Hi all,

I would like to boot a linux kernel on my hdd and then load a kernel from an USB key. Is there some kind of command that allows to launch a kernel ?

I insist I don't want to use a bootable usb key. I need to load the kernel after booting hdd.

Thanks,

Unfortunately, due to the inherent purpose of a kernel (to manage memory, etc.), you cannot have two kernels concurrently running, unless one of them is in a virtual machine.

Why, out of curiosity, do you need to have two kernels loaded?

If you want to specify which kernel to load, you should be able to start the computer and then use the interactive bootloader prompt and specify which kernel to boot.

Hi,

I need to do so because my computer is booting on a SD card and I only have 1 SD card slot. Before making a mistake, I would like to make a backup of the SD card. With dd, I was able to make an image of the sd card and I would like to copy it to another one. But as a partition from the SD card is mounted as /, I cannot unmount it to swap the sdcard...

Thanks for your attention.

Then you need an alternate boot method. You definitely can't umount your root file system.

Can't you boot from a livecd, an hd or any other thing?

There was a project that aimed at the possibility to boot a new kernel from userspace (which seemed pointless to me because it only saves you the 5 seconds that the POST test of the BIOS takes if you reset). Before you ask: no, I have no idea of it's name anymore and I have no idea of the state of that project either.

Other than booting from another device I see no easy way around your problem. If you can't do that, just take the drives to a pc with two card hubs and clone it. It will be easier. Alternatively, buy a card reader/writer and attach it to an usb port. I see drives of this kind on some shops nowadays around 6-10€ which accept all kind of sd card formats.