[ovirt-users] Best way to shutdown and restart hypervisor?

[Martin Perina]

Hi Gianluca,

so generally speaking when host is in Maintenance status, engine doesn't
communicate with this host, so you can do pretty much anything about it.

About the upgrade flow (host 4.0 -> 4.1), here's proper way(s) how to
achieve that:

1. Put host to Maintenance
2. Add 4.1 repositories to the host
3. Upgrade the host - you have 2 options here:
    a. UI
        - Go to Hosts tab in webadmin
        - Select host and click on Reinstall inside Installation menu
    b. Command line
        - Connect to the host using SSH and upgrade using yum
4. Activate the host

The main difference between UI and command line options is, that with UI
option only necessary packages like VDSM and it's dependencies are upgraded.

​Now regarding restart:
    1. If host is in Maintenance, restart using SSH and shutdown/reboot
execution is no problem​. But if host is Up, then executing shutdown/reboot
using SSH will make host NonResponsive and fencing will be executed

    2. If you select Restart using SSH from Maintenance menu, it just
connect using SSH and execute shutdown same way as it's done manually

    3. If you select Restart using Power Management from Maintenance menu,
it will execute restart using PM device and further actions are hardware
dependent. On some servers it will send shutdown signal to OS similarly as
if you execute reboot and afterwards it turns off power of the server (so
the result may be the same as using shutdown from command line). But on
different hardware it can just turn off power of the server.

So for planned restart using SSH restart either from UI or from command
line is preferred way.

​Martin​


On Fri, Feb 10, 2017 at 1:57 PM, Sandro Bonazzola <sbonazzo at redhat.com>
wrote:

> Adding some people
>
> On Thu, Feb 9, 2017 at 2:08 PM, Gianluca Cecchi <gianluca.cecchi at gmail.com
> > wrote:
>
>> On Wed, Feb 8, 2017 at 10:59 AM, Gianluca Cecchi <
>> gianluca.cecchi at gmail.com> wrote:
>>
>>> Hello,
>>> what is considered the best way to shutdown and restart an hypervisor,
>>> supposing plain CentOS 7 host?
>>>
>>> For example to cover these scenarios:
>>> 1) update host from 4.0 to 4.1
>>> 2) planned maintenance to the cabinet where the server is located and
>>> take the opportunity to update also OS packages
>>>
>>> My supposed workflow:
>>>
>>> - put host into maintenance
>>> - yum update on host
>>> - shutdown os from inside host (because from power mgmt it is brutal
>>> power off / power on)
>>> --> should I get any warning from web admin gui in this case, even if
>>> the host was in maintenance mode?
>>> - power mgmt -> start from webadmin gui
>>> (or power on button/virtual button at host side?)
>>>
>>> Would be advisable to put inside power mgmt functionality some logic
>>> about os mgmt, so for example, if action is restart, first try to shutdown
>>> OS and only in case of failure power off/power on?
>>>
>>> Thanks in advance,
>>> Gianluca
>>>
>>
>> I see that one of the new features of 4.1 is Host restart through SSH
>> Power Mgmt --> SSH Mgmt --> Restart
>>
>> How does it fit in question above?
>> Can I choose this way after having run "yum update" on host?
>> Thanks
>> Gianluca
>>
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>>
>>
>
>
> --
> Sandro Bonazzola
> Better technology. Faster innovation. Powered by community collaboration.
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>
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