I have no friendly unix admin expert to ask and I'm going cross eyed looking for info on the interworld webnet so I thought I'd give you guys a chance to dazzle with your expertise. I want to understand how a unix system, (Linux in my case), goes through the mechanics of recognising and attaching a disk drive. I've read a lot about the special files in /dev and their major and minor numbers. I thought I'd worked it out when I read that the major number identifies the driver for the specific device and the minor number the commumication port but then I realised that this also relates to partitions on single disks. Can anyone point me at or give me a difinitive explanation of what's going on, how the various bits and pieces bolt together? Cheers.

/dev/hda = master disk on 1st IDE
hdb = slave disk on 1st IDE
hdc = master on 2nd IDE
hdd = slave on 2nd IDE

That's the physical discs. Partitions add another number, so
hda1 = first partition on 1st master hard drive
hda2 = second partition on 1st master hard drive
hdb1 = first partition on 1st slave hard drive

Then you get the SCSI ones, but the basic convention is the same:
/dev/?? = basic device name - hd, sa, sd, etc
a,b,c,etc = order in which the devices are found
1,2,3,etc = partitions on the disk

Does that help?

Hi Oneandoneis2, thanks for you reply. Let me run what I've gleened from the web so far and I stress this is all conjecture on my part. I build a system from scratch. The server automatically locates the disk drive on the first relevant port and installs the boot partition there. After installation is complete I see:
Filesystem 1k-blocks Used Available Use% Mounted on
/dev/cciss/c0d0p3 67945696 12139224 52354996 19% /
/dev/cciss/c0d0p1 51342 14076 34615 29% /boot
none 1971924 0 1971924 0% /dev/shm

If I look at file /dev/ccis/c0d0p1 I see it has a major number of 104 and a minor number of 1. So it's using the driver code identified by 104 and using comms channel 1. The file /dev/ccis/c0d0p3 points to another partition on the same disk using 104 and 3. So if I add a new disk to this machine how does the system know it's there. Is it related to the major minor numbers? Am I barking up the wrong tree?
Mark.

Ah. You're using a SCSI array rather than a nice simple IDE arrangement then

I'm not sure I really understand your question. If you add a new disc, it'll find it when it looks for all the hardware, the same as with any hardware. If you mean how does it assign a disc to a /dev entry, that depends what you're using - udev, devfs, etc.

Incidentally, you might find it worth exploring the /proc/driver/cciss filesystem. . .

To be honest I just plugged the machine in and loaded the O/S using all the defaults from the cd's I didn't know what disks were in there. As you've probably guessed I'm not from this kind of background. I was intrigued as to how the system knows where disks are but that appears to be automatic. This all came about as I was trying to get my head around how the unix filesystem bolted together. I like to try to get a good mental picture of what's going on but rather than getting clearer, the more I looked the cloudier it became. I think I need to go work somewhere where there's a unix admin team. Thanks for your help anyway. Mark.