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           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
                  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  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-
                  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.
                  X3T9.2 working draft, revision 4a, April 19/93, and  later  edi-
                  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.
           -k     Get/set the "keep_settings_over_reset" flag for the drive.  When
                  this flag is set, the drive will preserve 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/adm/messages on  most
           -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,
                  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
                  disk.  EXCEPTIONALLY DANGEROUS. DO NOT USE THIS  OPTION!!   This
                  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
                  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 imme-
                  diately (rather than after several 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 gen-
                  uinely 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 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
                  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.
                  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 begin-
                  ning, 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  sup-
                  ported  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  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
                  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.
                  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.
           -s     Enable/disable  the power-on in standby feature, if supported by
                  the drive.  VERY DANGEROUS.  Do not use  unless  you  are  abso-
                  lutely  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 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  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
                  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!!
                  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 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 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  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.
                  Display extra diagnostics from some commands.
           -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.
                  for UltraDMA, the value is the desired UltraDMA mode number plus
           -y     Force  an  IDE drive to immediately enter the low power consump-
                  tion 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 con-
                  sumption sleep mode, causing it to shut down completely.  A hard
                  or soft reset is required before the drive can be accessed again
                  (the Linux IDE driver will automatically handle issuing a  reset
                  if/when  needed).   The current power mode status can be checked
                  using the -C 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.
           --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
                  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  combination with --security-
                  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.


           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 <>, 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-
           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.


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

    Version 9.36 November 2010 HDPARM(8)


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