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Re: SCSI Tapes and devfs

To: devfs@xxxxxxxxxxx
Subject: Re: SCSI Tapes and devfs
From: "Brett I. Holcomb" <brettholcomb@xxxxxxxxxxx>
Date: Fri, 17 Jan 2003 22:54:49 -0500
In-reply-to: <6134254DE87BD411908B00A0C99B044F03A0B5DF@MOWD019A>
Organization: Holcomb & Associates
References: <20030116224305.14135e68.brettholcomb@xxxxxxxxxxx> <6134254DE87BD411908B00A0C99B044F03A0B5DF@MOWD019A>
Sender: devfs-bounce@xxxxxxxxxxx
It's the backup program.  I created the symlink

ln -s /dev/sg/c1b0t1u0 /dev/auto_changer0

and it stays UNTIL I run the backup program an then the link disappears.
  As long as I tell the backup program to use /dev/sg2 for the changer
device everything works!  I'll contact the backup people to see what
they are doing.

However, let me summarize my lack of knowledge here so I don't get too
far off track.

1.  Don't mess with dev (don't create symlinks in it manually)

2.  I THINK I use /etc/devfsd.conf to create the entries in /dev when
the device has an event happen to it?.  So what I should do to create
the autochanger is go to /etc/devfsd.conf and put in something like the
CD line to create a symlink.  I should have done that for the tape, too
but somehow it got created anyway.  Is this correct - use
/etc/devfsd.conf for creating /dev entries.

3.  What have I missed?

Thank you.




On Fri, 17 Jan 2003 09:47:31 +0300
Borzenkov Andrey <Andrey.Borzenkov@xxxxxxxxxxx> wrote:

> Sorry, cannot say anything. Strace your backup program, if this does
> not give any clue - run devfsd in debug mode to see if somebody
> removes this link.
> 
> -andrey
> 
> > 
> > > Okay, I hit a problem.
> > >
> > > The /dev/tape0 symlink to my /dev/st/c1... works fine.
> > >
> > > However, if I create
> > >
> > > ln -s /dev/sg/c1b0t1u0 /dev/auto_changer0
> > >
> > > or
> > >
> > > ln -s /dev/sg2 /dev/auto_changer0
> > >
> > > and then run my tape program (supplied by the backup program
> > > vendor) I have problems.
> > >
> > > I create the link, use ls to show it's there, then run the program
> > > - I get an error "can't find /dev/auto_changer0".  I ls /dev/auto*
> > > and/dev/auto_changer0 is not there!
> > >
> 
> Is canonical name still there?
> /dev/scsi/host1/bus0/target1/lun0/generic. Is sg still loaded at this
> point?
> 
> > > cat/proc/scsi/scsi shows it's there (the Spectra) as does dmesg
> > > (Attached scsi generic sg2 at scsi1, channel 0, id 1, lun 0,  type
> > > 8)
> > >
> > > What's happening here?  The symlinks for /dev/tape0 and
> > > /dev/tape0n don't disappear.  Do I need to do something to the
> > > /etc/devfsd.conf or/etc/modules.conf files??
> > >
> > > Thank you.
> > >
> > >
> > > bash-2.05b$ cat /proc/scsi/scsi
> > > Attached devices:
> > > Host: scsi0 Channel: 00 Id: 00 Lun: 00
> > >   Vendor: ADAPTEC  Model: RAID-5           Rev: 370F
> > >   Type:   Direct-Access                    ANSI SCSI revision: 02
> > > Host: scsi1 Channel: 00 Id: 00 Lun: 00
> > >   Vendor: EXABYTE  Model: Mammoth2         Rev: v04b
> > >   Type:   Sequential-Access                ANSI SCSI revision: 02
> > > Host: scsi1 Channel: 00 Id: 01 Lun: 00
> > >   Vendor: SPECTRA  Model: 215              Rev: 1008
> > >   Type:   Medium Changer                   ANSI SCSI revision: 02
> > > Host: scsi1 Channel: 00 Id: 04 Lun: 00
> > >   Vendor: MATSHITA Model: DVD-RAM LF-D200  Rev: A120
> > >   Type:   CD-ROM                           ANSI SCSI revision: 04
> > >
> > > > *****
> > > > Here's the dmesg portion
> > > > st: Version 20020205, bufsize 32768, wrt 30720, max init. bufs
> > > > 4, s/g segs 16
> > > > Attached scsi tape st0 at scsi1, channel 0, id 0, lun 0
> > > > Attached scsi disk sda at scsi0, channel 0, id 0, lun 0
> > > > SCSI device sda: 286744576 512-byte hdwr sectors (146813 MB)
> > > > Partition check:
> > > >  /dev/scsi/host0/bus0/target0/lun0: p1 p2 p3 p4 < p5 p6 p7 p8 p9
> > > >  p10
> > > >  >
> > > > Attached scsi CD-ROM sr0 at scsi1, channel 0, id 4, lun 0
> > > > sr0: scsi3-mmc drive: 0x/0x dvd-ram cd/rw xa/form2 cdda tray
> > > > Attached scsi generic sg2 at scsi1, channel 0, id 1, lun 0, 
> > > > type 8
> > >
> 


-- 

Brett I. Holcomb


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