[yocto] PXE booting ISO image fails with message "Waiting for removable media..."

[Vincent Daanen]

Hi Raymond,

> I'd recently gone through similar issue that you're experiencing.  The "Waiting for Removable Media" hang had been there for at least 7-8 years.  A workaround was put in around 2013.  See here: https://patchwork.openembedded.org/patch/42291/
>
> Add "debugshell=30" (30 is in second, for timeout, or any other reasonable value that you like) to the append
> statement in your pxelinux.cfg/default file.  Then you'd timeout when you "normally" hangs, break into a shell,
> where you could initiate udhcpc to configure networking, after which you could transfer your bootable image onto
> your RAM, and write out onto your HDD/SSD.

Unfortunately, we cannot use this trick because the MB which boots using PXE is not accessible and we want to use PXE booting  for every boot...

> It seems this kernel boot option of debugshell isn't documented officially in kernel-parameters.txt file.

>  You could also look for init-live.sh on your yocto tree, and look for "Waiting for Removable Media", and see the
> surrounding code to get a fell how this debugshell thing works.
I think this is what we will have to do ..

I read the description of the internals of the initrd provided by Archlinux. The main difference is that Yocto initrd searches for the final rootfs on physical device (/dev/sdX) whereas the Archlinux initrd identifies (using LABEL) the support it was launched from and then searches on this support for the final rootfs.

I guess this approach would unify all booting: from USB, CD-ROM and PXE.. But at the moment, I don't know how to reproduce the archlinux initrd works with Yocto...

If only a guru of Yocto could help ...

Vincent

Date: Thu, 3 May 2018 14:27:46 +0000
From: Vincent Daanen <vincent.daanen at orthotaxy.com<mailto:vincent.daanen at orthotaxy.com>>
To: "yocto at yoctoproject.org<mailto:yocto at yoctoproject.org>" <yocto at yoctoproject.org<mailto:yocto at yoctoproject.org>>
Subject: [yocto] PXE booting ISO image fails with message "Waiting for
        removable media..."
Message-ID:
        <VI1P192MB01430B16A66D217CB44829098D870 at VI1P192MB0143.EURP192.PROD.OUTLOOK.COM<mailto:VI1P192MB01430B16A66D217CB44829098D870 at VI1P192MB0143.EURP192.PROD.OUTLOOK.COM>>

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Hi,

We want to deploy image created with Yocto (Rocko) via PXE.
The target board is a Intel-based SBC (AAEON GENE BT05).

At first, we tried with a ISO from Archlinux and the target-board successfully booted.

Then we create a ISO using Yocto but boot hangs with a message ?Waiting for removable media ...?.
Googling this message points me to this post: http://thread.gmane.org/gmane.linux.embedded.yocto.general/20611 which relates exactly the same problem, explain why the issue raises, gives an indication to how to fix .. and that?s all ?

So at this point, we know that the problem comes from the /recipes-core/initrdscripts/files/init-live.sh file.
It seems searching for an /dev/sdx should be protected by a timeout set by default to 30 secs but during our trials, no timeout seems to exist.

What we do not understand, is how to highlight the differences between the Yocto-based and the Archlinux ISO files so that we can ?unblock? the boot using the Yocto-based ISO file.

Is the someone here how could help?

Thanks

Vincent
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