Syslinux - Jul 2014 - Workaround for "hybriding" large ISO images?

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
  isohybrid: Not all BIOSes will be able to boot this device

I guess that's fully expected. And, as expected, we get boot failure
reports from users.

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?

Notes:

  * 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.

  * We currently use "--entry 4 --type 0x1c", for historical reasons;
    that doesn't impact whether the warning is displayed; however, it
    probably impacts on what hardware the USB stick boots or not.

Cheers,
-- 
intrigeri

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

Hi,

Thomas Schmitt wrote (31 Jul 2014 17:01:19 GMT) :
> -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.
Thanks a lot! I've amended our call for testing so that people also
try the latter.
>>   * 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.
Sure. I'll report back here when/if I get useful test results.

Cheers,
--
intrigeri