MT(1) FreeBSD General Commands Manual MT(1)
NAME
mt - magnetic tape manipulating program
SYNOPSIS
mt [-f tapename] command [count]
mt [-f tapename] command argument
DESCRIPTION
The mt utility is used to command a magnetic tape drive for operations
other than reading or writing data.
The -f option's tapename overrides the TAPE environment variable
described below.
The available commands are listed below. Only as many characters as are
required to uniquely identify a command need be specified.
The following commands optionally take a count, which defaults to 1.
weof Write count end-of-file (EOF) marks at the current position. This
returns when the file mark has been written to the media.
weofi Write count end-of-file (EOF) marks at the current position. This
returns as soon as the command has been validated by the tape
drive.
smk Write count setmarks at the current position (DDS drives only).
fsf Forward space count files.
fsr Forward space count records.
fss Forward space count setmarks (DDS drives only).
bsf Backward space count files.
bsr Backward space count records.
bss Backward space count setmarks (DDS drives only).
erase Erase the tape using a long (often very long) method. With a
count of 0, it will erase the tape using a quick method.
Operation is not guaranteed if the tape is not at its beginning.
The tape will be at its beginning upon completion.
The following commands ignore count.
rdhpos Read the hardware block position. The block number reported
is specific for that hardware only. With drive data
compression especially, this position may have more to do
with the amount of data sent to the drive than the amount of
data written to tape. Some drives do not support this.
rdspos Read the SCSI logical block position. This typically is
greater than the hardware position by the number of end-of-
file marks. Some drives do not support this.
rewind Rewind the tape.
offline, rewoffl
Rewind the tape and place the drive off line. Some drives
are never off line.
load Load the tape into the drive.
retension Re-tension the tape. This winds the tape from the current
position to the end and then to the beginning. This
sometimes improves subsequent reading and writing,
particularly for streaming drives. Some drives do not
support this.
ostatus Output status information about the drive. 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 outputs 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).
Also note that this is the old status command, and will be
eliminated in favor of the new status command (see below) in
a future release.
errstat Output (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 outputs this information. If
possible, this also clears any latched error information.
geteotmodel Output the current EOT filemark model. The model states how
many filemarks will be written at close if a tape was being
written.
eod, eom Wind the tape to the end of the recorded data, typically
after an EOF mark where another file may be written.
rblim Report the block limits of the tape drive, including the
minimum and maximum block size, and the block granularity if
any.
The following commands may require an argument.
sethpos Set the hardware block position. The argument is a hardware
block number to which to position the tape. Some drives do
not support this.
setspos Set the SCSI logical block position. The argument is a SCSI
logical block number to which to position the tape. Some
drives do not support this.
blocksize Set the block size for the drive. The argument is the
number of bytes per block, except 0 commands the drive to
use variable-length blocks.
seteotmodel Set the EOT filemark model to argument and output the old
and new models. Typically this will be 2 filemarks, but
some devices (typically QIC cartridge drives) can only write
1 filemark. You may only choose a value of 1 or 2.
status Output status information about the drive. 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 outputs that. If the tape
drive supports the long form report of the SCSI READ
POSITION command, the Reported File Number and Reported
Record Number will be numbers other than -1, and there may
be Flags reported as well.
The BOP flag means that the logical position of the drive is
at the beginning of the partition.
The EOP flag means that the logical position of the drive is
between Early Warning and End of Partition.
The BPEW flag means that the logical position of the drive
is in a Programmable Early Warning Zone or on the EOP side
of Early Warning.
Note that the Reported Record Number is the tape block or
object number relative to the beginning of the partition.
The Calculated Record Number is the tape block or object
number relative to the previous file mark.
Note that the Calculated File and Record Numbers are not
definitive. The Reported File and Record Numbers are
definitive, if they are numbers other than -1.
-v Print additional status information, such as the
maximum supported I/O size.
-x Print all available status data to stdout in XML
format.
getdensity Report density support information for the tape drive and
any media that is loaded. Most drives will report at least
basic density information similar to that reported by status
command. Newer tape drives that conform to the T-10 SSC and
newer tape specifications may report more detailed
information about the types of tapes they support and the
tape currently in the drive.
-x Print all available density data to stdout in XML
format. Because density information is currently
included in the general status XML report used for
mt status command, this will be the same XML output
via "mt status -x"
param Display or set parameters. One of -l, -s, or -x must be
specified to indicate which operation to perform. See sa(4)
for more detailed information on the parameters.
-l List parameters, values and descriptions. By
default all parameters will be displayed. To
display a specific parameter, specify the
parameter with -p.
-p name Specify the parameter name to list (with -l) or
set (with -s).
-q Enable quiet mode for parameter listing. This
will suppress printing of parameter descriptions.
-s value Specify the parameter value to set. The general
type of this argument (integer, unsigned integer,
string) is determined by the type of the variable
indicated by the sa(4) driver. More detailed
argument checking is done by the sa(4) driver.
-x Print out all parameter information in XML format.
protect Display or set drive protection parameters. This is used to
control checking and reporting a per-block checksum for tape
drives that support it. Some drives may only support some
parameters.
-b 0|1 Set the Recover Buffered Data Protected bit. If
set, this indicates that checksums are transferred
with the logical blocks transferred by the
RECOVERED BUFFERED DATA SCSI command.
-d Disable all protection information settings.
-e Enable all protection information settings. The
default protection method used is Reed-Solomon CRC
(protection method 1), as specified in ECMA-319.
The default protection information length used
with Reed-Solomon CRC is 4 bytes. To enable all
settings except one more setting, specify the -e
argument and then explicitly disable settings that
you do not wish to enable. For example,
specifying -e -w 0 will enable all settings except
for LBP_W.
-l List available protection parameters and their
current settings.
-L len Set the length of the protection information in
bytes. For Reed-Solomon CRC, the protection
information length should be 4 bytes.
-m num Specify the numeric value for the protection
method. The numeric value for Reed-Solomon CRC is
1.
-r 0|1 Set the LBP_R parameter. When set, this indicates
that each block read from the tape drive will have
a checksum at the end.
-v Enable verbose mode for parameter listing. This
will include descriptions of each parameter.
-w 0|1 Set the LBP_W parameter. When set, this indicates
that each block written to the tape drive will
have a checksum at the end. The drive will verify
the checksum before writing the block to tape.
locate Set the tape drive's logical position. One of -b, -e, -f,
or -s must be specified to indicate the type of position.
If the partition number is specified, the drive will first
relocate to the given partition (if it exists) and then to
the position indicated within that partition. If the
partition number is not specified, the drive will relocate
to the given position within the current partition.
-b block_addr Relocate to the given tape block or logical
object identifier. Note that the block
number is the Reported Record Number that is
relative to the beginning of the partition
(or beginning of tape).
-e Relocate to the end of data.
-f fileno Relocate to the given file number.
-p partition Specify the partition to change to.
-s setmark Relocate to the given set mark.
comp Set the drive's compression mode. The non-numeric values of
argument are:
off Turn compression off.
on Turn compression on.
none Same as off.
enable Same as on.
IDRC IBM Improved Data Recording Capability
compression (0x10).
DCLZ DCLZ compression algorithm (0x20).
In addition to the above recognized compression keywords,
the user can supply a numeric compression algorithm for the
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 from the
drive's specifications.
Note that for some older tape drives (for example the
Exabyte 8200 and 8500 series drives) it is necessary to
switch to a different density to tell the drive to record
data in its compressed format. If the user attempts to turn
compression on while the uncompressed density is selected,
the drive will return an error. This is generally not an
issue for modern tape drives.
density Set the density for the drive. 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 output about what the given string has been taken for.
The initial version of the density table below 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. Subsequent additions have come from a number of sources.
The density codes are:
0x0 default for device
0xE reserved for ECMA
Value Width Tracks Density Code Type Reference Note
mm in bpmm bpi
0x01 12.7 (0.5) 9 32 (800) NRZI R X3.22-1983 2
0x02 12.7 (0.5) 9 63 (1,600) PE R X3.39-1986 2
0x03 12.7 (0.5) 9 246 (6,250) GCR R X3.54-1986 2
0x05 6.3 (0.25) 4/9 315 (8,000) GCR C X3.136-1986 1,3
0x06 12.7 (0.5) 9 126 (3,200) PE R X3.157-1987 2
0x07 6.3 (0.25) 4 252 (6,400) IMFM C X3.116-1986 1
0x08 3.81 (0.15) 4 315 (8,000) GCR CS X3.158-1987 1
0x09 12.7 (0.5) 18 1,491 (37,871) GCR C X3.180 2
0x0A 12.7 (0.5) 22 262 (6,667) MFM C X3B5/86-199 1
0x0B 6.3 (0.25) 4 63 (1,600) PE C X3.56-1986 1
0x0C 12.7 (0.5) 24 500 (12,690) GCR C HI-TC1 1,6
0x0D 12.7 (0.5) 24 999 (25,380) GCR C HI-TC2 1,6
0x0F 6.3 (0.25) 15 394 (10,000) GCR C QIC-120 1,6
0x10 6.3 (0.25) 18 394 (10,000) GCR C QIC-150 1,6
0x11 6.3 (0.25) 26 630 (16,000) GCR C QIC-320 1,6
0x12 6.3 (0.25) 30 2,034 (51,667) RLL C QIC-1350 1,6
0x13 3.81 (0.15) 1 2,400 (61,000) DDS CS X3B5/88-185A 5
0x14 8.0 (0.315) 1 1,703 (43,245) RLL CS X3.202-1991 5,11
0x15 8.0 (0.315) 1 1,789 (45,434) RLL CS ECMA TC17 5,12
0x16 12.7 (0.5) 48 394 (10,000) MFM C X3.193-1990 1
0x17 12.7 (0.5) 48 1,673 (42,500) MFM C X3B5/91-174 1
0x18 12.7 (0.5) 112 1,673 (42,500) MFM C X3B5/92-50 1
0x19 12.7 (0.5) 128 2,460 (62,500) RLL C DLTapeIII 6,7
0x1A 12.7 (0.5) 128 3,214 (81,633) RLL C DLTapeIV(20) 6,7
0x1B 12.7 (0.5) 208 3,383 (85,937) RLL C DLTapeIV(35) 6,7
0x1C 6.3 (0.25) 34 1,654 (42,000) MFM C QIC-385M 1,6
0x1D 6.3 (0.25) 32 1,512 (38,400) GCR C QIC-410M 1,6
0x1E 6.3 (0.25) 30 1,385 (36,000) GCR C QIC-1000C 1,6
0x1F 6.3 (0.25) 30 2,666 (67,733) RLL C QIC-2100C 1,6
0x20 6.3 (0.25) 144 2,666 (67,733) RLL C QIC-6GB(M) 1,6
0x21 6.3 (0.25) 144 2,666 (67,733) RLL C QIC-20GB(C) 1,6
0x22 6.3 (0.25) 42 1,600 (40,640) GCR C QIC-2GB(C) ?
0x23 6.3 (0.25) 38 2,666 (67,733) RLL C QIC-875M ?
0x24 3.81 (0.15) 1 2,400 (61,000) CS DDS-2 5
0x25 3.81 (0.15) 1 3,816 (97,000) CS DDS-3 5
0x26 3.81 (0.15) 1 3,816 (97,000) CS DDS-4 5
0x27 8.0 (0.315) 1 3,056 (77,611) RLL CS Mammoth 5
0x28 12.7 (0.5) 36 1,491 (37,871) GCR C X3.224 1
0x29 12.7 (0.5)
0x2A
0x2B 12.7 (0.5) 3 ? ? ? C X3.267 5
0x40 12.7 (0.5) 384 4,800 (123,952) C LTO-1
0x41 12.7 (0.5) 208 3,868 (98,250) RLL C DLTapeIV(40) 6,7
0x42 12.7 (0.5) 512 7,398 (187,909) C LTO-2
0x44 12.7 (0.5) 704 9,638 (244,805) C LTO-3
0x46 12.7 (0.5) 896 12,725 (323,215) C LTO-4
0x47 3.81 (0.25) ? 6,417 (163,000) CS DAT-72
0x48 12.7 (0.5) 448 5,236 (133,000) PRML C SDLTapeI(110) 6,8,13
0x49 12.7 (0.5) 448 7,598 (193,000) PRML C SDLTapeI(160) 6,8
0x4A 12.7 (0.5) 768 ? PRML C T10000A 10
0x4B 12.7 (0.5) 1152 ? PRML C T10000B 10
0x4C 12.7 (0.5) 3584 ? PRML C T10000C 10
0x4D 12.7 (0.5) 4608 ? PRML C T10000D 10
0x51 12.7 (0.5) 512 11,800 (299,720) C 3592A1 (unencrypted)
0x52 12.7 (0.5) 896 11,800 (299,720) C 3592A2 (unencrypted)
0x53 12.7 (0.5) 1152 13,452 (341,681) C 3592A3 (unencrypted)
0x54 12.7 (0.5) 2560 19,686 (500,024) C 3592A4 (unencrypted)
0x55 12.7 (0.5) 5120 20,670 (525,018) C 3592A5 (unencrypted)
0x56 12.7 (0.5) 7680 20,670 (525,018) C 3592B5 (unencrypted)
0x57 12.7 (0.5) 8704 21,850 (554,990) C 3592A6 (unencrypted)
0x58 12.7 (0.5) 1280 15,142 (384,607) C LTO-5
0x59 12.7 (0.5)18944 21,850 (554,990) C 3592A7 (unencrypted)
0x5A 12.7 (0.5) 2176 15,142 (384,607) C LTO-6
0x5C 12.7 (0.5) 3584 19,107 (485,318) C LTO-7
0x5D 12.7 (0.5) 5376 19,107 (485,318) C LTO-M8 14
0x5E 12.7 (0.5) 6656 20,669 (524,993) C LTO-8
0x60 12.7 (0.5) 8960 23,031 (584,987) C LTO-9
0x62 12.7 (0.5)15104 21,657 (550,088) C LTO-10 15
0x63 12.7 (0.5)15104 22,441 (570,001) C LTO-10P 15
0x71 12.7 (0.5) 512 11,800 (299,720) C 3592A1 (encrypted)
0x72 12.7 (0.5) 896 11,800 (299,720) C 3592A2 (encrypted)
0x73 12.7 (0.5) 1152 13,452 (341,681) C 3592A3 (encrypted)
0x74 12.7 (0.5) 2560 19,686 (500,024) C 3592A4 (encrypted)
0x75 12.7 (0.5) 5120 20,670 (525,018) C 3592A5 (encrypted)
0x76 12.7 (0.5) 7680 20,670 (525,018) C 3592B5 (encrypted)
0x77 12.7 (0.5) 8704 21,850 (554,990) C 3592A6 (encrypted)
0x79 12.7 (0.5)18944 21,850 (554,990) C 3592A7 (encrypted)
0x8c 8.0 (0.315) 1 1,789 (45,434) RLL CS EXB-8500c 5,9
0x90 8.0 (0.315) 1 1,703 (43,245) RLL CS EXB-8200c 5,9
Code Description Type Description
---- -------------------------------------- ---- -----------
NRZI Non return to zero, change on ones R Reel-to-reel
GCR Group code recording C Cartridge
PE Phase encoded CS Cassette
IMFM Inverted modified frequency modulation
MFM Modified frequency modulation
DDS DAT data storage
RLL Run length limited
PRML Partial Response Maximum Likelihood
NOTES
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.
9. Vendor-specific Exabyte density code for compressed format.
10. bpi/bpmm values for the Oracle/StorageTek T10000 tape drives are
not listed in the manual. Someone with access to a drive can
supply the necessary values by running 'mt getdensity'.
11. This is Exabyte 8200 uncompressed format. The compressed format
density code is 0x90.
12. This is Exabyte 8500 uncompressed format. The compressed format
density code is 0x8c.
13. This density code (0x48) was also used for DAT-160.
14. Officially known as LTO-8 Type M, abbreviated M8. This is a pristine
LTO-7 cartridge initialized with a higher density format by an LTO-8
drive. It cannot be read by an LTO-7 drive. Uncompressed capacity
is 9TB, compared to 6TB for LTO-7 and 12TB for LTO-8.
15. LTO-10 Premium cartridges hold 40TB uncompressed vs. 30TB
uncompressed for standard LTO-10 cartridges due to slightly higher
density and stronger, thinner, longer tape. LTO-10 tape drives
are not backward compatible with previous generation LTO tape
cartridges.
NOTE ON QIC STREAMERS
The following is a table of Data Cartridge types as used in the 1/4 inch
tape drives such as the Archive Viper 150, Wangtek 5525ES, and Tandberg
TDC4220 tape drives:
Value Reference Format Cartridge Type Capacity Tracks Length
----- --------- ------ -------------- -------- ------ ------
0x05 QIC-11 DC300 15MB 4 300ft
0x05 QIC-11 DC300XL/P 20MB 4 450ft
0x05 QIC-11 DC600 27MB 4 600ft
0x05 X3.136-1986 QIC-24 DC615A 15MB 9 150ft
0x05 X3.136-1986 QIC-24 DC300XL/P 45MB 9 450ft
0x05 X3.136-1986 QIC-24 DC600A 60MB 9 600ft
0x0F QIC-120 QIC-120 DC600A/DC6150 120MB 15 620ft
0x10 QIC-150 QIC-150 DC600XTD/DC6150 150MB 18 620ft
0x10 QIC-150 QIC-150 DC6250 250MB 18 1,020ft
0x11 QIC-320 QIC-525 DC6320 320MB 26 620ft
0x11 QIC-320 QIC-525 DC6525 525MB 26 1,020ft
0x1E QIC-1000C QIC-1000 DC9100/DL9135 1.0GB 30 760ft
0x1E QIC-1000C QIC-1000 DC9150 1.2GB 30 950ft
0x22 QIC-2GB(C) QIC-2GB DC9200 2.0GB 42 950ft
0x22 QIC-2GB(C) QIC-2GB DC9250 2.5GB 42 1,200ft
Notes:
QIC-24, QIC-120, QIC-150 use fixed blocksize of 512 bytes, QIC-525,
QIC-1000 and QIC-2GB can use blocksize of 1,024 bytes. DDS (DAT) drives
generally use variable blocks.
QIC-02 and QIC-36 are interface standards for tape drives. The QIC-02
and QIC-36 streamers such as the Wangtek 5250EQ are otherwise identical
to their SCSI versions (i.e.: Wangtek 5250ES).
It seems that the 150MB and larger streamers cannot write QIC-24 9 track
formats, only read them.
DC600A cartridges marked "10,000ftpi" can only be used as QIC-11, QIC-24,
and QIC-120 format. DC600A cartridges marked 12,500ftpi can be used as
both QIC-120 and QIC-150 format.
Some manufacturers do not use "DC" on their cartridges. Verbatim uses
DL, Maxell uses MC, Sony uses QD, Quill uses DQ.
3M/Imation & Fuji use DC. Thus a DL6250, MC-6250, QD6250, DQ6250 are all
identical media to a DC6250.
QIC tape media is not "connected" to the take up reels and will de-spool
if the tape drive has dust covering the light sensor that looks for the
end of tape holes in the media.
ENVIRONMENT
TAPE This is the pathname of the tape drive. The default (if the
variable is unset, but not if it is null) is /dev/nsa0. It may be
overridden with the -f option.
FILES
/dev/*sa[0-9]* SCSI magnetic tape interface
DIAGNOSTICS
The exit status will be 0 when the drive operations were successful, 2
when the drive operations were unsuccessful, and 1 for other problems
like an unrecognized command or a missing drive device.
COMPATIBILITY
Some undocumented commands support old software.
SEE ALSO
dd(1), ioctl(2), mtio(4), sa(4), environ(7)
HISTORY
The mt command appeared in 4.3BSD.
Extensions regarding the st(4) driver appeared in 386BSD-0.1 as a
separate st command, and have been merged into the mt command in
FreeBSD 2.1.
The former eof command that used to be a synonym for weof has been
abandoned in FreeBSD 2.1 since it was often confused with eom, which is
fairly dangerous.
BUGS
The utility cannot be interrupted or killed during a long erase (which
can be longer than an hour), and it is easy to forget that the default
erase is long.
Hardware block numbers do not always correspond to blocks on the tape
when the drive uses internal compression.
Erasure is not guaranteed if the tape is not at its beginning.
Tape-related documentation is poor, here and elsewhere.
FreeBSD 15.1-STABLE-HBSD March 2, 2026 MT(1)