On Mon, 2016-02-01 at 06:03 -0200, Tiago Ilieve wrote: > Hi, > > I have a scenario[1] where the default Linux kernel compressed with XZ > (from Jessie and up) cannot be booted. The first thing that I've tried > was to uncompress it using "extract-linux"[2] and it didn't worked by > the time, so I decided to rebuild the entire "linux-image-*" package > changing "CONFIG_KERNEL_XZ=y" to "CONFIG_KERNEL_GZIP=y". This, of > course, implies that it would be needed to recompile the kernel every > time a new version of the package is released, which is an overkill > for a such simple requirement. > > Yesterday, Ben Hutchings itself suggested[3] me to write a hook that > decompresses the kernel at package installation time, something which > I find a great idea. The problem is that, again, I couldn't boot a > machine (tried on VirtualBox and Xen) after uncompressing its > "/boot/vmlinuz-*" using "extract-linux".
What does file(1) say about the resulting file? It should be a plain ELF file of some sort. I wouldn't expect such a kernel to be bootable by very much other than Xen PV. It won't work as native for sure, nor as Xen HVM. > I can generate an initrd file > from this uncompressed image, "update-grub" detects it fine, but if I > reboot it the following error appears: > > Loading Linux 3.16.0-4-amd64 ... > error: invalid magic number. > Loading initial ramdisk ... > error: you need to load the kernel first. Is this booting via pvgrub[1], if not then do you know how? What does the grub.cfg stanza look like? > - Is "extract-linux" stripping some essential information (the script > looks for an offset to start the decompression process) from the > kernel image that is needed to boot it later? If so, is there a way to > recover and insert it on the uncompressed image? It should just be the raw ELF file payload form the bzImage. Xen requires some particular ELF notes to be present, but I very much doubt extract- linux would be stripping those (since that would involve diving into the contents of the payload) Ian. [1] http://wiki.xen.org/wiki/PvGrub > > Regards, > Tiago. > > [1]: https://lists.debian.org/debian-cloud/2016/01/msg00052.html > [2]: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/plai > n/scripts/extract-vmlinux > [3]: https://lists.debian.org/debian-cloud/2016/01/msg00060.html > [4]: http://www.he1ix.org/2015/01/creating-a-xen-domu-on-debian-squeeze-6 > -0-6/ > [5]: http://noone.org/blog/English/Computer/Debian/Running%20a%20Sid%20Do > mU%20on%20a%20Squeeze%20Dom0.html >
