I had a lot more success getting flash drives bootable by loading a random ISO to them using unetbootin and then formatting them with

sudo mkfs.vfat -n UNRAID /dev/sde1[color=red][b] ##### IMPORTANT - replace sde1 with the correct device ########[/b][/color]

 

You might want to test booting the ISO first from the flash drive before installing unRaid. (If it still fail to work, some other, yet to be figured out, tricks might be needed...)

 

After formatting the drive,

sudo syslinux /dev/sde1

followed by copying unRaid to it should work....

 

If you then get a menu.c32 error on booting, you are probably using a newer version of sysLinux and editing syslinux.cfg to have the first line read "default unRAID OS" should work... (replacing menu.c32 with the version bundled with syslinux works as well (It is in /usr/lib/syslinux/menu.c32 on my Ubuntu)) (with the modified "default" line you need to press escape quickly if you want to use memtest)

 

(I had limited success using syslinux 4.x / makebootfat only, unetbootin seem to be doing something that work somewhat better than a simple syslinux /dev/sde1 (probably affecting the partition layout, since a format doesn't seem to undo it))

http://www.linuxquestions.org/questions/linux-mint-84/trying-to-boot-linux-mint-9-from-usb-flash-drive-vesamenu-c32-not-a-com32r-image-829397/

 

That fixed it for me in linux, specifically:

 

 

to correct this problem you must use the appropriate *.c32 from the correct version of syslinux

 

but you ca just copy your syslinux version stuff to usb and reinstall syslinux

assuminng usb is sdb1 and mounted at /media/disk

open terminal, become root with "sudo su" plus your password and

Code:

cp -r /usr/lib/syslinux/vesamenu.c32 /media/disk/syslinux/

syslinux /dev/sdb1

 

 

 

 

The problem appears to be that the menu.c32 is not the right one for the version of syslinux used to setup the flash drive, once the right menu.c32 is there and syslinux run again it worked