SYNOPSIS
hdparm [ flags ] [device] ..
DESCRIPTION
hdparm provides a command line interface to various hard disk ioctls
supported by the stock Linux ATA/IDE device driver subsystem. Some
options may work correctly only with the latest kernels. For best
results, compile hdparm with the include files from the latest kernel
source code.
OPTIONS
When no flags are given, -acdgkmnru 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 Disable/enable 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 sup‐
ported values include 0 to disable 32-bit I/O support, 1 to
enable 32-bit data transfers, and 3 to enable 32-bit data trans‐
fers 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 com‐
pletely 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 com‐
than the usual page cache method, giving a better indication of
raw device and driver performance.
-D Enable/disable the on-drive defect management feature, whereby
the drive firmware tries to automatically manage defective sec‐
tors by relocating them to "spare" sectors reserved by the fac‐
tory for such.
-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.
-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 "no seatbelts" 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.
--Istdout
This option simply dumps the identify data in hex to stdout, in
a format similar to that from /proc/, and suitable for later use
with the --Istdin option.
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 automati‐
cally, 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 fea‐
ture 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 Dig‐
ital recommends lower settings of 4 to 8 on many of their
drives, due tiny (32kB) drive buffers and non-optimized buffer‐
ing 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 move‐
ments 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 lev‐
els between 128 and 254. At the moment, most drives only sup‐
port 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 Set the maximum sector count for the drive´s internal prefetch
mechanism. Not all drives support this feature.
-q Handle the next flag quietly, suppressing normal output. 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) ker‐
nels, and only with the few drives that currently support it.
-r Get/set read-only flag for the device. When set, Linux disal‐
lows 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. If enabled, the drive is powered-up in the standby
mode to allow the controller to sequence the spin-up of devices.
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 to enable this feature by a jumper. Some SATA drives sup‐
port 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 sec‐
onds 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 pur‐
poses. 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,
flushed during the processing of -t using the BLKFLSBUF ioctl.
If the -T flag is also specified, then a correction factor based
on the outcome of -T will be incorporated into the result
reported for the -t operation.
-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 responsive‐
ness and eliminates "serial port overrun" errors. Use this fea‐
ture 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 par‐
ticular, 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 fea‐
ture 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 cau‐
tion 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 all settings, except -i (same as -acdgkmnru for IDE, -gr
for SCSI or -adgr for XT). This is also the default behaviour
when no flags are specified.
-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 Disable/enable the IDE drive´s write-caching feature (default
state is undeterminable; manufacturer/model specific).
-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
-Y Force an IDE drive to immediately enter the lowest power con‐
sumption 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/spinning-
down 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 func‐
tion 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
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.
FILES
/etc/hdparm.conf
BUGS
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 neces‐
sary 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 inter‐
faces.
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 suc‐
ceed on a locked drive because the second command will not be issued
PIO data out security commands by Leonard den Ottolander <leonard den
ottolander nl>, 2005. Parts by Benjamin Benz <bbe@heise.de> and oth‐
ers.
SEE ALSO
http://www.t13.org/ Technical Committee T13 ATA Attachment.
http://www.serialata.org/ Serial ATA International Organization.
Version 6.9 October 2006 HDPARM(8)
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