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 kernels.

       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 (enable).

       -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 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     Get/set (E)IDE 32-bit I/O support.  A numeric parameter  can  be
              used  to enable/disable 32-bit I/O support.  Currently supported
              values include 0 to disable 32-bit  I/O  support,  1  to  enable
              32-bit  data  transfers,  and  3 to enable 32-bit data transfers
              with a special sync sequence required  by  many  chipsets.   The
              value  3  works  with nearly all 32-bit IDE chipsets, but incurs
              slightly more overhead.   Note  that  "32-bit"  refers  to  data
              transfers  across  a  PCI or VLB bus to the interface card only;
              all (E)IDE drives still have only a 16-bit connection  over  the
              ribbon cable from the interface card.

       -C     Check  the  current  IDE power mode status, which will always be
              one  of  unknown  (drive  does  not   support   this   command),
              active/idle  (normal  operation), standby (low power mode, drive
              has spun down), or sleeping (lowest power mode,  drive  is  com-
              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  preventing  software (or malware) from changing any DCO
              settings until after the next power-on reset.

              Query and dump information regarding  drive  configuration  set-
              tings  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 dis-
              abled, 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-iden-
              tify 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

              Use the kernel's "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 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 imme-
              diately 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 sec-
              tors by relocating them to "spare" sectors reserved by the  fac-
              tory for such.  Control of this feature via the -D option is not
              supported for most modern drives since ATA-4; thus this  command
              may fail.
              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 sec-
              tor 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 cor-
              rupt during 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  interface,  and  thus not work beyond 8TB or 16TB.
              FIBMAP is also very slow, and does not deal well  with  preallo-
              cated  uncommitted  extents  in  ext4/xfs  filesystems, unless a
              sync() is done before using this option.

              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 COM-
              MAND.  The --fwdownload-mode3  ,  --fwdownload-mode3-max  ,  and
              --fwdownload-mode7  variations on basic --fwdownload allow over-
              riding 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

              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.  Usu-
              ally 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 failure, not to mention the performance  impact  of
              the drive often having to wake-up before doing routine I/O.

              WD  supply  a WDIDLE3.EXE DOS utility for tweaking this setting,
              and you should use that program instead of hdparm if at all pos-
              sible.   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 things.

              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     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 (e.g. 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 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  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 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 corruption.

              Deliberately  create  a  bad  sector (aka. "media error") on the
              can  be  useful for testing of device/RAID error recovery mecha-
              nisms.  The sector number 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 sec-
              tor 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_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

       -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

       -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 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 diagnostic software, and/or a copy of the origi-
              nally 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 tem-
              porary (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.

              PIO  mode  for both drives to be set.  Many IDE chipsets support
              either fewer or more than the standard six (0 to 5)  PIO  modes,
              so  the  exact  speed  setting that is actually implemented will
              vary by chipset/driver sophistication.  Use  with  extreme  cau-
              tion!  This feature includes zero protection for the unwary, and
              an unsuccessful outcome may result in severe filesystem  corrup-

       -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 official spec as of ATA-4.

              When  using the SAT (SCSI ATA Translation) protocol, hdparm nor-
              mally prefers to use the 16-byte command format whenever  possi-
              ble.   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. sector 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  disal-
              lows 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  bypassing  the  usual block layer read/write mecha-
              nisms) 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

              This is an alias for the --write-sector option.  VERY DANGEROUS.
              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  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 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 mea-
              surement is an indication of how  fast  the  drive  can  sustain
              sequential  data reads under Linux, without any filesystem over-
              head.  To ensure accurate  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 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,
              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  DANGER-
              OUS. DO NOT USE THIS OPTION!!

              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.

       -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 sec-
              tor.  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     Set  the IDE transfer mode for (E)IDE/ATA drives.  This is typi-
              cally 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 option is seldom nec-
              essary 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  multi-
              word DMA, the value used is the desired DMA mode number plus 32.
              using the -C option.

       -z     Force a kernel re-read of the partition table of  the  specified

       -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 func-
              tion 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

       --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  per-
              mitted 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 appli-
              cable 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  per-
              mitted 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
              unlock,  --security-set-pass,  --security-disable,   --security-
              erase or --security-erase-enhanced.
                      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 --security-set-pass.
                      h       high security
                      m       maximum security

              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 (e.g. -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 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  inter-

       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 necessary  com-
       mands that way.

       hdparm  has  been  written by Mark Lord <mlord@pobox.com>, the original
       primary developer and maintainer of the (E)IDE driver  for  Linux,  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 Leppikan-
       http://www.compactflash.org/ CompactFlash Association.

Version 9.48                       June 2015                         HDPARM(8)
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