NAME
pvecm - Proxmox VE Cluster Manager
SYNOPSIS
pvecm <COMMAND> [ARGS] [OPTIONS]
pvecm add <hostname>
[OPTIONS]
Adds the current node to an existing cluster.
-
<hostname>
string
-
Hostname (or IP) of an existing cluster member.
-
-force
boolean
-
Do not throw error if node already exists.
-
-nodeid
integer (1 - N)
-
Node id for this node.
-
-ring0_addr
string
-
Hostname (or IP) of the corosync ring0 address of this node. Defaults to nodes hostname.
-
-ring1_addr
string
-
Hostname (or IP) of the corosync ring1 address, this needs an valid configured ring 1 interface in the cluster.
-
-votes
integer (0 - N)
-
Number of votes for this node
pvecm addnode <node>
[OPTIONS]
Adds a node to the cluster configuration.
-
<node>
string
-
The cluster node name.
-
-force
boolean
-
Do not throw error if node already exists.
-
-nodeid
integer (1 - N)
-
Node id for this node.
-
-ring0_addr
string
-
Hostname (or IP) of the corosync ring0 address of this node. Defaults to nodes hostname.
-
-ring1_addr
string
-
Hostname (or IP) of the corosync ring1 address, this needs an valid bindnet1_addr.
-
-votes
integer (0 - N)
-
Number of votes for this node
pvecm create <clustername>
[OPTIONS]
Generate new cluster configuration.
-
<clustername>
string
-
The name of the cluster.
-
-bindnet0_addr
string
-
This specifies the network address the corosync ring 0 executive should bind to and defaults to the local IP address of the node.
-
-bindnet1_addr
string
-
This specifies the network address the corosync ring 1 executive should bind to and is optional.
-
-nodeid
integer (1 - N)
-
Node id for this node.
-
-ring0_addr
string
-
Hostname (or IP) of the corosync ring0 address of this node. Defaults to the hostname of the node.
-
-ring1_addr
string
-
Hostname (or IP) of the corosync ring1 address, this needs an valid bindnet1_addr.
-
-rrp_mode
(active | none | passive)
(default=none
) -
This specifies the mode of redundant ring, which may be none, active or passive. Using multiple interfaces only allows active or passive.
-
-votes
integer (1 - N)
-
Number of votes for this node.
pvecm delnode <node>
Removes a node to the cluster configuration.
-
<node>
string
-
Hostname or IP of the corosync ring0 address of this node.
pvecm expected <expected>
Tells corosync a new value of expected votes.
-
<expected>
integer (1 - N)
-
Expected votes
pvecm help [<cmd>]
[OPTIONS]
Get help about specified command.
-
<cmd>
string
-
Command name
-
-verbose
boolean
-
Verbose output format.
pvecm keygen <filename>
Generate new cryptographic key for corosync.
-
<filename>
string
-
Output file name
pvecm nodes
Displays the local view of the cluster nodes.
pvecm status
Displays the local view of the cluster status.
pvecm updatecerts [OPTIONS]
Update node certificates (and generate all needed files/directories).
-
-force
boolean
-
Force generation of new SSL certifate.
-
-silent
boolean
-
Ignore errors (i.e. when cluster has no quorum).
DESCRIPTION
The Proxmox VE cluster manager pvecm
is a tool to create a group of
physical servers. Such a group is called a cluster. We use the
Corosync Cluster Engine for reliable group
communication, and such clusters can consist of up to 32 physical nodes
(probably more, dependent on network latency).
pvecm
can be used to create a new cluster, join nodes to a cluster,
leave the cluster, get status information and do various other cluster
related tasks. The Proxmox Cluster File System (“pmxcfs”)
is used to transparently distribute the cluster configuration to all cluster
nodes.
Grouping nodes into a cluster has the following advantages:
-
Centralized, web based management
-
Multi-master clusters: each node can do all management task
-
pmxcfs
: database-driven file system for storing configuration files, replicated in real-time on all nodes usingcorosync
. -
Easy migration of virtual machines and containers between physical hosts
-
Fast deployment
-
Cluster-wide services like firewall and HA
Requirements
-
All nodes must be in the same network as
corosync
uses IP Multicast to communicate between nodes (also see Corosync Cluster Engine). Corosync uses UDP ports 5404 and 5405 for cluster communication.Some switches do not support IP multicast by default and must be manually enabled first. -
Date and time have to be synchronized.
-
SSH tunnel on TCP port 22 between nodes is used.
-
If you are interested in High Availability, you need to have at least three nodes for reliable quorum. All nodes should have the same version.
-
We recommend a dedicated NIC for the cluster traffic, especially if you use shared storage.
|
It is not possible to mix Proxmox VE 3.x and earlier with Proxmox VE 4.0 cluster nodes. |
Preparing Nodes
First, install Proxmox VE on all nodes. Make sure that each node is installed with the final hostname and IP configuration. Changing the hostname and IP is not possible after cluster creation.
Currently the cluster creation has to be done on the console, so you
need to login via ssh
.
Create the Cluster
Login via ssh
to the first Proxmox VE node. Use a unique name for your cluster.
This name cannot be changed later.
hp1# pvecm create YOUR-CLUSTER-NAME
|
The cluster name is used to compute the default multicast address. Please use unique cluster names if you run more than one cluster inside your network. |
To check the state of your cluster use:
hp1# pvecm status
Adding Nodes to the Cluster
Login via ssh
to the node you want to add.
hp2# pvecm add IP-ADDRESS-CLUSTER
For IP-ADDRESS-CLUSTER
use the IP from an existing cluster node.
|
A new node cannot hold any VMs, because you would get
conflicts about identical VM IDs. Also, all existing configuration in
/etc/pve is overwritten when you join a new node to the cluster. To
workaround, use vzdump to backup and restore to a different VMID after
adding the node to the cluster. |
To check the state of cluster:
# pvecm status
hp2# pvecm status
Quorum information
~~~~~~~~~~~~~~~~~~
Date: Mon Apr 20 12:30:13 2015
Quorum provider: corosync_votequorum
Nodes: 4
Node ID: 0x00000001
Ring ID: 1928
Quorate: Yes
Votequorum information
~~~~~~~~~~~~~~~~~~~~~~
Expected votes: 4
Highest expected: 4
Total votes: 4
Quorum: 2
Flags: Quorate
Membership information
~~~~~~~~~~~~~~~~~~~~~~
Nodeid Votes Name
0x00000001 1 192.168.15.91
0x00000002 1 192.168.15.92 (local)
0x00000003 1 192.168.15.93
0x00000004 1 192.168.15.94
If you only want the list of all nodes use:
# pvecm nodes
hp2# pvecm nodes
Membership information
~~~~~~~~~~~~~~~~~~~~~~
Nodeid Votes Name
1 1 hp1
2 1 hp2 (local)
3 1 hp3
4 1 hp4
Adding Nodes With Separated Cluster Network
When adding a node to a cluster with a separated cluster network you need to use the ringX_addr parameters to set the nodes address on those networks:
pvecm add IP-ADDRESS-CLUSTER -ring0_addr IP-ADDRESS-RING0
If you want to use the Redundant Ring Protocol you will also want to pass the ring1_addr parameter.
Remove a Cluster Node
|
Read carefully the procedure before proceeding, as it could not be what you want or need. |
Move all virtual machines from the node. Make sure you have no local data or backups you want to keep, or save them accordingly.
Log in to one remaining node via ssh. Issue a pvecm nodes
command to
identify the node ID:
hp1# pvecm status
Quorum information
~~~~~~~~~~~~~~~~~~
Date: Mon Apr 20 12:30:13 2015
Quorum provider: corosync_votequorum
Nodes: 4
Node ID: 0x00000001
Ring ID: 1928
Quorate: Yes
Votequorum information
~~~~~~~~~~~~~~~~~~~~~~
Expected votes: 4
Highest expected: 4
Total votes: 4
Quorum: 2
Flags: Quorate
Membership information
~~~~~~~~~~~~~~~~~~~~~~
Nodeid Votes Name
0x00000001 1 192.168.15.91 (local)
0x00000002 1 192.168.15.92
0x00000003 1 192.168.15.93
0x00000004 1 192.168.15.94
|
at this point you must power off the node to be removed and make sure that it will not power on again (in the network) as it is. |
hp1# pvecm nodes
Membership information
~~~~~~~~~~~~~~~~~~~~~~
Nodeid Votes Name
1 1 hp1 (local)
2 1 hp2
3 1 hp3
4 1 hp4
Log in to one remaining node via ssh. Issue the delete command (here
deleting node hp4
):
hp1# pvecm delnode hp4
If the operation succeeds no output is returned, just check the node
list again with pvecm nodes
or pvecm status
. You should see
something like:
hp1# pvecm status
Quorum information
~~~~~~~~~~~~~~~~~~
Date: Mon Apr 20 12:44:28 2015
Quorum provider: corosync_votequorum
Nodes: 3
Node ID: 0x00000001
Ring ID: 1992
Quorate: Yes
Votequorum information
~~~~~~~~~~~~~~~~~~~~~~
Expected votes: 3
Highest expected: 3
Total votes: 3
Quorum: 3
Flags: Quorate
Membership information
~~~~~~~~~~~~~~~~~~~~~~
Nodeid Votes Name
0x00000001 1 192.168.15.90 (local)
0x00000002 1 192.168.15.91
0x00000003 1 192.168.15.92
|
as said above, it is very important to power off the node before removal, and make sure that it will never power on again (in the existing cluster network) as it is. |
If you power on the node as it is, your cluster will be screwed up and it could be difficult to restore a clean cluster state.
If, for whatever reason, you want that this server joins the same cluster again, you have to
-
reinstall Proxmox VE on it from scratch
-
then join it, as explained in the previous section.
Separate A Node Without Reinstalling
|
This is not the recommended method, proceed with caution. Use the above mentioned method if you’re unsure. |
You can also separate a node from a cluster without reinstalling it from scratch. But after removing the node from the cluster it will still have access to the shared storages! This must be resolved before you start removing the node from the cluster. A Proxmox VE cluster cannot share the exact same storage with another cluster, as it leads to VMID conflicts.
Its suggested that you create a new storage where only the node which you want to separate has access. This can be an new export on your NFS or a new Ceph pool, to name a few examples. Its just important that the exact same storage does not gets accessed by multiple clusters. After setting this storage up move all data from the node and its VMs to it. Then you are ready to separate the node from the cluster.
|
Ensure all shared resources are cleanly separated! You will run into conflicts and problems else. |
First stop the corosync and the pve-cluster services on the node:
systemctl stop pve-cluster systemctl stop corosync
Start the cluster filesystem again in local mode:
pmxcfs -l
Delete the corosync configuration files:
rm /etc/pve/corosync.conf rm /etc/corosync/*
You can now start the filesystem again as normal service:
killall pmxcfs systemctl start pve-cluster
The node is now separated from the cluster. You can deleted it from a remaining node of the cluster with:
pvecm delnode oldnode
If the command failed, because the remaining node in the cluster lost quorum when the now separate node exited, you may set the expected votes to 1 as a workaround:
pvecm expected 1
And the repeat the pvecm delnode command.
Now switch back to the separated node, here delete all remaining files left from the old cluster. This ensures that the node can be added to another cluster again without problems.
rm /var/lib/corosync/*
As the configuration files from the other nodes are still in the cluster filesystem you may want to clean those up too. Remove simply the whole directory recursive from /etc/pve/nodes/NODENAME, but check three times that you used the correct one before deleting it.
|
The nodes SSH keys are still in the authorized_key file, this means the nodes can still connect to each other with public key authentication. This should be fixed by removing the respective keys from the /etc/pve/priv/authorized_keys file. |
Quorum
Proxmox VE use a quorum-based technique to provide a consistent state among all cluster nodes.
A quorum is the minimum number of votes that a distributed transaction has to obtain in order to be allowed to perform an operation in a distributed system.
— from Wikipedia
In case of network partitioning, state changes requires that a majority of nodes are online. The cluster switches to read-only mode if it loses quorum.
|
Proxmox VE assigns a single vote to each node by default. |
Cluster Network
The cluster network is the core of a cluster. All messages sent over it have to
be delivered reliable to all nodes in their respective order. In Proxmox VE this
part is done by corosync, an implementation of a high performance low overhead
high availability development toolkit. It serves our decentralized
configuration file system (pmxcfs
).
Network Requirements
This needs a reliable network with latencies under 2 milliseconds (LAN performance) to work properly. While corosync can also use unicast for communication between nodes its highly recommended to have a multicast capable network. The network should not be used heavily by other members, ideally corosync runs on its own network. never share it with network where storage communicates too.
Before setting up a cluster it is good practice to check if the network is fit for that purpose.
-
Ensure that all nodes are in the same subnet. This must only be true for the network interfaces used for cluster communication (corosync).
-
Ensure all nodes can reach each other over those interfaces, using
ping
is enough for a basic test. -
Ensure that multicast works in general and a high package rates. This can be done with the
omping
tool. The final "%loss" number should be < 1%.
omping -c 10000 -i 0.001 -F -q NODE1-IP NODE2-IP ...
-
Ensure that multicast communication works over an extended period of time. This covers up problems where IGMP snooping is activated on the network but no multicast querier is active. This test has a duration of around 10 minutes.
omping -c 600 -i 1 -q NODE1-IP NODE2-IP ...
Your network is not ready for clustering if any of these test fails. Recheck your network configuration. Especially switches are notorious for having multicast disabled by default or IGMP snooping enabled with no IGMP querier active.
In smaller cluster its also an option to use unicast if you really cannot get multicast to work.
Separate Cluster Network
When creating a cluster without any parameters the cluster network is generally shared with the Web UI and the VMs and its traffic. Depending on your setup even storage traffic may get sent over the same network. Its recommended to change that, as corosync is a time critical real time application.
Setting Up A New Network
First you have to setup a new network interface. It should be on a physical separate network. Ensure that your network fulfills the cluster network requirements.
Separate On Cluster Creation
This is possible through the ring0_addr and bindnet0_addr parameter of the pvecm create command used for creating a new cluster.
If you have setup a additional NIC with a static address on 10.10.10.1/25 and want to send and receive all cluster communication over this interface you would execute:
pvecm create test --ring0_addr 10.10.10.1 --bindnet0_addr 10.10.10.0
To check if everything is working properly execute:
systemctl status corosync
Separate After Cluster Creation
You can do this also if you have already created a cluster and want to switch its communication to another network, without rebuilding the whole cluster. This change may lead to short durations of quorum loss in the cluster, as nodes have to restart corosync and come up one after the other on the new network.
Check how to edit the corosync.conf file first. The open it and you should see a file similar to:
logging {
debug: off
to_syslog: yes
}
nodelist {
node {
name: due
nodeid: 2
quorum_votes: 1
ring0_addr: due
}
node {
name: tre
nodeid: 3
quorum_votes: 1
ring0_addr: tre
}
node {
name: uno
nodeid: 1
quorum_votes: 1
ring0_addr: uno
}
}
quorum {
provider: corosync_votequorum
}
totem {
cluster_name: thomas-testcluster
config_version: 3
ip_version: ipv4
secauth: on
version: 2
interface {
bindnetaddr: 192.168.30.50
ringnumber: 0
}
}
The first you want to do is add the name properties in the node entries if you do not see them already. Those must match the node name.
Then replace the address from the ring0_addr properties with the new addresses. You may use plain IP addresses or also hostnames here. If you use hostnames ensure that they are resolvable from all nodes.
In my example I want to switch my cluster communication to the 10.10.10.1/25 network. So I replace all ring0_addr respectively. I also set the bindetaddr in the totem section of the config to an address of the new network. It can be any address from the subnet configured on the new network interface.
After you increased the config_version property the new configuration file should look like:
logging {
debug: off
to_syslog: yes
}
nodelist {
node {
name: due
nodeid: 2
quorum_votes: 1
ring0_addr: 10.10.10.2
}
node {
name: tre
nodeid: 3
quorum_votes: 1
ring0_addr: 10.10.10.3
}
node {
name: uno
nodeid: 1
quorum_votes: 1
ring0_addr: 10.10.10.1
}
}
quorum {
provider: corosync_votequorum
}
totem {
cluster_name: thomas-testcluster
config_version: 4
ip_version: ipv4
secauth: on
version: 2
interface {
bindnetaddr: 10.10.10.1
ringnumber: 0
}
}
Now after a final check whether all changed information is correct we save it and see again the edit corosync.conf file section to learn how to bring it in effect.
As our change cannot be enforced live from corosync we have to do an restart.
On a single node execute:
systemctl restart corosync
Now check if everything is fine:
systemctl status corosync
If corosync runs again correct restart corosync also on all other nodes. They will then join the cluster membership one by one on the new network.
Redundant Ring Protocol
To avoid a single point of failure you should implement counter measurements. This can be on the hardware and operating system level through network bonding.
Corosync itself offers also a possibility to add redundancy through the so called Redundant Ring Protocol. This protocol allows running a second totem ring on another network, this network should be physically separated from the other rings network to actually increase availability.
RRP On Cluster Creation
The pvecm create command provides the additional parameters bindnetX_addr, ringX_addr and rrp_mode, can be used for RRP configuration.
|
See the glossary if you do not know what each parameter means. |
So if you have two networks, one on the 10.10.10.1/24 and the other on the 10.10.20.1/24 subnet you would execute:
pvecm create CLUSTERNAME -bindnet0_addr 10.10.10.1 -ring0_addr 10.10.10.1 \ -bindnet1_addr 10.10.20.1 -ring1_addr 10.10.20.1
RRP On A Created Cluster
When enabling an already running cluster to use RRP you will take similar steps as describe in separating the cluster network. You just do it on another ring.
First add a new interface
subsection in the totem
section, set its
ringnumber
property to 1
. Set the interfaces bindnetaddr
property to an
address of the subnet you have configured for your new ring.
Further set the rrp_mode
to passive
, this is the only stable mode.
Then add to each node entry in the nodelist
section its new ring1_addr
property with the nodes additional ring address.
So if you have two networks, one on the 10.10.10.1/24 and the other on the 10.10.20.1/24 subnet, the final configuration file should look like:
totem {
cluster_name: tweak
config_version: 9
ip_version: ipv4
rrp_mode: passive
secauth: on
version: 2
interface {
bindnetaddr: 10.10.10.1
ringnumber: 0
}
interface {
bindnetaddr: 10.10.20.1
ringnumber: 1
}
}
nodelist {
node {
name: pvecm1
nodeid: 1
quorum_votes: 1
ring0_addr: 10.10.10.1
ring1_addr: 10.10.20.1
}
node {
name: pvecm2
nodeid: 2
quorum_votes: 1
ring0_addr: 10.10.10.2
ring1_addr: 10.10.20.2
}
[...] # other cluster nodes here
}
[...] # other remaining config sections here
Bring it in effect like described in the edit the corosync.conf file section.
This is a change which cannot take live in effect and needs at least a restart of corosync. Recommended is a restart of the whole cluster.
If you cannot reboot the whole cluster ensure no High Availability services are configured and the stop the corosync service on all nodes. After corosync is stopped on all nodes start it one after the other again.
Corosync Configuration
The /ect/pve/corosync.conf
file plays a central role in Proxmox VE cluster. It
controls the cluster member ship and its network.
For reading more about it check the corosync.conf man page:
man corosync.conf
For node membership you should always use the pvecm
tool provided by Proxmox VE.
You may have to edit the configuration file manually for other changes.
Here are a few best practice tips for doing this.
Edit corosync.conf
Editing the corosync.conf file can be not always straight forward. There are
two on each cluster, one in /etc/pve/corosync.conf
and the other in
/etc/corosync/corosync.conf
. Editing the one in our cluster file system will
propagate the changes to the local one, but not vice versa.
The configuration will get updated automatically as soon as the file changes. This means changes which can be integrated in a running corosync will take instantly effect. So you should always make a copy and edit that instead, to avoid triggering some unwanted changes by an in between safe.
cp /etc/pve/corosync.conf /etc/pve/corosync.conf.new
Then open the Config file with your favorite editor, nano
and vim.tiny
are
preinstalled on Proxmox VE for example.
|
Always increment the config_version number on configuration changes, omitting this can lead to problems. |
After making the necessary changes create another copy of the current working configuration file. This serves as a backup if the new configuration fails to apply or makes problems in other ways.
cp /etc/pve/corosync.conf /etc/pve/corosync.conf.bak
Then move the new configuration file over the old one:
mv /etc/pve/corosync.conf.new /etc/pve/corosync.conf
You may check with the commands
systemctl status corosync journalctl -b -u corosync
If the change could applied automatically. If not you may have to restart the corosync service via:
systemctl restart corosync
On errors check the troubleshooting section below.
Troubleshooting
Issue: quorum.expected_votes must be configured
When corosync starts to fail and you get the following message in the system log:
[...]
corosync[1647]: [QUORUM] Quorum provider: corosync_votequorum failed to initialize.
corosync[1647]: [SERV ] Service engine 'corosync_quorum' failed to load for reason
'configuration error: nodelist or quorum.expected_votes must be configured!'
[...]
It means that the hostname you set for corosync ringX_addr in the configuration could not be resolved.
Write Configuration When Not Quorate
If you need to change /etc/pve/corosync.conf on an node with no quorum, and you know what you do, use:
pvecm expected 1
This sets the expected vote count to 1 and makes the cluster quorate. You can now fix your configuration, or revert it back to the last working backup.
This is not enough if corosync cannot start anymore. Here its best to edit the local copy of the corosync configuration in /etc/corosync/corosync.conf so that corosync can start again. Ensure that on all nodes this configuration has the same content to avoid split brains. If you are not sure what went wrong it’s best to ask the Proxmox Community to help you.
Corosync Configuration Glossary
- ringX_addr
-
This names the different ring addresses for the corosync totem rings used for the cluster communication.
- bindnetaddr
-
Defines to which interface the ring should bind to. It may be any address of the subnet configured on the interface we want to use. In general its the recommended to just use an address a node uses on this interface.
- rrp_mode
-
Specifies the mode of the redundant ring protocol and may be passive, active or none. Note that use of active is highly experimental and not official supported. Passive is the preferred mode, it may double the cluster communication throughput and increases availability.
Cluster Cold Start
It is obvious that a cluster is not quorate when all nodes are offline. This is a common case after a power failure.
|
It is always a good idea to use an uninterruptible power supply (“UPS”, also called “battery backup”) to avoid this state, especially if you want HA. |
On node startup, service pve-manager
is started and waits for
quorum. Once quorate, it starts all guests which have the onboot
flag set.
When you turn on nodes, or when power comes back after power failure, it is likely that some nodes boots faster than others. Please keep in mind that guest startup is delayed until you reach quorum.
Copyright and Disclaimer
Copyright © 2007-2016 Proxmox Server Solutions GmbH
This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License along with this program. If not, see http://www.gnu.org/licenses/