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),
              with  fast  I/O  throughput and low CPU usage.  But there are at
              least a few configurations of chipsets and drives for which  DMA
              does not make much of a difference, or may even slow things down
              (on really messed up hardware!).  Your mileage may vary.

              DCO stands for Device Configuration Overlay, a way  for  vendors
              to  selectively disable certain features of a drive.  The --dco-
              freeze option will freeze/lock the current drive  configuration,
              thereby  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

              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).
              refer  to  AT  Attachment  Interface  for  Disk Drives, ANSI ASC
              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,
              Jazz..), and setting it to 0 will  unlock  the  door  mechanism.
              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
              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
              space  has  been  incorporated for future expansion, should this
              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.

              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
              mechanism.  Not all drives support  this  feature,  and  it  was
              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.

              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
              hours.   A  value  of  252  signifies a timeout of 21 minutes. A
              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!!

              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.

       -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.
              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.

              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
              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.


       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-

       Security freeze command by Benjamin Benz, 2005.

       PIO data out security commands by Leonard den Ottolander,  2005.   Some
       other parts by Benjamin Benz and others.

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

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

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

Version 9.36                     November 2010                       HDPARM(8)
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