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 /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.
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 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 MachineConfig
object and add it to a file in the openshift
directory.
For example, name the file 98-var-partition.yaml
, 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:
apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfig
metadata:
labels:
machineconfiguration.openshift.io/role: worker
name: 98-var-partition
spec:
config:
ignition:
version: 3.1.0
storage:
disks:
- device: /dev/<device_name> (1)
partitions:
- label: var
startMiB: <partition_start_offset> (2)
sizeMiB: <partition_size> (3)
filesystems:
- device: /dev/disk/by-partlabel/var
path: /var
format: xfs
systemd:
units:
- name: var.mount (4)
enabled: true
contents: |
[Unit]
Before=local-fs.target
[Mount]
What=/dev/disk/by-partlabel/var
Where=/var
Options=defaults,prjquota (5)
[Install]
WantedBy=local-fs.target
1 |
The storage device name of the disk that you want to partition. |
2 |
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. |
3 |
The size of the data partition in mebibytes. |
4 |
The name of the mount unit must match the directory specified in the Where= directive. For example, for a filesystem mounted on /var/lib/containers , the unit must be named var-lib-containers.mount . |
5 |
The 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.
|
-
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.