红帽全球峰会19.6. Adding and modifying links in an existing cluster
In most cases, you can add or modify the links in an existing cluster without restarting the cluster.
19.6.1. Adding and removing links in an existing cluster
To add a new link to a running cluster, use the pcs cluster link add command.
- When adding a link, you must specify an address for each node.
-
Adding and removing a link is only possible when you are using the
knettransport protocol. - At least one link in the cluster must be defined at any time.
- The maximum number of links in a cluster is 8, numbered 0-7. It does not matter which links are defined, so, for example, you can define only links 3, 6 and 7.
-
When you add a link without specifying its link number,
pcsuses the lowest link available. -
The link numbers of currently configured links are contained in the
corosync.conffile. To display thecorosync.conffile, run thepcs cluster corosynccommand or thepcs cluster config [show]command.
Procedure
The following command adds link number 5 to a three node cluster.
[root@node1 ~] # pcs cluster link add node1=10.0.5.11 node2=10.0.5.12 node3=10.0.5.31 options linknumber=5To remove an existing link, use the
pcs cluster link deleteorpcs cluster link removecommand. Either of the following commands will remove link number 5 from the cluster.[root@node1 ~] # pcs cluster link delete 5 [root@node1 ~] # pcs cluster link remove 5
If there are multiple links in the cluster and you want to change one of them, perform the following procedure.
Procedure
Remove the link you want to change.
[root@node1 ~] # pcs cluster link remove 2Add the link back to the cluster with the updated addresses and options.
[root@node1 ~] # pcs cluster link add node1=10.0.5.11 node2=10.0.5.12 node3=10.0.5.31 options linknumber=2
If your cluster uses only one link and you want to modify that link to use different addresses, perform the following procedure. In this example, the original link is link 1.
Add a new link with the new addresses and options.
[root@node1 ~] # pcs cluster link add node1=10.0.5.11 node2=10.0.5.12 node3=10.0.5.31 options linknumber=2Remove the original link.
[root@node1 ~] # pcs cluster link remove 1
Note that you cannot specify addresses that are currently in use when adding links to a cluster. This means, for example, that if you have a two-node cluster with one link and you want to change the address for one node only, you cannot use the above procedure to add a new link that specifies one new address and one existing address. Instead, you can add a temporary link before removing the existing link and adding it back with the updated address, as in the following example.
In this example:
- The link for the existing cluster is link 1, which uses the address 10.0.5.11 for node 1 and the address 10.0.5.12 for node 2.
- You would like to change the address for node 2 to 10.0.5.31.
Procedure
To update only one of the addresses for a two-node cluster with a single link, use the following procedure.
Add a new temporary link to the existing cluster, using addresses that are not currently in use.
[root@node1 ~] # pcs cluster link add node1=10.0.5.13 node2=10.0.5.14 options linknumber=2Remove the original link.
[root@node1 ~] # pcs cluster link remove 1Add the new, modified link.
[root@node1 ~] # pcs cluster link add node1=10.0.5.11 node2=10.0.5.31 options linknumber=1Remove the temporary link you created
[root@node1 ~] # pcs cluster link remove 2
If your cluster uses only one link and you want to modify the options for that link but you do not want to change the address to use, you can add a temporary link before removing and updating the link to modify.
In this example:
- The link for the existing cluster is link 1, which uses the address 10.0.5.11 for node 1 and the address 10.0.5.12 for node 2.
-
You would like to change the link option
link_priorityto 11.
Procedure
Modify the link option in a cluster with a single link with the following procedure.
Add a new temporary link to the existing cluster, using addresses that are not currently in use.
[root@node1 ~] # pcs cluster link add node1=10.0.5.13 node2=10.0.5.14 options linknumber=2Remove the original link.
[root@node1 ~] # pcs cluster link remove 1Add back the original link with the updated options.
[root@node1 ~] # pcs cluster link add node1=10.0.5.11 node2=10.0.5.12 options linknumber=1 link_priority=11Remove the temporary link.
[root@node1 ~] # pcs cluster link remove 2
If for some reason adding a new link is not possible in your configuration and your only option is to modify a single existing link, you can use the following procedure, which requires that you shut your cluster down.
Procedure
The following example procedure updates link number 1 in the cluster and sets the link_priority option for the link to 11.
Stop the cluster services for the cluster.
[root@node1 ~] # pcs cluster stop --allUpdate the link addresses and options.
The
pcs cluster link updatecommand does not require that you specify all of the node addresses and options. Instead, you can specify only the addresses to change. This example modifies the addresses fornode1andnode3and thelink_priorityoption only.[root@node1 ~] # pcs cluster link update 1 node1=10.0.5.11 node3=10.0.5.31 options link_priority=11To remove an option, you can set the option to a null value with the
option=format.Restart the cluster
[root@node1 ~] # pcs cluster start --all
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