**** BEGIN LOGGING AT Thu Apr 25 02:59:59 2013
Apr 25 21:33:07 <derric> Hi, is it possible to boot a kernel on a differet drive with kexec?
Apr 25 22:03:27 <ant_home> hi derric
Apr 25 22:03:31 <ant_home> surely
Apr 25 22:10:34 <derric> Can you elaborate or point me in the direction of some reading material that would help.  I just found Kexecboot which looks promising.  The goal here is to boot a USB drive that fails to get detected by bios before any kernel is loaded.
Apr 25 22:11:14 <derric> So, I was thinking of booting a mininimal kernel, then kexecing to the kerner on the USB drive.
Apr 25 22:11:18 <ant_home> see last line of
Apr 25 22:11:20 <ant_home> http://kexecboot.org/documentation/how_to_write_config
Apr 25 22:11:44 <ant_home> you can put your boot.cfg on any device then redirect boot
Apr 25 22:11:59 <derric> Well, it seems like I was on the right track then.  Grub2 and plpbt both failed to do the trick.
Apr 25 22:12:47 <derric> I'm reading their page now, will carry on.  Thanks.
Apr 25 22:12:52 <ant_home> yw
Apr 25 22:13:43 <ant_home> kexecboot is 'just' a wrapper around kexec, making easy to customize cmdline
Apr 25 22:14:04 <ant_home> add gui as bonus :)
Apr 25 22:15:30 <ant_home> note you have to compile the appropriate drivers in kernel to allow boot from that device
Apr 25 22:15:40 <ant_home> (and filesystems ofc)
Apr 25 22:16:23 <derric> The only thing I'm unsure about is changing the root from the CD booted kernel to the the new one on the USB drive.
Apr 25 22:17:17 <derric> That's doable.  I've built countless kernel.
Apr 25 22:18:37 <derric> Would that would be the target kernel or the initial kernel?
Apr 25 22:21:07 <ant_home> the initial kernel must be able to find a boot.cfg somewhere
Apr 25 22:21:48 <ant_home> while the target kernel must be able to boot from the device specidied in boot.cfg item
Apr 25 22:25:48 <derric> Once the target kernel is booted, will it chroot automatically to the new root on the USB drive?
Apr 25 22:26:32 <ant_home> wait, don't mix switch-root and kexec
Apr 25 22:26:41 <ant_home> those are two different things
Apr 25 22:27:00 <ant_home> kexec doesn't switch root
Apr 25 22:28:00 <derric> I know, I need, at least I think I do, to do two different things here.  I need to boot a kernel loacated on a usb drive, and chroot to the root of that usb drive.
Apr 25 22:28:52 <derric> I may be getting it mixed up a bit, although I want to boot a live-image on a USB drive.
Apr 25 22:29:14 <ant_home> well, in this specific case one kernel should be enough...but you say it doesn't detect usb dongles
Apr 25 22:30:05 <ant_home> to overcome bios/bootloader limitations you can just boot a kexecboot-enabled kernel
Apr 25 22:30:13 <ant_home> from anywhere
Apr 25 22:30:24 <derric> Well, I guess I omitted that.  My bad, I've been asking in a few places.
Apr 25 22:30:55 <ant_home> see, we developed kexecboot for that specific reason years ago:)
Apr 25 22:31:27 <ant_home> sucky bootloader only allowed boot from MTD
Apr 25 22:31:58 <derric> The machine boots fine off the CD, although I want to avoid wearing out my cdrw by running a live-disto on it continuously.  Hence the motovation to move the OS to a usb drive.  However my machine is making that difficult.
Apr 25 22:32:31 <derric> It's seems so, and I'm glad.
Apr 25 22:33:22 <ant_home> where does your grub reside?
Apr 25 22:33:58 <derric> Maybe I lack any need to swap out kernels, I can use the same one, I just need to move the root to the USB drive.  One problem with that is that rootfs is squashed.
Apr 25 22:34:47 <derric> I have grub1 on a hdd in the system.  I also have grub2 on cd.
Apr 25 22:35:15 <ant_home> ok, the easy way would be to boot linux-kexecboot kernel from grub as second-stage bootloader
Apr 25 22:35:31 <ant_home> or directly from usb stick
Apr 25 22:35:48 <ant_home> ..but this seems impossible in yoiur case
Apr 25 22:36:07 <derric> Yes.
Apr 25 22:36:39 <derric> Lemme ask the live-debian guys about just chrooting to the usb drive.
Apr 25 22:37:01 <derric> After booting from a live-cd.
Apr 25 22:37:24 <ant_home> ok, for that you don't need kexec
Apr 25 22:38:20 <ant_home> just one of the many switch-root variants
Apr 25 22:38:29 <derric> I was originally thinking if I could just jump start the boot process to the usb drive.
Apr 25 22:39:10 <derric> Although I just thought that might be unnecessary.
Apr 25 22:40:01 <ant_home> if you use kexec you forcedly need 2 kernels
Apr 25 22:40:52 <derric> Two kernels is fine.  I just want to get my live-distro running off the usb drive before my cd burner wears out.
Apr 25 22:43:09 <ant_home> does the live-distro contain  a kernel in it?
Apr 25 22:43:19 <derric> Yes.
Apr 25 22:43:44 <derric> And it's kexec enabled and relocatable.
Apr 25 22:43:59 <ant_home> all seems fine then
Apr 25 22:44:23 <derric> It might have the required hardware drivers build as modules though.
Apr 25 22:44:33 <derric> s/build/built
Apr 25 22:45:05 <derric> Although that's easy enough to fix.  It just takes time.
Apr 25 22:45:09 <ant_home> you have to verify that
Apr 25 22:45:48 <ant_home> but afais you should just try to kexec from CD to usb
Apr 25 22:46:08 <ant_home> do that from console, don't care about unmounting if it's a CD
Apr 25 22:46:28 <derric> A minimal set of driver are included in vmlinuz.
Apr 25 22:47:08 <derric> Yeah, that's what I was fixing to just try.  Boot the cd, mount the usb, and go from thre.
Apr 25 22:49:31 <ant_home> see the notes about initramfs here  https://www.kernel.org/doc/Documentation/filesystems/ramfs-rootfs-initramfs.txt
Apr 25 22:50:47 <derric> What's your point?
Apr 25 22:51:03 <ant_home> iirc debian provides an initramfs to boot nowadays
Apr 25 22:51:26 <ant_home> from there you can switch_root
Apr 25 22:51:42 <derric> Yes, although debian mantains and runs everything in a ramdisk.
Apr 25 22:51:56 <derric> So it's different then a regular debian system.
Apr 25 22:52:11 <derric> I meant debian-live uses a ramdisk.
Apr 25 22:55:56 <ant_home> ok, in our case kexecboot + kexec are packed in an initramfs ( cpio)
Apr 25 22:56:44 <ant_home> atm we don't have any shell, kexecboot is the init process
Apr 25 22:57:01 <derric> Yes, that's the current way with debian too.  It's just the live version which is designed to be run from ROM does thing a little differently after the boot process is completed.
Apr 25 22:57:10 <ant_home> but we have been requested to add the switch_root option (and NFS boot FWIW)
Apr 25 22:57:49 <derric> I though the kexec boot material said it had a minimal shell.
Apr 25 22:57:57 <ant_home> nope
Apr 25 22:58:56 <ant_home> there are just three binaries atm
Apr 25 22:59:06 <derric> "The kexec-loader shell is designed to closely mimic a traditional UNIX shell, except.."
Apr 25 22:59:36 <ant_home> wait, that's not kexecboot :)
Apr 25 23:00:00 <ant_home> we are on the minimalistic side
Apr 25 23:00:20 <ant_home> (kernel + cpio size max 1MB)
Apr 25 23:01:02 <derric> That's kind of small, what's that for embedded systems?
Apr 25 23:01:34 <derric> Actually that's really small for both the kernel and cpio.
Apr 25 23:03:32 <derric> Ha, I'm working with two different websites.
Apr 25 23:04:12 <derric> I've been at this for freaking days from the time I get up till when I fall asleep.
Apr 25 23:04:20 <ant_home> see, atm I have only arm toolchain
Apr 25 23:04:37 <ant_home> on weekend I'll upload a cpio for x86 on kexecboot site
Apr 25 23:04:51 <derric> Oh, it's for micro-controllers.
Apr 25 23:04:51 <ant_home> I'll be around tomorrow, feel free to ping me
Apr 25 23:05:02 <derric> Yep, thanks.
Apr 25 23:05:23 <ant_home> kexecboot has been developed for handheld devices
Apr 25 23:05:44 <ant_home> today is used on some tablets as well
Apr 25 23:05:56 <ant_home> wow 1 o'clock here...
Apr 25 23:06:03 <ant_home> I have to go...
Apr 25 23:06:21 <ant_home> cu
Apr 25 23:22:24 <derric> I have some interest in that too.
**** ENDING LOGGING AT Fri Apr 26 02:59:58 2013