Finding correct sd* drive [unsolved]

[jonfr]

The latest minimal installation disk of Gentoo Linux does not reflect the change that has happened in the kernel recently. That is the change from hd* deprecation and to sd* only. Due to this issue it is quite hard to find the boot drive on PC's that are using a mix of ATA and SATA drives.

I was installing a Gentoo Linux on a computer that has this type of setup. But I cannot find the boot drive. I did try for sdd but that did not work. On the old stack the sda and sdb goes to the SATA drives already in the computer.

The layout is like this.

[krinn]

[jonfr]

In this setup the boot disk is hda, not sda. But in the new stack all the ATA disks get a sd id and it follows the sd* line. But what is hard to know is where the boot sector ends up being. Where that be sdd or sdc etc.

[krinn]

Kernel will name the drives as they appears sda, then sdb...


So how you can be sure your sata boot drive will be sda while your ata drives will get last_sata_drive+1 ?

Just tell the kernel to load SATA driver before ATA driver.
This just mean, set SATA drivers as include in kernel, and just set ATA driver as module, this way kernel MUST load SATA driver before the ATA driver (as it is module now)


edit: and if your boot were hda, then include PATA driver and module the SATA driver

[NeddySeagoon]

jonfr,

This is partly a BIOS issue and partly a kernel issue.

On some systems, you can alter if the SATA or IDE drives are detected first by the kernel by changing the boot order in the BIOS.
e.g. My A7N8X works that way. Its a matter of trial and error.

Grub can help you here. Boot to the grub prompt and press 'e'.
Edit the line root (x,y) so it reads root (0, and press tab.
Grub will show the partitions on drive 0, (the first drive detected by the BIOS)
repeat for root (1, press tab and see the partitions on drive 1.

You can often identify your drives from this.

You can also use the same technique to change the (real_)root=/dev/sd... until the kernel mounts root.
Then you know where root is. Once you have that, the rest is easier.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[Cyker]

<rant>
Ugh, this is a pet hate of mine.

The whole sd? system is completely useless for identifying drives as, unlike the hd? assignments, it is completely decoupled from anything.

The most fun thing is you can break the boot up by leaving an eSATA and/or USB drive plugged in while rebooting as it will often totally mess up drive order depending on what PCI order the controllers are and when the kernel loads that driver module.

I'm hoping at some point the sd? assignments will be split again (They were originally just nice sensible predictable hd? for ATA and FCFS* sd? for SCSI drives, but now *every* storage device, be it SATA, SCSI, USB, or ATA gets given a FCFS sd? assignment. It's like being back in DOS land)

The most annoying thing is you can't even use udev to 'kludge' more sensible names because there's not enough information to tell what kind of device is being connected!




*First Come First Served

[DuzaK]

I don't understand the hate with the "new" sd? assignments. There is nothing new about it only that hd isn't used, besides that the naming scheme is exactly the same.
If you want to be on the save side then just use the UUID of your partitions in grub/fstab and never have any problem with changing device nodes.

[Cyker]

The hate is because sd? is now completely abstracted from the hardware;

In my system right now I *know* that hda is always Primary Master, hdb is always Primary Slave etc.

I have no idea what sda is; It could be eSATA port 1, Sil SATA port 6 some USB stick or anything.

At the moment, I can't break my boot up by plugging in, say, an eSATA drive, but when I tried using libata for everything I could and that is just annoying.

I know you can use things like UUID (I prefer labels myself) as a disk identifier, but there are occasions where you have to use the base /dev/sd? assignment to access a disk or partition and where I could intuitively know what port was what, this is now lost on newer systems

If you could assign sda1-4 to IDE PM/PS/SM/SS, and sda 5-12 to SATA ports 1-8 then it wouldn't be so bad, but you can't even do that because the sd? naming is done on a first-come-first-served basis, and there is no sane way to get around it, even with udev!

And I don't understand why *all* storage has to use sd? now - Would it not be more sensible to keep hd? for ATA, sd? for SCSI, and then use new ones for other devices, e.g. um? for USB Mass storage, st? for SATA devices etc.?!

I'm just glad the madness hasn't spread to the RAID section (If my RAID array was given an sd? assignment I'd be screaming!)

[DuzaK]

I see, yes it is hard to know which drive is what.
I have it easy with just 5 different hard drives where each one has different sizes. A little fdisk -L helps me a lot when i need to know the exact location of some partitions. But i would be troubled if all of them were the same size.
In this light it sounds indeed pretty neat to have the old behavior back, but only if i even use this many different ports. I myself only have sata drives connected it would be useless for me.

I think the best solution would be to scrap all the sd? hd? naming and use Labels instead. Dunno if this would break something but it would make me pretty happy.

*edit*
discard the above. The names of HDDs are probably too long and have spaces, so it wouldn't be a good idea to use it in this way.

[Yak]

You're right it's a bunch of crap everything is sd*

I just installed a sas card and apparently it put it first because i got a kernel panic cannot mount root fs.. its bullshit.

Seriously putting parts as modules is the best current solution for this? There's udev rules in gentoo for net and cd for god's sake, and if those fuck up it's not like it makes the system totally unbootable.

So I have.. let's see..

Onboard SATA
Promise SATA pci card
SAS -> SATA card
USB mass storage

Tell me, which should I make modules or compile in??

[krinn]

It's simple, all as module except the one that hold your root disk

So for you it should be SAS build-in with logic
And without it, we can't guess it for you, but you can still keep crying for nothing.

[Yak]

I just did that, promise and sas as modules.. same thing kernel panic cannot mount root. Need to look into how system rescue cd does it, seems to be in a sane order. The whole plug in a monitor, cdrom, boot, mount, chroot, recompile kernel, reboot and hope it comes up in some kind of sane order is just a pita.

Edit: Okay apparently it didn't compile/install as modules.. not in lsmod noticed it after I changed /etc/fstab and grub.conf from sda to sde to boot and saw what was going on. Not sure whats up with that, maybe it depends on something else being compiled as a module?

[jburns]

See https://forums.gentoo.org/viewtopic-p-4588037.html#4588037 for how to reference disks by UUID in fstab and grub. It is also possible to reference partitions by labels.