[syslinux] lpxelinux.0 issues with larger initrd.img files from RHEL >= 7.5 on UCS servers?

[Mathieu Chouquet-Stringer]

	Hello,

On Wed, Jun 19, 2019 at 11:15:36PM +0000, Ady Ady via Syslinux wrote:
> Just some random and humble thoughts...
> 
> Perhaps it would be worth some additional tests?
> 
> Maybe a test with pxelinux.0 version 4.07? And using "LINUX", not 
> "KERNEL":
> 
> ###
> DEFAULT biginitrd
> PROMPT 0
> LABEL biginitrd
> LINUX mykernel
> INITRD mybiginitrd
> APPEND myoptions
> ###

I will try that.

> Maybe a packet capture might reveal something about the network setup?
> 
> Maybe it is not the size of the initrd file but rather a time 
> limitation (which gets triggered by a big-enough file)?

If it's a timing difference it's going to be tricky: I converted to http
instead of tftp because the transmission time is a least an order of
magnitude faster over http...

> What about trying with 6.04-pre1, and/or (even better) with Debian 
> Sid's packages and using debug.c32 (from the corresponding 
> package/version/build):

Tried that already (the version from debian that is), it failed the same way.

> ###
> DEFAULT dbg
> PROMPT 1
> SAY First press [Enter] for debug.c32, then [1][Enter] for OS.
> 
> # Once in the boot prompt, press "Enter".
> LABEL dbg
> COM32 debug.c32
> APPEND -e pxe_call,malloc
> # Additional functions for debug might be of interest.
> 
> 
> # After debug.c32 returns to the boot prompt,
> # press "1" and "Enter".
> LABEL 1
> LINUX mykernel
> INITRD mybiginitrd
> APPEND myoptions
> ###
> 
> 
> Once the label named "1" is launched, is there any info (that could 
> help)?
> 
> Please avoid using boot menus for these tests; use the boot prompt.

I'll give that a shot as well.

> Sometimes a "cold" boot behaves differently than a "warm" boot. This 
> might be (particularly) relevant when performing multiple cycles of 
> (network) booting (tests).

Tried that as well, doesn't make any difference.

> Another possible test could be to use UEFI mode instead of CSM; in such 
> case the bootloader would be (efi64's) syslinux.efi + ldlinux.e64 ( + 
> efi64's debug.c32). As usual, all files from the same set of 
> package/version/build.

I am not in charge of the configuration of the servers so while I could
test to boot over the network while using UEFI, even if it works, I'll
still be installing servers using CSM...

> Considering the lack of specific, knowledgeable replies about this 
> topic in this Syslinux mailing list so far, maybe a test with a 
> different bootloader (at least for comparison of resulting behavior) 
> would be worth?
> 
> Recurrent failures in all tests would probably indicate either:
>  _ a bug in the firmware; or,
>  _ some problem with the specific kernel+initrd combo (in this 
> hardware); or,
>  _ some problem with the network setup.
> 
> OTOH, if a successful boot can be achieved by at least one test, then 
> either a bug or a limitation in (l)pxelinux.0 might be exposed by this 
> hardware/firmware.

Well in my initial post, I pointed out these kinds of servers had no
problem booting older/smaller initrd files. As soon as the files grew,
they failed.

> As I mentioned, these are some random and humble thoughts; they might 
> not be 
> worth much (or even nothing at all).

Thanks for your input!

-- 
Mathieu Chouquet-Stringer                               m+syslinux at thi.eu.com
            The sun itself sees not till heaven clears.
	             -- William Shakespeare --