Re: [PATCH v2] allow ifup bring up network manually even without netroot

[Dave Young <dyoung-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On 01/11/2012 10:05 AM, Dave Young wrote:

> Hi, I have some additional comments
> 
> On 01/10/2012 11:41 PM, Cong Wang wrote:
> 
>> On Fri, 30 Dec 2011 at 08:38 GMT, Dave Young <dyoung-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
>>> For kdump we need scp vmcore to remote machine, the nic to be used is
>>> not limited to netroot one. we need a feature for manually bringing up
>>>  network interface. Also it is useful for emergency shell with
>>> ssh-client for recovery or test purpose
>>>
>>> I implement this by adding one argument to ifup script, user can use
>>> `/sbin/ifup eth0 -m` to bring up eth0, note ifup will regard it a
>>> manual operation for the nic specified in 1st argument if there's
>>> the 2nd argument.
>>>
>>> If same nic is used for netroot the 2nd argument will be ignored,
>>> in this case we will leave netroot bring up it automatically to
>>> avoid side effect. And in this case hooks such as kdump will need to
>>> execute after netroot mounted.
>>>
>>> `ifup eth0 -m` will create /tmp/net.eth0.manualup stamp file,
>>> later dhclient-script can check this and pass $2 to netroot,
>>> then netroot script will bring eth0 up
>>>
>>
>> As we talked on IRC, we still need to discuss if this is really
>> needed, from kdump perspective.
> 
> 
> manually ifup nic also benefit to emergency shell use case. I want to
> use dracut initramfs as a minimal system without real root for kernel
> testing
> 
>> If we need to invoke `ifup` by
>> ourselves, then we also need to determine which NIC we should bring
>> up, this will make kdump code larger.
>>
>> So, I hope, we can have some kernel cmdline (like ip=...) to tell
>> dracut which NIC we want to bring up in the second kernel, provided by
>> either ssh-client module or nfs module.
> 
> 
> If we need to pass the nic name to cmdline then we still need to
> determine which one should be use.
> 
> If we just bring up all nics, then use the manual ifup is also easy.
> 
> current dracut udev rules is: if there's no nic specified it will ifup
> all possible nics, but all will be put in initqueue which finally be
> brought up by netroot script.


And if without netroot cmdline set netroot script will just fail and
return, so in this case ifup will act as nop

> 
>>
>> Let's see what Harald thinks...
> 
>>
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> 
> 



-- 
Thanks
Dave