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From: Shanker Balan <shanker.balan@shapeblue.com>
To: "<users@cloudstack.apache.org>" <users@cloudstack.apache.org>
Subject: Re: how to pass kernel parameters to VMs
Thread-Topic: how to pass kernel parameters to VMs
Thread-Index: AQHOqOrXuGH6fEIFeEOhUpOQAQmePJm1SwgA
Date: Wed, 4 Sep 2013 09:09:21 +0000
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On 04-Sep-2013, at 2:45 AM, Steve Roth <steve.roth@oracle.com> wrote:

> Hi all,
>
> Is there any way when starting a VM to override/pass kernel parameters, s=
uch as single?  (for single-user mode)

Here is how I do it:

1) Open a console session to the VM
2) Reboot
3) Wait for boot loader prompt
4) Modify kernel boot options as applicable
5) Boot kernel


>
> I guess this presumes Linux VMs.
>
> We're looking for a way to pass a 'purpose' to a VM (other than its name)=
.   One way would appear to be the 'userdata' field in the deployVirtualMac=
hine API  (presuming there is a way to fetch this value once the VM boots u=
p).     I'm just wondering if we could use a kernel parameter as well.
>
> If it's helpful, we are using KVM as our hypervisor.


This is a little trick I did at previous $work:

1) All hosts are set to PXE boot first and then local HDD
2) For any host that needed a "rescue", PXE boot settings were put in place=
 with the correct hex id
3) Reboot host
4) Host picks up the netboot kernel with the special boot options and the c=
orrect root disk
5) Host lands into rescue mode
6) Rescue the OS using the console
7) Remove the PXE boot config
8) Reboot host, host boots as usual

Hth.

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