Re: tlug: Debian installation - scsi problem

["Stephen J. Turnbull" <turnbull@example.com>]

>>>>> "Selva" == Selva Nair <selva@example.com> writes:

    Selva> On Thu, 13 Apr 2000 ulrike@example.com wrote:

    >> I am currently at work trying to install (for the first time)
    >> Debian 2.1 on a Fujitsu FMV-590DE which seems to have a scsi
    >> CDROM, Adaptec, AHA-2940. I selected the modules for cdrom and
    >> sg - generic scsi-port, but I cannot mount the CDROM. Maybe
    >> something is wrong with my mounting attempts, I get "special
    >> device /dev/dcrom does not exist" or "the kernel does not
    >> recognize /dev/scd0

    Selva> I guess that /dev/cdrom is linked to /dev/sdc (by the way
    Selva> it is sdc, not scd, isn't it?). It seems either the device
    Selva> name is wrong or the scsi driver is not loaded.

No, it's /dev/scd*.  Unlike IDE where the kernel is told that the
CD-ROM is really a hard disk without write heads ;-)[1], the SCSI
implementation considers CD-ROM (/dev/scd*) and tape (/dev/st*) to be
different kinds of devices from hard drives.

    Selva> First check the boot message to see whether the card is
    Selva> recognised at boot time. Check /proc/modules to see whether
    Selva> aic7xxx is listed or not. If not /sbin/modprobe
    Selva> aic7xxx. Check /proc/scsi/scsi to see whether the cd drive
    Selva> is detected.

Right.

If your module dependencies are set up correctly, you should be able
to

    (1) modprobe sr_mod, which pulls in the SCSI CD-ROM support module
        -- /dev/sr* is the old name for SCSI CD-ROM devices -- and
        then, as a dependency, scsi_mod.  Both of these can be
        compiled into the kernel, so you may not need to do this
        depending on your kernel config.  Also, a properly configured
        kerneld or kmod will pull these in automatically on attempt to
        mount a SCSI CD-ROM.
    (2) modprobe aic7xxx.  Unfortunately, "virtual dependencies" are
        not available for kernel modules AFAIK.  So the SCSI support
        system can't know to request that the hardware driver (aic7xxx
        for Adaptec 2940s) be insmod'd (because the logic for
        detecting the right hardware is in the aic7xxx module, not in
        the SCSI code!).  You have to do this by hand.  (There must be
        some way to do this automagically, but depmod doesn't do it
        AFAIK.)  You can also put aic7xxx into /etc/modules, from
        where it will be automatically loaded at boot time.

    Selva> If it still doesn't work, I would think that /dev/cdrom is
    Selva> not linked to the correct device. The first scsi device is
    Selva> named /dev/sda, the second is /dev/sdb etc.. and partitions
    Selva> within are named /dev/sda1 to /dev/sda15 etc. (Has this
    Selva> changed in recent distributions?) If you dont have any
    Selva> other devices on the scsi bus, the cdrom may be on
    Selva> /dev/sda.  Try mounting that instead of /dev/cdrom. Once
    Selva> you identify the correct device make /dev/cdrom a link to
    Selva> that. (ls -l /dev/sd* will show you all the sd device files
    Selva> you have -- whatever be the names, the first device has
    Selva> major,minor = 8,0, the second is 8,32 etc...)

This is all incorrect.  /dev/sd* devices are all r/w devices (mostly
hard drives but also including removables, Zips, Jazz, MOs, etc.)
(I'm not 100% sure, but I believe SCSI CD-R and CD-R/W are implemented
with the generic SCSI devices /dev/sg*, not /dev/scd*.  It's
definitely _not_ /dev/sd*, though; you just don't need all the
complicated caching and queuing for something that is written once as
a long stream.)


Footnotes: 
[1]  Joke, OK?

-- 
University of Tsukuba                Tennodai 1-1-1 Tsukuba 305-8573 JAPAN
Institute of Policy and Planning Sciences       Tel/fax: +81 (298) 53-5091
_________________  _________________  _________________  _________________
What are those straight lines for?  "XEmacs rules."
--------------------------------------------------------------------
Next Nomikai Meeting: April 20 (Thu) Linux Conference 2000 Spring Ed.
Next Technical Meeting: May 13 (Sat) 13:30 Temple University Japan
* Topic: TBD
--------------------------------------------------------------------
more info: http://www.tlug.gr.jp        Sponsor: Global Online Japan