Provided by: hdparm_8.6-1ubuntu1_i386 bug

NAME

       hdparm - get/set SATA/ATA device parameters

SYNOPSIS

       hdparm [ flags ] [device] ..

DESCRIPTION

       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.   Some options may work correctly only with the
       latest kernels.

OPTIONS

       When no flags are given, -acdgkmur is assumed.  For Get/Set options,  a
       query  without  an  optional  parameter (e.g., -d) will query (get) the
       drive state, and with a parameter (e.g., -d0) will set the drive 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     Set Advanced Power Management feature, if the drive supports it.
              A low value means aggressive power management and a  high  value
              means better performance.  Possible settings range from values 1
              through 127 (which permit spin-down), and values 128 through 254
              (which  do  not  permit spin-down).  The highest degree of power
              management is attained with a setting of 1, and the highest  I/O
              performance  with a setting of 254.  A value of 255 tells hdparm
              to disable Advanced Power Management  altogether  on  the  drive
              (not all drives support disabling it, but most do).

       -c     Query/enable (E)IDE 32-bit I/O support.  A numeric parameter can
              be  used  to  enable/disable  32-bit  I/O   support:   Currently
              supported  values  include 0 to disable 32-bit I/O support, 1 to
              enable 32-bit data  transfers,  and  3  to  enable  32-bit  data
              transfers   with  a  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
              completely shut down).  The -S, -y, -Y, and -Z flags can be used
              to manipulate the IDE power modes.

       -d     Disable/enable the "using_dma" flag for this drive.  This option
              now works with most combinations of drives  and  PCI  interfaces
              which  support DMA and which are known to the kernel IDE driver.
              It is also a good idea to  use  the  appropriate  -X  option  in
              combination  with  -d1  to  ensure  that  the  drive  itself  is
              programmed for the correct DMA mode, although most BIOSs  should
              do this for you at boot time.  Using DMA nearly always gives the
              best performance, with fast I/O throughput and  low  CPU  usage.
              But  there  are  at  least  a few configurations of chipsets and
              drives for which DMA does not make much of a difference, or  may
              even  slow  things  down  (on really messed up hardware!).  Your
              mileage may vary.

       --direct
              Use the kernel O_DIRECT flag when performing a -t  timing  test.
              This  bypasses  the page cache, causing the reads to go directly
              from the drive into hdparm’s buffers, using so-called "raw" I/O.
              In  many cases, this can produce results that appear much faster
              than the usual page cache method, giving a better indication  of
              raw device and driver performance.

       --drq-hsm-error
              VERY  DANGEROUS,  DON’T  EVEN  THINK  ABOUT USING IT.  This flag
              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.   Control of this feature via the -D flag is
              not supported for most modern  drives  since  ATA-4;  thus  this
              command may fail.

       -E     Set  cdrom  speed.  This is NOT necessary for regular operation,
              as the drive will automatically switch speeds on its  own.   But
              if  you  want  to play with it, just supply a speed number after
              the option, usually a number like 2 or 4.

       -f     Sync and flush the buffer cache for the device  on  exit.   This
              operation  is also performed internally as part of the -t and -T
              timings and other flags.

       -F     Flush the on-drive write cache  buffer  (older  drives  may  not
              implement this).

       -g     Display the drive geometry (cylinders, heads, sectors), the size
              (in sectors) of the device, and the starting offset (in sectors)
              of the device from the beginning of the drive.

       -h     Display terse usage information (help).

       -i     Display the identification info that was obtained from the drive
              at boot time, if available.  This is a  feature  of  modern  IDE
              drives,  and  may  not  be supported by older devices.  The data
              returned may or may not be current, depending on activity  since
              booting  the  system.  However, the current multiple sector mode
              count is always shown.  For a more  detailed  interpretation  of
              the  identification  info,  refer to AT Attachment Interface for
              Disk Drives (ANSI ASC X3T9.2 working draft, revision  4a,  April
              19/93).

       -I     Request  identification  info  directly from the drive, which is
              displayed in a new expanded format with considerably more detail
              than with the older -i flag.

       --Istdin
              This  is  a  special 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.

       --Istdout
              This option dumps the drive’s identify data in hex to stdout, in
              a format similar to that from /proc/ide/*/identify, and suitable
              for later use with the --Istdin option.

       -k     Get/set  the  keep_settings_over_reset flag for the drive.  When
              this flag is set, the driver will preserve the -dmu options over
              a  soft  reset,  (as  done  during the error recovery sequence).
              This flag defaults to off, to prevent drive  reset  loops  which
              could  be  caused by combinations of -dmu settings.  The -k flag
              should therefore only be set after one has  achieved  confidence
              in  correct  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
              systems).

       -K     Set the drive´s  keep_features_over_reset  flag.   Setting  this
              enables the drive to retain the settings for -APSWXZ over a soft
              reset (as done during the error  recovery  sequence).   Not  all
              drives support this feature.

       -L     Set  the drive´s doorlock flag.  Setting this to 1 will lock the
              door mechanism of some removable hard drives (eg. Syquest,  ZIP,
              Jazz..),  and  setting  it  to 0 will unlock the door mechanism.
              Normally,   Linux   maintains   the   door   locking   mechanism
              automatically,  depending  on  drive  usage  (locked  whenever a
              filesystem is mounted).  But on system shutdown, this can  be  a
              nuisance if the root 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
              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 Digital recommends lower settings of 4 to 8 on
              many  of  their  drives,  due tiny (32kB) drive buffers and non-
              optimized buffering algorithms.  The -i flag can be used to find
              the  maximum  setting  supported by an installed drive (look for
              MaxMultSect in  the  output).   Some  drives  claim  to  support
              multiple  mode,  but  lose  data  at  some settings.  Under rare
              circumstances, such failures can result  in  massive  filesystem
              corruption.

       --make-bad-sector
              Deliberately  create  a  bad  sector (aka. "media error") on the
              disk.  EXCEPTIONALLY DANGEROUS.  DO NOT USE  THIS  FLAG!!   This
              can   be  useful  for  testing  of  device/RAID  error  recovery
              mechanisms.  The sector number is given as a (base10)  parameter
              after the flag.  Depending on the device, hdparm will choose one
              of two possible ATA commands for  corrupting  the  sector.   The
              WRITE_LONG  works  on  most  drives,  but  only up to the 28-bit
              sector boundary.  Some very recent drives (2008) may support the
              new  WRITE_UNCORRECTABLE_EXT  command, which works for any LBA48
              sector.  If available, hdparm will use  that  in  preference  to
              WRITE_LONG.  The WRITE_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 several retries).  Note also that
              the  --repair-sector  flag  can  be  used  to  restore (any) bad
              sectors when they are no longer needed, including  sectors  that
              were genuinely bad (the drive will likely remap those to a fresh
              area on the media).

       -M     Get/set Automatic Acoustic Management (AAM) setting. Most modern
              harddisk  drives  have  the  ability  to  speed  down  the  head
              movements to reduce their noise output.  The possible values are
              between 0 and 254. 128 is the most quiet (and therefore slowest)
              setting and 254 the fastest (and loudest). Some drives have only
              two  levels  (quiet  /  fast),  while  others may have different
              levels between 128 and 254.  At the  moment,  most  drives  only
              support  3  options,  off,  quiet,  and  fast.   These have been
              assigned the values 0, 128, and 254  at  present,  respectively,
              but  integer  space  has been incorporated for future expansion,
              should this change.

       -N     Get/set max visible number of sectors, also known  as  the  Host
              Protected  Area  setting.   Without a parameter, -N displays the
              current setting, which is reported  as  two  values:  the  first
              gives  the current max sectors setting, and the second shows the
              native (real) hardware  limit  for  the  disk.   The  difference
              between  these two values indicates how many sectors of the disk
              are currently hidden from the operating system, in the form of a
              Host  Protected Area (HPA).  This area is often used by computer
              makers to  hold  diagnostic  software,  and/or  a  copy  of  the
              originally  provided operating system for recovery purposes.  To
              change the current max (VERY DANGEROUS, DATA LOSS  IS  EXTREMELY
              LIKELY),  a new value should be provided (in base10) immediately
              following the -N flag.  This value is specified as  a  count  of
              sectors,  rather  than  the  "max  sector address" of the drive.
              Drives have the concept of a temporary (volatile) setting  which
              is  lost on the next hardware reset, as well as a more permanent
              (non-volatile) value which survives resets and power cycles.  By
              default,  -N  affects only the temporary (volatile) setting.  To
              change the permanent (non-volatile) value, prepend a  leading  p
              character  immediately  before  the  first  digit  of the value.
              Drives are supposed to allow only a single permanent change  per
              session.   A  hardware reset (or power cycle) is required before
              another permanent -N  operation  can  succeed.   Note  that  any
              attempt to set this value may fail if the disk is being accessed
              by other software at the same time.  This is because setting the
              value  requires a pair of back-to-back drive commands, but there
              is no way to prevent some  other  command  from  being  inserted
              between  them by the kernel.  So if it fails initially, just try
              again.

       -n     Get or set the "ignore write errors" flag in the driver.  Do NOT
              play with this without grokking the driver source code first.

       -p     Attempt to reprogram the IDE interface chipset for the specified
              PIO mode, or attempt  to  auto-tune  for  the  "best"  PIO  mode
              supported by the drive.  This feature is supported in the kernel
              for only a few "known" chipsets, and even then  the  support  is
              iffy  at  best.   Some  IDE chipsets are unable to alter the PIO
              mode for a single drive, in which case this flag may  cause  the
              PIO  mode  for both drives to be set.  Many IDE chipsets support
              either fewer or more than the standard six (0 to 5)  PIO  modes,
              so  the  exact  speed  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.

       -q     Handle the next flag quietly, suppressing normal output (but not
              error messages).  This is useful  for  reducing  screen  clutter
              when running from system startup scripts.  Not applicable to the
              -i or -v or -t or -T flags.

       -Q     Set tagged queue depth (1 or greater), or  turn  tagged  queuing
              off  (0).   This  only  works  with  the newer 2.5.xx (or later)
              kernels, and only with the few drives that currently support it.

       -r     Get/set   read-only  flag  for  the  device.   When  set,  Linux
              disallows write operations on the device.

       --read-sector
              Reads from the specified sector number, and dumps  the  contents
              in  hex  to  standard  output.   The sector number must be given
              (base10) after this flag.  hdparm will issue  a  low-level  read
              (completely   bypassing   the   usual   block  layer  read/write
              mechanisms) for the specified  sector.   This  can  be  used  to
              definitively  check  whether a given sector is bad (media error)
              or not (doing so through the usual mechanisms can sometimes give
              false positives).

       --repair-sector
              This is an alias for the --write-sector flag.  VERY DANGEROUS.

       -R     Register  an  IDE  interface (DANGEROUS).  See the -U option for
              more information.

       -s     Enable/disable the power-on in standby feature, if supported  by
              the   drive.   VERY  DANGEROUS.   Do  not  use  unless  you  are
              absolutely certain that both the system BIOS (or  firmware)  and
              the  operating  system  kernel (Linux >= 2.6.22) support probing
              for drives that use this feature.  When enabled,  the  drive  is
              powered-up  in  the  standby  mode  to  allow  the controller to
              sequence the spin-up  of  devices,  reducing  the  instantaneous
              current  draw  burden  when  many  drives  share a power supply.
              Primarily for use in large RAID 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     Set the standby (spindown) timeout for the drive.  This value is
              used by the drive to determine how long to wait  (with  no  disk
              activity)  before  turning  off the spindle motor to save power.
              Under such circumstances, the drive  may  take  as  long  as  30
              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  cache  reads  for benchmark and comparison
              purposes.  For meaningful  results,  this  operation  should  be
              repeated  2-3  times  on  an otherwise inactive system (no other
              active processes) with at least a couple of  megabytes  of  free
              memory.   This  displays  the speed of reading directly from the
              Linux buffer cache without disk  access.   This  measurement  is
              essentially  an  indication  of the throughput of the processor,
              cache, and memory of the system under test.

       -t     Perform timings of device reads  for  benchmark  and  comparison
              purposes.   For  meaningful  results,  this  operation should be
              repeated 2-3 times on an otherwise  inactive  system  (no  other
              active  processes)  with  at least a couple of megabytes of free
              memory.  This 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 accurate measurements, the buffer cache  is
              flushed during the processing of -t using the BLKFLSBUF ioctl.

       -u     Get/set  interrupt-unmask  flag  for  the drive.  A setting of 1
              permits the driver to unmask other interrupts during  processing
              of   a   disk   interrupt,   which   greatly   improves  Linux´s
              responsiveness and eliminates "serial port overrun" errors.  Use
              this feature with caution: some drive/controller combinations do
              not tolerate the increased  I/O  latencies  possible  when  this
              feature  is enabled, resulting in massive filesystem corruption.
              In particular, CMD-640B and  RZ1000  (E)IDE  interfaces  can  be
              unreliable  (due  to  a  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.

       -U     Un-register an IDE interface (DANGEROUS).  The companion for the
              -R option.  Intended for use with hardware made specifically for
              hot-swapping  (very  rare!).   Use  with  knowledge  and extreme
              caution as this can easily hang  or  damage  your  system.   The
              hdparm  source  distribution includes a ´contrib´ directory with
              some user-donated scripts for hot-swapping on the UltraBay of  a
              ThinkPad 600E.  Use at your own risk.

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

       --verbose
              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.

       --write-sector
              Writes zeros to the specified sector  number.   VERY  DANGEROUS.
              The  sector  number  must  be  given  (base10)  after this flag.
              hdparm will issue a low-level write  (completely  bypassing  the
              usual  block  layer  read/write  mechanisms)  to  the  specified
              sector.  This can be used to force  a  drive  to  repair  a  bad
              sector (media error).

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

       -x     Tristate device for hotswap (DANGEROUS).

       -X     Set  the IDE transfer mode for newer (E)IDE/ATA drives.  This is
              typically used in combination with -d1 when enabling DMA to/from
              a drive on a supported interface chipset, where -X mdma2 is used
              to select multiword DMA mode2 transfers and -X sdma1 is used  to
              select  simple mode 1 DMA transfers.  With systems which support
              UltraDMA burst timings, -X udma2  is  used  to  select  UltraDMA
              mode2 transfers (you´ll need to prepare the chipset for UltraDMA
              beforehand).  Apart from  that,  use  of  this  flag  is  seldom
              necessary  since  most/all  modern  IDE  drives default to their
              fastest PIO transfer mode at power-on.  Fiddling with  this  can
              be  both  needless and risky.  On drives which support alternate
              transfer modes, -X can be used to switch the mode of  the  drive
              only.   Prior  to  changing the transfer mode, the IDE interface
              should be jumpered or programmed (see -p flag) for the new  mode
              setting  to  prevent  loss  and/or corruption of data.  Use this
              with extreme caution!  For  the  PIO  (Programmed  Input/Output)
              transfer  modes  used by Linux, this value is simply the desired
              PIO mode number plus 8.  Thus, a value of 09 sets PIO mode1,  10
              enables  PIO  mode2,  and  11  selects  PIO  mode3.   Setting 00
              restores the drive´s "default" PIO mode, and 01 disables  IORDY.
              For multiword DMA, the value used is the desired DMA mode number
              plus 32.  for UltraDMA, the value is the desired  UltraDMA  mode
              number plus 64.

       -y     Force   an   IDE  drive  to  immediately  enter  the  low  power
              consumption standby mode, usually causing it to spin down.   The
              current power mode status can be checked using the -C flag.

       -Y     Force  an  IDE  drive  to  immediately  enter  the  lowest power
              consumption sleep mode, causing it to shut down  completely.   A
              hard  or soft reset is required before the drive can be accessed
              again (the Linux IDE driver will automatically handle issuing  a
              reset  if/when  needed).   The  current power mode status can be
              checked using the -C flag.

       -z     Force a kernel re-read of the partition table of  the  specified
              device(s).

       -Z     Disable  the  automatic power-saving function of certain Seagate
              drives (ST3xxx models?), to prevent them  from  idling/spinning-
              down at inconvenient times.

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

       ATA Security Feature Set

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

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

       --security-freeze
              Freeze the drive´s security settings.  The drive does not accept
              any security commands  until  next  power-on  reset.   Use  this
              function  in combination with --security-unlock to protect drive
              from any attempt to set a new password. Can be used  standalone,
              too.

       --security-unlock PWD
              Unlock  the  drive, using password PWD.  Password is given as an
              ASCII string and is padded with NULs to  reach  32  bytes.   The
              applicable  drive  password  is  selected with the --user-master
              switch.  THIS FEATURE IS EXPERIMENTAL AND NOT WELL  TESTED.  USE
              AT YOUR OWN RISK.

       --security-set-pass PWD
              Lock  the  drive, using password PWD (Set Password) (DANGEROUS).
              Password is given as an ASCII string and is padded with NULs  to
              reach  32 bytes.  The applicable drive password is selected with
              the --user-master switch and the applicable security  mode  with
              the  --security-mode  switch.   THIS FEATURE IS EXPERIMENTAL AND
              NOT WELL TESTED. USE AT YOUR OWN RISK.

       --security-disable PWD
              Disable drive locking, using password PWD.  Password is given as
              an  ASCII string and is padded with NULs to reach 32 bytes.  The
              applicable drive password is  selected  with  the  --user-master
              switch.   THIS  FEATURE IS EXPERIMENTAL AND NOT WELL TESTED. USE
              AT YOUR OWN RISK.

       --security-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.  The applicable  drive  password  is  selected  with  the
              --user-master switch.  THIS FEATURE IS EXPERIMENTAL AND NOT WELL
              TESTED. USE AT YOUR OWN RISK.

       --security-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.  THIS FEATURE IS EXPERIMENTAL AND NOT
              WELL TESTED. USE AT YOUR OWN RISK.

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

              THIS  FEATURE  IS  EXPERIMENTAL AND NOT WELL TESTED. USE AT YOUR
              OWN RISK.

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

              THIS  FEATURE  IS  EXPERIMENTAL AND NOT WELL TESTED. USE AT YOUR
              OWN RISK.

FILES

       /etc/hdparm.conf

BUGS

       As noted above, the -m sectcount and -u 1 options should be  used  with
       caution  at  first,  preferably on a read-only filesystem.  Most drives
       work well with these features, but a few drive/controller  combinations
       are  not  100%  compatible.   Filesystem corruption may result.  Backup
       everything before experimenting!

       Some options (eg. -r for  SCSI)  may  not  work  with  old  kernels  as
       necessary ioctl()´s were not supported.

       Although  this  utility  is intended primarily for use with (E)IDE hard
       disk devices, several of the options are also valid (and permitted) for
       use  with  SCSI  hard  disk  devices  and  MFM/RLL  hard  disks with XT
       interfaces.

       The Linux kernel up until 2.6.12 (and probably  later)  doesn´t  handle
       the  security  unlock and disable commands gracefully and will segfault
       and in some cases even  panic.  The  security  commands  however  might
       indeed  have  been  executed  by  the drive. This poor kernel behaviour
       makes the PIO data security commands rather useless at the moment.

       Note that the "security erase" and  "security  disable"  commands  have
       been  implemented  as  two  consecutive  PIO data commands and will not
       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.

AUTHOR

       hdparm has been written by Mark Lord  <mlord@pobox.com>,  the  original
       primary  developer  and maintainer of the (E)IDE driver for Linux, with
       suggestions from many netfolk.

       The  disable  Seagate  auto-powersaving  code  is  courtesy   of   Tomi
       Leppikangas(tomilepp@paju.oulu.fi).

       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

       http://www.t13.org/ Technical Committee T13 AT  Attachment  (ATA/ATAPI)
       Interface.

       http://www.serialata.org/ Serial ATA International Organization.

       http://www.compactflash.org/ CompactFlash Association