xref: /freebsd/usr.bin/mt/mt.1 (revision ee12faa062c04a49bf6fe4e6867bad8606e2413f)
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29.\"	@(#)mt.1	8.1 (Berkeley) 6/6/93
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31.Dd December 10, 2020
32.Dt MT 1
33.Os
34.Sh NAME
35.Nm mt
36.Nd magnetic tape manipulating program
37.Sh SYNOPSIS
38.Nm
39.Op Fl f Ar tapename
40.Ar command
41.Op Ar count
42.Nm
43.Op Fl f Ar tapename
44.Ar command
45.Ar argument
46.Sh DESCRIPTION
47The
48.Nm
49utility is used to command a magnetic tape drive for operations
50other than reading or writing data.
51.Pp
52The
53.Fl f
54option's
55.Ar tapename
56overrides the
57.Ev TAPE
58environment variable described below.
59.Pp
60The available commands are listed below.
61Only as many
62characters as are required to uniquely identify a command
63need be specified.
64.Pp
65The following commands optionally take a
66.Ar count ,
67which defaults to 1.
68.Bl -tag -width ".Cm erase"
69.It Cm weof
70Write
71.Ar count
72end-of-file (EOF) marks at the current position.
73This returns when the file mark has been written to the media.
74.It Cm weofi
75Write
76.Ar count
77end-of-file (EOF) marks at the current position.
78This returns as soon as the command has been validated by the tape drive.
79.It Cm smk
80Write
81.Ar count
82setmarks at the current position (DDS drives only).
83.It Cm fsf
84Forward space
85.Ar count
86files.
87.It Cm fsr
88Forward space
89.Ar count
90records.
91.It Cm fss
92Forward space
93.Ar count
94setmarks (DDS drives only).
95.It Cm bsf
96Backward space
97.Ar count
98files.
99.It Cm bsr
100Backward space
101.Ar count
102records.
103.It Cm bss
104Backward space
105.Ar count
106setmarks (DDS drives only).
107.It Cm erase
108Erase the tape using a long (often very long) method.
109With a
110.Ar count
111of 0, it will erase the tape using a quick method.
112Operation is not guaranteed if the tape is not at its beginning.
113The tape will be at its beginning upon completion.
114.El
115.Pp
116The following commands ignore
117.Ar count .
118.Bl -tag -width ".Cm geteotmodel"
119.It Cm rdhpos
120Read the hardware block position.
121The block
122number reported is specific for that hardware only.
123With drive data compression especially,
124this position may have more to do with the amount of data
125sent to the drive than the amount of data written to tape.
126Some drives do not support this.
127.It Cm rdspos
128Read the SCSI logical block position.
129This typically is greater than the hardware position
130by the number of end-of-file marks.
131Some drives do not support this.
132.It Cm rewind
133Rewind the tape.
134.It Cm offline , rewoffl
135Rewind the tape and place the drive off line.
136Some drives are never off line.
137.It Cm load
138Load the tape into the drive.
139.It Cm retension
140Re-tension the tape.
141This winds the tape from the current position to the end
142and then to the beginning.
143This sometimes improves subsequent reading and writing,
144particularly for streaming drives.
145Some drives do not support this.
146.It Cm ostatus
147Output status information about the drive.
148For SCSI magnetic tape devices,
149the current operating modes of density, blocksize, and whether compression
150is enabled is reported.
151The current state of the driver (what it thinks that
152it is doing with the device) is reported.
153If the driver knows the relative
154position from BOT (in terms of filemarks and records), it outputs that.
155Note
156that this information is not definitive (only BOT, End of Recorded Media, and
157hardware or SCSI logical block position (if the drive supports such) are
158considered definitive tape positions).
159.Pp
160Also note that this is the old status command, and will be eliminated in
161favor of the new status command (see below) in a future release.
162.It Cm errstat
163Output (and clear) error status information about this device.
164For every normal
165operation (e.g., a read or a write) and every control operation (e.g,, a
166rewind), the driver stores up the last command executed and it is associated
167status and any residual counts (if any).
168This command retrieves and outputs this
169information.
170If possible, this also clears any latched error information.
171.It Cm geteotmodel
172Output the current EOT filemark model.
173The model states how
174many filemarks will be written at close if a tape was being written.
175.It Cm eod , eom
176Wind the tape to the end of the recorded data,
177typically after an EOF mark where another file may be written.
178.It Cm rblim
179Report the block limits of the tape drive, including the minimum and
180maximum block size, and the block granularity if any.
181.El
182.Pp
183The following commands may require an
184.Ar argument .
185.Bl -tag -width ".Cm seteotmodel"
186.It Cm sethpos
187Set the hardware block position.
188The
189.Ar argument
190is a hardware block number to which to position the tape.
191Some drives do not support this.
192.It Cm setspos
193Set the SCSI logical block position.
194The
195.Ar argument
196is a SCSI logical block number to which to position the tape.
197Some drives do not support this.
198.It Cm blocksize
199Set the block size for the drive.
200The
201.Ar argument
202is the number of bytes per block,
203except 0 commands the drive to use variable-length blocks.
204.It Cm seteotmodel
205Set the EOT filemark model to
206.Ar argument
207and output the old and new models.
208Typically this will be 2
209filemarks, but some devices (typically QIC cartridge drives) can
210only write 1 filemark.
211You may only choose a value of
212.Ar 1
213or
214.Ar 2 .
215.It Cm status
216Output status information about the drive.
217For SCSI magnetic tape devices,
218the current operating modes of density, blocksize, and whether compression
219is enabled is reported.
220The current state of the driver (what it thinks that
221it is doing with the device) is reported.
222.Pp
223If the driver knows the relative
224position from BOT (in terms of filemarks and records), it outputs that.
225If the tape drive supports the long form report of the
226.Tn SCSI
227READ POSITION command, the Reported File Number and Reported Record Number
228will be numbers other than -1, and there may be Flags reported as well.
229.Pp
230The BOP flag means that the logical position of the drive is at the
231beginning of the partition.
232.Pp
233The EOP flag means that the logical position of the drive is between Early
234Warning and End of Partition.
235.Pp
236The BPEW flag means that the logical position of the drive is in a
237Programmable Early Warning Zone or on the EOP side of Early Warning.
238.Pp
239Note that the Reported Record Number is the tape block or object number
240relative to the beginning of the partition.
241The Calculated Record Number is the tape block or object number relative
242to the previous file mark.
243.Pp
244Note
245that the Calculated File and Record Numbers are not definitive.
246The Reported File and Record Numbers are definitive, if they are numbers
247other than -1.
248.Bl -tag -width 6n
249.It Fl v
250Print additional status information, such as the maximum supported I/O
251size.
252.It Fl x
253Print all available status data to stdout in XML format.
254.El
255.It Cm getdensity
256Report density support information for the tape drive and any media that is
257loaded.
258Most drives will report at least basic density information similar to that
259reported by
260.Nm status
261command.
262Newer tape drives that conform to the T-10 SSC and newer tape
263specifications may report more detailed information about the types of
264tapes they support and the tape currently in the drive.
265.Bl -tag -width 6n
266.It Fl x
267Print all available density data to stdout in XML format.
268Because density information is currently included in the general status XML
269report used for
270.Nm
271status command, this will be the same XML output via
272.Do
273.Nm
274status
275.Fl x
276.Dc
277.El
278.It Cm param
279Display or set parameters.
280One of
281.Fl l ,
282.Fl s ,
283or
284.Fl x
285must be specified to indicate which operation to perform.
286See
287.Xr sa 4
288for more detailed information on the parameters.
289.Bl -tag -width 8n
290.It Fl l
291List parameters, values and descriptions.
292By default all parameters will be displayed.
293To display a specific parameter, specify the parameter with
294.Fl p .
295.It Fl p Ar name
296Specify the parameter name to list (with
297.Fl l )
298or set (with
299.Fl s ) .
300.It Fl q
301Enable quiet mode for parameter listing.
302This will suppress printing of parameter descriptions.
303.It Fl s Ar value
304Specify the parameter value to set.
305The general type of this argument (integer, unsigned integer, string) is
306determined by the type of the variable indicated by the
307.Xr sa 4
308driver.
309More detailed argument checking is done by the
310.Xr sa 4
311driver.
312.It Fl x
313Print out all parameter information in XML format.
314.El
315.It Cm protect
316Display or set drive protection parameters.
317This is used to control checking and reporting a per-block checksum for
318tape drives that support it.
319Some drives may only support some parameters.
320.Bl -tag -width 8n
321.It Fl b Ar 0|1
322Set the Recover Buffered Data Protected bit.
323If set, this indicates that checksums are transferred with the logical
324blocks transferred by the RECOVERED BUFFERED DATA
325.Tn SCSI
326command.
327.It Fl d
328Disable all protection information settings.
329.It Fl e
330Enable all protection information settings.
331The default protection method used is Reed-Solomon CRC (protection method
3321), as specified in ECMA-319.
333The default protection information length used with Reed-Solomon CRC is
3344 bytes.
335To enable all settings except one more setting, specify the
336.Fl e
337argument and then explicitly disable settings that you do not wish to
338enable.
339For example, specifying
340.Fl e
341.Fl w Ar 0
342will enable all settings except for LBP_W.
343.It Fl l
344List available protection parmeters and their current settings.
345.It Fl L Ar len
346Set the length of the protection information in bytes.
347For Reed-Solomon CRC, the protection information length should be 4 bytes.
348.It Fl m Ar num
349Specify the numeric value for the protection method.
350The numeric value for Reed-Solomon CRC is 1.
351.It Fl r Ar 0|1
352Set the LBP_R parameter.
353When set, this indicates that each block read from the tape drive will
354have a checksum at the end.
355.It Fl v
356Enable verbose mode for parameter listing.
357This will include descriptions of each parameter.
358.It Fl w Ar 0|1
359Set the LBP_W parameter.
360When set, this indicates that each block written to the tape drive will have
361a checksum at the end.
362The drive will verify the checksum before writing the block to tape.
363.El
364.It Cm locate
365Set the tape drive's logical position.
366One of
367.Fl b ,
368.Fl e ,
369.Fl f ,
370or
371.Fl s
372must be specified to indicate the type of position.
373If the partition number is specified, the drive will first relocate to the
374given partition (if it exists) and then to the position indicated within
375that partition.
376If the partition number is not specified, the drive will relocate to the
377given position within the current partition.
378.Bl -tag -width 14n
379.It Fl b Ar block_addr
380Relocate to the given tape block or logical object identifier.
381Note that the block number is the Reported Record Number that is relative
382to the beginning of the partition (or beginning of tape).
383.It Fl e
384Relocate to the end of data.
385.It Fl f Ar fileno
386Relocate to the given file number.
387.It Fl p Ar partition
388Specify the partition to change to.
389.It Fl s Ar setmark
390Relocate to the given set mark.
391.El
392.It Cm comp
393Set the drive's compression mode.
394The non-numeric values of
395.Ar argument
396are:
397.Pp
398.Bl -tag -width 9n -compact
399.It off
400Turn compression off.
401.It on
402Turn compression on.
403.It none
404Same as
405.Ar off .
406.It enable
407Same as
408.Ar on .
409.It IDRC
410IBM Improved Data Recording Capability compression (0x10).
411.It DCLZ
412DCLZ compression algorithm (0x20).
413.El
414.Pp
415In addition to the above recognized compression keywords, the user can
416supply a numeric compression algorithm for the drive to use.
417In most
418cases, simply turning the compression
419.Sq on
420will have the desired effect of enabling the default compression algorithm
421supported by the drive.
422If this is not the case (see the
423.Cm status
424display to see which compression algorithm is currently in use), the user
425can manually specify one of the supported compression keywords (above), or
426supply a numeric compression value from the drive's specifications.
427.Pp
428Note that for some older tape drives (for example the Exabyte 8200 and 8500
429series drives) it is necessary to switch to a different density to tell the
430drive to record data in its compressed format.
431If the user attempts to turn compression on while the uncompressed density
432is selected, the drive will return an error.
433This is generally not an issue for modern tape drives.
434.It Cm density
435Set the density for the drive.
436For the density codes, see below.
437The density value could be given either numerically, or as a string,
438corresponding to the
439.Dq Reference
440field.
441If the string is abbreviated, it will be resolved in the order
442shown in the table, and the first matching entry will be used.
443If the
444given string and the resulting canonical density name do not match
445exactly, an informational message is output about what the given
446string has been taken for.
447.El
448.Pp
449The initial version of the density table below was taken from the
450.Sq Historical sequential access density codes
451table (A-1) in Revision 11 of the SCSI-3 Stream Device Commands (SSC)
452working draft, dated November 11, 1997.
453Subsequent additions have come from a number of sources.
454.Pp
455The density codes are:
456.Bd -literal -offset 2n
4570x0    default for device
4580xE    reserved for ECMA
459
460Value  Width        Tracks    Density         Code Type Reference   Note
461        mm    in              bpmm       bpi
4620x01   12.7  (0.5)    9         32     (800)  NRZI  R   X3.22-1983   2
4630x02   12.7  (0.5)    9         63   (1,600)  PE    R   X3.39-1986   2
4640x03   12.7  (0.5)    9        246   (6,250)  GCR   R   X3.54-1986   2
4650x05    6.3  (0.25)  4/9       315   (8,000)  GCR   C   X3.136-1986  1,3
4660x06   12.7  (0.5)    9        126   (3,200)  PE    R   X3.157-1987  2
4670x07    6.3  (0.25)   4        252   (6,400)  IMFM  C   X3.116-1986  1
4680x08    3.81 (0.15)   4        315   (8,000)  GCR   CS  X3.158-1987  1
4690x09   12.7  (0.5)   18      1,491  (37,871)  GCR   C   X3.180       2
4700x0A   12.7  (0.5)   22        262   (6,667)  MFM   C   X3B5/86-199  1
4710x0B    6.3  (0.25)   4         63   (1,600)  PE    C   X3.56-1986   1
4720x0C   12.7  (0.5)   24        500  (12,690)  GCR   C   HI-TC1       1,6
4730x0D   12.7  (0.5)   24        999  (25,380)  GCR   C   HI-TC2       1,6
4740x0F    6.3  (0.25)  15        394  (10,000)  GCR   C   QIC-120      1,6
4750x10    6.3  (0.25)  18        394  (10,000)  GCR   C   QIC-150      1,6
4760x11    6.3  (0.25)  26        630  (16,000)  GCR   C   QIC-320      1,6
4770x12    6.3  (0.25)  30      2,034  (51,667)  RLL   C   QIC-1350     1,6
4780x13    3.81 (0.15)   1      2,400  (61,000)  DDS   CS  X3B5/88-185A 5
4790x14    8.0  (0.315)  1      1,703  (43,245)  RLL   CS  X3.202-1991  5,11
4800x15    8.0  (0.315)  1      1,789  (45,434)  RLL   CS  ECMA TC17    5,12
4810x16   12.7  (0.5)   48        394  (10,000)  MFM   C   X3.193-1990  1
4820x17   12.7  (0.5)   48      1,673  (42,500)  MFM   C   X3B5/91-174  1
4830x18   12.7  (0.5)  112      1,673  (42,500)  MFM   C   X3B5/92-50   1
4840x19   12.7  (0.5)  128      2,460  (62,500)  RLL   C   DLTapeIII    6,7
4850x1A   12.7  (0.5)  128      3,214  (81,633)  RLL   C   DLTapeIV(20) 6,7
4860x1B   12.7  (0.5)  208      3,383  (85,937)  RLL   C   DLTapeIV(35) 6,7
4870x1C    6.3  (0.25)  34      1,654  (42,000)  MFM   C   QIC-385M     1,6
4880x1D    6.3  (0.25)  32      1,512  (38,400)  GCR   C   QIC-410M     1,6
4890x1E    6.3  (0.25)  30      1,385  (36,000)  GCR   C   QIC-1000C    1,6
4900x1F    6.3  (0.25)  30      2,666  (67,733)  RLL   C   QIC-2100C    1,6
4910x20    6.3  (0.25) 144      2,666  (67,733)  RLL   C   QIC-6GB(M)   1,6
4920x21    6.3  (0.25) 144      2,666  (67,733)  RLL   C   QIC-20GB(C)  1,6
4930x22    6.3  (0.25)  42      1,600  (40,640)  GCR   C   QIC-2GB(C)   ?
4940x23    6.3  (0.25)  38      2,666  (67,733)  RLL   C   QIC-875M     ?
4950x24    3.81 (0.15)   1      2,400  (61,000)        CS  DDS-2        5
4960x25    3.81 (0.15)   1      3,816  (97,000)        CS  DDS-3        5
4970x26    3.81 (0.15)   1      3,816  (97,000)        CS  DDS-4        5
4980x27    8.0  (0.315)  1      3,056  (77,611)  RLL   CS  Mammoth      5
4990x28   12.7  (0.5)   36      1,491  (37,871)  GCR   C   X3.224       1
5000x29   12.7  (0.5)
5010x2A
5020x2B   12.7  (0.5)    3          ?        ?     ?   C   X3.267       5
5030x40   12.7  (0.5)  384      4,800  (123,952)       C   LTO-1
5040x41   12.7  (0.5)  208      3,868  (98,250)  RLL   C   DLTapeIV(40) 6,7
5050x42   12.7  (0.5)  512      7,398  (187,909)       C   LTO-2
5060x44   12.7  (0.5)  704      9,638  (244,805)       C   LTO-3
5070x46   12.7  (0.5)  896      12,725 (323,215)       C   LTO-4
5080x47    3.81 (0.25)   ?      6,417  (163,000)       CS  DAT-72
5090x48   12.7  (0.5)  448      5,236  (133,000) PRML  C   SDLTapeI(110) 6,8,13
5100x49   12.7  (0.5)  448      7,598  (193,000) PRML  C   SDLTapeI(160) 6,8
5110x4A   12.7  (0.5)  768          ?            PRML  C   T10000A      10
5120x4B   12.7  (0.5) 1152          ?            PRML  C   T10000B      10
5130x4C   12.7  (0.5) 3584          ?            PRML  C   T10000C      10
5140x4D   12.7  (0.5) 4608          ?            PRML  C   T10000D      10
5150x51   12.7  (0.5)  512      11,800 (299,720)       C   3592A1 (unencrypted)
5160x52   12.7  (0.5)  896      11,800 (299,720)       C   3592A2 (unencrypted)
5170x53   12.7  (0.5) 1152      13,452 (341,681)       C   3592A3 (unencrypted)
5180x54   12.7  (0.5) 2560      19,686 (500,024)       C   3592A4 (unencrypted)
5190x55   12.7  (0.5) 5120      20,670 (525,018)       C   3592A5 (unencrypted)
5200x56   12.7  (0.5) 7680      20,670 (525,018)       C   3592B5 (unencrypted)
5210x57   12.7  (0.5) 8704      21,850 (554,990)       C   3592A6 (unencrypted)
5220x58   12.7  (0.5) 1280      15,142 (384,607)       C   LTO-5
5230x5A   12.7  (0.5) 2176      15,142 (384,607)       C   LTO-6
5240x5C   12.7  (0.5) 3584      19,107 (485,318)       C   LTO-7
5250x5D   12.7  (0.5) 5376      19,107 (485,318)       C   LTO-M8       14
5260x5E   12.7  (0.5) 6656      20,669 (524,993)       C   LTO-8
5270x60   12.7  (0.5) 8960      23,031 (584,987)       C   LTO-9
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