Tech Tips with Gnull and Voyd

Howdy. My husband is Chester Gnull and I'm Laverta Voyd, and I'm the lady to light a way for all you sweethearts out there who do fancy stuff with Linux. Me and my husband's gonna be bringing you tech tips just about every month now. I reckon you and yours are wondering why my husband's and me's last names don't match. Well, Chester don't like much in the way of attention, so he got the editor to change our last names so's we don't get no pesky e-mails or people messin' with us in real life.

I don't know nothing about Linux. Chester, he's the smart one, but he's not much of a talker. That's why I'm here. He don't do nothing without me, and I don't mind much cause I like talkin' and I like hosting. Chester don't understand why we gotta talk at all, but that's what the editor wants, and well, he's paying us, so we figure there ain't nothing wrong with that. So those LJ folks are gonna send us the tips, my Chester does the pickin' and I do the hosting. And, I say, I do love hosting, but seeing as this here's just writing stuff, we ain't gonna be serving up none of my specials like biscuits and gravy with sausage and real maple syrup, and it's all homemade but the maple syrup. But they tell me the tips are just as tasty to you Linux folk. That don't make much sense to me, but Chester says that's how it is and I believe my Chester.

Now honeys, we got some tips to start. One tip is by the editor to get things rolling. He don't get no $100 but I figure he gets enough just being editor. So, we want you to send us some of your tips. If we put your tech tip in this here column, you get $100. We know that ain't gonna get you no Fleetwood mobile home, and I'm talkin Park Models, not even them fancy Entertainer Models with two bathrooms. But $100 will get you some good eats at your local Piggly Wiggly. So send them tips in, sweethearts, and we'll appreciate it real nice. You send 'em on in to techtips@linuxjournal.com and the editors will pass 'em on to Chester for ya, and we'll do the rest.

This tip makes Ubuntu see a 3ware RAID controller as the first serial device on your system in Ubuntu. —Chester

As you can see, Chester's real wordy, huh? That's why he's wrangled me into doing this. I mean, he's my lovin' man and I know that 'cause he shows me. But it wouldn't kill ya to say three little words now and again, would it, Chester? —Laverta

Three little words. Happy? —Chester

You can install a RAID card in your PC and configure the BIOS to make the BIOS consider the RAID card to be the first SCSI device on your system. But, Ubuntu (and probably other distributions) do not necessarily respect your BIOS settings. For example, I have an ASUS M2N32 WS Professional motherboard, which includes a PCI-X slot for the 3ware 9550SX-4LP RAID card. I can set the BIOS to make this card the first device. However, if I add a SATA drive, the Ubuntu initrd will see the onboard SATA as the first SCSI device on the system, in spite of the BIOS settings.

There may be a kernel boot parameter to override this behavior, but I haven't found one that works. Regardless, I like the following solution if for no other reason than it teaches one how to extract, modify an Ubuntu initrd and then reassemble it for use.

Here's why the Ubuntu initrd defies the BIOS settings. The initrd for Ubuntu runs the script shown in Listing 1.

#!/bin/sh -e
# initramfs local-top script for udev

PREREQ=""

# Output pre-requisites
prereqs()
{
        echo "$PREREQ"
}

case "$1" in
    prereqs)
        prereqs
        exit 0
        ;;
esac


# Each call to udevplug can take up to three minutes
if [ -x /sbin/usplash_write ]; then
    /sbin/usplash_write "TIMEOUT 540"
    trap "/sbin/usplash_write 'TIMEOUT 15'" 0
fi

# Load drivers for storage controllers found on the
# PCI bus; these show up the same for both IDE and
# SCSI so there's no point differentiating between
# the two.  Do it in serial to try to provide some
# predictability for which wins each time.
/sbin/udevplug -s -Bpci -Iclass=0x01*

# We also need to load drivers for bridges (0x06),
# docking stations (0x0a), input devices (0x09),
# serial devices (0x0c) and "intelligent" devices
# (0x0e).  This is both to support filesystems on the
# end and just in case there's a keyboard on the end
# and things go wrong.
/sbin/udevplug -Bpci -Iclass=0x0[69ace]*

# If we're booting from IDE, it might not be a PCI
# controller, but might be an old-fashioned ISA
# controller; in which case we need to load ide-generic.
/sbin/modprobe -Qb ide-generic
/sbin/udevplug -W

The following line, which discovers storage controllers, happens to discover the NVIDIA SATA first:

/sbin/udevplug -s -Bpci -Iclass=0x01*

You can force this script to find the 3ware controller first by adding a line that explicitly loads the 3ware module before this line. Listing 2 shows how to modify the script to do that (Listing 2 is only an excerpt from the relevant part of the script).