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freebsd-dev/usr.bin/mt/mt.1
Kenneth D. Merry 78adacd4ea Add the LTO-9 density code to libmt and the mt(1) man page. 
These values are taken directly from the density report from an
IBM LTO-9 tape drive.  (Using mt getdensity)

A LTO-9 drive stores 18TB raw (45TB with compression) on an LTO-9 tape.

lib/libmt/mtlib.c:
        Add the LTO-9 density code, and bpmm/bpi values.

usr.bin/mt/mt.1:
        Add the LTO-9 density code, bpmm/bpi values and number of
	tracks.  Bump the man page date.

MFC after:	3 days
Sponsored by:	Spectra Logic
2020-12-10 21:06:06 +00:00

695 lines
25 KiB
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.\" Copyright (c) 1981, 1990, 1993
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.\" @(#)mt.1 8.1 (Berkeley) 6/6/93
.\" $FreeBSD$
.\"
.Dd December 10, 2020
.Dt MT 1
.Os
.Sh NAME
.Nm mt
.Nd magnetic tape manipulating program
.Sh SYNOPSIS
.Nm
.Op Fl f Ar tapename
.Ar command
.Op Ar count
.Nm
.Op Fl f Ar tapename
.Ar command
.Ar argument
.Sh DESCRIPTION
The
.Nm
utility is used to command a magnetic tape drive for operations
other than reading or writing data.
.Pp
The
.Fl f
option's
.Ar tapename
overrides the
.Ev TAPE
environment variable described below.
.Pp
The available commands are listed below.
Only as many
characters as are required to uniquely identify a command
need be specified.
.Pp
The following commands optionally take a
.Ar count ,
which defaults to 1.
.Bl -tag -width ".Cm erase"
.It Cm weof
Write
.Ar count
end-of-file (EOF) marks at the current position.
This returns when the file mark has been written to the media.
.It Cm weofi
Write
.Ar count
end-of-file (EOF) marks at the current position.
This returns as soon as the command has been validated by the tape drive.
.It Cm smk
Write
.Ar count
setmarks at the current position (DDS drives only).
.It Cm fsf
Forward space
.Ar count
files.
.It Cm fsr
Forward space
.Ar count
records.
.It Cm fss
Forward space
.Ar count
setmarks (DDS drives only).
.It Cm bsf
Backward space
.Ar count
files.
.It Cm bsr
Backward space
.Ar count
records.
.It Cm bss
Backward space
.Ar count
setmarks (DDS drives only).
.It Cm erase
Erase the tape using a long (often very long) method.
With a
.Ar count
of 0, it will erase the tape using a quick method.
Operation is not guaranteed if the tape is not at its beginning.
The tape will be at its beginning upon completion.
.El
.Pp
The following commands ignore
.Ar count .
.Bl -tag -width ".Cm geteotmodel"
.It Cm rdhpos
Read the hardware block position.
The block
number reported is specific for that hardware only.
With drive data compression especially,
this position may have more to do with the amount of data
sent to the drive than the amount of data written to tape.
Some drives do not support this.
.It Cm rdspos
Read the SCSI logical block position.
This typically is greater than the hardware position
by the number of end-of-file marks.
Some drives do not support this.
.It Cm rewind
Rewind the tape.
.It Cm offline , rewoffl
Rewind the tape and place the drive off line.
Some drives are never off line.
.It Cm load
Load the tape into the drive.
.It Cm retension
Re-tension the tape.
This winds the tape from the current position to the end
and then to the beginning.
This sometimes improves subsequent reading and writing,
particularly for streaming drives.
Some drives do not support this.
.It Cm ostatus
Output status information about the drive.
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 outputs 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).
.Pp
Also note that this is the old status command, and will be eliminated in
favor of the new status command (see below) in a future release.
.It Cm errstat
Output (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 outputs this
information.
If possible, this also clears any latched error information.
.It Cm geteotmodel
Output the current EOT filemark model.
The model states how
many filemarks will be written at close if a tape was being written.
.It Cm eod , eom
Wind the tape to the end of the recorded data,
typically after an EOF mark where another file may be written.
.It Cm rblim
Report the block limits of the tape drive, including the minimum and
maximum block size, and the block granularity if any.
.El
.Pp
The following commands may require an
.Ar argument .
.Bl -tag -width ".Cm seteotmodel"
.It Cm sethpos
Set the hardware block position.
The
.Ar argument
is a hardware block number to which to position the tape.
Some drives do not support this.
.It Cm setspos
Set the SCSI logical block position.
The
.Ar argument
is a SCSI logical block number to which to position the tape.
Some drives do not support this.
.It Cm blocksize
Set the block size for the drive.
The
.Ar argument
is the number of bytes per block,
except 0 commands the drive to use variable-length blocks.
.It Cm seteotmodel
Set the EOT filemark model to
.Ar argument
and output the old and new models.
Typically this will be 2
filemarks, but some devices (typically QIC cartridge drives) can
only write 1 filemark.
You may only choose a value of
.Ar 1
or
.Ar 2 .
.It Cm status
Output status information about the drive.
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.
.Pp
If the driver knows the relative
position from BOT (in terms of filemarks and records), it outputs that.
If the tape drive supports the long form report of the
.Tn SCSI
READ POSITION command, the Reported File Number and Reported Record Number
will be numbers other than -1, and there may be Flags reported as well.
.Pp
The BOP flag means that the logical position of the drive is at the
beginning of the partition.
.Pp
The EOP flag means that the logical position of the drive is between Early
Warning and End of Partition.
.Pp
The BPEW flag means that the logical position of the drive is in a
Programmable Early Warning Zone or on the EOP side of Early Warning.
.Pp
Note that the Reported Record Number is the tape block or object number
relative to the beginning of the partition.
The Calculated Record Number is the tape block or object number relative
to the previous file mark.
.Pp
Note
that the Calculated File and Record Numbers are not definitive.
The Reported File and Record Numbers are definitive, if they are numbers
other than -1.
.Bl -tag -width 6n
.It Fl v
Print additional status information, such as the maximum supported I/O
size.
.It Fl x
Print all available status data to stdout in XML format.
.El
.It Cm getdensity
Report density support information for the tape drive and any media that is
loaded.
Most drives will report at least basic density information similar to that
reported by
.Nm status
command.
Newer tape drives that conform to the T-10 SSC and newer tape
specifications may report more detailed information about the types of
tapes they support and the tape currently in the drive.
.Bl -tag -width 6n
.It Fl x
Print all available density data to stdout in XML format.
Because density information is currently included in the general status XML
report used for
.Nm
status command, this will be the same XML output via
.Do
.Nm
status
.Fl x
.Dc
.El
.It Cm param
Display or set parameters.
One of
.Fl l ,
.Fl s ,
or
.Fl x
must be specified to indicate which operation to perform.
See
.Xr sa 4
for more detailed information on the parameters.
.Bl -tag -width 8n
.It Fl l
List parameters, values and descriptions.
By default all parameters will be displayed.
To display a specific parameter, specify the parameter with
.Fl p .
.It Fl p Ar name
Specify the parameter name to list (with
.Fl l )
or set (with
.Fl s ) .
.It Fl q
Enable quiet mode for parameter listing.
This will suppress printing of parameter descriptions.
.It Fl s Ar value
Specify the parameter value to set.
The general type of this argument (integer, unsigned integer, string) is
determined by the type of the variable indicated by the
.Xr sa 4
driver.
More detailed argument checking is done by the
.Xr sa 4
driver.
.It Fl x
Print out all parameter information in XML format.
.El
.It Cm protect
Display or set drive protection parameters.
This is used to control checking and reporting a per-block checksum for
tape drives that support it.
Some drives may only support some parameters.
.Bl -tag -width 8n
.It Fl b Ar 0|1
Set the Recover Buffered Data Protected bit.
If set, this indicates that checksums are transferred with the logical
blocks transferred by the RECOVERED BUFFERED DATA
.Tn SCSI
command.
.It Fl d
Disable all protection information settings.
.It Fl e
Enable all protection information settings.
The default protection method used is Reed-Solomon CRC (protection method
1), as specified in ECMA-319.
The default protection information length used with Reed-Solomon CRC is
4 bytes.
To enable all settings except one more setting, specify the
.Fl e
argument and then explicitly disable settings that you do not wish to
enable.
For example, specifying
.Fl e
.Fl w Ar 0
will enable all settings except for LBP_W.
.It Fl l
List available protection parmeters and their current settings.
.It Fl L Ar len
Set the length of the protection information in bytes.
For Reed-Solomon CRC, the protection information length should be 4 bytes.
.It Fl m Ar num
Specify the numeric value for the protection method.
The numeric value for Reed-Solomon CRC is 1.
.It Fl r Ar 0|1
Set the LBP_R parameter.
When set, this indicates that each block read from the tape drive will
have a checksum at the end.
.It Fl v
Enable verbose mode for parameter listing.
This will include descriptions of each parameter.
.It Fl w Ar 0|1
Set the LBP_W parameter.
When set, this indicates that each block written to the tape drive will have
a checksum at the end.
The drive will verify the checksum before writing the block to tape.
.El
.It Cm locate
Set the tape drive's logical position.
One of
.Fl b ,
.Fl e ,
.Fl f ,
or
.Fl s
must be specified to indicate the type of position.
If the partition number is specified, the drive will first relocate to the
given partition (if it exists) and then to the position indicated within
that partition.
If the partition number is not specified, the drive will relocate to the
given position within the current partition.
.Bl -tag -width 14n
.It Fl b Ar block_addr
Relocate to the given tape block or logical object identifier.
Note that the block number is the Reported Record Number that is relative
to the beginning of the partition (or beginning of tape).
.It Fl e
Relocate to the end of data.
.It Fl f Ar fileno
Relocate to the given file number.
.It Fl p Ar partition
Specify the partition to change to.
.It Fl s Ar setmark
Relocate to the given set mark.
.El
.It Cm comp
Set the drive's compression mode.
The non-numeric values of
.Ar argument
are:
.Pp
.Bl -tag -width 9n -compact
.It off
Turn compression off.
.It on
Turn compression on.
.It none
Same as
.Ar off .
.It enable
Same as
.Ar on .
.It IDRC
IBM Improved Data Recording Capability compression (0x10).
.It DCLZ
DCLZ compression algorithm (0x20).
.El
.Pp
In addition to the above recognized compression keywords, the user can
supply a numeric compression algorithm for the drive to use.
In most
cases, simply turning the compression
.Sq on
will have the desired effect of enabling the default compression algorithm
supported by the drive.
If this is not the case (see the
.Cm 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 from the drive's specifications.
.Pp
Note that for some older tape drives (for example the Exabyte 8200 and 8500
series drives) it is necessary to switch to a different density to tell the
drive to record data in its compressed format.
If the user attempts to turn compression on while the uncompressed density
is selected, the drive will return an error.
This is generally not an issue for modern tape drives.
.It Cm density
Set the density for the drive.
For the density codes, see below.
The density value could be given either numerically, or as a string,
corresponding to the
.Dq 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 output about what the given
string has been taken for.
.El
.Pp
The initial version of the density table below was taken from the
.Sq 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.
Subsequent additions have come from a number of sources.
.Pp
The density codes are:
.Bd -literal -offset 2n
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 1,3
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 5,11
0x15 8.0 (0.315) 1 1,789 (45,434) RLL CS ECMA TC17 5,12
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
0x40 12.7 (0.5) 384 4,800 (123,952) C LTO-1
0x41 12.7 (0.5) 208 3,868 (98,250) RLL C DLTapeIV(40) 6,7
0x42 12.7 (0.5) 512 7,398 (187,909) C LTO-2
0x44 12.7 (0.5) 704 9,638 (244,805) C LTO-3
0x46 12.7 (0.5) 896 12,725 (323,215) C LTO-4
0x47 3.81 (0.25) ? 6,417 (163,000) CS DAT-72
0x48 12.7 (0.5) 448 5,236 (133,000) PRML C SDLTapeI(110) 6,8,13
0x49 12.7 (0.5) 448 7,598 (193,000) PRML C SDLTapeI(160) 6,8
0x4A 12.7 (0.5) 768 ? PRML C T10000A 10
0x4B 12.7 (0.5) 1152 ? PRML C T10000B 10
0x4C 12.7 (0.5) 3584 ? PRML C T10000C 10
0x4D 12.7 (0.5) 4608 ? PRML C T10000D 10
0x51 12.7 (0.5) 512 11,800 (299,720) C 3592A1 (unencrypted)
0x52 12.7 (0.5) 896 11,800 (299,720) C 3592A2 (unencrypted)
0x53 12.7 (0.5) 1152 13,452 (341,681) C 3592A3 (unencrypted)
0x54 12.7 (0.5) 2560 19,686 (500,024) C 3592A4 (unencrypted)
0x55 12.7 (0.5) 5120 20,670 (525,018) C 3592A5 (unencrypted)
0x56 12.7 (0.5) 7680 20,670 (525,018) C 3592B5 (unencrypted)
0x57 12.7 (0.5) 8704 21,850 (554,990) C 3592A6 (unencrypted)
0x58 12.7 (0.5) 1280 15,142 (384,607) C LTO-5
0x5A 12.7 (0.5) 2176 15,142 (384,607) C LTO-6
0x5C 12.7 (0.5) 3584 19,107 (485,318) C LTO-7
0x5D 12.7 (0.5) 5376 19,107 (485,318) C LTO-M8 14
0x5E 12.7 (0.5) 6656 20,669 (524,993) C LTO-8
0x60 12.7 (0.5) 8960 23,031 (584,987) C LTO-9
0x71 12.7 (0.5) 512 11,800 (299,720) C 3592A1 (encrypted)
0x72 12.7 (0.5) 896 11,800 (299,720) C 3592A2 (encrypted)
0x73 12.7 (0.5) 1152 13,452 (341,681) C 3592A3 (encrypted)
0x74 12.7 (0.5) 2560 19,686 (500,024) C 3592A4 (encrypted)
0x75 12.7 (0.5) 5120 20,670 (525,018) C 3592A5 (encrypted)
0x76 12.7 (0.5) 7680 20,670 (525,018) C 3592B5 (encrypted)
0x77 12.7 (0.5) 8704 21,850 (554,990) C 3592A6 (encrypted)
0x8c 8.0 (0.315) 1 1,789 (45,434) RLL CS EXB-8500c 5,9
0x90 8.0 (0.315) 1 1,703 (43,245) RLL CS EXB-8200c 5,9
.Ed
.Bd -literal -offset 2n
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
.Ed
.Bd -literal -offset 2n
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.
9. Vendor-specific Exabyte density code for compressed format.
10. bpi/bpmm values for the Oracle/StorageTek T10000 tape drives are
not listed in the manual. Someone with access to a drive can
supply the necessary values by running 'mt getdensity'.
11. This is Exabyte 8200 uncompressed format. The compressed format
density code is 0x90.
12. This is Exabyte 8500 uncompressed format. The compressed format
density code is 0x8c.
13. This density code (0x48) was also used for DAT-160.
14. Officially known as LTO-8 Type M, abbreviated M8. This is a pristine
LTO-7 cartridge initialized with a higher density format by an LTO-8
drive. It cannot be read by an LTO-7 drive. Uncompressed capacity
is 9TB, compared to 6TB for LTO-7 and 12TB for LTO-8.
.Ed
.Bd -literal -offset 2n
NOTE ON QIC STREAMERS
The following is a table of Data Cartridge types as used in the 1/4 inch
tape drives such as the Archive Viper 150, Wangtek 5525ES, and Tandberg
TDC4220 tape drives:
Value Reference Format Cartridge Type Capacity Tracks Length
----- --------- ------ -------------- -------- ------ ------
0x05 QIC-11 DC300 15MB 4 300ft
0x05 QIC-11 DC300XL/P 20MB 4 450ft
0x05 QIC-11 DC600 27MB 4 600ft
0x05 X3.136-1986 QIC-24 DC615A 15MB 9 150ft
0x05 X3.136-1986 QIC-24 DC300XL/P 45MB 9 450ft
0x05 X3.136-1986 QIC-24 DC600A 60MB 9 600ft
0x0F QIC-120 QIC-120 DC600A/DC6150 120MB 15 620ft
0x10 QIC-150 QIC-150 DC600XTD/DC6150 150MB 18 620ft
0x10 QIC-150 QIC-150 DC6250 250MB 18 1,020ft
0x11 QIC-320 QIC-525 DC6320 320MB 26 620ft
0x11 QIC-320 QIC-525 DC6525 525MB 26 1,020ft
0x1E QIC-1000C QIC-1000 DC9100/DL9135 1.0GB 30 760ft
0x1E QIC-1000C QIC-1000 DC9150 1.2GB 30 950ft
0x22 QIC-2GB(C) QIC-2GB DC9200 2.0GB 42 950ft
0x22 QIC-2GB(C) QIC-2GB DC9250 2.5GB 42 1,200ft
.Ed
.Pp
Notes:
.Pp
QIC-24, QIC-120, QIC-150 use fixed blocksize of 512 bytes, QIC-525, QIC-1000
and QIC-2GB can use blocksize of 1,024 bytes.
DDS (DAT) drives generally use variable blocks.
.Pp
QIC-02 and QIC-36 are interface standards for tape drives.
The QIC-02 and QIC-36 streamers such as the Wangtek 5250EQ are otherwise
identical to their SCSI versions (i.e.: Wangtek 5250ES).
.Pp
It seems that the 150MB and larger streamers cannot write QIC-24 9 track
formats, only read them.
.Pp
DC600A cartridges marked "10,000ftpi" can only be used as QIC-11, QIC-24,
and QIC-120 format.
DC600A cartridges marked 12,500ftpi can be used as both QIC-120 and QIC-150
format.
.Pp
Some manufacturers do not use "DC" on their cartridges.
Verbatim uses DL, Maxell uses MC, Sony uses QD, Quill uses DQ.
.Pp
3M/Imation & Fuji use DC.
Thus a DL6250, MC-6250, QD6250, DQ6250 are all identical media to a DC6250.
.Pp
QIC tape media is not "connected" to the take up reels and will de-spool
if the tape drive has dust covering the light sensor that looks for the end
of tape holes in the media.
.Sh ENVIRONMENT
.Bl -tag -width ".Ev TAPE"
.It Ev TAPE
This is the pathname of the tape drive.
The default (if the variable is unset, but not if it is null) is
.Pa /dev/nsa0 .
It may be overridden with the
.Fl f
option.
.El
.Sh FILES
.Bl -tag -width ".Pa /dev/*sa[0-9]*" -compact
.It Pa /dev/*sa[0-9]*
SCSI magnetic tape interface
.El
.Sh DIAGNOSTICS
The exit status will be 0 when the drive operations were successful,
2 when the drive operations were unsuccessful, and 1 for other
problems like an unrecognized command or a missing drive device.
.Sh COMPATIBILITY
Some undocumented commands support old software.
.Sh SEE ALSO
.Xr dd 1 ,
.Xr ioctl 2 ,
.Xr mtio 4 ,
.Xr sa 4 ,
.Xr environ 7
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.3 .
.Pp
Extensions regarding the
.Xr st 4
driver appeared in
.Bx 386 0.1
as a separate
.Nm st
command, and have been merged into the
.Nm
command in
.Fx 2.1 .
.Pp
The former
.Cm eof
command that used to be a synonym for
.Cm weof
has been abandoned in
.Fx 2.1
since it was often confused with
.Cm eom ,
which is fairly dangerous.
.Sh BUGS
The utility cannot be interrupted or killed during a long erase
(which can be longer than an hour), and it is easy to forget
that the default erase is long.
.Pp
Hardware block numbers do not always correspond to blocks on the tape
when the drive uses internal compression.
.Pp
Erasure is not guaranteed if the tape is not at its beginning.
.Pp
Tape-related documentation is poor, here and elsewhere.
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