Provided by: hdparm_9.27-2ubuntu2_i386 bug

NAME

       hdparm - get/set SATA/IDE 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.  Many newer (2008 and later) USB drive enclosures
       now also support "SAT" (SCSI-ATA Command Translation) and therefore may
       also  work  with  hdparm.   Eg.  recent WD "Passport" models and recent
       NexStar-3 enclosures.  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
       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     Query/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.

       --dco-freeze
              DCO stands for Device Configuration Overlay, a way  for  vendors
              to  selectively disable certain features of a drive.  The --dco-
              freeze flag 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 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,  DONT  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  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 flags.

       --fallocate
              This flag currently works only on ext4 and xfs filesystem types.
              When  used,  this  must be the only flag 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.

              Eg. Create a 10KByte file: hdparm --fallocate 10 temp_file

       --fibmap
              When used, this must be the only flag 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  flag  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  file  systems,
              unless a sync() is done before using this flag.

       --fwdownload
              When  used,  this  should be the only flag given.  It requires a
              file path immediately after the flag, 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).

       -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 flag.  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.

       -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.

       --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.

       --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.   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.

       -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.

       --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 flag 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  (eg.  sector  accesses  beyond
              28-bits).

       -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     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.

       --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     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 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.

       --trim-sector-ranges
              For Solid State Drives (SSDs).  EXCEPTIONALLY DANGEROUS. DO  NOT
              USE  THIS  FLAG!!   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
              flag: an LBA starting address, a colon, and a sector count, with
              no intervening spaces.  EXCEPTIONALLY DANGEROUS. DO NOT USE THIS
              FLAG!!

              Eg.  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 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  (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.  No other flags 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.  No other flags are permitted on the command  line  with
              this one.  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.  Use the special password NULL to set  an  empty
              password.   The  applicable  drive password is selected with the
              --user-master switch and the applicable security mode  with  the
              --security-mode  switch.   No  other  flags are permitted on the
              command line with this one.  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.  No other flags are permitted on the command  line  with
              this one.  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.  Use the special password  NULL  to  represent  an  empty
              password.   The  applicable  drive password is selected with the
              --user-master switch.  No  other  flags  are  permitted  on  the
              command  line  with  this one.  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.  No other flags are permitted on the
              command line with this one.  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 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