MT(1)

NAME
mt - magnetic tape manipulation

SYNOPSIS
mt [-f tapename] command [count]

DESCRIPTION
The mt program is used to give commands to a magnetic tape drive. By default mt performs the requested operation once. Operations may be performed multiple times by specifying count.

Note that tapename must reference a raw (not block) tape device. If tapename is of the form "host:tapename", or "user@host:tapename", mt writes to the named tape device on the remote host using rmt(8).

The rmt(8) process on the remote host is typically initiated via rsh(1), although an alternate method such as ssh(1) can be specified via the RCMD_CMD environment variable.

The available commands are listed below. Only as many characters as are required to uniquely identify a command need be specified.

asf Move forward count files from the beginning of the tape. This is accomplished by a rewind followed by fsf count.

eof, weof
    Write count end-of-file marks at the current position on the tape.

fsf Forward space count files.

fsr Forward space count records.

bsf Back space count files.

bsr Back space count records.

rewind
    Rewind the tape. (The count is ignored.)

offline, rewoffl
    Rewind the tape and place the tape unit off-line. Where supported, this ejects the tape. (The count is ignored.)

status
    Print status information about the tape unit. (The count is ignored.)

retension
    Retensions the tape. Not all tape drives support this feature. (The count is ignored.)

erase
    Erases the tape Not all tape drives support this feature. (The count is ignored.)

eew Enable or disable early warning EOM behaviour. Set count to nonzero to enable, zero to disable.

eom Forward space to the end of recorded media. (The count is ignored.)

blocksize, setblk
    Set the tape blocksize to count bytes. A count of zero sets variable blocksize.

density, setdensity
    Set the tape density code to count as specified in the SCSI-3 specification. See the DENSITY CODES section for a list of codes for commonly used media types.

rdspos
    Read the logical block position of the tape. Not all tape drives support this feature. (The count is ignored.)

rdhpos
    Read the hardware block position of the tape. Not all tape drives support this feature. (The count is ignored.)

setspos
    Set the logical block position of the tape to count. Not all tape drives support this feature.

sethpos
    Set the hardware block position of the tape to count. Not all tape drives support this feature.

compress
    If count is zero, disable compression. Otherwise enable compression. Not all tape drives support this feature.

cache
    Enable controller buffering.

nocache
    Disable controller buffering.

If a tape name is not specified, and the environment variable TAPE is not set, then mt uses the device /dev/nrst0.

ENVIRONMENT
If the following environment variables exist, they are used by mt.

TAPE
    mt uses device filename given in the TAPE environment variable if the tapename argument is not given.

RCMD_CMD
    mt will use RCMD_CMD rather than /usr/bin/rsh to invoke rmt(8) on a remote machine. The full path name must be specified.

FILES
/dev/rst*
    Raw SCSI tape device
/dev/rmt*
    Raw magnetic tape device

EXIT STATUS
mt returns a 0 exit status when the operation(s) were successful, 1 if the command was unrecognized, and 2 if an operation failed.

DENSITY CODES
The SCSI-3 specification defines a number of density codes for various tape media, some of which are listed here. Note that many tape drive vendors also define model-specific codes.

Code | Format
0 | Device default
1 | 1/2" 800 bpi
2 | 1/2" 1600 bpi
3 | 1/2" 6250 bpi
4 | QIC-11
5 | QIC-24
15 | QIC-120
16 | QIC-150
17 | QIC-320/525
18 | QIC-1320/1350
19 | DDS
28 | QIC-385M
29 | QIC-410M
30 | QIC-1000C
31 | QIC-2100C
32 | QIC-6GB
33 | QIC-20GB
34 | QIC-2GB
35 | QIC-875M
36 | DDS-2
37 | DDS-3
38 | DDS-4

SEE ALSO
dd(1), ioctl(2), mtio(4), st(4), environ(7)

HISTORY
The mt utility appeared in 4.3BSD.