mkcluster Command

Purpose

To create a single-site cluster.

Syntax

mkcluster -r reposdev [ -S sitename { [ cle_uuid=UUID, cle_globid=id, cle_prio=prio ] } ] [ -m node { [ cle_ip=addr, cle_uuid=UUID, cle_globid=id ] }] [,...] [ -d shareddisk [,...] ] [ -n clustername ] [ -s multi_cast_addr ] [ -c capability [,...] ] [ -v ] [ -b backupdisk [,...] ] [ -p comdisk ]

Description

The mkcluster command creates a cluster. A cluster is a collection of nodes and disks. Each node that is added to the cluster must have common storage area network (SAN) storage devices that are zoned. The SAN storage devices are used for the cluster repository disk and for any clustered shared disks.

A multicast address is used for cluster communications between the nodes in the cluster. If you need to review any network considerations before you create a cluster, consult your cluster systems administrator.

Flags

Table 1. Flags
Item	Description
-b `backupdisk` [,...]	Specifies a comma-separated list of SAN shared storage device such as `hdisk5` and `hdisk6`. These disks are used as the backup for the central repository of the cluster. When the central repository is inaccessible, the disk from the list is used as a replacement. These devices must be accessible from all nodes in the site.
-c `capability` [,...]	Specifies a comma-separated list of capabilities that the cluster requires upon creation. If the capabilities are not specified, the mkcluster command allows for the possibility that some nodes have earlier AIX® software that is not capable of supporting newer CAA capabilities. In that case, the cluster is created in such a way that it is compatible with nodes that run earlier AIX software. After the cluster is created and it is determined that nodes can support newer Cluster Aware AIX (CAA) capabilities, the cluster enables you to use those capabilities automatically. The -c flag allows the specified capabilities to be used without first determining that all nodes are able to support it. In some situations, it is necessary to enable the newer CAA capabilities immediately. For example, if one or more nodes do not have IPv4 connectivity to the other cluster nodes, specify that IPv6 capability must be enabled during cluster creation. Enabling IPv6 capability allows the nodes only with IPv6 connectivity to join the cluster. To determine that the cluster can support newer capabilities, all nodes must be online and must be able to join the cluster. If you need to create a cluster when one or more nodes are powered off, then specifying that the capability is needed during cluster creation allows you to use the capability before all of the nodes are able to join the cluster. Make sure that all of the nodes have an AIX software level that supports that capability. Otherwise, any nodes that have earlier AIX software that cannot support the capability are not allowed to join the cluster. The -c flag supports the following capability keywords: `ipv6` IPv6 connectivity is required because some nodes do not have IPv4 connectivity to the rest of the cluster, or IPv6 functions are needed before all nodes are able to join the cluster. `site` The cluster needs to allow one or more sites to be defined before all nodes are able to join the cluster. `auto_repos_replace` The created cluster can process and maintain the backup repository disks. `4kdisk` The cluster must be able to support a 4k-block disk as repository and backup repository disk. `pvm_wdog` The created cluster can process the POWER® hypervisor (PHYP) virtual machine watchdog (PVM WD) tunable parameter. `nvme` The created cluster can support NVMe disks.
-c `unicast` or `multicast`	Specifies the type of communication mode that is used by CAA to transfer CAA heartbeats and other protocol messages. If the `unicast` option is specified, CAA uses unicasting to transfer the protocol messages. If the `multicast` option is specified, CAA uses multicasting to transfer the protocol messages. If no option is specified, CAA uses the default multicast communication mode.
-p `comdisk`	Specifies a SAN shared storage device such as `hdisk5` and `hdisk6`. These disks are used by the shared storage pool cluster for inter-node communication when the network is down.
-r `reposdev`	Specifies the name of the SAN shared storage device that is used as the central repository for the cluster configuration data, such as `hdisk10`. This device must be accessible from all gateway nodes in the site. It is required that this device is a minimum of 1 GB, and a redundant and highly available SAN configuration backs up.
-S `sitename`	Specifies the name of the local site. If not specified, a default site with the name LOCAL is created. Currently, a cluster can support only 2 sites. To create a second site, use the chcluster command. The following site information can be specified: `cle_uuid` The site is UUID, which is acknowledged as unique across the cluster. If not specified, the site UUID is automatically generated. `cle_globid` The short ID of the site, which must be a unique unsigned number greater than zero. If not specified, the site short ID is automatically generated. The following site attribute can be specified: `cle_prio` The priority of a site. A lesser value indicates a higher priority. The priority is used in the context of synchronizing the repository metadata. If two sites split and the repository data becomes out of sync, then the data from the site with higher priority must be copied over to the site with lesser priority.
-m `node`[,...]	Lists the comma-separated hostnames or IP addresses for nodes that are members of the cluster. The local host must be included in the list. If the -m flag is not used, the local host is implied, causing a one-node local cluster to be created. The following node information can be specified: `cle_uuid` The node UUID, which is acknowledged as unique across the cluster. If not specified, the node UUID is automatically generated. `cle_globid` The short ID of the node, which must be a unique unsigned number greater than zero. If not specified, the node short ID is automatically generated. The following node attributes can be specified: `cle_ip` The nodes gateway address (in case the cluster spans across multiple sites). Typically, this attribute is an address through which this node can be reached from an external node. This address can be specified in either IP version 4 or version 6 format.
-d `shareddisk`[,...]	Specifies a comma-separated list of shared storage area network (SAN) devices, such as `hdisk12`, `hdisk34`, to be incorporated into the cluster configuration. Specified devices must not be open when the mkcluster command is run.
-n `clustername`	Sets the name of the cluster that is being created. If no name is specified when you run the mkcluster command, a default of `CL_hostname` is used, where `hostname` is the name of the local host. You can retrieve the name of the local host by running the gethostname() function.
-s `multi_cast_addr`	Sets the multicast address of the cluster that is created. This address is used for internal communication within the cluster. Only a multicast address in the IPv4 format is accepted. If an IPv6 multicast address is needed, it must be generated from the IPv4 address. If the -s flag is not specified when you first run the mkcluster command, the necessary multicast addresses are automatically generated.
-v	Specifies the verbose mode.

Examples

To create a cluster of one node and use the default values, enter the following command:
```
mkcluster -r hdisk
```
The output is a cluster that is named CL_myhostname with a single node in the cluster. The multicast address is automatically generated and no shared disks are created for this cluster. The
```
mkcluster -r hdisk1
```
repository is set up on hdisk1 and none of the disk can be used by the node for any other purpose. The repository device is dedicated as the cluster repository disk.
To create a multinode cluster, enter the following command:
```
mkcluster -n mkcluster -m nodeA,nodeB,nodeC
```
The output is a cluster of three nodes and uses the default values. The output also creates a cluster with the specified name and the multicast address is automatically created. Three disks are created as shared clustered disks for this cluster. The repository device is set up on hdisk1, and it cannot be used by any of the nodes for any other purpose. The repository device is now dedicated to being the cluster repository disk. A volume group of cvg is created for the cluster repository disk and these logical volumes are used exclusively by the clustering subsystem.
To create a cluster that is capable of IPv6 and sites, enter the following command:
```
mkcluster -n mkcluster -m nodeA,nodeB,nodeC -r hdisk1 -c ipv6, site
```
This command creates a cluster of three nodes that are immediately capable of using IPv6 networks and having sites that are defined. The cluster is named mycluster, and the local site and multicast address are automatically created with default values. If any IPv6 networks are configured, you can use them for cluster communication. The repository device is set up on the hdisk1, and none of the nodes can use it for any other purpose. The repository device is now dedicated to being a cluster repository disk.
To create a cluster with one site that is named as mysite, enter the following command:
```
mkcluster -n mycluster -S mysite -m nodeA,nodeB,nodeC -r hdisk1 -d hdisk10,hdisk11,hdisk12
```
The output is a single-site cluster of three nodes that uses the default attribute values for all sites and all nodes. The cluster is named as mycluster, and the local site is named as mysite. The multicast address is automatically created. Three disks are created as shared clustered disks for the local site. The repository device is set up on the hdisk1, and none of the nodes can use it for any other purpose. The repository device is now dedicated to being a cluster repository disk.
To create a cluster with one site that is named as mysite by specifying the site, and node information, enter the following command:
```
mkcluster -n mycluster -S mysite{cle_uuid=0551c722-92fe-11e1-97b0-1aae1ed14715,
cle_globid=5,cle_prio=2} 
-m nodeA,nodeB,nodeC{cle_uuid=e4ad47bc-92fd-11e1-8486-1aae1ed14715} 
-r hdisk1 -d hdisk10,hdisk11,hdisk12
```
The output is a single-site cluster of three nodes. Nodes such as nodeA and nodeB has generated UUIDs automatically, while nodeC has a UUID of e4ad47bc-92fd-11e1-8486-1aae1ed14715. The cluster is named as mycluster, and the local site is named as mysite and has a UUID of 0551c722-92fe-11e1-97b0-1aae1ed14715, a short ID of 5, and a priority of 2. The multicast address is automatically created. Three disks are created as shared clustered disks for the local site. The repository device is set up on the hdisk1, and none of the nodes can use it for any other purpose. The repository device is now dedicated to being a cluster repository disk.
To create a multinode unicast cluster with one site named mycluster, append -c unicast to the mkcluster command. The multicast cluster in example 2 can be made unicast by entering the following command:
```
mkcluster -r hdisk10 -m nodeA,nodeB,nodeC -n mycluster -r hdisk1 
-d hdisk10,hdisk11,hdisk12 -c unicast
```
To create a cluster that uses the backup disks that are added later, enter the following command:
```
mkcluster -n mkcluster -n nodeA,nodeB -r hdisk1 -c auto_repos_replace
```
To create a cluster and populate the disk list of the backup repository, enter the following command:
```
mkcluster -n mkcluster -n nodeA,nodeB -r hdisk1 -b hdisk5,hdisk6
```