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@(#)mt.1 8.1 (Berkeley) 6/6/93
.Dd September 1, 2018 .Dt MT 1 .Os .Sh NAME .Nm mt .Nd magnetic tape manipulation .Sh SYNOPSIS .Nm .Op Fl f Ar tapename .Ar command .Op Ar count .Sh DESCRIPTION The .Nm program 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 .
p Note that .Ar tapename must reference a raw (not block) tape device. If .Ar tapename is of the form .Qq host:tapename , or .Qq user@host:tapename , .Nm writes to the named tape device on the remote host using .Xr rmt 8 .
p The .Xr rmt 8 process on the remote host is typically initiated via .Xr rsh 1 , although an alternate method such as .Xr ssh 1 can be specified via the .Ev RCMD_CMD environment variable.
p The available commands are listed below. Only as many characters as are required to uniquely identify a command need be specified. l -tag -width "eof, weof" t Cm asf Move forward .Ar count files from the beginning of the tape. This is accomplished by a rewind followed by fsf .Ar count . t Cm eof , weof Write .Ar count end-of-file marks at the current position on the tape. t Cm fsf Forward space .Ar count files. t Cm fsr Forward space .Ar count records. t Cm bsf Back space .Ar count files. t Cm bsr Back space .Ar count records. t Cm rewind Rewind the tape. (The .Ar count is ignored.) t Cm offline , rewoffl Rewind the tape and place the tape unit off-line. Where supported, this ejects the tape. (The .Ar count is ignored.) t Cm status Print status information about the tape unit. (The .Ar count is ignored.) t Cm retension Retensions the tape. Not all tape drives support this feature. (The .Ar count is ignored.) t Cm erase Erases the tape Not all tape drives support this feature. (The .Ar count is ignored.) t Cm eew Enable or disable early warning EOM behaviour. Set .Ar count to nonzero to enable, zero to disable. t Cm eom Forward space to the end of recorded media. (The .Ar count is ignored.) t Cm blocksize , setblk Set the tape blocksize to .Ar count bytes. A .Ar count of zero sets variable blocksize. t Cm density , setdensity Set the tape density code to .Ar count as specified in the .Tn SCSI-3 specification. See the .Sx DENSITY CODES section for a list of codes for commonly used media types. t Cm rdspos Read the logical block position of the tape. Not all tape drives support this feature. (The .Ar count is ignored.) t Cm rdhpos Read the hardware block position of the tape. Not all tape drives support this feature. (The .Ar count is ignored.) t Cm setspos Set the logical block position of the tape to .Ar count . Not all tape drives support this feature. t Cm sethpos Set the hardware block position of the tape to .Ar count . Not all tape drives support this feature. t Cm compress If .Ar count is zero, disable compression. Otherwise enable compression. Not all tape drives support this feature. t Cm cache Enable controller buffering. t Cm nocache Disable controller buffering. .El
p If a tape name is not specified, and the environment variable .Ev TAPE is not set, then .Nm uses the device
a /dev/nrst0 . .Sh ENVIRONMENT If the following environment variables exist, they are used by .Nm . l -tag -width Fl t Ev TAPE .Nm uses device filename given in the .Ev TAPE environment variable if the .Ar tapename argument is not given. t Ev RCMD_CMD .Nm will use .Ev RCMD_CMD rather than
a /usr/bin/rsh to invoke .Xr rmt 8 on a remote machine. The full path name must be specified. .El .Sh FILES l -tag -width /dev/rst* -compact t Pa /dev/rst* Raw .Tn SCSI tape device t Pa /dev/rmt* Raw magnetic tape device .El .Sh EXIT STATUS .Nm returns a 0 exit status when the operation(s) were successful, 1 if the command was unrecognized, and 2 if an operation failed. .Sh 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.
p l -column "Code" "Format" -compact t Em Code Ta Em Format t Li 0 Ta Device default t Li 1 Ta 1/2" 800 bpi t Li 2 Ta 1/2" 1600 bpi t Li 3 Ta 1/2" 6250 bpi t Li 4 Ta QIC-11 t Li 5 Ta QIC-24 t Li 15 Ta QIC-120 t Li 16 Ta QIC-150 t Li 17 Ta QIC-320/525 t Li 18 Ta QIC-1320/1350 t Li 19 Ta DDS t Li 28 Ta QIC-385M t Li 29 Ta QIC-410M t Li 30 Ta QIC-1000C t Li 31 Ta QIC-2100C t Li 32 Ta QIC-6GB t Li 33 Ta QIC-20GB t Li 34 Ta QIC-2GB t Li 35 Ta QIC-875M t Li 36 Ta DDS-2 t Li 37 Ta DDS-3 t Li 38 Ta DDS-4 .El .Sh SEE ALSO .Xr dd 1 , .Xr ioctl 2 , .Xr mtio 4 , .Xr st 4 , .Xr environ 7 .Sh HISTORY The .Nm utility appeared in x 4.3 .
Indexes created Sat Sep 20 22:09:52 GMT 2025