focal (8) hdparm.8.gz

Provided by: hdparm_9.58+ds-4_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.

       --Iraw <pathname>
              This option dumps the drive's identify data in raw binary to the specified file.

       --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.

       --set-sector-size
              For  drives  which  support  reconfiguring  of  the  Logical Sector Size, this flag can be used to
              specify the new desired sector size in bytes.  VERY DANGEROUS. This most likely will scramble  all
              data  on  the  drive.  The specified size must be one of 512, 520, 528, 4096, 4160, or 4224.  Very
              few drives support values other than 512 and 4096.

       -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-prompt-for-password
              Prompt for the --security PWD rather than getting from the command line args.  This avoids  having
              passwords show up in shell history or in /proc/self/cmdline during execution.

       --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 contributor 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.