MT(1) BSD General Commands Manual MT(1)NAMEmt — magnetic tape manipulating program
SYNOPSISmt [-f tapename] command [count]
DESCRIPTION
The mt utility is used to give commands to a magnetic tape drive. By
default mt performs the requested operation once. Operations may be per‐
formed multiple times by specifying count. Note that tapename must ref‐
erence a raw (not block) tape device.
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
tape.
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
ignored).
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
ignored).
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
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).
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.
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.
geteotmodel
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.
seteotmodel
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
(0x10).
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
numeric 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
Device 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)
0x2A
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
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.
ENVIRONMENT
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.
FILES
/dev/*rwt* QIC-02/QIC-36 magnetic tape interface
/dev/*rsa[0-9]* SCSI magnetic tape interface
SEE ALSOdd(1), ioctl(2), mtio(4), sa(4), wt(4), environ(7)HISTORY
The mt command appeared in 4.3BSD.
Extensions regarding the st(4) driver appeared in 386BSD 0.1 as a sepa‐
rate st(1) 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
