Transfer Gentoo installation from hd to usb-stick

Pearlseattle

Hello

Well, hello everybody - this is my first post in this forum. Normally I'm active on www.linuxquestions.org, but I wanted to know if there are some particularities concerning Gentoo for the question I have.
A few weeks ago I tried to transfer the Gentoo installation I have on my harddisk (sata) to a USB stick. I created the directories, copied all the files, etc until the usb-key was a mirror of the harddisk, changed the entries in fstab and grub, ensured I had all USB options not compiled as modules but in the kernel itself (2.6.19), rebooted, grub was found, it loaded the kernel and..... it didn't want to find the root filesystem. On the USB stick I created the usual boot partition sdb1 which contains grub and the kernel, and the root partition is sdb2 - probably if the system would boot, those "sdb" would become "sda", right?
Any clue if I have to do something more than that? I was reading here and there and I saw some text speaking about something called "initrd" (not sure anymore it was called like that) concerning delaying the boot, so that the usb stick is correctly recognized and that it can be mounted. Do you think that would solve my problem?
I went through the guide "Gentoo liveusb" <http://www.gentoo.org/doc/en/liveusb.xml>, but that's not what I would like to have (or I didn't understand the article) - I just want the same stuff I have on the HD to be on the USBstick - my kernel, my root filesystem, etc... .
Thanks a lot to everybody...

PaulBredbury · Watchman Joined: 14 Jul 2005 Posts: 7310

merlijn · Posted: Thu Oct 04, 2007 12:45 pm Post subject:

Hiya,

Most of the stuff you did is just fine. Initrd is not needed when you have a separate ext2 boot partition, and the only thing you should care about on that liveusb guide is the bit about the syslinux bootloader. In my case grub has worked just fine, but apparently some chipsets won't recognize a grub MBR on a usb drive, so to be on the safe side it's better to use syslinux. In a lot of cases the device that is booted is called sda, but that is also chipset dependent. Also with some kernel options (I'm not really sure which) the device can be called /dev/uba.

As for other things to care about, there is tons of optimization tweaks you could apply when using a usb drive. Most importantly the speed is not that great (20 MB/s on usb2), so it might be a good idea to mount a few things into ram after booting. Also if you have a flash memory usb drive, you should be worried about the fact that generally you only have ~ 100.000 writes per bit on the device. Say you run a lot of compiles on the drive or use scripts that use lots of hard disk I/O, your usb drive might wear out quicker than you might expect.

Hope this helps,
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Pearlseattle · Posted: Fri Oct 05, 2007 6:34 am Post subject:

Guys, thanks a lot - I'll give it a try this weekend. Yes, I thought about the usb stick getting "old" quite quickly but I will initially compile everything on a normal hd and once it's done I will transfer everything to the usb stick. About log files, I thought I could mount the tmp directories into a small ramdisk. I'll think more in detail about this once I'm able to boot with the root filesystem... .
Thanks!

merlijn · Posted: Fri Oct 05, 2007 7:14 am Post subject:

whig · l33t Joined: 27 Nov 2004 Posts: 973 Location: New Zealand

On the kernel command line include "rootdelay=10" - it gives time for usb devices to appear.