Mon, 16 Jul 2007

Bootstrapping Gentoo Linux on a new laptop with a LiveUSB key … with an ext2 filesystem!

Been looking for a new laptop for a while now, and I found what appears to be a good one from ASUS (an “A8S”; Core 2 Duo T7100 chip with nice new 800MHz front side bus, an NVidia 8400M G as the graphics chip, 802.11a,b,g,n (what the hell is n?) wireless and bluetooth, and a nice glosy 1280x800 WXGA screen). Not only are the specs nice, and I found it at an awesome price (in London, would you believe?). Sweet!

But as I wasn’t expecting to be buying a new laptop, I wasn’t carrying any install CDs — and being on the road have no way to burn one. I know I’ll be around lots of hackers this week at GUADEC, but when you’ve got a brand new laptop, who wants to be patient? :)

I do have a small 256 MB usb key with me, though. So on a whim, I thought I’d see if I could bootstrap the laptop that way. None of the guys at the Gentoo conference I was at Saturday had heard of anyone doing it, but we thought it might be possible.

More than possible: it didn’t take me very long to come across an unofficial page in the online Gentoo documentation about boostrapping a Gentoo install from a LiveUSB. Sweet!

They talked about doing it from a CD sized image on the stick, but I didn’t have room for that. Gentoo also has a “minimal” install image which is only 57 MB or so (which you can use if you’ve got good net access); apparently the current release’s minimal installer is missing a needed kernel module for the root filesystem to mount — something to do with FAT codepages, whatever those are (and certainly no reason that Gentoo’s minimal bootstrap media would have it). Bummer.

The workaround is to use a much older release, but the point was to verify that the laptop I’d just bought would actually work with Linux, and that sorta implied using a really current kernel etc.

So me being stubborn, I tried it anyway.

Off I went following the brief LiveUSB instructions to put install-x86-minimal-2007.0-r1.iso onto my usbkey. You have to muck around for a minute or so to switch it from isolinux to syslinux, but no big deal. Then 2 seconds to fix the BIOS boot order, and wow! The syslinux bootloader came up. So cool. Predictably enough, however, I hit the bug and the root filesystem wouldn’t boot. Oh well.

Then I had a bit of a brainwave and thought, “well, if FAT16 is the problem, what about just using a real Linux filesystem instead?” So I went through the steps again, this time just whacking ext2 onto the usbkey (as I normally have there). But when I went to run syslinux to install the bootloader onto the usb key, it failed saying that the target wasn’t a FAT filesystem. “Ah”, I say. So that’s what the difference between isolinux and syslinux is. Oh well.

What I needed, obviously, was a bootloader that would work for a USB key with an ext2 filesystem. I did a brief search, and suddenly came across something rather new called extlinux, from the same person who (it turns out) does all the *linux bootloaders.

extlinux? That sounds promising… and ta-da, it worked!

    livecd ~ #

Awesome!

At the moment bootstrapping from USB is not supported by the Gentoo Release engineers, but maybe the fact that you don’t have to mess around with foreign filesystems will change their minds. A usbkey is, after all, a lot easier for users to “burn” than a CD is, and 1 GB usb devices are suprisingly affordable these days.

AfC

usb-bootstrap, posted by Andrew Cowie in /andrew/software/gentoo-linux at 09:44, 16 Jul 2007.

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