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MT(1)			  BSD 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 de-
     fault mt performs the requested operation once.  Operations may be	per-
     formed multiple times by specifying count.

     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 ig-

     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 do-
		ing 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 is	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 nu-
		meric 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 De-
     vice 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/*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.

BSD				 June 6, 1993				   BSD


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