HDPARM(8)                (November 2020)                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 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.

          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 sequen-
               tial reads of large files, by prefetching additional
               blocks in anticipation of them being needed by the run-
               ning 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 manage-
               ment and a high value means better performance.  Possi-
               ble 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 Manage-
               ment 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.

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               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

          -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 cor-
               rect 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 disable certain features of a
               drive.  The --dco-freeze option will freeze/lock the
               current drive configuration, thereby preventing soft-
               ware (or malware) from changing any DCO settings until
               after the next power-on reset.

               Query and dump information regarding drive configura-
               tion 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 oth-
               erwise hidden and will not show in the -I identify out-
               put.  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

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               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 capabili-
               ties.  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
               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.

               VERY DANGEROUS, DON'T EVEN THINK ABOUT This option
               causes hdparm to issue an IDENTIFY command to the ker-
               nel, 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

          -D   Enable/disable the on-drive defect management feature,
               whereby the drive firmware tries to automatically man-
               age 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

          -E   Set cd/dvd drive speed.  This is NOT necessary for reg-
               ular 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.


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               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 kibibytes (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 10 kibibyte file: hdparm --fallocate 10

               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 abso-
               lute LBA numbers, referenced from sector 0 of the phys-
               ical device rather than from the partition or filesys-
               tem.  This information can then be used for a variety
               of purposes, such as examining the degree of fragmenta-
               tion of larger files, or determining appropriate sec-
               tors 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 8 TB or 16 TB.  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 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 (seg-
               mented 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 varia-
               tions 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

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               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 cur-
               rent 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, revi-
               sion 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

               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 con-
               siderably 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.

               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 varia-
               tion is designed for use with collected "libraries" of
               drive identification information, and can also be used

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               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 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 consump-
               tion state.  The factory default is eight (8) seconds,
               which is a very poor choice for use with Linux.  Leav-
               ing it at the default will result in hundreds of thou-
               sands 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 perfor-
               mance 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 com-
               pletely (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 con-
               figuration settings.  In practice, all that is typi-
               cally 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 sys-

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          -K   Set the drive's "keep_features_over_reset" flag.  Set-
               ting 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 fea-

          -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 mul-
               tiple 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 30en50%.  On many systems, it also pro-
               vides 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 set-
               ting of 16 or 32 seems optimal on many systems.  West-
               ern Digital recommends lower settings of 4 to 8 on many
               of their drives, due tiny (32 KiB) 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.

               Deliberately create a bad sector (aka. "media error")
               on the disk.  EXCEPTIONALLY DANGEROUS. DO NOT USE THIS
               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 com-
               mands for corrupting the sector.  The WRITE_LONG works
               on most drives, but only up to the 28-bit sector

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               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 sub-
               sequent READs of the sector.  However, if a single let-
               ter 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 sec-
               tor 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) hard-
               ware 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

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               (e.g., most current {2010} BIOSs cannot deal with
               drives larger than 2 TB, so an HPA could be used to
               cause a 3 TB drive to report itself as a 2 TB 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 immedi-
               ately 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.

               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" chip-
               sets, 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 unsuc-
               cessful outcome may result in severe filesystem

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

               When using the SAT (SCSI ATA Translation) protocol,
               hdparm normally prefers to use the 16-byte command for-
               mat 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 out-
               put (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 sup-
               ported 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 sup-
               ports it.  Usage: -R0 (disable) or -R1 (enable).  This
               feature is intended to have the drive firmware automat-
               ically 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).

               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

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               This is an alias for the --write-sector option.  VERY

          -s   Enable/disable the power-on in standby feature, if sup-
               ported 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 fea-
               ture.  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 circum-
               stances, 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.

               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 The specified size must be one of 512,
               520, 528, 4096, 4160, or 4224.  Very few drives support
               values other than 512 and 4096.  Eg.  hdparm --set-
               sector-size 4096 /dev/sdb

          -t   Perform timings of device reads for benchmark and

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               comparison purposes.  For meaningful results, this
               operation should be repeated 2en3 times on an otherwise
               inactive system (no other active processes) with at
               least a couple of megabytes of free memory.  This dis-
               plays the speed of reading through the buffer cache to
               the disk without any prior caching of data.  This mea-
               surement 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 com-
               parison purposes.  For meaningful results, this opera-
               tion should be repeated 2en3 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 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.

               For Solid State Drives (SSDs).  EXCEPTIONALLY
               DANGEROUS. DO NOT USE THIS 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.

               E.g., hdparm --trim-sector-ranges 1000:4 7894:16

               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 inter-
               rupts during processing of a disk interrupt, which
               greatly improves Linux's responsiveness and eliminates
               "serial port overrun" errors.  Use this feature with

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               caution: some drive/controller combinations do not tol-
               erate 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 ker-

          -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.

               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 DAN-
               GEROUS.  The sector number must be given (base10) after
               this option.  hdparm will issue a low-level write (com-
               pletely 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

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               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 dis-
               ables 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.

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

               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.

               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 dur-
               ing execution.

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          --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-
                       u       user password
                       m       master password

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          --security-mode MODE
               Specifies which security mode (high/maximum) to set.
               Defaults to high. Only useful in combination with
                       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

          Some options (e.g., -r for SCSI) may not work with old ker-
          nels 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 exe-
          cuted 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" com-
          mands have been implemented as two consecutive PIO data com-
          mands 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 neces-
          sary 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 contributor to the libata sub-
          system, along with suggestions and patches from many net-

          The disable Seagate auto-powersaving code is courtesy of

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          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.

          http://www.t13.org/ Technical Committee T13 AT Attachment
          (ATA/ATAPI) Interface.

          http://www.serialata.org/ Serial ATA International Organiza-

          http://www.compactflash.org/ CompactFlash Association.

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