Provided by: hdparm_9.48+ds-1_amd64 bug

NAME

       hdparm - get/set SATA/IDE device parameters

SYNOPSIS

       hdparm [options] [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.   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.

OPTIONS

       When no options are given, -acdgkmur is assumed.  For "Get/set" options, a  query  without
       the  optional  parameter (e.g. -d) will query (get) the device state, and with a parameter
       (e.g., -d0) will set the device state.

       -a     Get/set sector count for filesystem (software) read-ahead.  This is used to improve
              performance in sequential reads of large files, by prefetching additional blocks in
              anticipation of them being needed by the running task.  Many IDE drives also have a
              separate  built-in  read-ahead  function, which augments this filesystem (software)
              read-ahead function.

       -A     Get/set the IDE drive´s read-lookahead feature (usually ON by default).  Usage: -A0
              (disable) or -A1 (enable).

       -b     Get/set bus state.

       -B     Get/set  Advanced  Power  Management feature, if the drive supports it. A low value
              means aggressive power management  and  a  high  value  means  better  performance.
              Possible  settings  range  from  values 1 through 127 (which permit spin-down), and
              values 128 through 254 (which do not permit  spin-down).   The  highest  degree  of
              power  management  is attained with a setting of 1, and the highest I/O performance
              with a setting of 254.  A value of 255  tells  hdparm  to  disable  Advanced  Power
              Management  altogether  on the drive (not all drives support disabling it, but most
              do).

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

       -C     Check the current IDE power mode status, which will always be one of unknown (drive
              does not support this command), active/idle (normal operation), standby (low  power
              mode,  drive  has  spun  down), or sleeping (lowest power mode, drive is completely
              shut down).  The -S, -y, -Y, and -Z options can be used to manipulate the IDE power
              modes.

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

       --dco-freeze
              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.

       --dco-identify
              Query and dump information regarding drive  configuration  settings  which  can  be
              disabled  by  the vendor or OEM installer.  These settings show capabilities of the
              drive which might be disabled by the vendor  for  "enhanced  compatibility".   When
              disabled,  they  are  otherwise hidden and will not show in the -I identify output.
              For example, system vendors sometimes disable 48_bit addressing  on  large  drives,
              for  compatibility  (and  loss  of  capacity) with a specific BIOS.  In such cases,
              --dco-identify will show that the drive is 48_bit capable, but -I will not show it,
              and nor will the drive accept 48_bit commands.

       --dco-restore
              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 COMMAND.

       --direct
              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.

       --drq-hsm-error
              VERY DANGEROUS, DON'T EVEN THINK ABOUT USING IT.   This  option  causes  hdparm  to
              issue  an  IDENTIFY  command  to the kernel, but incorrectly marked as a "non-data"
              command.  This results in the  drive  being  left  with  its  DataReQust(DRQ)  line
              "stuck"  high.   This  confuses  the  kernel  drivers,  and  may  crash  the system
              immediately with massive data loss.  The option  exists  to  help  in  testing  and
              fortifying   the  kernel  against  similar  real-world  drive  malfunctions.   VERY
              DANGEROUS, DO NOT USE!!

       -D     Enable/disable the on-drive defect management feature, whereby the  drive  firmware
              tries  to  automatically  manage  defective  sectors  by relocating them to "spare"
              sectors reserved by the factory for such.  Control  of  this  feature  via  the  -D
              option  is  not supported for most modern drives since ATA-4; thus this command may
              fail.

       -E     Set cd/dvd drive speed.  This is NOT necessary for regular operation, as the  drive
              will automatically switch speeds on its own.  But if you want to play with it, just
              supply a speed number after the option, usually a number like 2 or 4.  This can  be
              useful in some cases, though, to smooth out DVD video playback.

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

       --fallocate
              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

       --fibmap
              When  used,  this  must  be  the  only  option given.  It requires a file path as a
              parameter, and will print out a list of the block extents (sector ranges)  occupied
              by that file on disk.  Sector numbers are given as absolute LBA numbers, referenced
              from sector 0 of the physical device rather than from the partition or  filesystem.
              This  information can then be used for a variety of purposes, such as examining the
              degree of fragmenation of larger  files,  or  determining  appropriate  sectors  to
              deliberately corrupt 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  preallocated  uncommitted
              extents in ext4/xfs filesystems, unless a sync() is done before using this option.

       --fwdownload
              When  used,  this  should  be  the  only  option  given.   It  requires a file path
              immediately after the option, indicating where the new  drive  firmware  should  be
              read  from.   The  contents of this file will be sent to the drive using the (S)ATA
              DOWNLOAD MICROCODE command, using either transfer protocol 7 (entire file at once),
              or,  if  the  drive  supports  it,  transfer protocol 3 (segmented download).  This
              command is EXTREMELY DANGEROUS and could destroy both the drive and all data on it.
              DO  NOT  USE  THIS  COMMAND.  The --fwdownload-mode3 , --fwdownload-mode3-max , and
              --fwdownload-mode7 variations on  basic  --fwdownload  allow  overriding  automatic
              protocol detection in favour of forcing hdparm to use a specific transfer protocol,
              for testing purposes only.

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

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

       -h     Display terse usage information (help).

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

       -i     Display the identification info which the kernel drivers (IDE, libata) have  stored
              from  boot/configuration  time.   This  may  differ  from  the  current information
              obtainable directly from the drive itself with the -I option.   The  data  returned
              may  or  may not be current, depending on activity since booting the system.  For a
              more detailed interpretation of the identification info,  refer  to  AT  Attachment
              Interface for Disk Drives, ANSI ASC X3T9.2 working draft, revision 4a, April 19/93,
              and later editions.

       --idle-immediate
              Issue an ATA IDLE_IMMEDIATE command, to put the drive into  a  lower  power  state.
              Usually the device remains spun-up.

       --idle-unload
              Issue  an  ATA  IDLE_IMMEDIATE_WITH_UNLOAD command, to unload or park the heads and
              put the drive into a lower power state.  Usually the device remains spun-up.

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

       --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.

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

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

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

       -k     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/log/messages on most systems).

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

       -L     Set  the  drive´s doorlock flag.  Setting this to 1 will lock the door mechanism of
              some removable hard drives (e.g. Syquest, ZIP, Jazz..), and setting it  to  0  will
              unlock  the  door  mechanism.  Normally, Linux maintains the door locking mechanism
              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  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.

       --make-bad-sector
              Deliberately create a bad sector (aka. "media error") on the  disk.   EXCEPTIONALLY
              DANGEROUS.  DO NOT USE THIS OPTION!!  This can be useful for testing of device/RAID
              error recovery mechanisms.  The sector 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 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 option can be used to restore (any) bad sectors  when  they  are  no  longer
              needed,  including  sectors  that  were  genuinely bad (the drive will likely remap
              those to a fresh area on the media).

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

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

       -N     Get/set max visible number of sectors,  also  known  as  the  Host  Protected  Area
              setting.   Without  a 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.  Another possible use
              is to hide the true capacity of a very large disk from a  BIOS/system  that  cannot
              normally  cope  with drives of that size (eg. most current {2010} BIOSs cannot deal
              with drives larger than 2TB, so an HPA could be used to cause a 3TB drive to report
              itself  as  a  2TB drive).  To change the current max (VERY DANGEROUS, DATA LOSS IS
              EXTREMELY LIKELY), a new value should be provided (in base10) immediately following
              the -N option.  This value is specified as a count of sectors, rather than the "max
              sector address" of the drive.  Drives have the concept of  a  temporary  (volatile)
              setting which is lost on the next hardware reset, as well as a more permanent (non-
              volatile) value which survives resets and power cycles.   By  default,  -N  affects
              only  the  temporary  (volatile)  setting.   To change the 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.

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

       -p     Attempt  to  reprogram  the  IDE  interface  chipset for the specified PIO mode, or
              attempt to auto-tune for the "best" PIO mode supported by the drive.  This  feature
              is  supported  in  the  kernel  for  only a few "known" chipsets, and even then the
              support is iffy at best.  Some IDE chipsets are unable to alter the PIO mode for  a
              single  drive,  in which case this option may cause the PIO mode for both drives to
              be set.  Many IDE chipsets support either fewer or more than the standard six (0 to
              5)  PIO modes, so the exact speed setting that is actually implemented will vary by
              chipset/driver sophistication.  Use with extreme caution!   This  feature  includes
              zero  protection  for  the unwary, and an unsuccessful outcome may result in severe
              filesystem corruption!

       -P     Set the maximum sector count for the drive´s internal prefetch mechanism.  Not  all
              drives support this feature, and it was dropped from the official spec as of ATA-4.

       --prefer-ata12
              When  using the SAT (SCSI ATA Translation) protocol, hdparm normally prefers to use
              the 16-byte command format whenever possible.  But some USB drive enclosures  don't
              work  correctly with 16-byte commands.  This option can be used to force use of the
              smaller 12-byte command format with such  drives.   hdparm  will  still  revert  to
              16-byte  commands  for  things  that  cannot  be done with the 12-byte format (e.g.
              sector accesses beyond 28-bits).

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

       -Q     Get or set the device's command queue_depth, if supported by  the  hardware.   This
              only  works  with  2.6.xx  (or  later)  kernels,  and  only  with device and driver
              combinations which support changing the queue_depth.  For SATA disks, this  is  the
              Native Command Queuing (NCQ) queue depth.

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

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

       --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 option.  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 option.  VERY DANGEROUS.

       -s     Enable/disable  the  power-on  in standby feature, if supported by the drive.  VERY
              DANGEROUS.  Do not use unless you are absolutely certain that both the system  BIOS
              (or firmware) and the operating system 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     Put  the  drive  into  idle  (low-power)  mode, and also set the standby (spindown)
              timeout for the drive.  This timeout value is used by the drive  to  determine  how
              long  to  wait (with no disk activity) before turning off the spindle motor to save
              power.  Under such circumstances, the drive may take  as  long  as  30  seconds  to
              respond  to  a  subsequent  disk  access, though most drives are much quicker.  The
              encoding of the timeout  value  is  somewhat  peculiar.   A  value  of  zero  means
              "timeouts  are  disabled":  the  device  will not automatically enter standby mode.
              Values from 1 to 240 specify multiples of  5  seconds,  yielding  timeouts  from  5
              seconds  to  20  minutes.   Values from 241 to 251 specify from 1 to 11 units of 30
              minutes, yielding timeouts from 30 minutes to 5.5 hours.  A value of 252  signifies
              a  timeout  of  21  minutes.  A  value  of 253 sets a vendor-defined timeout period
              between 8 and 12 hours, and the value 254 is reserved.  255 is  interpreted  as  21
              minutes  plus  15  seconds.   Note  that  some older drives may have very different
              interpretations of these values.

       -t     Perform timings of  device  reads  for  benchmark  and  comparison  purposes.   For
              meaningful  results,  this  operation  should be repeated 2-3 times on an otherwise
              inactive system (no other active processes) with at least a couple of megabytes  of
              free  memory.   This  displays the speed of reading through the buffer cache to the
              disk without any prior caching of data.  This measurement is an indication  of  how
              fast  the  drive  can  sustain  sequential  data  reads  under  Linux,  without any
              filesystem overhead.  To ensure 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  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.

       --trim-sector-ranges
              For Solid State Drives (SSDs).  EXCEPTIONALLY DANGEROUS. DO NOT USE  THIS  OPTION!!
              Tells the drive firmware to discard unneeded data sectors, destroying any data that
              may have been  present  within  them.   This  makes  those  sectors  available  for
              immediate use by the firmware's garbage collection mechanism, to improve scheduling
              for wear-leveling of the flash media.  This option expects one or more sector range
              pairs  immediately after the option: an LBA starting address, a colon, and a sector
              count (max 65535), with no intervening spaces.  EXCEPTIONALLY DANGEROUS. DO NOT USE
              THIS OPTION!!

              E.g.  hdparm --trim-sector-ranges 1000:4 7894:16 /dev/sdz

       --trim-sector-ranges-stdin
              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  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.

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

       -V     Display program version and exit immediately.

       --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 option.  hdparm  will  issue  a  low-level  write
              (completely bypassing the usual block layer read/write mechanisms) to the specified
              sector.  This can be used to force a drive to repair a bad sector (media error).

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

       -X     Set the IDE transfer mode  for  (E)IDE/ATA  drives.   This  is  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
              option is seldom necessary since  most/all  modern  IDE  drives  default  to  their
              fastest PIO transfer mode at power-on.  Fiddling with this can be both needless and
              risky.  On drives which support alternate transfer modes, -X can be used to  switch
              the mode of the drive only.  Prior to changing the transfer mode, the IDE interface
              should be jumpered or programmed (see -p  option)  for  the  new  mode  setting  to
              prevent  loss  and/or  corruption of data.  Use this with extreme caution!  For the
              PIO (Programmed Input/Output) transfer modes used by Linux, this  value  is  simply
              the desired PIO mode number plus 8.  Thus, a value of 09 sets PIO mode1, 10 enables
              PIO mode2, and 11 selects PIO mode3.  Setting 00 restores the drive´s "default" PIO
              mode,  and 01 disables IORDY.  For multiword DMA, the value used is the desired DMA
              mode number plus 32.  for 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 option.

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

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

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

       ATA Security Feature Set

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

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

       --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.  No other options are permitted on the command line with this
              one.

       --security-unlock PWD
              Unlock  the drive, using password PWD.  Password is given as an ASCII string and is
              padded with NULs to reach 32 bytes.  The applicable drive password is selected with
              the  --user-master  switch  (default  is  "user"  password).   No other options are
              permitted on the command line with this one.

       --security-set-pass PWD
              Lock the drive, using password PWD (Set Password) (DANGEROUS).  Password  is  given
              as  an  ASCII  string  and  is padded with NULs to reach 32 bytes.  Use the special
              password NULL to set an empty password.  The applicable drive password is  selected
              with  the  --user-master  switch  (default  is  "user" password) and the applicable
              security mode with the --security-mode switch.  No other options are  permitted  on
              the command line with this one.

       --security-disable PWD
              Disable  drive  locking,  using password PWD.  Password is given as an ASCII string
              and is padded with NULs to reach  32  bytes.   The  applicable  drive  password  is
              selected  with  the  --user-master  switch  (default is "user" password).  No other
              options are permitted on the command line with this one.

       --security-erase PWD
              Erase (locked) drive, using password PWD (DANGEROUS).   Password  is  given  as  an
              ASCII  string  and is padded with NULs to reach 32 bytes.  Use the special password
              NULL to represent an empty password.  The applicable  drive  password  is  selected
              with  the  --user-master switch (default is "user" password).  No other options are
              permitted on the command line with this one.

       --security-erase-enhanced PWD
              Enhanced erase (locked) drive, using password PWD (DANGEROUS).  Password  is  given
              as an ASCII string and is padded with NULs to reach 32 bytes.  The applicable drive
              password is selected with the --user-master switch (default  is  "user"  password).
              No other options are permitted on the command line with this one.

       --user-master USER
              Specifies which password (user/master) to select.  Defaults to user password.  Only
              useful in  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

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

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

       The Linux kernel up until 2.6.12 (and probably later) doesn´t handle the  security  unlock
       and  disable  commands  gracefully  and  will  segfault  and in some cases even panic. The
       security commands however might indeed have been executed by the drive. This  poor  kernel
       behaviour makes the PIO data security commands rather useless at the 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,  and  current  contributer  to  the  libata
       subsystem, along with suggestions and patches from many netfolk.

       The     disable     Seagate     auto-powersaving     code     is    courtesy    of    Tomi
       Leppikangas(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.