hdparm

HDPARM(8)                   System Manager's Manual                  HDPARM(8)



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.



Version 9.58                     October 2018                        HDPARM(8)