t or -T flags.
- -Q
- Set tagged queue depth (1 or greater), or turn tagged queuing
off (0). This only works with the newer 2.5.xx (or later) kernels,
and only with the few drives that currently support it.
- -r
- Get/set read-only flag for the device. When set, Linux disallows
write operations on the device.
- -R
- Register an IDE interface (DANGEROUS). See the -U option for
more information.
- -s
- Enable/disable the power-on in standby feature, if supported by
the drive. VERY DANGEROUS. Do not use unless you are absolutely
certain that both the system BIOS (or firmware) and the
operating system kernel (Linux >= 2.6.22) support probing for
drives that use this feature. When enabled, the drive is powered-up
in the standby mode to allow the controller to sequence
the spin-up of devices, reducing the instantaneous current draw
burden when many drives share a power supply. Primarily for use
in large RAID setups. This feature is usually disabled and the
drive is powered-up in the active mode (see -C above). Note
that a drive may also allow enabling this feature by a jumper.
Some SATA drives support the control of this feature by pin 11
of the SATA power connector. In these cases, this command may be
unsupported or may have no effect.
- -S
- Set the standby (spindown) timeout for the drive. This value is
used by the drive to determine how long to wait (with no disk
activity) before turning off the spindle motor to save power.
Under such circumstances, the drive may take as long as 30 seconds
to respond to a subsequent disk access, though most drives
are much quicker. The encoding of the timeout value is somewhat
peculiar. A value of zero means “timeouts are disabled": the
device will not automatically enter standby mode. Values from 1
to 240 specify multiples of 5 seconds, yielding timeouts from 5
seconds to 20 minutes. Values from 241 to 251 specify from 1 to
11 units of 30 minutes, yielding timeouts from 30 minutes to 5.5
hours. A value of 252 signifies a timeout of 21 minutes. A
value of 253 sets a vendor-defined timeout period between 8 and
12 hours, and the value 254 is reserved. 255 is interpreted as
21 minutes plus 15 seconds. Note that some older drives may
have very different interpretations of these values.
- -T
- Perform timings of cache reads for benchmark and comparison purposes.
For meaningful results, this operation should be
repeated 2-3 times on an otherwise inactive system (no other
active processes) with at least a couple of megabytes of free
memory. This displays the speed of reading directly from the
Linux buffer cache without disk access. This measurement is
essentially an indication of the throughput of the processor,
cache, and memory of the system under test.
- -t
- Perform timings of device reads for benchmark and comparison
purposes. For meaningful results, this operation should be
repeated 2-3 times on an otherwise inactive system (no other
active processes) with at least a couple of megabytes of free
memory. This displays the speed of reading through the buffer
cache to the disk without any prior caching of data. This measurement
is an indication of how fast the drive can sustain
sequential data reads under Linux, without any filesystem overhead.
To ensure accurate measurements, the buffer cache is
flushed during the processing of -t using the BLKFLSBUF ioctl.
- -u
- Get/set interrupt-unmask flag for the drive. A setting of 1
permits the driver to unmask other interrupts during processing
of a disk interrupt, which greatly improves Linux´s responsiveness
and eliminates “serial port overrun” errors. Use this feature
with caution: some drive/controller combinations do not
tolerate the increased I/O latencies possible when this feature
is enabled, resulting in massive filesystem corruption. In particular,
CMD-640B and RZ1000 (E)IDE interfaces can be unreliable
(due to a hardware flaw) when this option is used with kernel
versions earlier than 2.0.13. Disabling the IDE prefetch feature
of these interfaces (usually a BIOS/CMOS setting) provides
a safe fix for the problem for use with earlier kernels.
- -U
- Un-register an IDE interface (DANGEROUS). The companion for the
-R option. Intended for use with hardware made specifically for
hot-swapping (very rare!). Use with knowledge and extreme caution
as this can easily hang or damage your system. The hdparm
source distribution includes a ´contrib´ directory with some
user-donated scripts for hot-swapping on the UltraBay of a
ThinkPad 600E. Use at your own risk.
- -v
- Display some basic settings, similar to -acdgkmur for IDE. This
is also the default behaviour when no flags are specified.
- --verbose
-
Display extra diagnostics from some commands.
- -w
- Perform a device reset (DANGEROUS). Do NOT use this option. It
exists for unlikely situations where a reboot might otherwise be
required to get a confused drive back into a useable state.
- -W
- Get/set the IDE/SATA drive´s write-caching feature.
- -x
- Tristate device for hotswap (DANGEROUS).
- -X
- Set the IDE transfer mode for newer (E)IDE/ATA drives. This is
typically used in combination with -d1 when enabling DMA to/from
a drive on a supported interface chipset, where -X mdma2 is used
to select multiword DMA mode2 transfers and -X sdma1 is used to
select simple mode 1 DMA transfers. With systems which support
UltraDMA burst timings, -X udma2 is used to select UltraDMA
mode2 transfers (you´ll need to prepare the chipset for UltraDMA
beforehand). Apart from that, use of this flag is seldom neces_sary
since most/all modern IDE drives default to their fastest
PIO transfer mode at power-on. Fiddling with this can be both
needless and risky. On drives which support alternate transfer
modes, -X can be used to switch the mode of the drive only.
Prior to changing the transfer mode, the IDE interface should be
jumpered or programmed (see -p flag) for the new mode setting to
prevent loss and/or corruption of data. Use this with extreme
caution! For the PIO (Programmed Input/Output) transfer modes
used by Linux, this value is simply the desired PIO mode number
plus 8. Thus, a value of 09 sets PIO mode1, 10 enables PIO
mode2, and 11 selects PIO mode3. Setting 00 restores the
drive´s “default” PIO mode, and 01 disables IORDY. For multiword
DMA, the value used is the desired DMA mode number plus 32.
for UltraDMA, the value is the desired UltraDMA mode number plus
64.
- -y
- Force an IDE drive to immediately enter the low power consumption
standby mode, usually causing it to spin down. The current
power mode status can be checked using the -C flag.
- -Y
- Force an IDE drive to immediately enter the lowest power consumption
sleep mode, causing it to shut down completely. A hard
or soft reset is required before the drive can be accessed again
(the Linux IDE driver will automatically handle issuing a reset
if/when needed). The current power mode status can be checked
using the -C flag.
- -z
- Force a kernel re-read of the partition table of the specified
device(s).
- -Z
- Disable the automatic power-saving function of certain Seagate
drives (ST3xxx models?), to prevent them from idling/spinningdown
at inconvenient times.
- -H
- Read the temperature from some (mostly Hitachi) drives. Also
reports if the temperature is within operating condition range
(this may not be reliable). Does not cause the drive to spin up
if idle.
ATA Security Feature Set
These switches are DANGEROUS to experiment with, and might not work
with every kernel. USE AT YOUR OWN RISK.
- --security-help
-
Display terse usage info for all of the --security-* flags.
- --security-freeze
-
Freeze the drive´s security settings. The drive does not accept
any security commands until next power-on reset. Use this function
in combination with --security-unlock to protect drive from
any attempt to set a new password. Can be used standalone, too.
- --security-unlock PWD
-
Unlock the drive, using password PWD. Password is given as an
ASCII string and is padded with NULs to reach 32 bytes. The
applicable drive password is selected with the --user-master
switch. THIS FEATURE IS EXPERIMENTAL AND NOT WELL TESTED. USE
AT YOUR OWN RISK.
- --security-set-pass PWD
-
Lock the drive, using password PWD (Set Password) (DANGEROUS).
Password is given as an ASCII string and is padded with NULs to
reach 32 bytes. The applicable drive password is selected with
the --user-master switch and the applicable security mode with
the --security-mode switch. THIS FEATURE IS EXPERIMENTAL AND
NOT WELL TESTED. USE AT YOUR OWN RISK.
- --security-disable PWD
-
Disable drive locking, using password PWD. Password is given as
an ASCII string and is padded with NULs to reach 32 bytes. The
applicable drive password is selected with the --user-master
switch. THIS FEATURE IS EXPERIMENTAL AND NOT WELL TESTED. USE
AT YOUR OWN RISK.
- --security-erase PWD
-
Erase (locked) drive, using password PWD (DANGEROUS). Password
is given as an ASCII string and is padded with NULs to reach 32
bytes. The applicable drive password is selected with the
--user-master switch. THIS FEATURE IS EXPERIMENTAL AND NOT WELL
TESTED. USE AT YOUR OWN RISK.
- --security-erase-enhanced PWD
-
Enhanced erase (locked) drive, using password PWD (DANGEROUS).
Password is given as an ASCII string and is padded with NULs to
reach 32 bytes. The applicable drive password is selected with
the --user-master switch. THIS FEATURE IS EXPERIMENTAL AND NOT
WELL TESTED. USE AT YOUR OWN RISK.
- --user-master USER
-
Specifies which password (user/master) to select. Defaults to
master. Only useful in combination with --security-unlock,
--security-set-pass, --security-disable, --security-erase or
--security-erase-enhanced.
- u
- user password
- m
- master password
- THIS
- FEATURE IS EXPERIMENTAL AND NOT WELL TESTED. USE AT YOUR
OWN RISK.
- --security-mode MODE
-
Specifies which security mode (high/maximum) to set. Defaults
to high. Only useful in combination with --security-set-pass.
- h
- high security
- m
- maximum security
- THIS
- FEATURE IS EXPERIMENTAL AND NOT WELL TESTED. USE AT YOUR
OWN RISK.
As noted above, the -m sectcount and -u 1 options should be used with
caution at first, preferably on a read-only filesystem. Most drives
work well with these features, but a few drive/controller combinations
are not 100% compatible. Filesystem corruption may result. Backup
everything before experimenting!
Some options (eg. -r for SCSI) may not work with old kernels as necessary
ioctl()´s were not supported.
Although this utility is intended primarily for use with (E)IDE hard
disk devices, several of the options are also valid (and permitted) for
use with SCSI hard disk devices and MFM/RLL hard disks with XT interfaces.
The Linux kernel up until 2.6.12 (and probably later) doesn´t handle
the security unlock and disable commands gracefully and will segfault
and in some cases even panic. The security commands however might
indeed have been executed by the drive. This poor kernel behaviour
makes the PIO data security commands rather useless at the moment.
Note that the “security erase” and “security disable” commands have
been implemented as two consecutive PIO data commands and will not succeed
on a locked drive because the second command will not be issued
after the segfault. See the code for hints how patch it to work around
this problem. Despite the segfault it is often still possible to run
two instances of hdparm consecutively and issue the two necessary commands
that way.
hdparm has been written by Mark Lord <mlord@pobox.com>, the original
primary developer and maintainer of the (E)IDE driver for Linux, with
suggestions from many netfolk.
The disable Seagate auto-powersaving code is courtesy of Tomi Leppikangas(tomilepp@paju.oulu.fi).
Security freeze command by Benjamin Benz <bbe@heise.de>, 2005.
PIO data out security commands by Leonard den Ottolander <leonard den
ottolander nl>, 2005. Parts by Benjamin Benz <bbe@heise.de> and others.
http://www.t13.org/ Technical Committee T13 AT Attachment (ATA/ATAPI)
Interface.
http://www.serialata.org/ Serial ATA International Organization.
http://www.compactflash.org/ CompactFlash Association
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