что лучший способ - к chainload это

Debian и Ubuntu назвали пакет bootcd чье описание, кажется, отвечает на Ваш вопрос, хотя я никогда не использовал его:

 Build an image of your running Debian System with the command bootcdwrite.
 You can also build a bootcd ISO image via NFS on a remote System.
 When you run your system from CD you do not need any disks. All
 changes will be done in ram. To reuse this changes at next boot time
 you can save them on FLOPPY with the command bootcdflopcp. If booting
 from your CD-drive is not supported, booting from FLOPPY is possible.
 It is possible to install a new system from the running CD with the
 command bootcd2disk. Bootcd2disk can also find a target disk, format
 it and make it bootable automatically. Bootcd also supports lilo,
 grub, initrd, udev, lvm, transparent-compression ISO 9660 fs and
 syslinux/isolinux. The included FAQ describes how bootcd can do
 online or offline backups of other Linux distributions, resulting
 in restore-bootcds. The bootcdbackupwizard helps to create online
 backups.