HDPARM(8) System Manager's Manual HDPARM(8)
hdparm - get/set SATA/IDE device parameters
hdparm [ flags ] [device] ..
hdparm provides a command line interface to various kernel interfaces supported by the Linux SATA/PATA/SAS "libata" subsystem and the older
IDE driver subsystem. Many newer (2008 and later) USB drive enclosures now also support "SAT" (SCSI-ATA Command Translation) and therefore
may also work with hdparm. Eg. recent WD "Passport" models and recent NexStar-3 enclosures. Some options may work correctly only with the
When no flags are given, -acdgkmur is assumed. For Get/Set options, a query without an optional parameter (e.g. -d) will query (get) the
device state, and with a parameter (e.g., -d0) will set the device state.
-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 Query/set Advanced Power Management feature, if the drive supports it. A low value means aggressive power management and a high
value means better performance. Possible settings range from values 1 through 127 (which permit spin-down), and values 128 through
254 (which do not permit spin-down). The highest degree of power management is attained with a setting of 1, and the highest I/O
performance with a setting of 254. A value of 255 tells hdparm to disable Advanced Power Management altogether on the drive (not
all drives support disabling it, but most do).
-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 spe-
cial sync sequence required by many chipsets. The value 3 works with nearly all 32-bit IDE chipsets, but incurs slightly more over-
head. 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.
DCO stands for Device Configuration Overlay, a way for vendors to selectively disable certain features of a drive. The --dco-freeze
flag will freeze/lock the current drive configuration, thereby preventing software (or malware) from changing any DCO settings until
after the next power-on reset.
Query and dump information regarding drive configuration settings which can be disabled by the vendor or OEM installer. These set-
tings show capabilities of the drive which might be disabled by the vendor for "enhanced compatibility". When disabled, they are
otherwise hidden and will not show in the -I identify output. For example, system vendors sometimes disable 48_bit addressing on
large drives, for compatibility (and loss of capacity) with a specific BIOS. In such cases, --dco-identify will show that the drive
is 48_bit capable, but -I will not show it, and nor will the drive accept 48_bit commands.
Reset all drive settings, features, and accessible capacities back to factory defaults and full capabilities. This command will
fail if DCO is frozen/locked, or if a -Np maximum size restriction has also been set. This is EXTREMELY DANGEROUS and will very
likely cause massive loss of data. DO NOT USE THIS COMMAND.
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.
VERY DANGEROUS, DON'T EVEN THINK ABOUT USING IT. This flag causes hdparm to issue an IDENTIFY command to the kernel, but incor-
rectly marked as a "non-data" command. This results in the drive being left with its DataReQust(DRQ) line "stuck" high. This con-
fuses 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 cd/dvd drive 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. This can be useful in some
cases, though, to smooth out DVD video playback.
-f Sync and flush the buffer cache for the device on exit. This operation is also performed internally as part of the -t and -T tim-
ings and other flags.
This flag currently works only on ext4 and xfs filesystem types. When used, this must be the only flag given. It requires two
parameters: the desired file size in kilo-bytes (byte count divided by 1024), followed by the pathname for the new file. It will
create a new file of the specified size, but without actually having to write any data to the file. This will normally complete
very quickly, and without thrashing the storage device.
Eg. Create a 10KByte file: hdparm --fallocate 10 temp_file
When used, this must be the only flag given. It requires a file path as a parameter, and will print out a list of the block extents
(sector ranges) occupied by that file on disk. Sector numbers are given as absolute LBA numbers, referenced from sector 0 of the
physical device rather than from the partition or filesystem. This information can then be used for a variety of purposes, such as
examining the degree of fragmenation of larger files, or determining appropriate sectors to deliberately corrupt during fault-injec-
tion testing procedures.
This flag uses the new FIEMAP (file extent map) ioctl() when available, and falls back to the older FIBMAP (file block map) ioctl()
otherwise. Note that FIBMAP suffers from a 32-bit block-number interface, and thus not work beyond 8TB or 16TB. FIBMAP is also
very slow, and does not deal well with preallocated uncommitted extents in ext4/xfs file systems, unless a sync() is done before
using this flag.
When used, this should be the only flag given. It requires a file path immediately after the flag, indicating where the new drive
firmware should be read from. The contents of this file will be sent to the drive using the (S)ATA DOWNLOAD MICROCODE command,
using either transfer protocol 7 (entire file at once), or, if the drive supports it, transfer protocol 3 (segmented download).
This command is EXTREMELY DANGEROUS and could destroy both the drive and all data on it. DO NOT USE THIS COMMAND. The --fwdown-
load-mode3 , --fwdownload-mode3-max , and --fwdownload-mode7 variations on basic --fwdownload allow overriding automatic protocol
detection in favour of forcing hdparm to use a specific transfer protocol, for testing purposes only.
-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 which the kernel drivers (IDE, libata) have stored from boot/configuration time. This may differ
from the current information obtainable directly from the drive itself with the -I flag. The data returned may or may not be cur-
rent, depending on activity since booting the system. 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, and later editions.
-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.
Issue an ATA IDLE_IMMEDIATE command, to put the drive into a lower power state. Usually the device remains spun-up.
Issue an ATA IDLE_IMMEDIATE_WITH_UNLOAD command, to unload or park the heads and put the drive into a lower power state. Usually
the device remains spun-up.
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 iden-
tification 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.
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 sys-
tem 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 par-
tition is on a removable 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 set-
tings of 2, 4, 8, or 16 (sectors). Larger settings may also be possible, depending on the drive. A setting of 16 or 32 seems opti-
mal 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.
Deliberately create a bad sector (aka. "media error") on the disk. EXCEPTIONALLY DANGEROUS. DO NOT USE THIS FLAG!! This can be
useful for testing of device/RAID error recovery mechanisms. The sector number is given as a (base10) parameter after the flag.
Depending on the device, hdparm will choose one of two possible ATA commands for corrupting the sector. The WRITE_LONG works on
most drives, but only up to the 28-bit sector boundary. Some very recent drives (2008) may support the new WRITE_UNCORRECTABLE_EXT
command, which works for any LBA48 sector. If available, hdparm will use that in preference to WRITE_LONG. The WRITE_UNCOR-
RECTABLE_EXT command itself presents a choice of how the new bad sector should behave. By default, it will look like any other bad
sector, and the drive may take some time to retry and fail on subsequent READs of the sector. However, if a single letter f is
prepended immediately in front of the first digit of the sector number parameter, then hdparm will issue a "flagged" WRITE_UNCOR-
RECTABLE_EXT, which causes the drive to merely flag the sector as bad (rather than genuinely corrupt it), and subsequent READs of
the sector will fail immediately (rather than after several retries). Note also that the --repair-sector flag can be used to
restore (any) bad sectors when they are no longer needed, including sectors that were genuinely bad (the drive will likely remap
those to a fresh area on the media).
-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/set max visible number of sectors, also known as the Host Protected Area setting. Without a parameter, -N displays the current
setting, which is reported as two values: the first gives the current max sectors setting, and the second shows the native (real)
hardware limit for the disk. The difference between these two values indicates how many sectors of the disk are currently hidden
from the operating system, in the form of a Host Protected Area (HPA). This area is often used by computer makers to hold diagnos-
tic software, and/or a copy of the originally provided operating system for recovery purposes. To change the current max (VERY DAN-
GEROUS, DATA LOSS IS EXTREMELY LIKELY), a new value should be provided (in base10) immediately following the -N flag. This value is
specified as a count of sectors, rather than the "max sector address" of the drive. Drives have the concept of a temporary
(volatile) setting which is lost on the next hardware reset, as well as a more permanent (non-volatile) value which survives resets
and power cycles. By default, -N affects only the temporary (volatile) setting. To change the permanent (non-volatile) value,
prepend a leading p character immediately before the first digit of the value. Drives are supposed to allow only a single permanent
change per session. A hardware reset (or power cycle) is required before another permanent -N operation can succeed. Note that any
attempt to set this value may fail if the disk is being accessed by other software at the same time. This is because setting the
value requires a pair of back-to-back drive commands, but there is no way to prevent some other command from being inserted between
them by the kernel. So if it fails initially, just try again. Kernel support for -N is buggy for many adapter types across many
kernel versions, in that an incorrect (too small) max size value is sometimes reported. As of the 2.6.27 kernel, this does finally
seem to be working on most hardware.
-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 set-
ting that is actually implemented will vary by chipset/driver sophistication. Use with extreme caution! This feature includes zero
protection for the unwary, and an unsuccessful outcome may result in severe filesystem corruption!
-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.
When using the SAT (SCSI ATA Translation) protocol, hdparm normally prefers to use the 16-byte command format whenever possible.
But some USB drive enclosures don't work correctly with 16-byte commands. This flag can be used to force use of the smaller 12-byte
command format with such drives. hdparm will still revert to 16-byte commands for things that cannot be done with the 12-byte for-
mat (eg. sector accesses beyond 28-bits).
-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 Get or set the device's command queue_depth, if supported by the hardware. This only works with 2.6.xx (or later) kernels, and only
with device and driver combinations which support changing the queue_depth. For SATA disks, this is the Native Command Queuing
(NCQ) queue depth.
-r Get/set read-only flag for the device. When set, Linux disallows write operations on the device.
Reads from the specified sector number, and dumps the contents in hex to standard output. The sector number must be given (base10)
after this flag. hdparm will issue a low-level read (completely bypassing the usual block layer read/write mechanisms) for the
specified sector. This can be used to definitively check whether a given sector is bad (media error) or not (doing so through the
usual mechanisms can sometimes give false positives).
This is an alias for the --write-sector flag. VERY DANGEROUS.
-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 set-
ups. 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 connec-
tor. In these cases, this command may be unsupported or may have no effect.
-S Put the drive into idle (low-power) mode, and also set the standby (spindown) timeout for the drive. This timeout 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 cir-
cumstances, 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 automat-
ically 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
-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 dis-
plays the speed of reading through the buffer cache to the disk without any prior caching of data. This measurement is an indica-
tion of how fast the drive can sustain sequential data reads under Linux, without any filesystem overhead. To ensure accurate mea-
surements, the buffer cache is flushed during the processing of -t using the BLKFLSBUF ioctl.
For Solid State Drives (SSDs). EXCEPTIONALLY DANGEROUS. DO NOT USE THIS FLAG!! Tells the drive firmware to discard unneeded data
sectors, destroying any data that may have been present within them. This makes those sectors available for immediate use by the
firmware's garbage collection mechanism, to improve scheduling for wear-leveling of the flash media. This option expects one or
more sector range pairs immediately after the flag: an LBA starting address, a colon, and a sector count, with no intervening spa-
ces. EXCEPTIONALLY DANGEROUS. DO NOT USE THIS FLAG!!
Eg. hdparm --trim-sector-ranges 1000:4 7894:16 /dev/sdz
Identical to --trim-sector-ranges above, except the list of lba:count pairs is read from stdin rather than being specified on the
command line. This can be used to avoid problems with excessively long command lines. It also permits batching of many more sector
ranges into single commands to the drive, up to the currently configured transfer limit (max_sectors_kb).
-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 hard-
ware flaw) when this option is used with kernel versions earlier than 2.0.13. Disabling the IDE prefetch feature of these inter-
faces (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.
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.
Writes zeros to the specified sector number. VERY DANGEROUS. The sector number must be given (base10) after this flag. hdparm
will issue a low-level write (completely bypassing the usual block layer read/write mechanisms) to the specified sector. This can
be used to force a drive to repair a bad sector (media error).
-W Get/set the IDE/SATA drive's write-caching feature.
-x Tristate device for hotswap (DANGEROUS).
-X Set the IDE transfer mode for (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 sim-
ple 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 necessary 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/spinning-down at
-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.
Display terse usage info for all of the --security-* flags.
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. No
other flags are permitted on the command line with this one.
Unlock the drive, using password PWD. Password is given as an ASCII string and is padded with NULs to reach 32 bytes. The applica-
ble drive password is selected with the --user-master switch. No other flags are permitted on the command line with this one. THIS
FEATURE IS EXPERIMENTAL AND NOT WELL TESTED. USE AT YOUR OWN RISK.
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. Use the special password NULL to set an empty password. The applicable drive password is selected with the --user-
master switch and the applicable security mode with the --security-mode switch. No other flags are permitted on the command line
with this one. THIS FEATURE IS EXPERIMENTAL AND NOT WELL TESTED. USE AT YOUR OWN RISK.
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. No other flags are permitted on the command line with this
one. THIS FEATURE IS EXPERIMENTAL AND NOT WELL TESTED. USE AT YOUR OWN RISK.
Erase (locked) drive, using password PWD (DANGEROUS). Password is given as an ASCII string and is padded with NULs to reach 32
bytes. Use the special password NULL to represent an empty password. The applicable drive password is selected with the --user-
master switch. No other flags are permitted on the command line with this one. THIS FEATURE IS EXPERIMENTAL AND NOT WELL TESTED.
USE AT YOUR OWN RISK.
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. No other flags are permitted on the com-
mand line with this one. THIS FEATURE IS EXPERIMENTAL AND NOT WELL TESTED. USE AT YOUR OWN RISK.
Specifies which password (user/master) to select. Defaults to master. Only useful in combination with --security-unlock, --secu-
rity-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.
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 SATA/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 suc-
ceed 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 neces-
sary commands that way.
hdparm has been written by Mark Lord <firstname.lastname@example.org>, the original primary developer and maintainer of the (E)IDE driver for Linux, and
current contributer to the libata subsystem, along with suggestions and patches from many netfolk.
The disable Seagate auto-powersaving code is courtesy of Tomi Leppikangas(email@example.com).
Security freeze command by Benjamin Benz, 2005.
PIO data out security commands by Leonard den Ottolander , 2005. Some other parts by Benjamin Benz 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
Version 9.28 March 2010 HDPARM(8)