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MT(1)                   FreeBSD General Commands Manual                  MT(1)

     mt - magnetic tape manipulating program

     mt [-f tapename] command [count]
     mt [-f tapename] command argument

     The mt utility is used to command a magnetic tape drive for operations
     other than reading or writing data.

     The -f option's tapename overrides the TAPE environment variable
     described below.

     The available commands are listed below.  Only as many characters as are
     required to uniquely identify a command need be specified.

     The following commands optionally take a count, which defaults to 1.

     weof       Write count end-of-file (EOF) marks at the current position.

     smk        Write count setmarks at the current position (DDS drives

     fsf        Forward space count files.

     fsr        Forward space count records.

     fss        Forward space count setmarks (DDS drives only).

     bsf        Backward space count files.

     bsr        Backward space count records.

     bss        Backward space count setmarks (DDS drives only).

     erase      Erase the tape using a long (often very long) method.  With a
                count of 0, it will erase the tape using a quick method.
                Operation is not guaranteed if the tape is not at its
                beginning.  The tape will be at its beginning upon completion.

     The following commands ignore count.

     rdhpos           Read the hardware block position.  The block number
                      reported is specific for that hardware only.  With drive
                      data compression especially, this position may have more
                      to do with the amount of data sent to the drive than the
                      amount of data written to tape.  Some drives do not
                      support this.

     rdspos           Read the SCSI logical block position.  This typically is
                      greater than the hardware position by the number of end-
                      of-file marks.  Some drives do not support this.

     rewind           Rewind the tape.

     offline, rewoffl
                      Rewind the tape and place the drive off line.  Some
                      drives are never off line.

     retension        Re-tension the tape.  This winds the tape from the
                      current position to the end and then to the beginning.
                      This sometimes improves subsequent reading and writing,
                      particularly for streaming drives.  Some drives do not
                      support this.

     status           Output status information about the drive.  For SCSI
                      magnetic tape devices, the current operating modes of
                      density, blocksize, and whether compression is enabled
                      is reported.  The current state of the driver (what it
                      thinks that it is doing with the device) is reported.
                      If the driver knows the relative position from BOT (in
                      terms of filemarks and records), it outputs that.  Note
                      that this information is not definitive (only BOT, End
                      of Recorded Media, and hardware or SCSI logical block
                      position (if the drive supports such) are considered
                      definitive tape positions).

     errstat          Output (and clear) error status information about this
                      device.  For every normal operation (e.g., a read or a
                      write) and every control operation (e.g,, a rewind), the
                      driver stores up the last command executed and it is
                      associated status and any residual counts (if any).
                      This command retrieves and outputs this information.  If
                      possible, this also clears any latched error

     geteotmodel      Output the current EOT filemark model.  The model states
                      how many filemarks will be written at close if a tape
                      was being written.

     eod, eom         Wind the tape to the end of the recorded data, typically
                      after an EOF mark where another file may be written.

     The following commands require an argument.

     sethpos          Set the hardware block position.  The argument is a
                      hardware block number to which to position the tape.
                      Some drives do not support this.

     setspos          Set the SCSI logical block position.  The argument is a
                      SCSI logical block number to which to position the tape.
                      Some drives do not support this.

     blocksize        Set the block size for the drive.  The argument is the
                      number of bytes per block, except 0 commands the drive
                      to use variable-length blocks.

     seteotmodel      Set the EOT filemark model to argument and output the
                      old and new models.  Typically this will be 2 filemarks,
                      but some devices (typically QIC cartridge drives) can
                      only write 1 filemark.  You may only choose a value of 1
                      or 2.

     comp             Set the drive's compression mode.  The non-numeric
                      values of argument are:

                      off        Turn compression off.
                      on         Turn compression on.
                      none       Same as off.
                      enable     Same as on.
                      IDRC       IBM Improved Data Recording Capability
                                 compression (0x10).
                      DCLZ       DCLZ compression algorithm (0x20).

                      In addition to the above recognized compression
                      keywords, the user can supply a numeric compression
                      algorithm for the drive to use.  In most cases, simply
                      turning the compression `on' will have the desired
                      effect of enabling the default compression algorithm
                      supported by the drive.  If this is not the case (see
                      the status display to see which compression algorithm is
                      currently in use), the user can manually specify one of
                      the supported compression keywords (above), or supply a
                      numeric compression value from the drive's

     density          Set the density for the drive.  For the density codes,
                      see below.  The density value could be given either
                      numerically, or as a string, corresponding to the
                      ``Reference'' field.  If the string is abbreviated, it
                      will be resolved in the order shown in the table, and
                      the first matching entry will be used.  If the given
                      string and the resulting canonical density name do not
                      match exactly, an informational message is output about
                      what the given string has been taken for.

     The following density table was taken from the `Historical sequential
     access density codes' table (A-1) in Revision 11 of the SCSI-3 Stream
     Device Commands (SSC) working draft, dated November 11, 1997.

     The density codes are:

        0x0    default for device
        0xE    reserved for ECMA

        Value  Width        Tracks    Density         Code Type Reference   Note
                mm    in              bpmm       bpi
        0x01   12.7  (0.5)    9         32     (800)  NRZI  R   X3.22-1983   2
        0x02   12.7  (0.5)    9         63   (1,600)  PE    R   X3.39-1986   2
        0x03   12.7  (0.5)    9        246   (6,250)  GCR   R   X3.54-1986   2
        0x05    6.3  (0.25)  4/9       315   (8,000)  GCR   C   X3.136-1986  1
        0x06   12.7  (0.5)    9        126   (3,200)  PE    R   X3.157-1987  2
        0x07    6.3  (0.25)   4        252   (6,400)  IMFM  C   X3.116-1986  1
        0x08    3.81 (0.15)   4        315   (8,000)  GCR   CS  X3.158-1987  1
        0x09   12.7  (0.5)   18      1,491  (37,871)  GCR   C   X3.180       2
        0x0A   12.7  (0.5)   22        262   (6,667)  MFM   C   X3B5/86-199  1
        0x0B    6.3  (0.25)   4         63   (1,600)  PE    C   X3.56-1986   1
        0x0C   12.7  (0.5)   24        500  (12,690)  GCR   C   HI-TC1       1,6
        0x0D   12.7  (0.5)   24        999  (25,380)  GCR   C   HI-TC2       1,6
        0x0F    6.3  (0.25)  15        394  (10,000)  GCR   C   QIC-120      1,6
        0x10    6.3  (0.25)  18        394  (10,000)  GCR   C   QIC-150      1,6
        0x11    6.3  (0.25)  26        630  (16,000)  GCR   C   QIC-320      1,6
        0x12    6.3  (0.25)  30      2,034  (51,667)  RLL   C   QIC-1350     1,6
        0x13    3.81 (0.15)   1      2,400  (61,000)  DDS   CS  X3B5/88-185A 5
        0x14    8.0  (0.315)  1      1,703  (43,245)  RLL   CS  X3.202-1991  5
        0x15    8.0  (0.315)  1      1,789  (45,434)  RLL   CS  ECMA TC17    5
        0x16   12.7  (0.5)   48        394  (10,000)  MFM   C   X3.193-1990  1
        0x17   12.7  (0.5)   48      1,673  (42,500)  MFM   C   X3B5/91-174  1
        0x18   12.7  (0.5)  112      1,673  (42,500)  MFM   C   X3B5/92-50   1
        0x19   12.7  (0.5)  128      2,460  (62,500)  RLL   C   DLTapeIII    6,7
        0x1A   12.7  (0.5)  128      3,214  (81,633)  RLL   C   DLTapeIV(20) 6,7
        0x1B   12.7  (0.5)  208      3,383  (85,937)  RLL   C   DLTapeIV(35) 6,7
        0x1C    6.3  (0.25)  34      1,654  (42,000)  MFM   C   QIC-385M     1,6
        0x1D    6.3  (0.25)  32      1,512  (38,400)  GCR   C   QIC-410M     1,6
        0x1E    6.3  (0.25)  30      1,385  (36,000)  GCR   C   QIC-1000C    1,6
        0x1F    6.3  (0.25)  30      2,666  (67,733)  RLL   C   QIC-2100C    1,6
        0x20    6.3  (0.25) 144      2,666  (67,733)  RLL   C   QIC-6GB(M)   1,6
        0x21    6.3  (0.25) 144      2,666  (67,733)  RLL   C   QIC-20GB(C)  1,6
        0x22    6.3  (0.25)  42      1,600  (40,640)  GCR   C   QIC-2GB(C)   ?
        0x23    6.3  (0.25)  38      2,666  (67,733)  RLL   C   QIC-875M     ?
        0x24    3.81 (0.15)   1      2,400  (61,000)        CS  DDS-2        5
        0x25    3.81 (0.15)   1      3,816  (97,000)        CS  DDS-3        5
        0x26    3.81 (0.15)   1      3,816  (97,000)        CS  DDS-4        5
        0x27    8.0  (0.315)  1      3,056  (77,611)  RLL   CS  Mammoth      5
        0x28   12.7  (0.5)   36      1,491  (37,871)  GCR   C   X3.224       1
        0x29   12.7  (0.5)
        0x2B   12.7  (0.5)    3          ?        ?     ?   C   X3.267       5
        0x41   12.7  (0.5)  208      3,868  (98,250)  RLL   C   DLTapeIV(40) 6,7
        0x48   12.7  (0.5)  448      5,236  (133,000) PRML  C   SDLTapeI(110) 6,8
        0x49   12.7  (0.5)  448      7,598  (193,000) PRML  C   SDLTapeI(160) 6,8

        Code    Description                                Type Description
        ----    --------------------------------------     ---- -----------
        NRZI    Non return to zero, change on ones         R    Reel-to-reel
        GCR     Group code recording                       C    Cartridge
        PE      Phase encoded                              CS   Cassette
        IMFM    Inverted modified frequency modulation
        MFM     Modified frequency modulation
        DDS     DAT data storage
        RLL     Run length limited
        PRML    Partial Response Maximum Likelihood

        1. Serial recorded.
        2. Parallel recorded.
        3. Old format known as QIC-11.
        5. Helical scan.
        6. This is not an American National Standard.  The reference is based on
           an industry standard definition of the media format.
        7. DLT recording: serially recorded track pairs (DLTapeIII and
           DLTapeIV(20)), or track quads (DLTapeIV(35) and DLTapeIV(40)).
        8. Super DLT (SDLT) recording: 56 serially recorded logical tracks with
           8 physical tracks each.

     TAPE      This is the pathname of the tape drive.  The default (if the
               variable is unset, but not if it is null) is /dev/nsa0.  It may
               be overridden with the -f option.

     /dev/*wt*           QIC-02/QIC-36 magnetic tape interface
     /dev/*sa[0-9]*      SCSI magnetic tape interface

     The exit status will be 0 when the drive operations were successful, 2
     when the drive operations were unsuccessful, and 1 for other problems
     like an unrecognized command or a missing drive device.

     Some undocumented commands support old software.

     dd(1), ioctl(2), ast(4), mtio(4), sa(4), environ(7)

     The mt command appeared in 4.3BSD.

     Extensions regarding the st(4) driver appeared in 386BSD-0.1 as a
     separate st command, and have been merged into the mt command in
     FreeBSD 2.1.

     The former eof command that used to be a synonym for weof has been
     abandoned in FreeBSD 2.1 since it was often confused with eom, which is
     fairly dangerous.

     The utility cannot be interrupted or killed during a long erase (which
     can be longer than an hour), and it is easy to forget that the default
     erase is long.

     Hardware block numbers do not always correspond to blocks on the tape
     when the drive uses internal compression.

     Erasure is not guaranteed if the tape is not at its beginning.

     Tape-related documentation is poor, here and elsewhere.

FreeBSD 11.0-PRERELEASE        January 20, 2008        FreeBSD 11.0-PRERELEASE


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