Write count end-of-file marks at the current position on the tape.
Write count setmarks at the current position on the tape.
Forward space count files.
Forward space count records.
Forward space count setmarks.
Backward space count files.
Backward space count records.
Backward space count setmarks.
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.
Read SCSI logical block position. Some drives do not support this. The count argument is ignored.
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.
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 the tape (Count is ignored).
Rewind the tape and place the tape unit off-line (Count is ignored).
Erase the tape. A count of 0 disables long erase, which is on by default.
Re-tension the tape (one full wind forth and back, Count is ignored).
Print status information about the tape unit. For SCSI magnetic 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).
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 is associated status and any residual counts (if any). This command retrieves and prints this information. If possible, this also clears any latched error information.
Set the block size for the tape unit. Zero means variable-length blocks.
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.
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.
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.
Forward space to end of recorded medium (Count is ignored).
Forward space to end of data, identical to eom.
Set compression mode. There are currently several possible values for the compression mode:
Turn compression off.
Turn compression on.
Same as off.
Same as on.
IBM Improved Data Recording Capability compression (0x10).
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 compression algorithm supported by the drive. If this is not the case (see the status display to see which compression algorithm 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 successful, 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.
Code DescriptionType Description
NRZI Non return to zero, change on ones R Reel-to-reel
GCRGroup code recording C Cartridge
PE Phase encodedCS Cassette
IMFM Inverted modified frequency modulation
MFMModified frequency modulation
DDSDAT data storage
RLLRun length limited
PRML Partial Response Maximum Likelihood
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.