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 specifying 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 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 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 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 its 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.

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 (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 (0x10).
    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 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.

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 successful, 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)
    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 utilized by mt.

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

FILES
/dev/*rsa[0-9]*
    SCSI magnetic tape interface

SEE ALSO
dd(1), ioctl(2), 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(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 abandoned in FreeBSD 2.1 since it was often confused with eom, which is fairly dangerous.