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Allways boot from the USB-Stick not from a attached HD

Posted by truehl 
Hi,
how can I be sure to allways boot from the USB-Stick and not from a attached HD? Does the system allways try to boot from a device with a boot sector? What if the usb-stick is sometimes sda and sometimes sdb?

Thx, Thomas
Re: Allways boot from the USB-Stick not from a attached HD
November 28, 2010 08:52PM
Have you actually noticed this happening, truehl? This is indeed a perplexing problem on the SheevaPlug, along with the closely related problem of which /dev entry each device gets. (Usually, the mapping is consistent on all warm boots and all cold boots, but if there is a problem, it is that warm boots are consistently different from cold boots.) I've attributed this to the fact that the HD takes a few seconds to spin up and become available, and thus the HD turns out to be sda on warm boots when it is spinning and readily available, but the thumb drive grabs the sda designation when the HD disk is spun down in a cold boot.

On the Dockstar, I have not had this problem. Frankly, it seems to me that the mounting of disk-like devices has been super consistent -- perhaps attributed to the fact that there is no external USB hub to interact with -- but maybe I've just been lucky.

Of course, one obvious way to ensure the USB stick is always the one to boot from is to make sure there is no bootable kernel on the HD.

Good luck.
Re: Allways boot from the USB-Stick not from a attached HD
November 28, 2010 09:57PM
Restamp,

hi,

i've had this problem as well .. it all worked fine (booting from usb stick and auto mounting external usb hd with just media files on)

BUT

once i activated the swap file then from cold and warm boot it just tried to boot to usb HD with result nothing .. i had to remove the usb hd and it immediately booted the flash stick with debian on it

check out this thread with more detail

http://forum.doozan.com/read.php?2,2725


any ideas ?

rgds

ian
Re: Allways boot from the USB-Stick not from a attached HD
November 29, 2010 12:02PM
I have a flash drive with my bootable partition and a hard disk for storage.

When I installed Debian the flash disk was /dev/sda1 but when I added the HD that swapped to /dev/sdb1.

My approach has been to use UUIDs in /etc/fstab and to make sure my HD is not bootable. This has worked perfectly and doesn't appear to depend which device name is allocated to which device.
rat
Re: Allways boot from the USB-Stick not from a attached HD
November 30, 2010 05:42AM
I have a similar problem but with the LCD Keychain Picture Frame taking the /sda designation and causing bootup hangs or issues. All I can do is remove the LCD, cycle it and wait for it to finish booting before I plug it in.
Do you have an entry for the root partition in your fstab or just one for the external HD?
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