Understanding Management Stations

Mirror Syncing

A management station mirrors software sources to serve content to on-premises or third-party cloud instances. When a station registers with OS Management Hub, the service also creates a recurring scheduled mirror sync job for the station. You can modify the execution time and frequency of the mirror sync job, but you can't delete the sync job.

When the mirror sync job runs, the station checks if it needs to update the mirrored software sources. The sync job updates the local mirror with the any changes in the vendor and custom software sources. The station also checks for new software sources to add to the local mirror.

When do mirror syncs occur?

• When the recurring scheduled mirror sync job for a management station runs.
• When you trigger an immediate mirror sync for specific software sources.
• When you update a custom software source that's already mirrored.

How should I configure the mirror storage?

The following are best practices for configuring mirror storage.

Location

• Use a volume that's separate from the root file system. This prevents OS issues if the mirror volume reaches capacity.

• Consider using a network volume with either NFS or iSCSI protocol to make disaster recovery easier.

Size

When provisioning storage to use for the mirror, verify it's large enough to contain the mirrored software sources. Consider the following guidelines:

• Enough storage allocated and mounted for Oracle Linux content mirrors. Storage requirements are relative to the scope and size of the Oracle Linux software sources needed by instances using the management station. Several hundred gigabytes (GB) to a few terabytes (TB) is commonly required.
• Enough storage in /var/cache/dnf for repository metadata. Storage requirements are relative to the Oracle Linux software sources needed by instances using the management station. Large software sources can require 100 MB to 200 MB of storage per repository.

As you associate instances to the management station, monitor the mirror storage capacity and make changes as needed.

Which software sources does the management station mirror?

After registering a management station, its list of mirrored software sources is empty. OS Management Hub updates the mirror list dynamically based on the profiles and instances that use the station.

To initialize and sync a station before registering instances, you can create the registration profiles needed for your instances, selecting the new management station in the profile. The service identifies the software sources used by the profiles and adds them to the station mirror list. The next mirror sync job updates the station mirror, or you can trigger an immediate sync.

As you create new profiles or attach new software sources to instances, the station mirror list updates automatically. If you delete profiles or detach software sources from instances, mirror list entries are only removed if no instances or profiles reference the software source.

When mirroring custom software sources, the management station also mirrors any vendor software sources that the custom software source relies on. When a station no longer needs to mirror a software source, it's immediately deleted from the mirror volume.

If using a high availability (HA) configuration, the mirror list is unified across all stations. A profile or instance referencing one of the stations also updates the mirrored software sources on all other stations in the HA configuration. When using shared mirror storage with HA, the software source mirror sync status on a management station might incorrectly show as 'Unsynced'. See Known Issue: 'Unsynced' status on stations using shared storage.

Example mirrored software source list

Consider a case where you've created a profile that uses the station, but haven't registered instances yet. The following table lists the software sources associated with the profile and the resulting mirror list.

Profile 1	List of Mirrored Software Sources
ol8_baseos_latest-x86_64 ol8_appstream-x86_64 ol8_addons-x86_64	ol8_baseos_latest-x86_64 ol8_appstream-x86_64 ol8_addons-x86_64

Next let's look at what happens when you:

• Register Instance 1 and Instance 2 with Profile 1

The software sources defined in the profile are attached to each instance. The mirror list remains the same as no new sources have been added or removed.

Profile 1	Instance 1	Instance 2	List of Mirrored Software Sources
ol8_baseos_latest-x86_64 ol8_appstream-x86_64 ol8_addons-x86_64	ol8_baseos_latest-x86_64 ol8_appstream-x86_64 ol8_addons-x86_64	ol8_baseos_latest-x86_64 ol8_appstream-x86_64 ol8_addons-x86_64	ol8_baseos_latest-x86_64 ol8_appstream-x86_64 ol8_addons-x86_64

Next, let's look at what happens if:

• Instance 1 attaches a software source (ol8_custom_source which is based on ol8_developer-x86_64).
• Instance 1 and 2 each detach a software source (ol8_addons-x86_64).

The list of software sources on the management station updates to reflect the change. The service adds ol8_custom_source and ol8_developer-x86_64 to the list because Instance 1 is using ol8_custom_source which depends on ol8_developer-x86_64. The source ol8_addons-x86_64 remains on the station because Profile 1 is still referencing it.

Profile 1	Instance 1	Instance 2	List of Mirrored Software Sources
ol8_baseos_latest-x86_64 ol8_appstream-x86_64 ol8_addons-x86_64	ol8_baseos_latest-x86_64 ol8_appstream-x86_64 Detach:ol8_addons-x86_64 Attach: ol8_custom_source	ol8_baseos_latest-x86_64 ol8_appstream-x86_64 Detach: ol8_addons-x86_64	ol8_baseos_latest-x86_64 ol8_appstream-x86_64 ol8_addons-x86_64 (not removed because Profile 1 uses this source) Added: ol8_custom_source Added: ol8_developer-x86_64

Finally, let's look at what happens when you delete Profile 1.

Software source ol8_addons-x86_64 is removed from the list because it's no longer used by a profile or instance.

Profile 1	Instance 1	Instance 2	List of Mirrored Software Sources
Deleted	ol8_baseos_latest-x86_64 ol8_appstream-x86_64 ol8_custom_source	ol8_baseos_latest-x86_64 ol8_appstream-x86_64	ol8_baseos_latest-x86_64 ol8_appstream-x86_64 Removed:ol8_addons-x86_64 ol8_custom_source ol8_developer-x86_64

Maintaining the Management Station Instance

By default, only Oracle Linux 8 BaseOS and Appstream software sources are attached to the instance that's assigned the role of management station. To update the management station instance, you need to first attach any additional software sources and then create an update job. The software sources that you attach to the management station are different and separate from the sources mirrored and distributed to other instances.

What data is stored in OCI for management stations?