Using tape autochanger? - HP UX

This is a discussion on Using tape autochanger? - HP UX ; On a HP 9000/800 server running HP-UX 11.11, I have a tape autochanger identified in SAM thusly: Hardware Path: 0/3/1/0/4/1.0.0 Driver: schgr Description: HP MSL6000 Series (Autochanger) Device File: /dev/rac/c5t0d0 I have compiled mtx 1.3.9 on the box; it gives ...

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Thread: Using tape autochanger?

  1. Using tape autochanger?

    On a HP 9000/800 server running HP-UX 11.11, I have a tape autochanger
    identified in SAM thusly:

    Hardware Path: 0/3/1/0/4/1.0.0
    Driver: schgr
    Description: HP MSL6000 Series (Autochanger)
    Device File: /dev/rac/c5t0d0

    I have compiled mtx 1.3.9 on the box; it gives me this output:

    # ./mtx -f /dev/rac/c5t0d0 status
    cannot open SCSI device '/dev/rac/c5t0d0' - No such device

    However, the file exists:

    # ls -l /dev/rac
    total 0
    crw------- 1 bin sys 231 0x050000 May 24 2006 c5t0d0


    So apparently, mtx in its unaltered state, cannot deal with the device.

    I've not been able to find any useful information on the web. What
    options _do_ I have for dealing with this device?

    Thanks,
    Steve


  2. Re: Using tape autochanger?

    In article ,
    allen@doobie.itdl.ds.boeing.com (Steve Allen) writes:
    > On a HP 9000/800 server running HP-UX 11.11, I have a tape autochanger
    > identified in SAM thusly:
    >
    > Hardware Path: 0/3/1/0/4/1.0.0
    > Driver: schgr
    > Description: HP MSL6000 Series (Autochanger)
    > Device File: /dev/rac/c5t0d0
    >
    > I have compiled mtx 1.3.9 on the box; it gives me this output:
    >
    > # ./mtx -f /dev/rac/c5t0d0 status
    > cannot open SCSI device '/dev/rac/c5t0d0' - No such device
    >
    > However, the file exists:
    >
    > # ls -l /dev/rac
    > total 0
    > crw------- 1 bin sys 231 0x050000 May 24 2006 c5t0d0
    >
    >
    > So apparently, mtx in its unaltered state, cannot deal with the device.
    >
    > I've not been able to find any useful information on the web. What
    > options _do_ I have for dealing with this device?


    More info:

    The tree goes like this:

    0/3 lba Local PCI-X Bus Adapter (783)
    0/3/1/0 PCItoPCI PCI to PCI Bridge
    0/3/1/0/4/0 mpt HP AB290-60001 PCI/PCI U320 SCSI 2-port 1000B-T Combo Adapter
    (at /dev/mpt4)
    0/3/1/0/4/0.2.0 stape HP Ultrium 3-SCSI (Tape Drive)
    (at /dev/rmt/c4t2d0BEST)
    0/3/1/0/4/0.7.0 sctl Initiator
    (at /dev/rscsi/c4t7d0)
    0/3/1/0/4/1 mpt HP AB290-60001 PCI/PCI U320 SCSI 2-port 1000B-T Combo Adapter
    (at /dev/mpt5)
    0/3/1/0/4/1/0.0 schgr HP MSL6000 Series (Autochanger)
    (at /dev/rac/c5t0d0)
    0/3/1/0/4/1.1.0 stape HP Ultrium 3-SCSI (Tape Drive)
    (at /dev/rmt/c5t1d0BEST)
    0/3/1/0/4/1.7.0 sctl Initiator
    (at /dev/rscsi/c5t7s0)


    I can access both tapes using the `mt` command, I just need to know how
    to talk to the changer.

    Thanks,
    Steve


  3. Re: Using tape autochanger?

    Steve,

    I had similar problems using a Scalar tape library. It is fibre, but it
    operates the same... I ended up having to get atdd drivers for it from
    IBM... Not too much support came from scalar , was sort of a self
    research from HP and myself.



    Atdd is a driver for tape libraries, and schgr is the scsi changer
    device drivers, both are needed.


  4. Re: Using tape autochanger?

    In article <1169502611.095622.79340@l53g2000cwa.googlegroups.c om>,
    "thesoulcrusher" writes:
    > Steve,
    >
    > I had similar problems using a Scalar tape library. It is fibre, but it
    > operates the same... I ended up having to get atdd drivers for it from
    > IBM... Not too much support came from scalar , was sort of a self
    > research from HP and myself.
    >
    > Atdd is a driver for tape libraries, and schgr is the scsi changer
    > device drivers, both are needed.


    Huh. Thanks for the info. I'll look into it.

    Steve


  5. Re: Using tape autochanger?

    In article <1169502611.095622.79340@l53g2000cwa.googlegroups.c om>,
    "thesoulcrusher" writes:
    > I had similar problems using a Scalar tape library. It is fibre, but it
    > operates the same... I ended up having to get atdd drivers for it from
    > IBM... Not too much support came from scalar , was sort of a self
    > research from HP and myself.
    >
    > Atdd is a driver for tape libraries, and schgr is the scsi changer
    > device drivers, both are needed.


    So, I've installed atdd and the tapeutil programs. Still isn't helping me.
    I'm talking to the tapes OK with the normal OS utilities; what I need is to
    talk to the changer. I've tried making the atdd utility claim the changer
    with:

    /opt/atdd/bin/atdd_claim -c

    And that gives me these device files in /dev/rmt:

    crw-rw-rw- 1 bin bin 118 0xfffffc Jan 23 08:36 acdd.cfg
    crw-rw-rw- 1 bin bin 118 0xfffffa Jan 23 08:36 acdd.ctrl
    crw-rw-rw- 1 bin bin 118 0xfffffd Jan 23 08:36 acdd.dbg

    But those are not usable with either mtx nor mc. And when I try to list
    the device files for the changer with sam, it tells me there are none.

    Anything else I can try?

    Thanks,
    Steve


  6. Re: Using tape autochanger?

    Steve Allen wrote:
    [deleted]

    > But those are not usable with either mtx nor mc.


    [Earlier:]

    > 0/3/1/0/4/1 mpt HP AB290-60001 PCI/PCI U320 SCSI 2-port 1000B-T ComboAdapter
    > (at /dev/mpt5)
    > 0/3/1/0/4/1/0.0 schgr HP MSL6000 Series (Autochanger)
    > (at /dev/rac/c5t0d0)
    > 0/3/1/0/4/1.1.0 stape HP Ultrium 3-SCSI (Tape Drive)
    > (at /dev/rmt/c5t1d0BEST)
    > 0/3/1/0/4/1.7.0 sctl Initiator
    > (at /dev/rscsi/c5t7s0)


    Have you tried mc(1) with the /dev/rscsi/c5t7s0 device file?

    mc(1) is the only (HP) supported utility for a changer, and mc(1)
    requires the SCSI pass through driver (sctl) device file.

    --
    Frank "Hoping that he still got this right after (nearly) 4 years." Slootweg

  7. Re: Using tape autochanger?

    In article <45b662a4$0$75077$dbd43001@news.wanadoo.nl>,
    Frank Slootweg writes:
    > Steve Allen wrote:
    > [deleted]
    >
    >> But those are not usable with either mtx nor mc.

    >
    > [Earlier:]
    >
    >> 0/3/1/0/4/1 mpt HP AB290-60001 PCI/PCI U320 SCSI 2-port 1000B-T ComboAdapter
    >> (at /dev/mpt5)
    >> 0/3/1/0/4/1/0.0 schgr HP MSL6000 Series (Autochanger)
    >> (at /dev/rac/c5t0d0)
    >> 0/3/1/0/4/1.1.0 stape HP Ultrium 3-SCSI (Tape Drive)
    >> (at /dev/rmt/c5t1d0BEST)
    >> 0/3/1/0/4/1.7.0 sctl Initiator
    >> (at /dev/rscsi/c5t7s0)

    >
    > Have you tried mc(1) with the /dev/rscsi/c5t7s0 device file?
    >
    > mc(1) is the only (HP) supported utility for a changer, and mc(1)
    > requires the SCSI pass through driver (sctl) device file.


    Yes, I did. It says: ERROR: I/O error
    c5t7d0 would be the device ID for the bus controller.
    I don't see how that would translate into being the library controller...

    But (consulting the scsi_ctl man page) I made the
    device /dev/rscsi/c5t0d0 as follows:
    # cd /dev/rscsi
    # /usr/sbin/mknod c5t0d0 c 203 0x050000

    And that works:
    # mc -p /dev/rscsi/c5t0d0 -r IDSM
    MT_slot_1 EMPTY
    IE_slot_1 EMPTY
    DT_slot_1 EMPTY
    DT_slot_2 EMPTY
    ST_slot_1 FULL
    ST_slot_2 FULL
    ST_slot_3 FULL
    ST_slot_4 FULL
    ST_slot_5 FULL
    ST_slot_6 FULL
    ST_slot_7 FULL
    ST_slot_8 FULL
    ST_slot_9 FULL
    ST_slot_10 FULL
    ST_slot_11 FULL
    ST_slot_12 FULL
    ST_slot_13 FULL
    ST_slot_14 FULL
    ST_slot_15 FULL
    ST_slot_16 FULL
    ST_slot_17 FULL
    ST_slot_18 FULL
    ST_slot_19 FULL
    ST_slot_20 FULL
    ST_slot_21 EMPTY
    ST_slot_22 EMPTY
    ST_slot_23 EMPTY
    ST_slot_24 EMPTY
    ST_slot_25 EMPTY
    ST_slot_26 EMPTY
    ST_slot_27 EMPTY
    ST_slot_28 EMPTY
    ST_slot_29 EMPTY

    How do I make that be a permanent thing?


    Thanks,
    Steve


  8. Re: Using tape autochanger?

    Steve Allen wrote:
    > In article <45b662a4$0$75077$dbd43001@news.wanadoo.nl>,
    > Frank Slootweg writes:
    > > Steve Allen wrote:
    > > [deleted]
    > >
    > >> But those are not usable with either mtx nor mc.

    > >
    > > [Earlier:]
    > >
    > >> 0/3/1/0/4/1 mpt HP AB290-60001 PCI/PCI U320 SCSI 2-port 1000B-T ComboAdapter
    > >> (at /dev/mpt5)
    > >> 0/3/1/0/4/1/0.0 schgr HP MSL6000 Series (Autochanger)
    > >> (at /dev/rac/c5t0d0)
    > >> 0/3/1/0/4/1.1.0 stape HP Ultrium 3-SCSI (Tape Drive)
    > >> (at /dev/rmt/c5t1d0BEST)
    > >> 0/3/1/0/4/1.7.0 sctl Initiator
    > >> (at /dev/rscsi/c5t7s0)

    > >
    > > Have you tried mc(1) with the /dev/rscsi/c5t7s0 device file?
    > >
    > > mc(1) is the only (HP) supported utility for a changer, and mc(1)
    > > requires the SCSI pass through driver (sctl) device file.

    >
    > Yes, I did. It says: ERROR: I/O error
    > c5t7d0 would be the device ID for the bus controller.
    > I don't see how that would translate into being the library controller...
    >
    > But (consulting the scsi_ctl man page) I made the
    > device /dev/rscsi/c5t0d0 as follows:


    Good! Most people don't find their way to the scsi_ctl(7) manual page.
    You can be proud of yourself!

    > # cd /dev/rscsi
    > # /usr/sbin/mknod c5t0d0 c 203 0x050000
    >
    > And that works:


    Good!

    > # mc -p /dev/rscsi/c5t0d0 -r IDSM
    > MT_slot_1 EMPTY
    > IE_slot_1 EMPTY
    > DT_slot_1 EMPTY
    > DT_slot_2 EMPTY
    > ST_slot_1 FULL
    > ST_slot_2 FULL
    > ST_slot_3 FULL
    > ST_slot_4 FULL
    > ST_slot_5 FULL
    > ST_slot_6 FULL
    > ST_slot_7 FULL
    > ST_slot_8 FULL
    > ST_slot_9 FULL
    > ST_slot_10 FULL
    > ST_slot_11 FULL
    > ST_slot_12 FULL
    > ST_slot_13 FULL
    > ST_slot_14 FULL
    > ST_slot_15 FULL
    > ST_slot_16 FULL
    > ST_slot_17 FULL
    > ST_slot_18 FULL
    > ST_slot_19 FULL
    > ST_slot_20 FULL
    > ST_slot_21 EMPTY
    > ST_slot_22 EMPTY
    > ST_slot_23 EMPTY
    > ST_slot_24 EMPTY
    > ST_slot_25 EMPTY
    > ST_slot_26 EMPTY
    > ST_slot_27 EMPTY
    > ST_slot_28 EMPTY
    > ST_slot_29 EMPTY
    >
    > How do I make that be a permanent thing?


    How do you make *what* a permanent thing? The device file? That will
    stick, i.e. also after a reboot.

    If you mean that you had to do it manually and would like it to be
    done automatically, it can't. That's the nature of the beast. The SCSI
    Pass-Thru driver is exactly that, pass-thru. I.e. the driver has no
    knowledge at all about what device it is talking to (in this case the
    robot of the Autochanger) and hence *cannot* configure automatically
    (like for example the stape driver can), so you have to do it manually.

    Sorry for not pointing you directly to the scsi_ctl(7) manual page. I
    could (should? :-)) have realized that you probably would not be aware
    of it, because you didn't say that you had created a device file
    yourself. My excuse is that I haven't touched an HP-UX system nor this
    subject matter in nearly four years! :-)

  9. Re: Using tape autochanger?

    In article <45b68a4c$0$70117$dbd45001@news.wanadoo.nl>,
    Frank Slootweg writes:
    > Steve Allen wrote:
    >> But (consulting the scsi_ctl man page) I made the
    >> device /dev/rscsi/c5t0d0 as follows:
    >> # cd /dev/rscsi
    >> # /usr/sbin/mknod c5t0d0 c 203 0x050000
    >>
    >> How do I make that be a permanent thing?

    >
    > How do you make *what* a permanent thing? The device file? That will
    > stick, i.e. also after a reboot.


    Well, I figured that since it was able to automatically create all the other
    device files, that there was probably some mechanism that one could invoke
    to have the autochanger device file automatically created as well. So if
    the changer were to be switched around to another SCSI port, or if some
    system upgrade required all the device files to be rebuilt, etc.

    > If you mean that you had to do it manually and would like it to be
    > done automatically, it can't. That's the nature of the beast. The SCSI
    > Pass-Thru driver is exactly that, pass-thru. I.e. the driver has no
    > knowledge at all about what device it is talking to (in this case the
    > robot of the Autochanger) and hence *cannot* configure automatically
    > (like for example the stape driver can), so you have to do it manually.


    OK. I'm going to have to read more about this Pass-Thru thing, as I fail
    to see how the system can recognize a device but fail to create a device
    file that is useable by the system's own utilities...

    > Sorry for not pointing you directly to the scsi_ctl(7) manual page. I
    > could (should? :-)) have realized that you probably would not be aware
    > of it, because you didn't say that you had created a device file
    > yourself. My excuse is that I haven't touched an HP-UX system nor this
    > subject matter in nearly four years! :-)


    I've been a SGI admin for many years, and can usually find what I need if
    given sufficient clue. But I'm new to HP admin. SGI IRIX also finds and
    configures tape libraries, and the device files it creates are usable with
    programs like mtx. This is the first time I've encountered a situation
    where I had to manually create the device file. It doesn't help that I'm
    becoming an Old Man, and it's taking longer for info to sink in. ;-)
    (And actually, I hadn't created the working device file until immediately
    prior to the previous post... And guess what -- it works with mtx, too! :-)

    Thanks,
    Steve


  10. Re: Using tape autochanger?

    Steve Allen wrote:
    > In article <45b68a4c$0$70117$dbd45001@news.wanadoo.nl>,
    > Frank Slootweg writes:

    [deleted]

    > > If you mean that you had to do it manually and would like it to be
    > > done automatically, it can't. That's the nature of the beast. The SCSI
    > > Pass-Thru driver is exactly that, pass-thru. I.e. the driver has no
    > > knowledge at all about what device it is talking to (in this case the
    > > robot of the Autochanger) and hence *cannot* configure automatically
    > > (like for example the stape driver can), so you have to do it manually.

    >
    > OK. I'm going to have to read more about this Pass-Thru thing, as I fail
    > to see how the system can recognize a device but fail to create a device
    > file that is useable by the system's own utilities...


    The point is that the pass-thru driver does *not* "recognize a
    device". I.e. it doesn't know what a robot is, or any other device for
    that matter. That's why you need to manually create the device file and
    tell it (the driver) all it needs to know.

    [deleted]

    > (And actually, I hadn't created the working device file until immediately
    > prior to the previous post... And guess what -- it works with mtx, too! :-)


    Great!

    > Thanks,


    You're welcome. I'm glad that my comment helped you solving the
    problem.

  11. Re: Using tape autochanger?

    In article <45b7bee5$0$71733$dbd45001@news.wanadoo.nl>,
    Frank Slootweg writes:
    > Steve Allen wrote:
    >> OK. I'm going to have to read more about this Pass-Thru thing, as I fail
    >> to see how the system can recognize a device but fail to create a device
    >> file that is useable by the system's own utilities...

    >
    > The point is that the pass-thru driver does *not* "recognize a
    > device". I.e. it doesn't know what a robot is, or any other device for
    > that matter. That's why you need to manually create the device file and
    > tell it (the driver) all it needs to know.


    Not to belabor the point, I'm just trying to understand...

    When I use SAM to show the device list, the tape unit is listed as:
    0/3/1/0/4/1.0.0 schgr HP MSL6000 Series (Autochanger)
    0/3/1/0/4/1.1.0 stape HP Ultrium 3-SCSI (Tape Device)

    That says to me that the system is recognizing it as a tape library and a
    tape drive. Not necessarily through the pass-thru device. It creates a
    device node for it in /dev/rac (which I take to be for Raw Auto Changer,
    along the lines of rdsk, rmt and rscsi). I just fail to see why mc cannot
    use the device /dev/rac/c5t0d0, but I instead have to create a pass-thru
    device for it... Or to put it another way, what is /dev/rac/c5t0d0 good for?

    Thanks,
    Steve


  12. Re: Using tape autochanger?

    Steve Allen wrote:
    > In article <45b7bee5$0$71733$dbd45001@news.wanadoo.nl>,
    > Frank Slootweg writes:
    >
    >>Steve Allen wrote:
    >>
    >>>OK. I'm going to have to read more about this Pass-Thru thing, as I fail
    >>>to see how the system can recognize a device but fail to create a device
    >>>file that is useable by the system's own utilities...

    >>
    >> The point is that the pass-thru driver does *not* "recognize a
    >>device". I.e. it doesn't know what a robot is, or any other device for
    >>that matter. That's why you need to manually create the device file and
    >>tell it (the driver) all it needs to know.

    >
    >
    > Not to belabor the point, I'm just trying to understand...
    >
    > When I use SAM to show the device list, the tape unit is listed as:
    > 0/3/1/0/4/1.0.0 schgr HP MSL6000 Series (Autochanger)
    > 0/3/1/0/4/1.1.0 stape HP Ultrium 3-SCSI (Tape Device)
    >
    > That says to me that the system is recognizing it as a tape library and a
    > tape drive. Not necessarily through the pass-thru device. It creates a
    > device node for it in /dev/rac (which I take to be for Raw Auto Changer,
    > along the lines of rdsk, rmt and rscsi). I just fail to see why mc cannot
    > use the device /dev/rac/c5t0d0, but I instead have to create a pass-thru
    > device for it... Or to put it another way, what is /dev/rac/c5t0d0 good for?
    >
    > Thanks,
    > Steve
    >

    SAM is always an abstraction layer away from the OS. I dealt with it for
    years, tape changers and disk arrays that could only be accessed with
    pass-thru's and it was always a PITA to get people to understand it. You
    have to talk through the spt to the device.

  13. Re: Using tape autochanger?

    Steve Allen wrote:
    > In article <45b7bee5$0$71733$dbd45001@news.wanadoo.nl>,
    > Frank Slootweg writes:
    > > Steve Allen wrote:
    > >> OK. I'm going to have to read more about this Pass-Thru thing, as I fail
    > >> to see how the system can recognize a device but fail to create a device
    > >> file that is useable by the system's own utilities...

    > >
    > > The point is that the pass-thru driver does *not* "recognize a
    > > device". I.e. it doesn't know what a robot is, or any other device for
    > > that matter. That's why you need to manually create the device file and
    > > tell it (the driver) all it needs to know.

    >
    > Not to belabor the point, I'm just trying to understand...


    Good! I appreciate it when people try to understand instead of just
    accepting what some dude on Usenet says (even if that dude has supported
    this stuff for two decades :-)).

    > When I use SAM to show the device list, the tape unit is listed as:
    > 0/3/1/0/4/1.0.0 schgr HP MSL6000 Series (Autochanger)
    > 0/3/1/0/4/1.1.0 stape HP Ultrium 3-SCSI (Tape Device)
    >
    > That says to me that the system is recognizing it as a tape library and a
    > tape drive.


    What SAM *displays* is *not* "recognizing". It just displays what the
    device answers when you send it a SCSI describe (or whatever) command.

    > Not necessarily through the pass-thru device.


    Indeed. IIRC, SAM and ioscan(1M) and friends use the diag driver to
    get their *hardware* information.

    > It creates a device node for it in /dev/rac (which I take to be for
    > Raw Auto Changer, along the lines of rdsk, rmt and rscsi).


    My memory is becoming a little vague on this, but I'm quite sure that
    that is because your kernel contains the schgr driver. The schgr driver
    is for a changer, but not for a *tape* changer. It is (mainly was) for a
    MO (Magneto-Optical) *disk* changer, which are hardly used anymore.

    *If* you want to look into this, you can remove the schgr driver and
    reboot. You will see that the *tape* changer still works. QED. (You will
    also note that one of the tape-changer related lines in the "ioscan -f"
    output will say "UNKNOWN" and "UNCLAIMED". That is nothing to worry
    about, but makes many admins nervous. The 'solution' for this is to
    include the schgr driver. I put solution in quotes, because it's not a
    real solution. First there is no problem, hence no solution. Second, the
    'solution' gets rid of the "UNKNOWN" and "UNCLAIMED", so far so good,
    but it also lists "schgr" as the driver associated with the tape
    changer, i.e. it lists the *wrong* driver, because schgr is for a *disk*
    changer. Catch-22.)

    > I just fail to see why mc cannot use the device /dev/rac/c5t0d0, but I
    > instead have to create a pass-thru device for it... Or to put it
    > another way, what is /dev/rac/c5t0d0 good for?


    See above. Please do a "lssf /dev/rac/c5t0d0" (and post the output).
    I'm quite sure that it will list schgr as the driver.

    BTW, don't use ls(1), mknod(1M) (except when *specifically* told
    so, i.e. in the case of scsi_ctl(7)) and rm(1) for device files. For
    device files you use the *sf(1M) commands, i.e. lssf, mksf, insf, rmsf.
    You *can* use ls/mknod/rm, but you *should* not. They only lead to
    confusion and errors. Coding/decoding (Series 800/700) major and minor
    number is not a humans job, but a programs job. That is why the *sf(1M)
    commands were created.

    I hope this helps.

  14. Re: Using tape autochanger?

    In article <45b8d5ec$0$67886$dbd45001@news.wanadoo.nl>,
    Frank Slootweg writes:
    > Steve Allen wrote:
    >> 0/3/1/0/4/1.0.0 schgr HP MSL6000 Series (Autochanger)
    >> 0/3/1/0/4/1.1.0 stape HP Ultrium 3-SCSI (Tape Device)
    >>
    >> That says to me that the system is recognizing it as a tape library and a
    >> tape drive.

    > What SAM *displays* is *not* "recognizing". It just displays what the
    > device answers when you send it a SCSI describe (or whatever) command.


    Huh. I had no idea that the devices were so verbose. But then, when I
    use the `mt status` command on IRIX (which is considerably more informative
    than its HP counterpart), it tells me, among other things:
    Device: QUANTUM: DLT7000 1E48qH
    and `hinv` tells me:
    Jukebox: unit 4 on SCSI controller 2
    Tape drive: unit 5 on SCSI controller 2: DLT

    I rather doubt that "Jukebox" and "Autochanger" are part of the device ID
    string returned in response to a query. I imagine that the query must
    return a code that is then interpreted by the system to determine the
    device type. And the code for "changer" doesn't differentiate between
    MO and tape type robots.

    >> Not necessarily through the pass-thru device.

    > Indeed. IIRC, SAM and ioscan(1M) and friends use the diag driver to
    > get their *hardware* information.


    Ah.

    >> It creates a device node for it in /dev/rac (which I take to be for
    >> Raw Auto Changer, along the lines of rdsk, rmt and rscsi).

    > My memory is becoming a little vague on this, but I'm quite sure that
    > that is because your kernel contains the schgr driver. The schgr driver
    > is for a changer, but not for a *tape* changer. It is (mainly was) for a
    > MO (Magneto-Optical) *disk* changer, which are hardly used anymore.


    Yes, I do recall the man page for autochanger talking exclusively about
    MO devices. But mc talks about tapes, though it does mention the -p device
    option, for pass-though device, and that is where it lost me.

    > 'solution' gets rid of the "UNKNOWN" and "UNCLAIMED", so far so good,
    > but it also lists "schgr" as the driver associated with the tape
    > changer, i.e. it lists the *wrong* driver, because schgr is for a *disk*
    > changer. Catch-22.)


    Following some googling, I located and installed an IBM tape library control
    program, which replaced the "schgr" driver with "atdd", but I couldn't get
    that to work -- probably still needed the pass-through device, or it works
    only with IBM changers... But it's no longer on the system.

    >> I just fail to see why mc cannot use the device /dev/rac/c5t0d0, but I
    >> instead have to create a pass-thru device for it... Or to put it
    >> another way, what is /dev/rac/c5t0d0 good for?

    > See above. Please do a "lssf /dev/rac/c5t0d0" (and post the output).
    > I'm quite sure that it will list schgr as the driver.


    Yes:
    # lssf /dev/rac/c5t0d0
    schgr card instance 5 SCSI target 0 SCSI LUN 0 control at address 0/3/1/0/4/1.0.0 /dev/rac/c5t0d0

    > BTW, don't use ls(1), mknod(1M) (except when *specifically* told
    > so, i.e. in the case of scsi_ctl(7)) and rm(1) for device files. For
    > device files you use the *sf(1M) commands, i.e. lssf, mksf, insf, rmsf.


    Yes, I have noted those commands. Hopefully, the next time I need to use
    them, it will be at the direction of some well-documented install procedure.
    ;-)

    > I hope this helps.


    It does. Thank you very much.

    Steve

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