--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 address).

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 _ATTACHED API.

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 without 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 commands). 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 destination.

[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 depending upon the library, consult your library's SCSI-level documentation).

first [<drivenum>]

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 drive.

last [<drivenum>]

Loads drive <drivenum> from the last slot in the media changer. Unloads the drive if there is already a tape in it.

next [<drivenum>]

Unloads the drive and loads the next tape in sequence. If the drive was empty, loads the first tape into the drive.

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 Allocation_Size in the SCSI command block for the REQUEST_ELEMENT_STATUS command 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. Versions 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 transfer (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 command 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 <eric@badtux.org>.