mt —
magnetic tape manipulation
  
    | mt | [ -ftapename]
      command [count] | 
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.
If the following environment variables exist, they are used by
  mt.
  - TAPE
- mtuses device filename given in the- TAPEenvironment variable if the
      tapename argument is not given.
- RCMD_CMD
- mtwill use- RCMD_CMDrather than /usr/bin/rsh to invoke
      rmt(8) on a remote machine. The
      full path name must be specified.
  - /dev/rst*
- Raw SCSI tape device
- /dev/rmt*
- Raw magnetic tape device
mt returns a 0 exit status when the operation(s) were
  successful, 1 if the command was unrecognized, and 2 if an operation failed.
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 | 
The mt utility appeared in
  4.3BSD.