[syslinux] Isohybrid wiki page and UEFI

[Bruno Cornec]

Hello,

Ady via Syslinux said on Sun, Oct 25, 2015 at 08:15:37PM +0200:
>_ Creating filesystem that _does_ conform to ISO-9660;

I think the only issue is with a tag. That same image boots with grub
0.99

>_ The fat image should not be bigger than 32MiB, and it should be
>aligned. The latter suggestion is usually ignored by almost everyone,
>but if we are troubleshooting...

Tried with more and less than 30 MB without impatc.
Aligned: could you give me an example of how you would create it with dd
?

>_ Creating a UEFI-boot-only image...

I can try that indeed. Don't think it's creating an impact as I do see
the bootable VFAT32 part of my media and can navigate to it.

>_ genisoimage is not the same as mkisofs; do not use the former (which
>has been unmaintained since 2010). BTW, the EFI parameters for mkisofs
>are documented in its manual (year 2012 is the latest version of the
>manual available, with 2010 being the prior version of the manual).

I mentioned that I'm using RHEL7 to make my tests as a source. And their
version is highly moified. They *do* produce UEfI bootable images with
grub2 BTW using their toolset. Their mkisofs is a link to genisoimage

# mkisofs -v
I: -input-charset not specified, using utf-8 (detected in locale
settings)
genisoimage 1.1.11 (Linux)
genisoimage: Missing pathspec.
Usage: genisoimage [options] -o file directory ...

Use genisoimage -help
to get a list of valid options.

Report problems to debburn-devel at lists.alioth.debian.org.

>_ "eltorito-alt-boot -efi-boot 1.img -no-emul-boot" will be inadequate
>for mkisofs.

Yes but not for their version.
My tool is working on a large variety of Linux distributions so it tries
to first find the historical mkisofs command to burn. If found it uses
it, if not it tries with genisoimage as params are very similar for what
I do.

>_ Since you don't even get to the Syslinux prompt, I would suggest, for
>troubleshooting purposes, to not even care about the kernel+initrd;
>don't add these files. Let's just see syslinux.efi + ldlinux.e* get to
>the Syslinux boot prompt.

How can I *see* that ? 
I still need to try the virtual serial port part but I'm surprised there
is no way to make syslinux more verbose so we know in which step it is.
For PXE boot, at least I can do tcpdump to monitor what happens. Here
I'm lost :-(

>You mentioned some MBR. The efi image should not have any MBR, and if
>the ISO image was treated with isohybrid, I would suggest avoiding it
>at this time, for troubleshooting purposes.

MBR for the image created which is then used as a parm to the -efi-boot
option of genisoimage.

>For troubleshooting, KISS.

That's really what II try to do. But I've not found an easy way to make
syslinux.efi verbose :-(

BTW I've reproduced the red screen I get with another case: when using the
option -r blksize for the tftp server in PXE mode. Maybe it can give an
idea to someone.

I'm unsure of what is printing this screen.
Bruno.
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