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.

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.