[syslinux] fail-safe boot - how can this be done?

ganapathy murali krishnan gmurali at cs.uchicago.edu
Thu Oct 7 15:33:28 PDT 2004

I had a similar problem, which I solved as follows: Make the default 
kernel a "COMBOOT image". The comboot image, looks around and decides 
which kernel to boot, and calls SYSLINUX with the right argument. If the 
COMBOOT image does not find anything, it boots a user specified kernel 
(either fail-safe or the normal kernel).

In my case, I was working with read only media (CD), so I would write 
this auxillary information to an unused sector of the hard disk. This 
approach has worked for me, but your mileage may vary. In any case, this 
"autoboot" COMBOOT image and its partner "writeker" linux utility (which 
writes to the hard disk) are both available at
http://gui.mahamurali.net (will redirect to the longer address).

Hope this helps.
- Murali

Thorsten von Eicken wrote:

>I'm installing syslinux on an embedded board that will only be reachable via boat+hike or helicopter. This will be a somewhat experimental platform, so I can't make a read-only filesystem on CF. What I'd like is to have two root filesystems on a CF card, one that is a read-only "fail-safe", and a 2nd that is the "normal" system I experiment with. What I'm looking for is a fail-safe where anytime the system does not shut down cleanly the fail-safe boot is invoked. Is there support for this in syslinux?
>One scheme that would work is to list the fail-safe system as default in syslinux.cfg, and the normal one with a label. A file on the boot partition (say 'syslinux.ptr') would contain the name of the kernel to invoke and would be deleted by syslinux just before invoking the kernel. The 'normal' kernel would create this file with contents 'normal' during the shutdown procedure. The net effect is that anytime syslinux boots it will invoke the default kernel unless the normal kernel shut down cleanly, or someone created the file manually. (All this would be augmented with a hardware watchdog that resets the board if the system locks up.)
>Thanks for any suggestions,
>	Thorsten - Santa Barbara Amateur Radio Club
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