try adding rootdelay=10 to kernel options

Added to handbook :
http://doc.slitaz.org/en:handbook:installation#install-on-an-usb-device
in french :
http://doc.slitaz.org/fr:handbook:installation#installation-sur-un-peripherique-usb

I can't test it right now; can someone verify that all is working correctly ?

Thanks. That worked perfectly.

@MSaadat
What worked, the rootdelay=10 or the handbook modifications?

I ask it because the handbook example has root=UUID="***" and, as far as i know, UUID are not supported directly by the kernel itself but only if you boot from an initramfs. HD installation does not use an initramfs so, in my opinion, can't use UUID for root device.
I've tried it and UUID does not work, the rootdelay=10 is required for usb disks.

Ok thanks.

I had test UUID that there's some month and don't remember the result. So what is the correct variable for root= ?

if i'm right, as in a usual HD install, you must know the hd* or sd* to put in your kernel row root= option.
for example, i have slitaz 3.0 in 5th partition of my usb disk.
while the root=(hd0,4) grub option is always true, if i boot in my pc inside virtualbox using my whole disk as a virtual disk i must use hda5 in the kernel option. if i boot in my pc from usb i must use sdb5, because in my pc i have an ide disk and a serial ata disk. if i have another usb disk or key connected while booting it's a guessing game. as always if i'm not wrong i think that this could be fixed building an initramfs suitable for being used in an HD install.
i was looking how to do this but i don't know if i have the skills and i have very little time now.
meanwhile i would not change the handbook with the UUID method because i think that it will never works unless you are using an initramfs or UUID support will be built inside the kernel. handbook as it is now creates confusion in slitaz users.

When testing USB install with another user I had tryied in vain to build an initramfs. One problem was that I didn't knew bout rootdelay option.

Another solution can be using partitions labels, I don't know if it work for root= but I'm sure it work for home=

in my opinion there is no solution other than an initramfs.
home= kernel option is not parsed by the kernel but from /etc/init.d/bootopts.sh at line 87, after that / is already mounted and before that user has logged in.
i think that an idea for an initramfs could be a base version of slitaz live with a modified /init script which mounts the rootfs in the physical partition instead of staying inside initramfs