[Buildroot] Udev on a live CD system does not appear to populate /dev

Antony Vennard antony.vennard at macrium.com
Fri Nov 9 12:20:08 UTC 2012


On 08/11/2012 21:17, Arnout Vandecappelle wrote:
>  If you build a cpio rootfs, you shouldn't need any additional command line
> parameters because the kernel never gets to mounting the root
> filesystem.  It
> just runs the /init in the initramfs.
> 
>  Using a cpio rootfs should also solve your problems with the device nodes,
> because we provide a /init that mounts devtmpfs explicitly.
> 
>  Regards,
>  Arnout
> 

Yep, I'd come to the conclusion I needed an /init to exist, constructing
the root file system. Manually creating the CD as a test, the kernel
panics (root file system not found) if init doesn't exist. I used the
one from fs/cpio/init as you suggested.

The ram_disk_size parameter does appear to be entirely optional.

I'm now on to the next problem - that script exec's /sbin/init which is
really /bin/busybox... which is exiting straight away or crashing, as
the kernel is now panicking about an exiting init :(

I'm going to have an experiment with this, see if I can understand what
the issue is.

I have also grabbed a copy of buildroot git. Once I've got this working,
I'll have a go at modifying buildroot to build iso9660 targets via this
mechanism. I'm no expert in this kind of thing, but it'll be a good
learning experience.

I may also potentially be looking to integrate EFI boot into our live CD
at some stage - if this is of interest I can have a go at adding this to
buildroot also.

Thanks for your help,

Antony


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