freebsd/usr.bin/mt/mt.1

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.\"	@(#)mt.1	8.1 (Berkeley) 6/6/93
.\"
.Dd June 6, 1993
.Dt MT 1
.Os BSD 4
.Sh NAME
.Nm mt
.Nd magnetic tape manipulating program
.Sh SYNOPSIS
.Nm
.Op Fl f Ar tapename
.Ar command
.Op Ar count
.Sh DESCRIPTION
.Nm Mt
is used to give commands to a magnetic tape drive.
By default
.Nm
performs the requested operation once.  Operations
may be performed multiple times by specifying
.Ar count  .
Note
that
.Ar tapename
must reference a raw (not block) tape device.
.Pp
The available commands are listed below.  Only as many
characters as are required to uniquely identify a command
need be specified.
.Bl -tag -width "eof, weof"
.It Cm weof
Write
.Ar count
end-of-file marks at the current position on the tape.
.It Cm smk
Write
.Ar count
setmarks at the current position on the tape.
.It Cm fsf
Forward space
.Ar count
files.
.It Cm fsr
Forward space
.Ar count
records.
.It Cm fss
Forward space
.Ar count
setmarks.
.It Cm bsf
Backward space
.Ar count
files.
.It Cm bsr
Backward space
.Ar count
records.
.It Cm bss
Backward space
.Ar count
setmarks.
.It Cm 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
.It Cm rdspos
Read SCSI logical block position. Some drives do not support this. The
count argument is ignored.
.It Cm sethpos
Set Hardware block position. Some drives do not support this. The count
argument is interpreted as a hardware block to position to.
.It Cm setspos
Set SCSI logical block position. Some drives do not support this. The count
argument is interpreted as a hardware block to position to.
.It Cm rewind
Rewind the tape
(Count is ignored).
.It Cm offline , rewoffl
Rewind the tape and place the tape unit off-line
(Count is ignored).
.It Cm erase
Erase the tape.
A count of 0 disables long erase, which is on by default.
.It Cm retension
Re-tension the tape
(one full wind forth and back, Count is ignored).
.It Cm status
Print status information about the tape unit. 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 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.
.It Cm 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.
.It Cm blocksize
Set the block size for the tape unit.  Zero means variable-length
blocks.
.It Cm 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
.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 printed about what the given
string has been taken for.
.It Cm eom
Forward space to end of recorded medium
(Count is ignored).
.It Cm eod
Forward space to end of data, identical to
.Cm eom .
.It Cm comp
Set compression mode.
There are currently several possible values for the compression mode:
.Pp
.Bl -tag -width 123456789 -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 tape 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.
.El
.Pp
If a tape name is not specified, and the environment variable
.Ev TAPE
does not exist;
.Nm
uses the device
.Pa /dev/nrsa0 .
.Pp
.Nm Mt
returns a 0 exit status when the operation(s) were successful,
1 if the command was unrecognized, and 2 if an operation failed.
.Pp
The following density table 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.
.Pp
The different density codes are as follows:
.Pp
.Dl 0x0	default for device
.Dl 0xE	reserved for ECMA
.Bd -literal -offset 3n
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
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
.Ed

.Bd -literal -offset 3n
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
.Ed

.Bd -literal -offset 3n
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.
.Ed

.Sh ENVIRONMENT
If the following environment variable exists, it is utilized by
.Nm mt .
.Bl -tag -width Fl
.It Ev TAPE
.Nm Mt
checks the
.Ev TAPE
environment variable if the
argument
.Ar tapename
is not given.
.Sh FILES
.Bl -tag -width /dev/*rst[0-9]*xx -compact
.It Pa /dev/*rwt*
QIC-02/QIC-36 magnetic tape interface
.It Pa /dev/*rsa[0-9]*
SCSI magnetic tape interface
.El
.Sh SEE ALSO
.Xr dd 1 ,
.Xr ioctl 2 ,
.Xr mtio 4 ,
.Xr sa 4 ,
.Xr wt 4 ,
.Xr environ 7
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.3 .
.Pp
Extensions regarding the
.Xr st 4
driver appeared in 386BSD 0.1 as a separate
.Xr st 1
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.