05.12.2018 13:04, Eitan Raviv пишет:
After further investigation I would like to share one more important
piece of information that explains the "reset" behaviour of the network
configuration:
Thanks for that detailed clarification.
When a VM is started in 'Run once' mode, the initialization parameters
supplied for that run are always passed by engine to cloud-init in the
guest for application.
It's clear and work as intended.
But if a VM is started in 'Run' mode, the initialization parameters are
passed to cloud-init on the guest only if this is the first run (be it
'Run' or 'Run once'). On every consecutive run in 'Run' mode no
parameters are passed to the guest, and therefore (as I quoted from the
cloud-init documentation earlier in this thread) cloud-init falls back
to DHCP configuration on the guest.
When this behaviour was introduced into engine the reasoning was that
after the initial configuration of the VM, there is no reason to resend
the configuration on every 'Run' but only on 'Run once'.
Yes, there is no reason, but for new user it looks very confusing:
- create VM
- configure cloud-init parameters (like IP addr)
- Run VM (not once), parameters applied (all OK? as it seems)
- work with/in VM
- Stop VM (maybe after period of time when VM counts as 'configured
successfully') for some maintetance
- Run VM and try to access it (it is 'configured successfully' some
time ago, isn't it?)
- NO ACCESS to VM and configurаtion is LOST
- try to access via console with 'WTF?' exclamation ....
Why cloud-init in this scenario after successful configuration is not
turn off/disable himself (by touch that file, for example) ?
Instead of it cloud-init+ovirt force user to:
- try to figure why configuration is lost, learn "custom script" format
- write "custom script" for touch /etc/cloud/cloud-init.disabled and
reboot
- run once VM to apply parameters
- run VM as usual ?
Due to the behaviour of the current cloud-init package, this causes an
unexpected side effect that should be dealt with by disabling cloud-init
in one of the methods I described earlier in this thread.
Are there use cases when cloud-init (as a service) may require to start
repeatedly on consecutive usual VM runs?
If will need to change parameters user may use "Run Once" start with new
parameters - in this case a 'disabled' file may be ignored.
But what reason to finding a configuration while usual run at all?
--
BR, Mike
On Wed, Nov 28, 2018 at 10:12 AM Eitan Raviv <era...@redhat.com
<mailto:era...@redhat.com>> wrote:
On Wed, Nov 28, 2018 at 7:29 AM Mike Lykov <co...@ya.ru
<mailto:co...@ya.ru>> wrote:
>
> 27.11.2018 16:15, Eitan Raviv пишет:
> > According to cloud-init 0.7.9 documentation cloud-init is
configured
> > to run by default on each boot [1] and to render the user-selected
> > network configuration on first boot [2]. Also, in absence of a data
> > source to configure the network, it will fall back to
configuring DHCP
> > on eth0 [2].
> >
> > As you noted, if you run a VM once, and then in the next
regular run
> > the cloud-init flag is not selected in the VM configuration in
engine,
> > there is no data-source and cloud-init falls back to dhcp as
> > documented.
>
> Thanks for the explanation. What intended use of this
subsystem/feature
> are supposed to?
>
> My setup is not in cloud, it's local and use static IP adresses
for VM.
> I do not want to configure each VM network in console by hand.
> I create VM from template (template have installed cloud-init
package),
> configure cloud-init hostname/eth0 network in engine, and as "custom
> script" (at the same moment) I set a "touch
> /etc/cloud/cloud-init.disabled" ?
Either that or add custom script to disable just cloud-init network
re-config as you did manually.
Please consult the documentation for the custom script syntax and format
(e.g. search for 'runcmd' in
https://cloudinit.readthedocs.io/en/0.7.9/topics/examples.html)
> Then I "Run once" a VM, stop it, and run as usual without data source
> and fallback.
> Or I name network interface not "eth0" and therefore without need for
> custom script?
I did not test the outcome of assigning the static IP to another NIC.
Just sharing a thought...
>
>
> > The 'marker' file you refer to are also documented as follows:
> >
> > * disabling cloud-init altogether [1] with: touch
/etc/cloud/cloud-init.disabled
> > * preventing cloud-init from configuring the network [2] with: echo
> > ‘network: {config: disabled}‘ >> /etc/cloud/cloud.cfg
> > whichever scenario is used to run a VM, this can be accomplished by
> > adding the above commands to the custom_script that cloud-init
runs at
> > the last stage of its operation [3].
> >
> > There is possibly a third 'hack' that would not require any
marker file:
> > * assign your static IP to a NIC not named 'eth0'
> > I have not tested it myself but it looks like a corollary of [2]
> >
> > HTH
> >
> > [1]
https://cloudinit.readthedocs.io/en/0.7.9/topics/boot.html#generator
> > [2]
https://cloudinit.readthedocs.io/en/0.7.9/topics/boot.html#local
> > [3]
https://cloudinit.readthedocs.io/en/0.7.9/topics/boot.html#final
> >
> > On Wed, Nov 21, 2018 at 10:51 AM Mike Lykov <co...@ya.ru
<mailto:co...@ya.ru>> wrote:
> >>
> >> 20.11.2018 15:30, Mike Lykov пишет:
> >>
> >>> "cloud-init used to use a "marker" file that it created on
initial
> >>> execution. If that "marker" file existed it would not rerun
on reboot. "
> >>> - are it not working in ovirt/this cloud-init version ?
> >>
> >> new restart:
> >>
> >> ----------
> >> 2018-11-21 12:40:53,314 - main.py[DEBUG]: Checking to see if
files that
> >> we need already exist from a previous run that would allow us
to stop early.
> >> 2018-11-21 12:40:53,315 - main.py[DEBUG]: Execution continuing, no
> >> previous run detected that would allow us to stop early.
> >> -------------
> >>
> >> which files it try to find ?
> >>
> >> --
> >> Mike
> >>
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