[ClusterLabs] Creating pacemaker cluster starting with one node

[Eugen Block]

Since we are familiar with SUSE products, we based our deployment on  
the SUSE High Availability docs:

https://documentation.suse.com/en-us/sle-ha/15-SP7/single-html/SLE-HA-installation/index.html

So in short, we run „crm cluster init“ on the bootstrap node, and when  
everything works as expected, „crm node join“ on the further nodes. Of  
course, there’s some more details required, like the corosync config,  
csync2 etc.

Our own cluster was based on openSUSE, but when SUSE discontinued the  
OpenStack product, we couldn’t upgrade anymore on openSUSE. So last  
year, we reinstalled our cloud on Ubuntu by redeploying a pacemaker  
cluster (single node), brought OpenStack back up, then joined the  
second server. And it works great, we’re just waiting for the latest  
updates to arrive in the distro for better systemd management.

Zitat von Andreas Mock <andreas.mock at drumedar.de>:

> Hi Thomas, hi Eugen,
>
> thank you for the reply.
>
> Is there anywhere a howto to bootstrap such an one node cluster?
>
> Best regards
> Andreas
>
>
> -
> -----Ursprüngliche Nachricht-----
> Von: Users <users-bounces at clusterlabs.org> Im Auftrag von Eugen Block
> Gesendet: Samstag, 2. August 2025 11:18
> An: Cluster Labs - All topics related to open-source clustering  
> welcomed <users at clusterlabs.org>
> Betreff: Re: [ClusterLabs] Creating pacemaker cluster starting with one node
>
> Hi,
>
> that's how we usually set up our Openstack cluster(s). We bootstrap  
> our first node so we have a single-node pacemaker cluster running  
> all Openstack control services, then "join" the other control nodes,  
> expanding the cluster.
> I'd recommend to practice in a test cluster, that has helped me a lot!
>
> Regards,
> Eugen
>
> Zitat von Tomas Jelinek <tojeline at redhat.com>:
>
>> Hi Andreas,
>>
>> From the point of view of pcs, pacemaker and corosync, it is possible
>> to create a one-node cluster, run resources in it, and  add another
>> node afterwards. Obviously, when the single node is lost for whatever
>> reason, there is no other node to run the resources.
>>
>> You should also consider whether the cluster's workload supports this
>> and what steps are necessary to make it work in this scenario.
>>
>> Regards,
>> Tomas
>>
>>
>> Dne 31. 07. 25 v 8:46 Andreas Mock napsal(a):
>>> Hi all,
>>>
>>> I have to upgrade an old pacemaker cluster consisting of two nodes.
>>> (There is no chance of rolling update).
>>>
>>> Is it possible to create a pacemaker “cluster” starting with only one
>>> node and afterwards attach the second node?
>>>
>>> Best regards
>>>
>>> Andreas
>>>
>>>
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