bug#32944: Optionally copy kernel to specified directory

[Ricardo Wurmus]

Currently, the kernel and the initrd are stored somewhere in /gnu/store
and the GRUB configuration is generated to point to these things
directly.  This means that the disk containing /gnu/store must be
readable in GRUB.  This is not always the case.

Consider the case where /gnu/store should be hosted on an external
storage array connected redundantly via HBAs.  The disks might not be
visible in GRUB and only become available once Linux has booted.

This could be made to work by adding an option to “guix system
reconfigure” to copy all things that are needed for starting Linux
(e.g. the kernel, the initrd, …), and then mount /gnu/store from the
specified location once Linux is up.

--
Ricardo