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

     mt -- magnetic tape manipulating program

     mt [-f tapename] command [count]

     The mt utility is used to give commands to a magnetic tape drive.  By
     default mt performs the requested operation once.  Operations may be per-
     formed multiple times by specifying count.  Note that tapename must ref-
     erence a raw (not block) tape device.

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

     weof       Write count end-of-file marks at the current position on the

     smk        Write count setmarks at the current position on the tape.

     fsf        Forward space count files.

     fsr        Forward space count records.

     fss        Forward space count setmarks.

     bsf        Backward space count files.

     bsr        Backward space count records.

     bss        Backward space count setmarks.

     rdhpos     Read Hardware block position.  Some drives do not support
                this.  The block number reported is specific for that hardware
                only.  The count argument is ignored.

     rdspos     Read SCSI logical block position.  Some drives do not support
                this.  The count argument is ignored.

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

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

     rewind     Rewind the tape (Count is ignored).

     offline, rewoffl
                Rewind the tape and place the tape unit off-line (Count is

     erase      Erase the tape.  A count of 0 disables long erase, which is on
                by default.

     retension  Re-tension the tape (one full wind forth and back, Count is

     status     Print status information about the tape unit.  For SCSI mag-
                netic 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 prints 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    Print (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's associated status and any
                residual counts (if any). This command retrieves and prints
                this information.  If possible, this also clears any latched
                error information.

     blocksize  Set the block size for the tape unit.  Zero means variable-
                length blocks.

     density    Set the density for the tape unit.  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 printed
                about what the given string has been taken for.

                Fetch and print out the current EOT filemark model.  The model
                states how many filemarks will be written at close if a tape
                was being written.

                Set (from the count argument) and print out the current and
                EOT filemark model.  Typically this will be 2 filemarks, but
                some devices (typically QIC cartridge drives) can only write 1
                filemark.  Currently you can only choose a value of 1 or 2.

     eom        Forward space to end of recorded medium (Count is ignored).

     eod        Forward space to end of data, identical to eom.

     comp       Set compression mode.  There are currently several possible
                values for the compression mode:

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

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

     If a tape name is not specified, and the environment variable TAPE does
     not exist; mt uses the device /dev/nsa0.

     The mt utility returns a 0 exit status when the operation(s) were suc-
     cessful, 1 if the command was unrecognized, and 2 if an operation failed.

     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 different density codes are as follows:

           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.

     If the following environment variable exists, it is utilized by mt.

     TAPE        The mt utility checks the TAPE environment variable if the
                 argument tapename is not given.

     /dev/*rwt*         QIC-02/QIC-36 magnetic tape interface
     /dev/*rsa[0-9]*    SCSI magnetic tape interface

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

     The mt command appeared in 4.3BSD.

     Extensions regarding the st(4) driver appeared in 386BSD 0.1 as a sepa-
     rate st(1) 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 aban-
     doned in FreeBSD 2.1 since it was often confused with eom, which is
     fairly dangerous.

FreeBSD 4.10                     June 6, 1993                     FreeBSD 4.10


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