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From Shanker Balan <>
Subject Re: how to pass kernel parameters to VMs
Date Wed, 04 Sep 2013 09:09:21 GMT
On 04-Sep-2013, at 2:45 AM, Steve Roth <> wrote:

> Hi all,
> Is there any way when starting a VM to override/pass kernel parameters, such 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 deployVirtualMachine API  (presuming there
is a way to fetch this value once the VM boots up).     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 correct 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



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