Re: Does the order of kernel parameters matter?

[Jakob Bohm]

On 2020-10-14 20:39, Salvatore Mazzarino wrote:

I'm facing some interesting issues. Changing the order of kernel parameters passed to the `-append`, it changes the outcome.

Running my QEMU VM with the following works:

-append "root=/dev/disk/by-id/virtio-rootfs rootflags=rw flatcar.first_boot=1 tsc=reliable no_timer_check= rcupdate.rcu_expedited=1 i8042.direct=1 i8042.dumbkbd=1 i8042.nopnp=1 i8042.noaux=1 noreplace-smp= reboot=k console=hvc0 console=hvc1 cryptomgr.notests= net.ifnames=0 pci=lastbus=0"

However, if put the `root=` to the end then it does not work and the root volume is not found so not mounted.

So I'm now wondering. the order does it really matter? And if so there is any logic behind it? Any rules to follow? 

    This happens generally with the Linux kernel, probably because
      the mechanism for
    passing the options to the kernel has a character limit,
      causing the last of your
      long line to be thrown away.
      
      I suggest looking at the kernel documentation to see if there is a
      limit and then
      check if you exceed it.
      
      As for qemu, I suspect that qemu uses a generic method of passing
      the string into 
      the VM, which has a much higher limit to support non-Linux
      kernels.
    
Enjoy

Jakob
-- 
Jakob Bohm, CIO, Partner, WiseMo A/S.  https://www.wisemo.com
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