[gentoo-user] Re: mount: "special device /dev/hdc does not exist". What does this mean?

[Nikos Chantziaras <realnc@arcor.de>]

Alan Mackenzie wrote:
> On Sun, Jul 20, 2008 at 12:29:19AM +0300, Nikos Chantziaras wrote:
>> The CD/DVD-ROM can show up as /dev/sd* even with the old legacy drivers 
>> if you have enable "SCSI Emulation" for it.
>> 
>> In any event, try to build a new kernel using the new drivers.  The old 
>> legacy driver you're using will probably get declared "deprecated" at 
>> some point (if it didn't happen already).
> [...]
> In a philosophical mood, one might say that the new "unified",
> "enhanced", "better" IDE support is inadequate for my setup.  What I
> actually said, I'm not going to repeat in a public mailing list.

I must admit that I'm not affected much by this since, as I mentioned in 
another post, I use labels and don't look at what /dev/sd* my drive is 
mapped.

For unpartitioned drivers where I'm not sure which /dev/sd* entry to 
use, I simply use /dev/disk/by-id instead ;)


> So the kernel guys have decided that nobody would ever want more than 15
> partitions on a drive.  It's a bit like the old MS-DOS restriction to 512
> MB all over again.  Hey, guys, hard drives nowadays are like 200 gig, not
> 512meg.  What's so wrong about having partitions with sizes 1Gb, 2Gb, 4Gb,
> with maybe 100Mb for a boot partition?

Unlike the above, this one is a real problem.  Fortunately, as long as 
the new drivers are still labeled "experimental" there's little chance 
of the legacy drivers being removed from the kernel.  Performance-wise, 
I don't think you're missing much by not using the new drivers (though 
that's just a guess; don't take my word on it :P)

If some day the legacy drivers are kicked out, you might have to go the 
LVM route by force :P  But I guess this isn't like to happen anytime 
soon now, since not all hardware seems supported by the new drivers.


> Both of these created /dev/sdc and /dev/sdc1, but no /dev/sdd.  When I
> tried # mount -t iso9660 /dev/sdc /cdrom, I got the "something's gone
> wrong, but we're not telling you what" error message.  Trying to mount
> /dev/sdc1 gave exactly the same result.  Actually, thinking about it,
> this was probably my USB stick it was trying to access.

I know that everyone is using his/her own system as he/she sees fit, but 
I don't mount CD/DVD and USB drives by hand anymore.  And no entries at 
all in fstab either.  I just plug it in and let dbus (+ HAL if you're on 
KDE/Gnome) handle the rest :P


> Nikos, do you happen to know the appropriate kernel mailing list where I
> could express the opinion that restricting the number of partitions on a
> drive to 15 isn't a good tradeoff?

LKML should be OK.  At least last time I checked, regulars there are 
against directing people to "more appropriate" lists, meaning that LKML 
is the most appropriate of all if the issue is about things that are 
officially in the kernel.

In any event, I remember this issue being raised back in 2004, so I 
guess it has been discussed to death by now.  (And I did not follow the 
discussion, so I can't give you a summary, I'm afraid.  Google is your 
friend.)


> All in all, I really amn't impressed with this "modern" drive support.
> Besides quartering the max number of partitions on a drive, it confuses
> IDE and SCSI drives, thus confusing me, too.  Previously, when I
> attached devices to the IDE1 socket, I knew they would appear at
> /dev/hd[cd].  Now, it would seem, the kernel assigns drives at random to
> /dev/sd[abcd...], so you can only determine by experiment which devices
> are at which "device".  Nothing personal, Nikos.  ;-)

I'm on PATA+SATA+USB here, so I know what you mean.  However, I found 
the /dev/disk/ tree to be very helpful here.