OpenShift Container Platform

Creating a separate `/var` partition

In general, disk partitioning for OpenShift Container Platform should be left to the installer. However, there are cases where you might want to create separate partitions in a part of the filesystem that you expect to grow.

OpenShift Container Platform supports the addition of a single partition to attach storage to either the /var partition or a subdirectory of /var. For example:

/var/lib/containers: Holds container-related content that can grow as more images and containers are added to a system.
/var/lib/etcd: Holds data that you might want to keep separate for purposes such as performance optimization of etcd storage.
/var: Holds data that you might want to keep separate for purposes such as auditing.

For disk sizes larger than 100GB, and especially larger than 1TB, create a separate /var partition.

Storing the contents of a /var directory separately makes it easier to grow storage for those areas as needed and reinstall OpenShift Container Platform at a later date and keep that data intact. With this method, you will not have to pull all your containers again, nor will you have to copy massive log files when you update systems.

Because /var must be in place before a fresh installation of Red Hat Enterprise Linux CoreOS (RHCOS), the following procedure sets up the separate /var partition by creating a machine config manifest that is inserted during the openshift-install preparation phases of an OpenShift Container Platform installation.

Procedure

Create a directory to hold the OpenShift Container Platform installation files:
```
$ mkdir $HOME/clusterconfig
```

Run openshift-install to create a set of files in the manifest and openshift subdirectories. Answer the system questions as you are prompted:

$ openshift-install create manifests --dir $HOME/clusterconfig
? SSH Public Key ...
$ ls $HOME/clusterconfig/openshift/
99_kubeadmin-password-secret.yaml
99_openshift-cluster-api_master-machines-0.yaml
99_openshift-cluster-api_master-machines-1.yaml
99_openshift-cluster-api_master-machines-2.yaml
...

Create a Butane config that configures the additional partition. For example, name the file $HOME/clusterconfig/98-var-partition.bu, change the disk device name to the name of the storage device on the worker systems, and set the storage size as appropriate. This example places the /var directory on a separate partition:
```
variant: openshift
version: {product-version}.0
metadata:
  labels:
    machineconfiguration.openshift.io/role: worker
  name: 98-var-partition
storage:
  disks:
  - device: /dev/disk/by-id/<device_name>
    partitions:
    - label: var
      start_mib: <partition_start_offset>
      size_mib: <partition_size>
      number: 5
  filesystems:
    - device: /dev/disk/by-partlabel/var
      path: /var
      format: xfs
      mount_options: [defaults, prjquota]
      with_mount_unit: true
```
where:

<device_name>

Specifies the storage device name of the disk that you want to partition.

<partition_start_offset>

When adding a data partition to the boot disk, a minimum value of 25000 mebibytes is recommended. The root file system is automatically resized to fill all available space up to the specified offset. If no value is specified, or if the specified value is smaller than the recommended minimum, the resulting root file system will be too small, and future reinstalls of RHCOS might overwrite the beginning of the data partition.

<partition_size>

Specifies the size of the data partition in mebibytes.

prjquota

This mount option must be enabled for filesystems used for container storage.

When creating a separate /var partition, you cannot use different instance types for worker nodes, if the different instance types do not have the same device name.
Create a manifest from the Butane config and save it to the clusterconfig/openshift directory. For example, run the following command:
```
$ butane $HOME/clusterconfig/98-var-partition.bu -o $HOME/clusterconfig/openshift/98-var-partition.yaml
```
Run openshift-install again to create Ignition configs from a set of files in the manifest and openshift subdirectories:
```
$ openshift-install create ignition-configs --dir $HOME/clusterconfig
$ ls $HOME/clusterconfig/
auth  bootstrap.ign  master.ign  metadata.json  worker.ign
```
Now you can use the Ignition config files as input to the vSphere installation procedures to install Red Hat Enterprise Linux CoreOS (RHCOS) systems.

OpenShift Container Platform

Creating a separate /var partition

Creating a separate `/var` partition