Update notes

This section describes the specific actions you need to complete to accurately plan and successfully perform the update. Consider this information as a supplement to the generic update procedures published in Operations Guide: Update to a patch version.

Cluster update schema

You can update to the 26.1.1 version from the following cluster versions:

• 26.1 (2026-03-10) - patch update

• 25.2.9 (2026-06-15) - major update

Important

The next major MOSK 26.2 version will be released in September. If your cluster is running 26.1, Mirantis recommends waiting for the 26.2 release and updating directly to it instead of applying the 26.1 series patches.

For the detailed cluster update schema, refer to MOSK cluster update schema.

Patch update impact and maintenance windows planning

The following table provides details on the impact of a MOSK cluster update to a patch release within the 26.1 series.

Note

For the detailed workflow of update to a patch release, refer to Update to a patch version.

Expected update impact

Updated component	Impact on cloud users	Impact on cloud workloads
OpenStack and OpenSDN	~1% of read operations on cloud API resources may fail ~8% of create and update operations on cloud API resources may fail	Open vSwitch networking - interruption of North-South connectivity, depending on the type of virtual routers used by a workload: Distributed (DVR) routers - no interruption Non-distributed routers, High Availability (HA) mode - interruption up to 1 minute, usually less than 5 seconds [0] Non-distributed routers, non-HA mode - interruption up to 10 minutes [0] OpenSDN networking - no impact
Ceph	~1% of read operations on object storage API may fail	IO performance degradation for Ceph-backed virtual storage devices.
Host OS components	No impact	No impact

[0] (1,2)

You can bypass updating components of the cloud data plane to avoid the network downtime during Update to a patch version. By using this technique, you accept the risk that some security fixes may not be applied.

Major update impact and maintenance windows planning

The following table provides details on the impact of a MOSK cluster major update from 25.2.9 to 26.1.1.

Expected update impact

Updated component	Impact on cloud users	Impact on cloud workloads
OpenStack and OpenSDN	~1% of read operations on cloud API resources may fail ~8% of create and update operations on cloud API resources may fail	Open vSwitch networking - interruption of the North-South connectivity, depending on the type of virtual routers used by a workload: Distributed (DVR) routers - no interruption Non-distributed routers, High Availability (HA) mode - interruption up to 1 minute, usually less than 5 seconds Non-distributed routers, non-HA mode - interruption up to 10 minutes OpenSDN networking - no impact
Ceph	~1% of read operations on object storage API may fail	No expected performance impact During the update to 26.1.1, existing MiraCeph custom resources will be automatically migrated to the new CephDeployment custom resources. No manual action is required. The change affects only user experience, as the configuration entrypoint has been updated. Post-migration, all Ceph cluster configuration and management operations must be performed through the CephDeployment custom resource located in the ceph-lcm-mirantis namespace. For the mapping of migrated custom resources, refer to MiraCeph resources vs. CephDeployment resources.
Host OS components	No expected performance impact	Instance network connectivity interruption up to 5 minutes
Host OS kernel	No expected performance impact	Restart of instances due to the hypervisor reboot [1]

[1]

Host operating system needs to be rebooted for the kernel update to be applied. Configure live-migration of workloads to avoid the impact on the instances running on a host.

Known issues during the update

Before updating the cluster, be sure to review the potential issues that may arise during the process and the recommended solutions to address them, as outlined in Known issues: Cluster update.

Pre-update actions

There are no specific pre-update actions required when updating to version 26.1.1.

Post-update actions

The following post-update actions are required when updating from 25.2.9 (major update). If you are updating from 26.1 (patch update), complete them only if you have not already done so after updating to 26.1.

Upgrade Ubuntu to 24.04

MOSK 26.1 release series is the last one to support Ubuntu 22.04 as the host operating system. Therefore, Mirantis encourages all MOSK users to upgrade their clusters to Ubuntu 24.04 as soon as possible after getting to MOSK 26.1.x.

A host operating system upgrade requires reboot of the servers and can be performed in small batches. For the detailed procedure of the Ubuntu upgrade, refer to Upgrade an operating system distribution.

Warning

The Cluster release update of the Ubuntu 22.04-based MOSK clusters will no longer be possible starting with MOSK management 2.32.0, where Ubuntu 24.04 is the only supported version.

Caution

Usage of third-party software, which is not part of Mirantis-supported configurations, for example, the use of custom DPDK modules, may block upgrade of an operating system distribution. Users are fully responsible for ensuring the compatibility of such custom components with the latest supported Ubuntu version.

Update MOSK configuration modules

MOSK 26.1 introduced support for Ubuntu 24.04 LTS (Noble Numbat) as the default host operating system for several configuration modules provided by Mirantis. Therefore, if you use the following configuration modules, make sure to update them to the latest versions supporting Ubuntu 24.04 after updating the MOSK cluster:

• cpushield

• grub_settings

• irqbalance

• package

• sysctl

For more information, see mosk-host-os-modules documentation.

See also

• Operations Guide: Modules provided by MOSK

• Operations Guide: Host operating system configuration

Migrate auditd settings from the Cluster object to the auditd module

MOSK 26.1 introduced support for the auditd host operating system configuration module that replaces the deprecated auditd section of the Cluster object to manage auditd settings for machines of both management and MOSK clusters.

The auditd parameters of the Cluster object are no longer applied to the host operating system after the cluster update to 26.1.x for MOSK clusters and to 2.31.0 for management clusters.

Therefore, if auditd is enabled on the management or MOSK clusters, migrate its settings to the dedicated auditd module after updating to the releases mentioned above to unblock the feature.

For the migration procedure, see Migrate auditd settings from the Cluster object to the auditd module.

Configure remote backup storage and encryption for MKE

MOSK 26.1 introduced support for remote backup storage and encryption of MKE backups on management and MOSK clusters. Mirantis highly recommends that you configure remote backup storage and encryption for MKE after updating to 26.1.x for MOSK clusters and to 2.31.0 for management clusters. This enables you to store backups securely and restore them in case of issues with future cluster updates.

For the procedure, see Create backups of Mirantis Kubernetes Engine.