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HDPARM(8)                                                            HDPARM(8)

       hdparm - get/set SATA/IDE device parameters

       hdparm [options] [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.  E.g. recent WD
       "Passport" models and recent NexStar-3 enclosures.  Some options may work correctly only with the  latest  ker-

       When no options are given, -acdgkmur is assumed.  For "Get/set" options, a query without the 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

       -b     Get/set bus state.

       -B     Get/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 set-
              ting 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     Get/set  (E)IDE  32-bit  I/O support.  A numeric parameter can be used to enable/disable 32-bit I/O sup-
              port.  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 sleep-
              ing (lowest power mode, drive is completely shut down).  The -S, -y, -Y, and -Z options can be  used  to
              manipulate the IDE power modes.

       -d     Get/set 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 option will freeze/lock the current drive configuration, thereby  prevent-
              ing 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 settings 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  compati-
              bility  (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 capabil-
              ities.   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

              Use  the kernel?s "O_DIRECT" flag when performing a -t timing test.  This bypasses the page cache, caus-
              ing 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 bet-
              ter indication of raw device and driver performance.

              VERY DANGEROUS, DON'T EVEN THINK ABOUT USING IT.  This option 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.  Con-
              trol of this feature via the -D option 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 play-

       -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 timings and other options.

              This  option  currently  works  only on ext4 and xfs filesystem types.  When used, this must be the only
              option 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.

              E.g. Create a 10KByte file: hdparm --fallocate 10 temp_file

              When  used,  this must be the only option 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 dur-
              ing fault-injection testing procedures.

              This option 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 inter-
              face, and thus not work beyond 8TB or 16TB.  FIBMAP is also very slow, and does not deal well with  pre-
              allocated uncommitted extents in ext4/xfs filesystems, unless a sync() is done before using this option.

              When used, this must be the only flag given.  It requires a file path followed by  a  sector  number  as
              parameters.   This  sector  number  is  given  relative to the start of the file itself, not the device.
              hdparm will scan the device extents occupied by the file, and print out the absolute LBA number  of  the
              requested  sector  of the file.  This LBA number is referenced from sector 0 of the physical device (not
              the partition or filesystem).  This LBA value can then be used for  a  variety  of  purposes,  including
              determining an appropriate sector to deliberately corrupt during fault-injection testing procedures.

              When  used, this should be the only option given.  It requires a file path immediately after the option,
              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
              --fwdownload-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).

       -H     Read the temperature from some (mostly Hitachi) drives.  Also reports if the temperature is within oper-
              ating condition range (this may not be reliable). Does not cause the drive to spin up if idle.

       -i     Display the identification info which the kernel drivers (IDE, libata) have stored from  boot/configura-
              tion  time.  This may differ from the current information obtainable directly from the drive itself with
              the -I option.  The data returned may or may not be current, 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.

              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.

       -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 option.

              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.

              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.

       -J     Get/set  the  Western Digital (WD) Green Drive's "idle3" timeout value.  This timeout controls how often
              the drive parks its heads and enters a low power consumption state.  The factory default  is  eight  (8)
              seconds,  which is a very poor choice for use with Linux.  Leaving it at the default will result in hun-
              dreds of thousands of head load/unload cycles in a very short period of time.  The  drive  mechanism  is
              only rated for 300,000 to 1,000,000 cycles, so leaving it at the default could result in premature fail-
              ure, not to mention the performance impact of the drive often having to  wake-up  before  doing  routine

              WD  supply  a WDIDLE3.EXE DOS utility for tweaking this setting, and you should use that program instead
              of hdparm if at all possible.  The reverse-engineered implementation in hdparm is not as complete as the
              original  official  program,  even though it does seem to work on at a least a few drives.  A full power
              cycle is required for any change in setting to take effect, regardless of which program is used to tweak

              A  setting  of  30 seconds is recommended for Linux use.  Permitted values are from 8 to 12 seconds, and
              from 30 to 300 seconds in 30-second increments.  Specify a value of zero (0) to  disable  the  WD  idle3
              timer completely (NOT RECOMMENDED!).

       -k     Get/set  the  "keep_settings_over_reset" flag for the drive.  When this flag is set, the drive will pre-
              serve the -dmu settings over a soft reset, (as done during the error recovery  sequence).   This  option
              defaults  to  off,  to prevent drive reset loops which could be caused by combinations of -dmu settings.
              The -k option 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/log/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

       -L     Set  the  drive?s  doorlock flag.  Setting this to 1 will lock the door mechanism of some removable hard
              drives (e.g. 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 filesys-
              tem is mounted).  But on system shutdown, this can be a nuisance if the root partition 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.  Mul-
              tiple 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 Dig-
              ital recommends lower settings of 4 to 8 on many of their drives, due tiny (32kB) drive buffers and non-
              optimized buffering algorithms.  The -i option 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

              Deliberately  create a bad sector (aka. "media error") on the disk.  EXCEPTIONALLY DANGEROUS. DO NOT USE
              THIS OPTION!!  This can be useful for testing of device/RAID error recovery mechanisms.  The sector num-
              ber  is given as a (base10) parameter after the option.  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_UNCOR-
              RECTABLE_EXT command, which works for any LBA48 sector.  If available, hdparm will use that  in  prefer-
              ence  to  WRITE_LONG.   The  WRITE_UNCORRECTABLE_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_UNCORRECTABLE_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  sev-
              eral  retries).  Note also that the --repair-sector option 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  or  set  the  "ignore_write_errors" flag in the driver.  Do NOT play with this without grokking the
              driver source code first.

       -N     Get/set max visible number of sectors, also known as the Host Protected Area setting.  Without a parame-
              ter,  -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
              diagnostic  software,  and/or  a copy of the originally provided operating system for recovery purposes.
              Another possible use is to hide the true capacity of a very large disk from a  BIOS/system  that  cannot
              normally  cope  with  drives  of that size (eg. most current {2010} BIOSs cannot deal with drives larger
              than 2TB, so an HPA could be used to cause a 3TB drive to report itself as a 2TB drive).  To change  the
              current  max (VERY DANGEROUS, DATA LOSS IS EXTREMELY LIKELY), a new value should be provided (in base10)
              immediately following the -N option.  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 perma-
              nent (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.

              Offsets to given number of GiB (1024*1024*1024) when performing  -t  timings  of  device  reads.   Speed
              changes  (about  twice)  along many mechanical drives.  Usually the maximum is at the beginning, but not
              always.  Solid-state drives (SSDs) should show similar timings regardless of offset.

       -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 option 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
              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 option 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 format (e.g. sec-
              tor accesses beyond 28-bits).

       -q     Handle the next option 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 options.

       -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.

       -R     Get/set Write-Read-Verify feature, if the drive supports it.  Usage:  -R0  (disable)  or  -R1  (enable).
              This  feature is intended to have the drive firmware automatically read-back any data that is written by
              software, to verify that the data was successfully written.  This is generally overkill,  and  can  slow
              down disk writes by as much as a factor of two (or more).

              Reads  from  the  specified sector number, and dumps the contents in hex to standard output.  The sector
              number must be given (base10) after this option.  hdparm will issue a low-level read (completely bypass-
              ing  the usual block layer read/write mechanisms) for the specified sector.  This can be used to defini-
              tively 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 option.  VERY DANGEROUS.

       -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  ker-
              nel (Linux >= 2.6.22) support probing for drives that use this feature.  When enabled, the drive is pow-
              ered-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     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 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  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 accu-
              rate measurements, the buffer cache is flushed during the processing of -t using the BLKFLSBUF ioctl.

       -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.

              For Solid State Drives (SSDs).  EXCEPTIONALLY DANGEROUS. DO NOT  USE  THIS  OPTION!!   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 option: an LBA starting address, a colon, and a sector  count  (max  65535),
              with no intervening spaces.  EXCEPTIONALLY DANGEROUS. DO NOT USE THIS OPTION!!

              E.g.  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 com-
              mand  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).

              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 two parameters immediately
              after the flag: an LBA starting address, and a sector count.  EXCEPTIONALLY DANGEROUS. DO NOT  USE  THIS

       -u     Get/set  the  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 combina-
              tions 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.

       -v     Display some basic settings, similar to -acdgkmur for IDE.  This is also the default behaviour  when  no
              options are specified.

       -V     Display program version and exit immediately.

              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  option.   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  sec-
              tor (media error).

       -W     Get/set the IDE/SATA drive?s write-caching feature.

       -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  multi-
              word 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 pre-
              pare  the  chipset  for  UltraDMA  beforehand).  Apart from that, use of this option 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 option) 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 Ultra-
              DMA, 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 option.

       -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 option.

       -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.

       ATA Security Feature Set

       These switches are DANGEROUS to experiment with, and might not work with some kernels.  USE AT YOUR OWN RISK.

              Display terse usage info for all of the --security-* options.

              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 options are permitted on the command line
              with this one.

       --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 (default is
              "user" password).  No other options are permitted on the command line with this one.

       --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.  Use the special password NULL to set an empty password.  The
              applicable drive password is selected with the --user-master switch (default is "user" password) and the
              applicable security mode with the --security-mode switch.  No other options are permitted on the command
              line with this one.

       --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 (default is
              "user" password).  No other options are permitted on the command line with this one.

       --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.  Use the special password NULL to represent an empty password.  The
              applicable drive password is selected with the --user-master switch (default is  "user"  password).   No
              other options are permitted on the command line with this one.

       --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  (default is "user" password).  No other options are permitted on the command line with this one.

       --user-master USER
              Specifies which password (user/master) to select.  Defaults to user password.  Only useful  in  combina-
              tion  with  --security-unlock,  --security-set-pass, --security-disable, --security-erase or --security-
                      u       user password
                      m       master password

       --security-mode MODE
              Specifies which security mode (high/maximum) to set.  Defaults to high.  Only useful in combination with
                      h       high security
                      m       maximum security



       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 (e.g. -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

       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 <>, 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(

       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.

SEE ALSO Technical Committee T13 AT Attachment (ATA/ATAPI) Interface. Serial ATA International Organization. CompactFlash Association.

Version 9.43                     November 2012                       HDPARM(8)