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     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

		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

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


     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 sepa-
     rate 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 aban-
     doned in FreeBSD 2.1 since it was often confused with eom, which is
     fairly dangerous.

FreeBSD 5.4			 June 6, 1993			   FreeBSD 5.4


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