Separate cluster node: remove strange sentence
[pve-docs.git] / pvecm.adoc
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1ifdef::manvolnum[]
2PVE({manvolnum})
3================
4include::attributes.txt[]
5
6NAME
7----
8
74026b8f 9pvecm - Proxmox VE Cluster Manager
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10
11SYNOPSYS
12--------
13
14include::pvecm.1-synopsis.adoc[]
15
16DESCRIPTION
17-----------
18endif::manvolnum[]
19
20ifndef::manvolnum[]
21Cluster Manager
22===============
23include::attributes.txt[]
24endif::manvolnum[]
25
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26The {PVE} cluster manager `pvecm` is a tool to create a group of
27physical servers. Such a group is called a *cluster*. We use the
8a865621 28http://www.corosync.org[Corosync Cluster Engine] for reliable group
5eba0743 29communication, and such clusters can consist of up to 32 physical nodes
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30(probably more, dependent on network latency).
31
8c1189b6 32`pvecm` can be used to create a new cluster, join nodes to a cluster,
8a865621 33leave the cluster, get status information and do various other cluster
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34related tasks. The **P**rox**m**o**x** **C**luster **F**ile **S**ystem (``pmxcfs'')
35is used to transparently distribute the cluster configuration to all cluster
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36nodes.
37
38Grouping nodes into a cluster has the following advantages:
39
40* Centralized, web based management
41
5eba0743 42* Multi-master clusters: each node can do all management task
8a865621 43
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44* `pmxcfs`: database-driven file system for storing configuration files,
45 replicated in real-time on all nodes using `corosync`.
8a865621 46
5eba0743 47* Easy migration of virtual machines and containers between physical
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48 hosts
49
50* Fast deployment
51
52* Cluster-wide services like firewall and HA
53
54
55Requirements
56------------
57
8c1189b6 58* All nodes must be in the same network as `corosync` uses IP Multicast
8a865621 59 to communicate between nodes (also see
ceabe189 60 http://www.corosync.org[Corosync Cluster Engine]). Corosync uses UDP
ff72a2ba 61 ports 5404 and 5405 for cluster communication.
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62+
63NOTE: Some switches do not support IP multicast by default and must be
64manually enabled first.
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65
66* Date and time have to be synchronized.
67
ceabe189 68* SSH tunnel on TCP port 22 between nodes is used.
8a865621 69
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70* If you are interested in High Availability, you need to have at
71 least three nodes for reliable quorum. All nodes should have the
72 same version.
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73
74* We recommend a dedicated NIC for the cluster traffic, especially if
75 you use shared storage.
76
77NOTE: It is not possible to mix Proxmox VE 3.x and earlier with
ceabe189 78Proxmox VE 4.0 cluster nodes.
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79
80
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81Preparing Nodes
82---------------
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83
84First, install {PVE} on all nodes. Make sure that each node is
85installed with the final hostname and IP configuration. Changing the
86hostname and IP is not possible after cluster creation.
87
88Currently the cluster creation has to be done on the console, so you
8c1189b6 89need to login via `ssh`.
8a865621 90
8a865621 91Create the Cluster
ceabe189 92------------------
8a865621 93
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94Login via `ssh` to the first {pve} node. Use a unique name for your cluster.
95This name cannot be changed later.
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96
97 hp1# pvecm create YOUR-CLUSTER-NAME
98
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99CAUTION: The cluster name is used to compute the default multicast
100address. Please use unique cluster names if you run more than one
101cluster inside your network.
102
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103To check the state of your cluster use:
104
105 hp1# pvecm status
106
107
108Adding Nodes to the Cluster
ceabe189 109---------------------------
8a865621 110
8c1189b6 111Login via `ssh` to the node you want to add.
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112
113 hp2# pvecm add IP-ADDRESS-CLUSTER
114
115For `IP-ADDRESS-CLUSTER` use the IP from an existing cluster node.
116
5eba0743 117CAUTION: A new node cannot hold any VMs, because you would get
7980581f 118conflicts about identical VM IDs. Also, all existing configuration in
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119`/etc/pve` is overwritten when you join a new node to the cluster. To
120workaround, use `vzdump` to backup and restore to a different VMID after
7980581f 121adding the node to the cluster.
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122
123To check the state of cluster:
124
125 # pvecm status
126
ceabe189 127.Cluster status after adding 4 nodes
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128----
129hp2# pvecm status
130Quorum information
131~~~~~~~~~~~~~~~~~~
132Date: Mon Apr 20 12:30:13 2015
133Quorum provider: corosync_votequorum
134Nodes: 4
135Node ID: 0x00000001
136Ring ID: 1928
137Quorate: Yes
138
139Votequorum information
140~~~~~~~~~~~~~~~~~~~~~~
141Expected votes: 4
142Highest expected: 4
143Total votes: 4
144Quorum: 2
145Flags: Quorate
146
147Membership information
148~~~~~~~~~~~~~~~~~~~~~~
149 Nodeid Votes Name
1500x00000001 1 192.168.15.91
1510x00000002 1 192.168.15.92 (local)
1520x00000003 1 192.168.15.93
1530x00000004 1 192.168.15.94
154----
155
156If you only want the list of all nodes use:
157
158 # pvecm nodes
159
5eba0743 160.List nodes in a cluster
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161----
162hp2# pvecm nodes
163
164Membership information
165~~~~~~~~~~~~~~~~~~~~~~
166 Nodeid Votes Name
167 1 1 hp1
168 2 1 hp2 (local)
169 3 1 hp3
170 4 1 hp4
171----
172
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173Adding Nodes With Separated Cluster Network
174~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
175
176When adding a node to a cluster with a separated cluster network you need to
177use the 'ringX_addr' parameters to set the nodes address on those networks:
178
179[source,bash]
180pvecm add IP-ADDRESS-CLUSTER -ring0_addr IP-ADDRESS-RING0
181
182If you want to use the Redundant Ring Protocol you will also want to pass the
183'ring1_addr' parameter.
184
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185
186Remove a Cluster Node
ceabe189 187---------------------
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188
189CAUTION: Read carefully the procedure before proceeding, as it could
190not be what you want or need.
191
192Move all virtual machines from the node. Make sure you have no local
193data or backups you want to keep, or save them accordingly.
194
8c1189b6 195Log in to one remaining node via ssh. Issue a `pvecm nodes` command to
7980581f 196identify the node ID:
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197
198----
199hp1# pvecm status
200
201Quorum information
202~~~~~~~~~~~~~~~~~~
203Date: Mon Apr 20 12:30:13 2015
204Quorum provider: corosync_votequorum
205Nodes: 4
206Node ID: 0x00000001
207Ring ID: 1928
208Quorate: Yes
209
210Votequorum information
211~~~~~~~~~~~~~~~~~~~~~~
212Expected votes: 4
213Highest expected: 4
214Total votes: 4
215Quorum: 2
216Flags: Quorate
217
218Membership information
219~~~~~~~~~~~~~~~~~~~~~~
220 Nodeid Votes Name
2210x00000001 1 192.168.15.91 (local)
2220x00000002 1 192.168.15.92
2230x00000003 1 192.168.15.93
2240x00000004 1 192.168.15.94
225----
226
227IMPORTANT: at this point you must power off the node to be removed and
228make sure that it will not power on again (in the network) as it
229is.
230
231----
232hp1# pvecm nodes
233
234Membership information
235~~~~~~~~~~~~~~~~~~~~~~
236 Nodeid Votes Name
237 1 1 hp1 (local)
238 2 1 hp2
239 3 1 hp3
240 4 1 hp4
241----
242
243Log in to one remaining node via ssh. Issue the delete command (here
8c1189b6 244deleting node `hp4`):
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245
246 hp1# pvecm delnode hp4
247
248If the operation succeeds no output is returned, just check the node
8c1189b6 249list again with `pvecm nodes` or `pvecm status`. You should see
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250something like:
251
252----
253hp1# pvecm status
254
255Quorum information
256~~~~~~~~~~~~~~~~~~
257Date: Mon Apr 20 12:44:28 2015
258Quorum provider: corosync_votequorum
259Nodes: 3
260Node ID: 0x00000001
261Ring ID: 1992
262Quorate: Yes
263
264Votequorum information
265~~~~~~~~~~~~~~~~~~~~~~
266Expected votes: 3
267Highest expected: 3
268Total votes: 3
269Quorum: 3
270Flags: Quorate
271
272Membership information
273~~~~~~~~~~~~~~~~~~~~~~
274 Nodeid Votes Name
2750x00000001 1 192.168.15.90 (local)
2760x00000002 1 192.168.15.91
2770x00000003 1 192.168.15.92
278----
279
280IMPORTANT: as said above, it is very important to power off the node
281*before* removal, and make sure that it will *never* power on again
282(in the existing cluster network) as it is.
283
284If you power on the node as it is, your cluster will be screwed up and
285it could be difficult to restore a clean cluster state.
286
287If, for whatever reason, you want that this server joins the same
288cluster again, you have to
289
26ca7ff5 290* reinstall {pve} on it from scratch
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291
292* then join it, as explained in the previous section.
d8742b0c 293
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294Separate A Node Without Reinstalling
295~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
296
297CAUTION: This is *not* the recommended method, proceed with caution. Use the
298above mentioned method if you're unsure.
299
300You can also separate a node from a cluster without reinstalling it from
301scratch. But after removing the node from the cluster it will still have
302access to the shared storages! This must be resolved before you start removing
303the node from the cluster. A {pve} cluster cannot share the exact same
304storage with another cluster, as it leads to VMID conflicts.
305
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306Its suggested that you create a new storage where only the node which you want
307to separate has access. This can be an new export on your NFS or a new Ceph
308pool, to name a few examples. Its just important that the exact same storage
309does not gets accessed by multiple clusters. After setting this storage up move
310all data from the node and its VMs to it. Then you are ready to separate the
311node from the cluster.
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312
313WARNING: Ensure all shared resources are cleanly separated! You will run into
314conflicts and problems else.
315
316First stop the corosync and the pve-cluster services on the node:
317[source,bash]
318systemctl stop pve-cluster
319systemctl stop corosync
320
321Start the cluster filesystem again in local mode:
322[source,bash]
323pmxcfs -l
324
325Delete the corosync configuration files:
326[source,bash]
327rm /etc/pve/corosync.conf
328rm /etc/corosync/*
329
330You can now start the filesystem again as normal service:
331[source,bash]
332killall pmxcfs
333systemctl start pve-cluster
334
335The node is now separated from the cluster. You can deleted it from a remaining
336node of the cluster with:
337[source,bash]
338pvecm delnode oldnode
339
340If the command failed, because the remaining node in the cluster lost quorum
341when the now separate node exited, you may set the expected votes to 1 as a workaround:
342[source,bash]
343pvecm expected 1
344
345And the repeat the 'pvecm delnode' command.
346
347Now switch back to the separated node, here delete all remaining files left
348from the old cluster. This ensures that the node can be added to another
349cluster again without problems.
350
351[source,bash]
352rm /var/lib/corosync/*
353
354As the configuration files from the other nodes are still in the cluster
355filesystem you may want to clean those up too. Remove simply the whole
356directory recursive from '/etc/pve/nodes/NODENAME', but check three times that
357you used the correct one before deleting it.
358
359CAUTION: The nodes SSH keys are still in the 'authorized_key' file, this means
360the nodes can still connect to each other with public key authentication. This
361should be fixed by removing the respective keys from the
362'/etc/pve/priv/authorized_keys' file.
d8742b0c 363
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364Quorum
365------
366
367{pve} use a quorum-based technique to provide a consistent state among
368all cluster nodes.
369
370[quote, from Wikipedia, Quorum (distributed computing)]
371____
372A quorum is the minimum number of votes that a distributed transaction
373has to obtain in order to be allowed to perform an operation in a
374distributed system.
375____
376
377In case of network partitioning, state changes requires that a
378majority of nodes are online. The cluster switches to read-only mode
5eba0743 379if it loses quorum.
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380
381NOTE: {pve} assigns a single vote to each node by default.
382
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383Cluster Network
384---------------
385
386The cluster network is the core of a cluster. All messages sent over it have to
387be delivered reliable to all nodes in their respective order. In {pve} this
388part is done by corosync, an implementation of a high performance low overhead
389high availability development toolkit. It serves our decentralized
390configuration file system (`pmxcfs`).
391
392[[cluster-network-requirements]]
393Network Requirements
394~~~~~~~~~~~~~~~~~~~~
395This needs a reliable network with latencies under 2 milliseconds (LAN
396performance) to work properly. While corosync can also use unicast for
397communication between nodes its **highly recommended** to have a multicast
398capable network. The network should not be used heavily by other members,
399ideally corosync runs on its own network.
400*never* share it with network where storage communicates too.
401
402Before setting up a cluster it is good practice to check if the network is fit
403for that purpose.
404
405* Ensure that all nodes are in the same subnet. This must only be true for the
406 network interfaces used for cluster communication (corosync).
407
408* Ensure all nodes can reach each other over those interfaces, using `ping` is
409 enough for a basic test.
410
411* Ensure that multicast works in general and a high package rates. This can be
412 done with the `omping` tool. The final "%loss" number should be < 1%.
413[source,bash]
414----
415omping -c 10000 -i 0.001 -F -q NODE1-IP NODE2-IP ...
416----
417
418* Ensure that multicast communication works over an extended period of time.
419 This covers up problems where IGMP snooping is activated on the network but
420 no multicast querier is active. This test has a duration of around 10
421 minutes.
422[source,bash]
423omping -c 600 -i 1 -q NODE1-IP NODE2-IP ...
424
425Your network is not ready for clustering if any of these test fails. Recheck
426your network configuration. Especially switches are notorious for having
427multicast disabled by default or IGMP snooping enabled with no IGMP querier
428active.
429
430In smaller cluster its also an option to use unicast if you really cannot get
431multicast to work.
432
433Separate Cluster Network
434~~~~~~~~~~~~~~~~~~~~~~~~
435
436When creating a cluster without any parameters the cluster network is generally
437shared with the Web UI and the VMs and its traffic. Depending on your setup
438even storage traffic may get sent over the same network. Its recommended to
439change that, as corosync is a time critical real time application.
440
441Setting Up A New Network
442^^^^^^^^^^^^^^^^^^^^^^^^
443
444First you have to setup a new network interface. It should be on a physical
445separate network. Ensure that your network fulfills the
446<<cluster-network-requirements,cluster network requirements>>.
447
448Separate On Cluster Creation
449^^^^^^^^^^^^^^^^^^^^^^^^^^^^
450
451This is possible through the 'ring0_addr' and 'bindnet0_addr' parameter of
452the 'pvecm create' command used for creating a new cluster.
453
454If you have setup a additional NIC with a static address on 10.10.10.1/25
455and want to send and receive all cluster communication over this interface
456you would execute:
457
458[source,bash]
459pvecm create test --ring0_addr 10.10.10.1 --bindnet0_addr 10.10.10.0
460
461To check if everything is working properly execute:
462[source,bash]
463systemctl status corosync
464
465[[separate-cluster-net-after-creation]]
466Separate After Cluster Creation
467^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
468
469You can do this also if you have already created a cluster and want to switch
470its communication to another network, without rebuilding the whole cluster.
471This change may lead to short durations of quorum loss in the cluster, as nodes
472have to restart corosync and come up one after the other on the new network.
473
474Check how to <<edit-corosync-conf,edit the corosync.conf file>> first.
475The open it and you should see a file similar to:
476
477----
478logging {
479 debug: off
480 to_syslog: yes
481}
482
483nodelist {
484
485 node {
486 name: due
487 nodeid: 2
488 quorum_votes: 1
489 ring0_addr: due
490 }
491
492 node {
493 name: tre
494 nodeid: 3
495 quorum_votes: 1
496 ring0_addr: tre
497 }
498
499 node {
500 name: uno
501 nodeid: 1
502 quorum_votes: 1
503 ring0_addr: uno
504 }
505
506}
507
508quorum {
509 provider: corosync_votequorum
510}
511
512totem {
513 cluster_name: thomas-testcluster
514 config_version: 3
515 ip_version: ipv4
516 secauth: on
517 version: 2
518 interface {
519 bindnetaddr: 192.168.30.50
520 ringnumber: 0
521 }
522
523}
524----
525
526The first you want to do is add the 'name' properties in the node entries if
527you do not see them already. Those *must* match the node name.
528
529Then replace the address from the 'ring0_addr' properties with the new
530addresses. You may use plain IP addresses or also hostnames here. If you use
531hostnames ensure that they are resolvable from all nodes.
532
533In my example I want to switch my cluster communication to the 10.10.10.1/25
534network. So I replace all 'ring0_addr' respectively. I also set the bindetaddr
535in the totem section of the config to an address of the new network. It can be
536any address from the subnet configured on the new network interface.
537
538After you increased the 'config_version' property the new configuration file
539should look like:
540
541----
542
543logging {
544 debug: off
545 to_syslog: yes
546}
547
548nodelist {
549
550 node {
551 name: due
552 nodeid: 2
553 quorum_votes: 1
554 ring0_addr: 10.10.10.2
555 }
556
557 node {
558 name: tre
559 nodeid: 3
560 quorum_votes: 1
561 ring0_addr: 10.10.10.3
562 }
563
564 node {
565 name: uno
566 nodeid: 1
567 quorum_votes: 1
568 ring0_addr: 10.10.10.1
569 }
570
571}
572
573quorum {
574 provider: corosync_votequorum
575}
576
577totem {
578 cluster_name: thomas-testcluster
579 config_version: 4
580 ip_version: ipv4
581 secauth: on
582 version: 2
583 interface {
584 bindnetaddr: 10.10.10.1
585 ringnumber: 0
586 }
587
588}
589----
590
591Now after a final check whether all changed information is correct we save it
592and see again the <<edit-corosync-conf,edit corosync.conf file>> section to
593learn how to bring it in effect.
594
595As our change cannot be enforced live from corosync we have to do an restart.
596
597On a single node execute:
598[source,bash]
599systemctl restart corosync
600
601Now check if everything is fine:
602
603[source,bash]
604systemctl status corosync
605
606If corosync runs again correct restart corosync also on all other nodes.
607They will then join the cluster membership one by one on the new network.
608
609Redundant Ring Protocol
610~~~~~~~~~~~~~~~~~~~~~~~
611To avoid a single point of failure you should implement counter measurements.
612This can be on the hardware and operating system level through network bonding.
613
614Corosync itself offers also a possibility to add redundancy through the so
615called 'Redundant Ring Protocol'. This protocol allows running a second totem
616ring on another network, this network should be physically separated from the
617other rings network to actually increase availability.
618
619RRP On Cluster Creation
620~~~~~~~~~~~~~~~~~~~~~~~
621
622The 'pvecm create' command provides the additional parameters 'bindnetX_addr',
623'ringX_addr' and 'rrp_mode', can be used for RRP configuration.
624
625NOTE: See the <<corosync-conf-glossary,glossary>> if you do not know what each parameter means.
626
627So if you have two networks, one on the 10.10.10.1/24 and the other on the
62810.10.20.1/24 subnet you would execute:
629
630[source,bash]
631pvecm create CLUSTERNAME -bindnet0_addr 10.10.10.1 -ring0_addr 10.10.10.1 \
632-bindnet1_addr 10.10.20.1 -ring1_addr 10.10.20.1
633
634RRP On A Created Cluster
635~~~~~~~~~~~~~~~~~~~~~~~~
636
637When enabling an already running cluster to use RRP you will take similar steps
638as describe in <<separate-cluster-net-after-creation,separating the cluster
639network>>. You just do it on another ring.
640
641First add a new `interface` subsection in the `totem` section, set its
642`ringnumber` property to `1`. Set the interfaces `bindnetaddr` property to an
643address of the subnet you have configured for your new ring.
644Further set the `rrp_mode` to `passive`, this is the only stable mode.
645
646Then add to each node entry in the `nodelist` section its new `ring1_addr`
647property with the nodes additional ring address.
648
649So if you have two networks, one on the 10.10.10.1/24 and the other on the
65010.10.20.1/24 subnet, the final configuration file should look like:
651
652----
653totem {
654 cluster_name: tweak
655 config_version: 9
656 ip_version: ipv4
657 rrp_mode: passive
658 secauth: on
659 version: 2
660 interface {
661 bindnetaddr: 10.10.10.1
662 ringnumber: 0
663 }
664 interface {
665 bindnetaddr: 10.10.20.1
666 ringnumber: 1
667 }
668}
669
670nodelist {
671 node {
672 name: pvecm1
673 nodeid: 1
674 quorum_votes: 1
675 ring0_addr: 10.10.10.1
676 ring1_addr: 10.10.20.1
677 }
678
679 node {
680 name: pvecm2
681 nodeid: 2
682 quorum_votes: 1
683 ring0_addr: 10.10.10.2
684 ring1_addr: 10.10.20.2
685 }
686
687 [...] # other cluster nodes here
688}
689
690[...] # other remaining config sections here
691
692----
693
694Bring it in effect like described in the <<edit-corosync-conf,edit the
695corosync.conf file>> section.
696
697This is a change which cannot take live in effect and needs at least a restart
698of corosync. Recommended is a restart of the whole cluster.
699
700If you cannot reboot the whole cluster ensure no High Availability services are
701configured and the stop the corosync service on all nodes. After corosync is
702stopped on all nodes start it one after the other again.
703
704Corosync Configuration
705----------------------
706
707The `/ect/pve/corosync.conf` file plays a central role in {pve} cluster. It
708controls the cluster member ship and its network.
709For reading more about it check the corosync.conf man page:
710[source,bash]
711man corosync.conf
712
713For node membership you should always use the `pvecm` tool provided by {pve}.
714You may have to edit the configuration file manually for other changes.
715Here are a few best practice tips for doing this.
716
717[[edit-corosync-conf]]
718Edit corosync.conf
719~~~~~~~~~~~~~~~~~~
720
721Editing the corosync.conf file can be not always straight forward. There are
722two on each cluster, one in `/etc/pve/corosync.conf` and the other in
723`/etc/corosync/corosync.conf`. Editing the one in our cluster file system will
724propagate the changes to the local one, but not vice versa.
725
726The configuration will get updated automatically as soon as the file changes.
727This means changes which can be integrated in a running corosync will take
728instantly effect. So you should always make a copy and edit that instead, to
729avoid triggering some unwanted changes by an in between safe.
730
731[source,bash]
732cp /etc/pve/corosync.conf /etc/pve/corosync.conf.new
733
734Then open the Config file with your favorite editor, `nano` and `vim.tiny` are
735preinstalled on {pve} for example.
736
737NOTE: Always increment the 'config_version' number on configuration changes,
738omitting this can lead to problems.
739
740After making the necessary changes create another copy of the current working
741configuration file. This serves as a backup if the new configuration fails to
742apply or makes problems in other ways.
743
744[source,bash]
745cp /etc/pve/corosync.conf /etc/pve/corosync.conf.bak
746
747Then move the new configuration file over the old one:
748[source,bash]
749mv /etc/pve/corosync.conf.new /etc/pve/corosync.conf
750
751You may check with the commands
752[source,bash]
753systemctl status corosync
754journalctl -b -u corosync
755
756If the change could applied automatically. If not you may have to restart the
757corosync service via:
758[source,bash]
759systemctl restart corosync
760
761On errors check the troubleshooting section below.
762
763Troubleshooting
764~~~~~~~~~~~~~~~
765
766Issue: 'quorum.expected_votes must be configured'
767^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
768
769When corosync starts to fail and you get the following message in the system log:
770
771----
772[...]
773corosync[1647]: [QUORUM] Quorum provider: corosync_votequorum failed to initialize.
774corosync[1647]: [SERV ] Service engine 'corosync_quorum' failed to load for reason
775 'configuration error: nodelist or quorum.expected_votes must be configured!'
776[...]
777----
778
779It means that the hostname you set for corosync 'ringX_addr' in the
780configuration could not be resolved.
781
782
783Write Configuration When Not Quorate
784^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
785
786If you need to change '/etc/pve/corosync.conf' on an node with no quorum, and you
787know what you do, use:
788[source,bash]
789pvecm expected 1
790
791This sets the expected vote count to 1 and makes the cluster quorate. You can
792now fix your configuration, or revert it back to the last working backup.
793
794This is not enough if corosync cannot start anymore. Here its best to edit the
795local copy of the corosync configuration in '/etc/corosync/corosync.conf' so
796that corosync can start again. Ensure that on all nodes this configuration has
797the same content to avoid split brains. If you are not sure what went wrong
798it's best to ask the Proxmox Community to help you.
799
800
801[[corosync-conf-glossary]]
802Corosync Configuration Glossary
803~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
804
805ringX_addr::
806This names the different ring addresses for the corosync totem rings used for
807the cluster communication.
808
809bindnetaddr::
810Defines to which interface the ring should bind to. It may be any address of
811the subnet configured on the interface we want to use. In general its the
812recommended to just use an address a node uses on this interface.
813
814rrp_mode::
815Specifies the mode of the redundant ring protocol and may be passive, active or
816none. Note that use of active is highly experimental and not official
817supported. Passive is the preferred mode, it may double the cluster
818communication throughput and increases availability.
819
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820
821Cluster Cold Start
822------------------
823
824It is obvious that a cluster is not quorate when all nodes are
825offline. This is a common case after a power failure.
826
827NOTE: It is always a good idea to use an uninterruptible power supply
8c1189b6 828(``UPS'', also called ``battery backup'') to avoid this state, especially if
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829you want HA.
830
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831On node startup, service `pve-manager` is started and waits for
832quorum. Once quorate, it starts all guests which have the `onboot`
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833flag set.
834
835When you turn on nodes, or when power comes back after power failure,
836it is likely that some nodes boots faster than others. Please keep in
837mind that guest startup is delayed until you reach quorum.
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838
839
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840ifdef::manvolnum[]
841include::pve-copyright.adoc[]
842endif::manvolnum[]