In most cases, data partitions are originally created by installing RHCOS, rather than by installing another operating system. In such cases, the OpenShift Container Platform installer should be allowed to configure your disk partitions.
However, there are two cases where you might want to intervene to override the default partitioning when installing an
OpenShift Container Platform node:
Create separate partitions: For greenfield installations on an empty
disk, you might want to add separate storage to a partition. This is
officially supported for making
/var or a subdirectory of
/var, such as
/var/lib/etcd, a separate partition, but not both.
Kubernetes supports only two filesystem partitions. If you add more than one partition to the original configuration, Kubernetes cannot monitor all of them.
Retain existing partitions: For a brownfield installation where you are reinstalling OpenShift Container Platform on an existing node and want to retain data partitions installed from your previous operating system, there are both boot arguments and options to
coreos-installer that allow you to retain existing data partitions.
Creating a separate
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/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.
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.
/var must be in place before a fresh installation of
Red Hat Enterprise Linux CoreOS (RHCOS), the following procedure sets up the separate
by creating a machine config manifest that is inserted during the
preparation phases of an OpenShift Container Platform installation.
Create a directory to hold the OpenShift Container Platform installation files:
$ mkdir $HOME/clusterconfig
openshift-install to create a set of files in the
openshift subdirectories. Answer the system questions as you are prompted:
$ openshift-install create manifests --dir $HOME/clusterconfig
? SSH Public Key ...
$ ls $HOME/clusterconfig/openshift/
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:
- device: /dev/<device_name> (1)
- label: var
start_mib: <partition_start_offset> (2)
size_mib: <partition_size> (3)
- device: /dev/disk/by-partlabel/var
mount_options: [defaults, prjquota] (4)
||The storage device name of the disk that you want to partition.
||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.
||The size of the data partition in mebibytes.
prjquota 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
openshift-install again to create Ignition configs from a set of files in the
$ 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.