[syslinux] Workaround for "hybriding" large ISO images?

[Thomas Schmitt]

Hi,

> since the Tails ISO grew from ~900MB to ~1.1GB, we see this warning
> when running isohybrid on it:
> 
>   isohybrid: Warning: more than 1024 cylinders: 1045

That would be the default cylinder size of 64*32*512 = 1 MiB.

Try isohybrid options
    -h 255 -s 63
to get the maximum cylinder size of a bit less than 8 MiB.
This will suffice for ISOs up to nearly 8 GiB.


> So, my question is: is there a "known optimal" combination of
> isohybrid options that makes the resulting hybrid'd ISO boot on as
> much hardware as possible?

-h 64 -s 32 is said to be the best guess for images up to 1 GiB.
-h 255 -s 63 is said to be the second best one. Needed for > 1 GiB.


>   * I've sent a call for testing to the Tails community in order to
>     gather experimental results in this area, but it might be that
>     someone in here already knows better.

It would be interesting to see how many firmwares fail resp.
succeed whith above geometries in an ISO > 1 GiB.


Have a nice day :)

Thomas