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Linux 2.6 - man page for hdparm (linux section 8)

HDPARM(8)										HDPARM(8)

       hdparm - get/set SATA/IDE device parameters

       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 Transla-
       tion) 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 ker-

       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.   Pos-
	      sible 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  man-
	      agement  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/dis-
	      able 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 trans-
	      fers 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

       -d     Get/set the "using_dma" flag for this drive.  This option now works with most  com-
	      binations 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 com-
	      bination 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 stands for Device Configuration Overlay, a way for vendors to selectively  dis-
	      able  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 settings which can be dis-
	      abled 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.

	      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.

	      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  buf-
	      fers,  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  immedi-
	      ately  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

       -D     Enable/disable  the  on-drive defect management feature, whereby the drive firmware
	      tries to automatically manage defective sectors by relocating them to "spare"  sec-
	      tors  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.

	      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 with-
	      out 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 param-
	      eter, 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 suf-
	      fers  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.

	      When  used,  this should be the only option given.  It requires a file path immedi-
	      ately 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 DOWN-
	      LOAD 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 --fwdown-
	      load-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  tem-
	      perature	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 obtain-
	      able 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  Inter-
	      face  for Disk Drives, ANSI ASC X3T9.2 working draft, revision 4a, April 19/93, and
	      later editions.

	      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.  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.

	      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

       -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 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  recov-
	      ery 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 remov-
	      able 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 mod-
	      ern 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  sys-
	      tems,  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 multi-
	      ple 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 set-
	      tings.  Under rare circumstances, such failures can result  in  massive  filesystem

	      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_UNCOR-
	      RECTABLE_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 sin-
	      gle 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 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 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 lev-
	      els (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  set-
	      ting.   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 operat-
	      ing 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  pro-
	      vided  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  ini-
	      tially,  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 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 sup-
	      port 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 offical spec as of ATA-4.

	      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. sec-
	      tor 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 combina-
	      tions 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.

	      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 mech-
	      anisms) 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).

	      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) time-
	      out 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 mean-
	      ingful results, this operation should be repeated 2-3 times on an  otherwise  inac-
	      tive 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 meaning-
	      ful  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 mem-
	      ory.  This displays the speed of reading directly from the Linux buffer cache with-
	      out disk access.	This measurement is essentially an indication of  the  throughput
	      of the processor, cache, and memory of the system under test.

	      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 immedi-
	      ate 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

	      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 con-
	      figured 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 (usu-
	      ally a BIOS/CMOS setting) provides a safe fix for the problem for use with  earlier

       -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     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.

	      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 combi-
	      nation 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 pre-
	      pare 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

       -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 mod-
	      els?), 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.

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

	      Freeze  the drive's security settings.  The drive does not accept any security com-
	      mands 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 stand-
	      alone, 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  per-
	      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 applicable secu-
	      rity  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-dis-
	      able, --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  use-
	      ful in combination with --security-set-pass.
		      h       high security
		      m       maximum security



       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, sev-
       eral 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  secu-
       rity  commands  however might indeed have been executed by the drive. This poor kernel be-
       haviour 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 sec-
       ond 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.

       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 subsys-
       tem, 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 Ben-
       jamin Benz and others.

       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.

Version 9.36				  November 2010 				HDPARM(8)

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