Requirements
------------
-* All nodes must be able to connect to each other via UDP ports 5404 and 5405
+* All nodes must be able to connect to each other via UDP ports 5405-5412
for corosync to work.
* Date and time must be synchronized.
Adding Nodes to the Cluster
---------------------------
-CAUTION: A node that is about to be added to the cluster cannot hold any guests.
-All existing configuration in `/etc/pve` is overwritten when joining a cluster,
-since guest IDs could otherwise conflict. As a workaround, you can create a
-backup of the guest (`vzdump`) and restore it under a different ID, after the
-node has been added to the cluster.
+CAUTION: All existing configuration in `/etc/pve` is overwritten when joining a
+cluster. In particular, a joining node cannot hold any guests, since guest IDs
+could otherwise conflict, and the node will inherit the cluster's storage
+configuration. To join a node with existing guest, as a workaround, you can
+create a backup of each guest (using `vzdump`) and restore it under a different
+ID after joining. If the node's storage layout differs, you will need to re-add
+the node's storages, and adapt each storage's node restriction to reflect on
+which nodes the storage is actually available.
Join Node to Cluster via GUI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[source,bash]
----
-pvecm add IP-ADDRESS-CLUSTER -link0 LOCAL-IP-ADDRESS-LINK0
+# pvecm add IP-ADDRESS-CLUSTER --link0 LOCAL-IP-ADDRESS-LINK0
----
If you want to use the built-in xref:pvecm_redundancy[redundancy] of the
* then join it, as explained in the previous section.
+The configuration files for the removed node will still reside in
+'/etc/pve/nodes/hp4'. Recover any configuration you still need and remove the
+directory afterwards.
+
NOTE: After removal of the node, its SSH fingerprint will still reside in the
'known_hosts' of the other nodes. If you receive an SSH error after rejoining
a node with the same IP or hostname, run `pvecm updatecerts` once on the
[[pvecm_cluster_network_requirements]]
Network Requirements
~~~~~~~~~~~~~~~~~~~~
-This needs a reliable network with latencies under 2 milliseconds (LAN
-performance) to work properly. The network should not be used heavily by other
-members; ideally corosync runs on its own network. Do not use a shared network
-for corosync and storage (except as a potential low-priority fallback in a
-xref:pvecm_redundancy[redundant] configuration).
+
+The {pve} cluster stack requires a reliable network with latencies under 5
+milliseconds (LAN performance) between all nodes to operate stably. While on
+setups with a small node count a network with higher latencies _may_ work, this
+is not guaranteed and gets rather unlikely with more than three nodes and
+latencies above around 10 ms.
+
+The network should not be used heavily by other members, as while corosync does
+not uses much bandwidth it is sensitive to latency jitters; ideally corosync
+runs on its own physically separated network. Especially do not use a shared
+network for corosync and storage (except as a potential low-priority fallback
+in a xref:pvecm_redundancy[redundant] configuration).
Before setting up a cluster, it is good practice to check if the network is fit
for that purpose. To ensure that the nodes can connect to each other on the
xref:pvecm_corosync_addresses[Link Address Types]).
In this example, we want to switch cluster communication to the
-10.10.10.1/25 network, so we change the 'ring0_addr' of each node respectively.
+10.10.10.0/25 network, so we change the 'ring0_addr' of each node respectively.
NOTE: The exact same procedure can be used to change other 'ringX_addr' values
as well. However, we recommend only changing one link address at a time, so
* Storage replication
-.Pitfalls due to automatic execution of `.bashrc` and siblings
-[IMPORTANT]
-====
+SSH setup
+~~~~~~~~~
+
+On {pve} systems, the following changes are made to the SSH configuration/setup:
+
+* the `root` user's SSH client config gets setup to prefer `AES` over `ChaCha20`
+
+* the `root` user's `authorized_keys` file gets linked to
+ `/etc/pve/priv/authorized_keys`, merging all authorized keys within a cluster
+
+* `sshd` is configured to allow logging in as root with a password
+
+NOTE: Older systems might also have `/etc/ssh/ssh_known_hosts` set up as symlink
+pointing to `/etc/pve/priv/known_hosts`, containing a merged version of all
+node host keys. This system was replaced with explicit host key pinning in
+`pve-cluster <<INSERT VERSION>>`, the symlink can be deconfigured if still in
+place by running `pvecm updatecerts --unmerge-known-hosts`.
+
+Pitfalls due to automatic execution of `.bashrc` and siblings
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
In case you have a custom `.bashrc`, or similar files that get executed on
login by the configured shell, `ssh` will automatically run it once the session
is established successfully. This can cause some unexpected behavior, as those
*) return;;
esac
----
-====
-
Corosync External Vote Support
------------------------------
for Debian based hosts, and other Linux distributions should also have a package
available through their respective package manager.
-NOTE: In contrast to corosync itself, a QDevice connects to the cluster over
-TCP/IP. The daemon may even run outside of the cluster's LAN and can have longer
-latencies than 2 ms.
+NOTE: Unlike corosync itself, a QDevice connects to the cluster over TCP/IP.
+The daemon can also run outside the LAN of the cluster and isn't limited to the
+low latencies requirements of corosync.
Supported Setups
~~~~~~~~~~~~~~~~
The SSH key from the cluster will be automatically copied to the QDevice.
-NOTE: Make sure that the SSH configuration on your external server allows root
-login via password, if you are asked for a password during this step.
+NOTE: Make sure to setup key-based access for the root user on your external
+server, or temporarily allow root login with password during the setup phase.
+If you receive an error such as 'Host key verification failed.' at this
+stage, running `pvecm updatecerts` could fix the issue.
-After you enter the password and all the steps have successfully completed, you
-will see "Done". You can verify that the QDevice has been set up with:
+After all the steps have successfully completed, you will see "Done". You can
+verify that the QDevice has been set up with:
----
pve# pvecm status
Membership information
~~~~~~~~~~~~~~~~~~~~~~
Nodeid Votes Qdevice Name
- 0x00000001 1 A,V,NMW 192.168.22.180 (local)
- 0x00000002 1 A,V,NMW 192.168.22.181
- 0x00000000 1 Qdevice
+ 0x00000001 1 A,V,NMW 192.168.22.180 (local)
+ 0x00000002 1 A,V,NMW 192.168.22.181
+ 0x00000000 1 Qdevice
----
+[[pvecm_qdevice_status_flags]]
+QDevice Status Flags
+^^^^^^^^^^^^^^^^^^^^
+
+The status output of the QDevice, as seen above, will usually contain three
+columns:
+
+* `A` / `NA`: Alive or Not Alive. Indicates if the communication to the external
+ `corosync-qnetd` daemon works.
+* `V` / `NV`: If the QDevice will cast a vote for the node. In a split-brain
+ situation, where the corosync connection between the nodes is down, but they
+ both can still communicate with the external `corosync-qnetd` daemon,
+ only one node will get the vote.
+* `MW` / `NMW`: Master wins (`MV`) or not (`NMW`). Default is `NMW`, see
+ footnote:[`votequorum_qdevice_master_wins` manual page
+ https://manpages.debian.org/bookworm/libvotequorum-dev/votequorum_qdevice_master_wins.3.en.html].
+* `NR`: QDevice is not registered.
+
+NOTE: If your QDevice is listed as `Not Alive` (`NA` in the output above),
+ensure that port `5403` (the default port of the qnetd server) of your external
+server is reachable via TCP/IP!
+
Frequently Asked Questions
~~~~~~~~~~~~~~~~~~~~~~~~~~
mind that guest startup is delayed until you reach quorum.
+[[pvecm_next_id_range]]
+Guest VMID Auto-Selection
+------------------------
+
+When creating new guests the web interface will ask the backend for a free VMID
+automatically. The default range for searching is `100` to `1000000` (lower
+than the maximal allowed VMID enforced by the schema).
+
+Sometimes admins either want to allocate new VMIDs in a separate range, for
+example to easily separate temporary VMs with ones that choose a VMID manually.
+Other times its just desired to provided a stable length VMID, for which
+setting the lower boundary to, for example, `100000` gives much more room for.
+
+To accommodate this use case one can set either lower, upper or both boundaries
+via the `datacenter.cfg` configuration file, which can be edited in the web
+interface under 'Datacenter' -> 'Options'.
+
+NOTE: The range is only used for the next-id API call, so it isn't a hard
+limit.
+
Guest Migration
---------------
Migrating virtual guests to other nodes is a useful feature in a
cluster. There are settings to control the behavior of such
migrations. This can be done via the configuration file
-`datacenter.cfg` or for a specific migration via API or command line
+`datacenter.cfg` or for a specific migration via API or command-line
parameters.
It makes a difference if a guest is online or offline, or if it has
The migration type defines if the migration data should be sent over an
encrypted (`secure`) channel or an unencrypted (`insecure`) one.
-Setting the migration type to insecure means that the RAM content of a
+Setting the migration type to `insecure` means that the RAM content of a
virtual guest is also transferred unencrypted, which can lead to
information disclosure of critical data from inside the guest (for
example, passwords or encryption keys).
always sends the storage content over a secure channel.
Encryption requires a lot of computing power, so this setting is often
-changed to "unsafe" to achieve better performance. The impact on
+changed to `insecure` to achieve better performance. The impact on
modern systems is lower because they implement AES encryption in
hardware. The performance impact is particularly evident in fast
networks, where you can transfer 10 Gbps or more.
Here, we will use the network 10.1.2.0/24 as a migration network. For
a single migration, you can do this using the `migration_network`
-parameter of the command line tool:
+parameter of the command-line tool:
----
# qm migrate 106 tre --online --migration_network 10.1.2.0/24
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