MT(1)                     BSD General Commands Manual                    MT(1)

NAME
     mt -- magnetic tape manipulating program

SYNOPSIS
     mt [-f tapename] command [count]

DESCRIPTION
     The mt utility is used to give commands to a magnetic tape
     drive.  By default mt performs the requested operation
     once.  Operations may be performed multiple times by spec-
     ifying count.  Note that tapename must reference 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 tape.

     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 inter-
                preted 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 ignored).

     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 ignored).

     status     Print status information about the tape unit.
                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
                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 defini-
                tive 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 associ-
                ated status and any residual counts (if any).
                This command retrieves and prints this informa-
                tion.  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 informa-
                tional message is printed about what the given
                string has been taken for.

     geteotmodel
                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.

     seteotmodel
                Set (from the count argument) and print out the
                current and EOT filemark model.  Typically this
                will be 2 filemarks, but some devices (typi-
                cally 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 sev-
                eral 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 Capabil-
                           ity compression (0x10).
                DCLZ       DCLZ compression algorithm (0x20).

                In addition to the above recognized compression
                keywords, the user can supply a numeric com-
                pression algorithm for the tape 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 algo-
                rithm is currently in use), the user can manu-
                ally specify one of the supported compression
                keywords (above), or supply a numeric compres-
                sion value.

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

     The mt utility returns a 0 exit status when the opera-
     tion(s) were successful, 1 if the command was unrecog-
     nized, 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)
        0x2A
        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

        NOTES
        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.

ENVIRONMENT
     If the following environment variable exists, it is uti-
     lized by mt.

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

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

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

HISTORY
     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 con-
     fused with eom, which is fairly dangerous.

BSD                              June 6, 1993                              BSD
