xref: /freebsd/usr.bin/mt/mt.1 (revision 732a02b4e77866604a120a275c082bb6221bd2ff)
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29.\"	@(#)mt.1	8.1 (Berkeley) 6/6/93
30.\" $FreeBSD$
31.\"
32.Dd March 4, 2019
33.Dt MT 1
34.Os
35.Sh NAME
36.Nm mt
37.Nd magnetic tape manipulating program
38.Sh SYNOPSIS
39.Nm
40.Op Fl f Ar tapename
41.Ar command
42.Op Ar count
43.Nm
44.Op Fl f Ar tapename
45.Ar command
46.Ar argument
47.Sh DESCRIPTION
48The
49.Nm
50utility is used to command a magnetic tape drive for operations
51other than reading or writing data.
52.Pp
53The
54.Fl f
55option's
56.Ar tapename
57overrides the
58.Ev TAPE
59environment variable described below.
60.Pp
61The available commands are listed below.
62Only as many
63characters as are required to uniquely identify a command
64need be specified.
65.Pp
66The following commands optionally take a
67.Ar count ,
68which defaults to 1.
69.Bl -tag -width ".Cm erase"
70.It Cm weof
71Write
72.Ar count
73end-of-file (EOF) marks at the current position.
74This returns when the file mark has been written to the media.
75.It Cm weofi
76Write
77.Ar count
78end-of-file (EOF) marks at the current position.
79This returns as soon as the command has been validated by the tape drive.
80.It Cm smk
81Write
82.Ar count
83setmarks at the current position (DDS drives only).
84.It Cm fsf
85Forward space
86.Ar count
87files.
88.It Cm fsr
89Forward space
90.Ar count
91records.
92.It Cm fss
93Forward space
94.Ar count
95setmarks (DDS drives only).
96.It Cm bsf
97Backward space
98.Ar count
99files.
100.It Cm bsr
101Backward space
102.Ar count
103records.
104.It Cm bss
105Backward space
106.Ar count
107setmarks (DDS drives only).
108.It Cm erase
109Erase the tape using a long (often very long) method.
110With a
111.Ar count
112of 0, it will erase the tape using a quick method.
113Operation is not guaranteed if the tape is not at its beginning.
114The tape will be at its beginning upon completion.
115.El
116.Pp
117The following commands ignore
118.Ar count .
119.Bl -tag -width ".Cm geteotmodel"
120.It Cm rdhpos
121Read the hardware block position.
122The block
123number reported is specific for that hardware only.
124With drive data compression especially,
125this position may have more to do with the amount of data
126sent to the drive than the amount of data written to tape.
127Some drives do not support this.
128.It Cm rdspos
129Read the SCSI logical block position.
130This typically is greater than the hardware position
131by the number of end-of-file marks.
132Some drives do not support this.
133.It Cm rewind
134Rewind the tape.
135.It Cm offline , rewoffl
136Rewind the tape and place the drive off line.
137Some drives are never off line.
138.It Cm load
139Load the tape into the drive.
140.It Cm retension
141Re-tension the tape.
142This winds the tape from the current position to the end
143and then to the beginning.
144This sometimes improves subsequent reading and writing,
145particularly for streaming drives.
146Some drives do not support this.
147.It Cm ostatus
148Output status information about the drive.
149For SCSI magnetic tape devices,
150the current operating modes of density, blocksize, and whether compression
151is enabled is reported.
152The current state of the driver (what it thinks that
153it is doing with the device) is reported.
154If the driver knows the relative
155position from BOT (in terms of filemarks and records), it outputs that.
156Note
157that this information is not definitive (only BOT, End of Recorded Media, and
158hardware or SCSI logical block position (if the drive supports such) are
159considered definitive tape positions).
160.Pp
161Also note that this is the old status command, and will be eliminated in
162favor of the new status command (see below) in a future release.
163.It Cm errstat
164Output (and clear) error status information about this device.
165For every normal
166operation (e.g., a read or a write) and every control operation (e.g,, a
167rewind), the driver stores up the last command executed and it is associated
168status and any residual counts (if any).
169This command retrieves and outputs this
170information.
171If possible, this also clears any latched error information.
172.It Cm geteotmodel
173Output the current EOT filemark model.
174The model states how
175many filemarks will be written at close if a tape was being written.
176.It Cm eod , eom
177Wind the tape to the end of the recorded data,
178typically after an EOF mark where another file may be written.
179.It Cm rblim
180Report the block limits of the tape drive, including the minimum and
181maximum block size, and the block granularity if any.
182.El
183.Pp
184The following commands may require an
185.Ar argument .
186.Bl -tag -width ".Cm seteotmodel"
187.It Cm sethpos
188Set the hardware block position.
189The
190.Ar argument
191is a hardware block number to which to position the tape.
192Some drives do not support this.
193.It Cm setspos
194Set the SCSI logical block position.
195The
196.Ar argument
197is a SCSI logical block number to which to position the tape.
198Some drives do not support this.
199.It Cm blocksize
200Set the block size for the drive.
201The
202.Ar argument
203is the number of bytes per block,
204except 0 commands the drive to use variable-length blocks.
205.It Cm seteotmodel
206Set the EOT filemark model to
207.Ar argument
208and output the old and new models.
209Typically this will be 2
210filemarks, but some devices (typically QIC cartridge drives) can
211only write 1 filemark.
212You may only choose a value of
213.Ar 1
214or
215.Ar 2 .
216.It Cm status
217Output status information about the drive.
218For SCSI magnetic tape devices,
219the current operating modes of density, blocksize, and whether compression
220is enabled is reported.
221The current state of the driver (what it thinks that
222it is doing with the device) is reported.
223.Pp
224If the driver knows the relative
225position from BOT (in terms of filemarks and records), it outputs that.
226If the tape drive supports the long form report of the
227.Tn SCSI
228READ POSITION command, the Reported File Number and Reported Record Number
229will be numbers other than -1, and there may be Flags reported as well.
230.Pp
231The BOP flag means that the logical position of the drive is at the
232beginning of the partition.
233.Pp
234The EOP flag means that the logical position of the drive is between Early
235Warning and End of Partition.
236.Pp
237The BPEW flag means that the logical position of the drive is in a
238Programmable Early Warning Zone or on the EOP side of Early Warning.
239.Pp
240Note that the Reported Record Number is the tape block or object number
241relative to the beginning of the partition.
242The Calculated Record Number is the tape block or object number relative
243to the previous file mark.
244.Pp
245Note
246that the Calculated File and Record Numbers are not definitive.
247The Reported File and Record Numbers are definitive, if they are numbers
248other than -1.
249.Bl -tag -width 6n
250.It Fl v
251Print additional status information, such as the maximum supported I/O
252size.
253.It Fl x
254Print all available status data to stdout in XML format.
255.El
256.It Cm getdensity
257Report density support information for the tape drive and any media that is
258loaded.
259Most drives will report at least basic density information similar to that
260reported by
261.Nm status
262command.
263Newer tape drives that conform to the T-10 SSC and newer tape
264specifications may report more detailed information about the types of
265tapes they support and the tape currently in the drive.
266.Bl -tag -width 6n
267.It Fl x
268Print all available density data to stdout in XML format.
269Because density information is currently included in the general status XML
270report used for
271.Nm
272status command, this will be the same XML output via
273.Do
274.Nm
275status
276.Fl x
277.Dc
278.El
279.It Cm param
280Display or set parameters.
281One of
282.Fl l ,
283.Fl s ,
284or
285.Fl x
286must be specified to indicate which operation to perform.
287See
288.Xr sa 4
289for more detailed information on the parameters.
290.Bl -tag -width 8n
291.It Fl l
292List parameters, values and descriptions.
293By default all parameters will be displayed.
294To display a specific parameter, specify the parameter with
295.Fl p .
296.It Fl p Ar name
297Specify the parameter name to list (with
298.Fl l )
299or set (with
300.Fl s ) .
301.It Fl q
302Enable quiet mode for parameter listing.
303This will suppress printing of parameter descriptions.
304.It Fl s Ar value
305Specify the parameter value to set.
306The general type of this argument (integer, unsigned integer, string) is
307determined by the type of the variable indicated by the
308.Xr sa 4
309driver.
310More detailed argument checking is done by the
311.Xr sa 4
312driver.
313.It Fl x
314Print out all parameter information in XML format.
315.El
316.It Cm protect
317Display or set drive protection parameters.
318This is used to control checking and reporting a per-block checksum for
319tape drives that support it.
320Some drives may only support some parameters.
321.Bl -tag -width 8n
322.It Fl b Ar 0|1
323Set the Recover Buffered Data Protected bit.
324If set, this indicates that checksums are transferred with the logical
325blocks transferred by the RECOVERED BUFFERED DATA
326.Tn SCSI
327command.
328.It Fl d
329Disable all protection information settings.
330.It Fl e
331Enable all protection information settings.
332The default protection method used is Reed-Solomon CRC (protection method
3331), as specified in ECMA-319.
334The default protection information length used with Reed-Solomon CRC is
3354 bytes.
336To enable all settings except one more setting, specify the
337.Fl e
338argument and then explicitly disable settings that you do not wish to
339enable.
340For example, specifying
341.Fl e
342.Fl w Ar 0
343will enable all settings except for LBP_W.
344.It Fl l
345List available protection parmeters and their current settings.
346.It Fl L Ar len
347Set the length of the protection information in bytes.
348For Reed-Solomon CRC, the protection information length should be 4 bytes.
349.It Fl m Ar num
350Specify the numeric value for the protection method.
351The numeric value for Reed-Solomon CRC is 1.
352.It Fl r Ar 0|1
353Set the LBP_R parameter.
354When set, this indicates that each block read from the tape drive will
355have a checksum at the end.
356.It Fl v
357Enable verbose mode for parameter listing.
358This will include descriptions of each parameter.
359.It Fl w Ar 0|1
360Set the LBP_W parameter.
361When set, this indicates that each block written to the tape drive will have
362a checksum at the end.
363The drive will verify the checksum before writing the block to tape.
364.El
365.It Cm locate
366Set the tape drive's logical position.
367One of
368.Fl b ,
369.Fl e ,
370.Fl f ,
371or
372.Fl s
373must be specified to indicate the type of position.
374If the partition number is specified, the drive will first relocate to the
375given partition (if it exists) and then to the position indicated within
376that partition.
377If the partition number is not specified, the drive will relocate to the
378given position within the current partition.
379.Bl -tag -width 14n
380.It Fl b Ar block_addr
381Relocate to the given tape block or logical object identifier.
382Note that the block number is the Reported Record Number that is relative
383to the beginning of the partition (or beginning of tape).
384.It Fl e
385Relocate to the end of data.
386.It Fl f Ar fileno
387Relocate to the given file number.
388.It Fl p Ar partition
389Specify the partition to change to.
390.It Fl s Ar setmark
391Relocate to the given set mark.
392.El
393.It Cm comp
394Set the drive's compression mode.
395The non-numeric values of
396.Ar argument
397are:
398.Pp
399.Bl -tag -width 9n -compact
400.It off
401Turn compression off.
402.It on
403Turn compression on.
404.It none
405Same as
406.Ar off .
407.It enable
408Same as
409.Ar on .
410.It IDRC
411IBM Improved Data Recording Capability compression (0x10).
412.It DCLZ
413DCLZ compression algorithm (0x20).
414.El
415.Pp
416In addition to the above recognized compression keywords, the user can
417supply a numeric compression algorithm for the drive to use.
418In most
419cases, simply turning the compression
420.Sq on
421will have the desired effect of enabling the default compression algorithm
422supported by the drive.
423If this is not the case (see the
424.Cm status
425display to see which compression algorithm is currently in use), the user
426can manually specify one of the supported compression keywords (above), or
427supply a numeric compression value from the drive's specifications.
428.Pp
429Note that for some older tape drives (for example the Exabyte 8200 and 8500
430series drives) it is necessary to switch to a different density to tell the
431drive to record data in its compressed format.
432If the user attempts to turn compression on while the uncompressed density
433is selected, the drive will return an error.
434This is generally not an issue for modern tape drives.
435.It Cm density
436Set the density for the drive.
437For the density codes, see below.
438The density value could be given either numerically, or as a string,
439corresponding to the
440.Dq Reference
441field.
442If the string is abbreviated, it will be resolved in the order
443shown in the table, and the first matching entry will be used.
444If the
445given string and the resulting canonical density name do not match
446exactly, an informational message is output about what the given
447string has been taken for.
448.El
449.Pp
450The initial version of the density table below was taken from the
451.Sq Historical sequential access density codes
452table (A-1) in Revision 11 of the SCSI-3 Stream Device Commands (SSC)
453working draft, dated November 11, 1997.
454Subsequent additions have come from a number of sources.
455.Pp
456The density codes are:
457.Bd -literal -offset 2n
4580x0    default for device
4590xE    reserved for ECMA
460
461Value  Width        Tracks    Density         Code Type Reference   Note
462        mm    in              bpmm       bpi
4630x01   12.7  (0.5)    9         32     (800)  NRZI  R   X3.22-1983   2
4640x02   12.7  (0.5)    9         63   (1,600)  PE    R   X3.39-1986   2
4650x03   12.7  (0.5)    9        246   (6,250)  GCR   R   X3.54-1986   2
4660x05    6.3  (0.25)  4/9       315   (8,000)  GCR   C   X3.136-1986  1,3
4670x06   12.7  (0.5)    9        126   (3,200)  PE    R   X3.157-1987  2
4680x07    6.3  (0.25)   4        252   (6,400)  IMFM  C   X3.116-1986  1
4690x08    3.81 (0.15)   4        315   (8,000)  GCR   CS  X3.158-1987  1
4700x09   12.7  (0.5)   18      1,491  (37,871)  GCR   C   X3.180       2
4710x0A   12.7  (0.5)   22        262   (6,667)  MFM   C   X3B5/86-199  1
4720x0B    6.3  (0.25)   4         63   (1,600)  PE    C   X3.56-1986   1
4730x0C   12.7  (0.5)   24        500  (12,690)  GCR   C   HI-TC1       1,6
4740x0D   12.7  (0.5)   24        999  (25,380)  GCR   C   HI-TC2       1,6
4750x0F    6.3  (0.25)  15        394  (10,000)  GCR   C   QIC-120      1,6
4760x10    6.3  (0.25)  18        394  (10,000)  GCR   C   QIC-150      1,6
4770x11    6.3  (0.25)  26        630  (16,000)  GCR   C   QIC-320      1,6
4780x12    6.3  (0.25)  30      2,034  (51,667)  RLL   C   QIC-1350     1,6
4790x13    3.81 (0.15)   1      2,400  (61,000)  DDS   CS  X3B5/88-185A 5
4800x14    8.0  (0.315)  1      1,703  (43,245)  RLL   CS  X3.202-1991  5,11
4810x15    8.0  (0.315)  1      1,789  (45,434)  RLL   CS  ECMA TC17    5,12
4820x16   12.7  (0.5)   48        394  (10,000)  MFM   C   X3.193-1990  1
4830x17   12.7  (0.5)   48      1,673  (42,500)  MFM   C   X3B5/91-174  1
4840x18   12.7  (0.5)  112      1,673  (42,500)  MFM   C   X3B5/92-50   1
4850x19   12.7  (0.5)  128      2,460  (62,500)  RLL   C   DLTapeIII    6,7
4860x1A   12.7  (0.5)  128      3,214  (81,633)  RLL   C   DLTapeIV(20) 6,7
4870x1B   12.7  (0.5)  208      3,383  (85,937)  RLL   C   DLTapeIV(35) 6,7
4880x1C    6.3  (0.25)  34      1,654  (42,000)  MFM   C   QIC-385M     1,6
4890x1D    6.3  (0.25)  32      1,512  (38,400)  GCR   C   QIC-410M     1,6
4900x1E    6.3  (0.25)  30      1,385  (36,000)  GCR   C   QIC-1000C    1,6
4910x1F    6.3  (0.25)  30      2,666  (67,733)  RLL   C   QIC-2100C    1,6
4920x20    6.3  (0.25) 144      2,666  (67,733)  RLL   C   QIC-6GB(M)   1,6
4930x21    6.3  (0.25) 144      2,666  (67,733)  RLL   C   QIC-20GB(C)  1,6
4940x22    6.3  (0.25)  42      1,600  (40,640)  GCR   C   QIC-2GB(C)   ?
4950x23    6.3  (0.25)  38      2,666  (67,733)  RLL   C   QIC-875M     ?
4960x24    3.81 (0.15)   1      2,400  (61,000)        CS  DDS-2        5
4970x25    3.81 (0.15)   1      3,816  (97,000)        CS  DDS-3        5
4980x26    3.81 (0.15)   1      3,816  (97,000)        CS  DDS-4        5
4990x27    8.0  (0.315)  1      3,056  (77,611)  RLL   CS  Mammoth      5
5000x28   12.7  (0.5)   36      1,491  (37,871)  GCR   C   X3.224       1
5010x29   12.7  (0.5)
5020x2A
5030x2B   12.7  (0.5)    3          ?        ?     ?   C   X3.267       5
5040x40   12.7  (0.5)  384      4,800  (123,952)       C   LTO-1
5050x41   12.7  (0.5)  208      3,868  (98,250)  RLL   C   DLTapeIV(40) 6,7
5060x42   12.7  (0.5)  512      7,398  (187,909)       C   LTO-2
5070x44   12.7  (0.5)  704      9,638  (244,805)       C   LTO-3
5080x46   12.7  (0.5)  896      12,725 (323,215)       C   LTO-4
5090x47    3.81 (0.25)   ?      6,417  (163,000)       CS  DAT-72
5100x48   12.7  (0.5)  448      5,236  (133,000) PRML  C   SDLTapeI(110) 6,8,13
5110x49   12.7  (0.5)  448      7,598  (193,000) PRML  C   SDLTapeI(160) 6,8
5120x4A   12.7  (0.5)  768          ?            PRML  C   T10000A      10
5130x4B   12.7  (0.5) 1152          ?            PRML  C   T10000B      10
5140x4C   12.7  (0.5) 3584          ?            PRML  C   T10000C      10
5150x4D   12.7  (0.5) 4608          ?            PRML  C   T10000D      10
5160x51   12.7  (0.5)  512      11,800 (299,720)       C   3592A1 (unencrypted)
5170x52   12.7  (0.5)  896      11,800 (299,720)       C   3592A2 (unencrypted)
5180x53   12.7  (0.5) 1152      13,452 (341,681)       C   3592A3 (unencrypted)
5190x54   12.7  (0.5) 2560      19,686 (500,024)       C   3592A4 (unencrypted)
5200x55   12.7  (0.5) 5120      20,670 (525,018)       C   3592A5 (unencrypted)
5210x56   12.7  (0.5) 7680      20,670 (525,018)       C   3592B5 (unencrypted)
5220x57   12.7  (0.5) 8704      21,850 (554,990)       C   3592A6 (unencrypted)
5230x58   12.7  (0.5) 1280      15,142 (384,607)       C   LTO-5
5240x5A   12.7  (0.5) 2176      15,142 (384,607)       C   LTO-6
5250x5C   12.7  (0.5) 3584      19,107 (485,318)       C   LTO-7
5260x5D   12.7  (0.5) 5376      19,107 (485,318)       C   LTO-M8       14
5270x5E   12.7  (0.5) 6656      20,669 (524,993)       C   LTO-8
5280x71   12.7  (0.5)  512      11,800 (299,720)       C   3592A1 (encrypted)
5290x72   12.7  (0.5)  896      11,800 (299,720)       C   3592A2 (encrypted)
5300x73   12.7  (0.5) 1152      13,452 (341,681)       C   3592A3 (encrypted)
5310x74   12.7  (0.5) 2560      19,686 (500,024)       C   3592A4 (encrypted)
5320x75   12.7  (0.5) 5120      20,670 (525,018)       C   3592A5 (encrypted)
5330x76   12.7  (0.5) 7680      20,670 (525,018)       C   3592B5 (encrypted)
5340x77   12.7  (0.5) 8704      21,850 (554,990)       C   3592A6 (encrypted)
5350x8c    8.0  (0.315)  1      1,789  (45,434)  RLL   CS  EXB-8500c    5,9
5360x90    8.0  (0.315)  1      1,703  (43,245)  RLL   CS  EXB-8200c    5,9
537.Ed
538.Bd -literal -offset 2n
539Code    Description                                Type Description
540----    --------------------------------------     ---- -----------
541NRZI    Non return to zero, change on ones         R    Reel-to-reel
542GCR     Group code recording                       C    Cartridge
543PE      Phase encoded                              CS   Cassette
544IMFM    Inverted modified frequency modulation
545MFM     Modified frequency modulation
546DDS     DAT data storage
547RLL     Run length limited
548PRML    Partial Response Maximum Likelihood
549.Ed
550.Bd -literal -offset 2n
551NOTES
5521.  Serial recorded.
5532.  Parallel recorded.
5543.  Old format known as QIC-11.
5555.  Helical scan.
5566.  This is not an American National Standard.  The reference is based
557    on an industry standard definition of the media format.
5587.  DLT recording: serially recorded track pairs (DLTapeIII and
559    DLTapeIV(20)), or track quads (DLTapeIV(35) and DLTapeIV(40)).
5608.  Super DLT (SDLT) recording: 56 serially recorded logical tracks
561    with 8 physical tracks each.
5629.  Vendor-specific Exabyte density code for compressed format.
56310. bpi/bpmm values for the Oracle/StorageTek T10000 tape drives are
564    not listed in the manual.  Someone with access to a drive can
565    supply the necessary values by running 'mt getdensity'.
56611. This is Exabyte 8200 uncompressed format.  The compressed format
567    density code is 0x90.
56812. This is Exabyte 8500 uncompressed format.  The compressed format
569    density code is 0x8c.
57013. This density code (0x48) was also used for DAT-160.
57114. Officially known as LTO-8 Type M, abbreviated M8.  This is a pristine
572    LTO-7 cartridge initialized with a higher density format by an LTO-8
573    drive.  It cannot be read by an LTO-7 drive.  Uncompressed capacity
574    is 9TB, compared to 6TB for LTO-7 and 12TB for LTO-8.
575.Ed
576.Bd -literal -offset 2n
577NOTE ON QIC STREAMERS
578
579The following is a table of Data Cartridge types as used in the 1/4 inch
580tape drives such as the Archive Viper 150, Wangtek 5525ES, and Tandberg
581TDC4220 tape drives:
582
583Value Reference     Format    Cartridge Type  Capacity   Tracks  Length
584----- ---------     ------    --------------  --------   ------  ------
585
5860x05                QIC-11    DC300           15MB       4        300ft
5870x05                QIC-11    DC300XL/P       20MB       4        450ft
5880x05                QIC-11    DC600           27MB       4        600ft
5890x05  X3.136-1986   QIC-24    DC615A          15MB       9        150ft
5900x05  X3.136-1986   QIC-24    DC300XL/P       45MB       9        450ft
5910x05  X3.136-1986   QIC-24    DC600A          60MB       9        600ft
5920x0F  QIC-120       QIC-120   DC600A/DC6150   120MB      15       620ft
5930x10  QIC-150       QIC-150   DC600XTD/DC6150 150MB      18       620ft
5940x10  QIC-150       QIC-150   DC6250          250MB      18     1,020ft
5950x11  QIC-320       QIC-525   DC6320          320MB      26       620ft
5960x11  QIC-320       QIC-525   DC6525          525MB      26     1,020ft
5970x1E  QIC-1000C     QIC-1000  DC9100/DL9135   1.0GB      30       760ft
5980x1E  QIC-1000C     QIC-1000  DC9150          1.2GB      30       950ft
5990x22  QIC-2GB(C)    QIC-2GB   DC9200          2.0GB      42       950ft
6000x22  QIC-2GB(C)    QIC-2GB   DC9250          2.5GB      42     1,200ft
601.Ed
602.Pp
603Notes:
604.Pp
605QIC-24, QIC-120, QIC-150 use fixed blocksize of 512 bytes, QIC-525, QIC-1000
606and QIC-2GB can use blocksize of 1,024 bytes.
607DDS (DAT) drives generally use variable blocks.
608.Pp
609QIC-02 and QIC-36 are interface standards for tape drives.
610The QIC-02 and QIC-36 streamers such as the Wangtek 5250EQ are otherwise
611identical to their SCSI versions (i.e.: Wangtek 5250ES).
612.Pp
613It seems that the 150MB and larger streamers cannot write QIC-24 9 track
614formats, only read them.
615.Pp
616DC600A cartridges marked "10,000ftpi" can only be used as QIC-11, QIC-24,
617and QIC-120 format.
618DC600A cartridges marked 12,500ftpi can be used as both QIC-120 and QIC-150
619format.
620.Pp
621Some manufacturers do not use "DC" on their cartridges.
622Verbatim uses DL, Maxell uses MC, Sony uses QD, Quill uses DQ.
623.Pp
6243M/Imation & Fuji use DC.
625Thus a DL6250, MC-6250, QD6250, DQ6250 are all identical media to a DC6250.
626.Pp
627QIC tape media is not "connected" to the take up reels and will de-spool
628if the tape drive has dust covering the light sensor that looks for the end
629of tape holes in the media.
630.Sh ENVIRONMENT
631.Bl -tag -width ".Ev TAPE"
632.It Ev TAPE
633This is the pathname of the tape drive.
634The default (if the variable is unset, but not if it is null) is
635.Pa /dev/nsa0 .
636It may be overridden with the
637.Fl f
638option.
639.El
640.Sh FILES
641.Bl -tag -width ".Pa /dev/*sa[0-9]*" -compact
642.It Pa /dev/*sa[0-9]*
643SCSI magnetic tape interface
644.El
645.Sh DIAGNOSTICS
646The exit status will be 0 when the drive operations were successful,
6472 when the drive operations were unsuccessful, and 1 for other
648problems like an unrecognized command or a missing drive device.
649.Sh COMPATIBILITY
650Some undocumented commands support old software.
651.Sh SEE ALSO
652.Xr dd 1 ,
653.Xr ioctl 2 ,
654.Xr mtio 4 ,
655.Xr sa 4 ,
656.Xr environ 7
657.Sh HISTORY
658The
659.Nm
660command appeared in
661.Bx 4.3 .
662.Pp
663Extensions regarding the
664.Xr st 4
665driver appeared in
666.Bx 386 0.1
667as a separate
668.Nm st
669command, and have been merged into the
670.Nm
671command in
672.Fx 2.1 .
673.Pp
674The former
675.Cm eof
676command that used to be a synonym for
677.Cm weof
678has been abandoned in
679.Fx 2.1
680since it was often confused with
681.Cm eom ,
682which is fairly dangerous.
683.Sh BUGS
684The utility cannot be interrupted or killed during a long erase
685(which can be longer than an hour), and it is easy to forget
686that the default erase is long.
687.Pp
688Hardware block numbers do not always correspond to blocks on the tape
689when the drive uses internal compression.
690.Pp
691Erasure is not guaranteed if the tape is not at its beginning.
692.Pp
693Tape-related documentation is poor, here and elsewhere.
694