mtx - control SCSI media changer devices
mtx [-f <scsi-generic-device>] [nobarcode] [invert] [noattach] command
[ command ... ]
The mtx command controls single or multi-drive SCSI media changers such
as tape changers, autoloaders, tape libraries, or optical media juke-
boxes. It can also be used with media changers that use the ’ATTACHED’
API, presuming that they properly report the MChanger bit as required
by the SCSI T-10 SMC specification.
The first argument, given following -f , is the SCSI generic device
corresponding to your media changer. Consult your operating system’s
documentation for more information (for example, under Linux these are
generally /dev/sg0 through /dev/sg15, under FreeBSD these are
/dev/pass0 through /dev/passX, under SunOS it may be a file under
The ’invert’ option will invert (flip) the media (for optical jukeboxes
that allow such) before inserting it into the drive or returning it to
the storage slot.
The ’noattach’ option forces the regular media changer API even if the
media changer incorrectly reported that it uses the ’ATTACHED’ API.
The ’nobarcode’ option forces the loader to not request barcodes even
if the loader is capable of reporting them.
Following these options there may follow one or more robotics control
commands. Note that the ’invert’ and ’noattach’ options apply to ALL of
robotics control commands.
--version Report the mtx version number (e.g. mtx 1.2.8) and exit.
inquiry Report the product type (Medium Changer, Tape Drive, etc.),
Vendor ID, Product ID, Revision, and whether this uses the
Attached Changer API (some tape drives use this rather than
reporting a Medium Changer on a separate LUN or SCSI
noattach Make further commands use the regular media changer API
rather than the _ATTACHED API, no matter what the "Attached"
bit said in the Inquiry info. Needed with some brain-dead
changers that report Attached bit but don’t respond to
inventory Makes the robot arm go and check what elements are in the
slots. This is needed for a few libraries like the Breece
Hill ones that do not automatically check the tape inventory
at system startup.
status Reports how many drives and storage elements are contained in
the device. For each drive, reports whether it has media
loaded in it, and if so, from which storage slot the media
originated. For each storage slot, reports whether it is
empty or full, and if the media changer has a bar code, MIC
reader, or some other way of uniquely identifying media with-
out loading it into a drive, this reports the volume tag
and/or alternate volume tag for each piece of media. For
historical reasons drives are numbered from 0 and storage
slots are numbered from 1.
load <slotnum> [ <drivenum> ]
Load media from slot <slotnum> into drive <drivenum>. Drive 0
is assumed if the drive number is omitted.
unload [<slotnum>] [ <drivenum> ]
Unloads media from drive <drivenum> into slot <slotnum>. If
<drivenum> is omitted, defaults to drive 0 (as do all com-
mands). If <slotnum> is omitted, defaults to the slot that
the drive was loaded from. Note that there’s currently no way
to say ’unload drive 1’s media to the slot it came from’,
other than to explicitly use that slot number as the destina-
[eepos <operation>] transfer <slotnum> <slotnum>
Transfers media from one slot to another, assuming that your
mechanism is capable of doing so. Usually used to move media
to/from an import/export port. ’eepos’ is used to
extend/retract the import/export tray on certain mid-range to
high end tape libraries (if, e.g., the tray was slot 32, you
might say say ’eepos 1 transfer 32 32’ to extend the tray).
Valid values for eepos <operation> are 0 (do nothing to the
import/export tray), 1, and 2 (what 1 and 2 do varies depend-
ing upon the library, consult your library’s SCSI-level docu-
Loads drive <drivenum> from the first slot in the media
changer. Unloads the drive if there is already media in it.
Note that this command may not be what you want on large tape
libraries -- e.g. on Exabyte 220, the first slot is usually a
cleaning tape. If <drivenum> is omitted, defaults to first
Loads drive <drivenum> from the last slot in the media
changer. Unloads the drive if there is already a tape in it.
Unloads the drive and loads the next tape in sequence. If the
drive was empty, loads the first tape into the drive.
The original ’mtx’ program was written by Leonard Zubkoff and exten-
sively revised for large multi-drive libraries with bar code readers by
Eric Lee Green <firstname.lastname@example.org>, to whom all problems should be
reported for this revision. See ’mtx.c’ for other contributors.
BUGS AND LIMITATIONS
You may need to do a ’mt offline’ on the tape drive to eject the tape
before you can issue the ’mtx unload’ command. The Exabyte EZ-17 and
220 in particular will happily sit there snapping the robot arm’s claws
around thin air trying to grab a tape that’s not there.
For some Linux distributions, you may need to re-compile the kernel to
scan SCSI LUN’s in order to detect the media changer. Check
/proc/scsi/scsi to see what’s going on.
If you try to unload a tape to its ’source’ slot, and said slot is
full, it will instead put the tape into the first empty slot. Unfortu-
nately the list of empty slots is not updated between commands on the
command line, so if you try to unload another drive to a full ’source’
slot during the same invocation of ’mtx’, it will try to unload to the
same (no longer empty) slot and will urp with a SCSI error.
This program reads the Mode Sense Element Address Assignment Page
(SCSI) and requests data on all available elements. For larger
libraries (more than a couple dozen elements) this sets a big Alloca-
tion_Size in the SCSI command block for the REQUEST_ELEMENT_STATUS com-
mand in order to be able to read the entire result of a big tape
library. Some operating systems may not be able to handle this. Ver-
sions of Linux earlier than 2.2.6, in particular, may fail this request
due to inability to find contiguous pages of memory for the SCSI trans-
fer (later versions of Linux ’sg’ device do scatter-gather so that this
should no longer be a problem).
The eepos command remains in effect for all further commands on a com-
mand line. Thus you might want to follow eepos 1 transfer 32 32 with
eepos 0 as the next command (which clears the eepos bits).
Need a better name for ’eepos’ command! (’eepos’ is the name of the bit
field in the actual low-level SCSI command, and has nothing to do with
what it does).
This program has only been tested on Linux with a limited number of
tape loaders (a dual-drive Exabyte 220 tape library, with bar-code
reader and 21 slots, an Exabyte EZ-17 7-slot autoloader, and a Seagate
DDS-4 autochanger with 6 slots). It may not work on other operating
systems with larger libraries, due to the big SCSI request size.
Report problems to Eric Lee Green <email@example.com>.
Under Linux, cat /proc/scsi/scsi will tell you what SCSI devices you
have. You can then refer to them as /dev/sga, /dev/sgb, etc. by the
order they are reported.
Under FreeBSD, camcontrol devlist will tell you what SCSI devices you
have, along with which pass device controls them.
Under Solaris, set up your ’sgen’ driver so that it’ll look for tape
changers (see /kernel/drv/sgen.conf and the sgen man page), type touch
/reconfigure then reboot. You can find your changer in /devices by typ-
ing /usr/sbin/devfsadm -C to clean out no-longer-extant entries in your
/devices directory, then find /devices -name hanger -print to find the
device name. Set the symbolic link /dev/changer to point to that device
name (if it is not doing so already).
With BRU, set your mount and unmount commands as described on the EST
web site at http://www.estinc.com to move to the next tape when backing
up or restoring. With GNU tar, see mtx.doc for an example of how to use
tar and mtx to make multi-tape backups.
This version of mtx is currently being maintained by Eric Lee Green
<firstname.lastname@example.org> formerly of Enhanced Software Technologies Inc. The
’mtx’ home page is http://mtx.sourceforge.net and the actual code is
currently available there and via CVS from http://source-
Man(1) output converted with