## Before Upgrading

Consider the following changes, limitations, and guidelines before you upgrade:

* The kubelet now fails if swap is enabled on a node. To override the default and run with /proc/swaps on, set `--fail-swap-on=false`. The experimental flag `--experimental-fail-swap-on` is deprecated in this release, and will be removed in a future release.

* Used inline func to ensure unlock is executed ([#61644](https://github.com/kubernetes/kubernetes/pull/61644), [@resouer](https://github.com/resouer))
* kubernetes-master charm now properly clears the client-ca-file setting on the apiserver snap ([#61479](https://github.com/kubernetes/kubernetes/pull/61479), [@hyperbolic2346](https://github.com/hyperbolic2346))

- Added full cgroup v2 swap support for both `Limited` and `Unlimited` swap.
  
  When `LimitedSwap` is enabled the swap limit would be automatically calculated for
  Burstable QoS pods. For Best-Effort/Guaranteed QoS pods, swap would be disabled.
  
  Containers with memory requests equal to their memory limits also won't have
  swap access, and it is a way to opt-out of swap for a single container.
  

- `kubeadm`: updated warning message when swap space is detected. When swap is
  active on Linux, `kubeadm` explains that swap is supported for cgroup v2 only and
  is beta but disabled by default. ([#120198](https://github.com/kubernetes/kubernetes/pull/120198), [@pacoxu](https://github.com/pacoxu))

- Changed Linux swap handling to restrict access to swap for containers in high priority Pods.
  New Pods that have a node- or cluster-critical priority are prohibited from accessing swap on Linux,

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### Kubernetes Node system swap support

Every system administrator or Kubernetes user has been in the same boat regarding setting up and using Kubernetes: disable swap space. With the release of Kubernetes 1.22, *alpha* support is available to run nodes with swap memory. This change lets administrators opt in to configuring swap on Linux nodes, treating a portion of block storage as additional virtual memory.

- Kubeadm: switch the preflight check (called 'Swap') that verifies if swap is enabled on Linux hosts to report a warning instead of an error. This is related to the graduation of the NodeSwap feature gate in the kubelet to Beta and being enabled by default in 1.23 - allows swap support on Linux hosts. In the next release of kubeadm (1.24) the preflight check will be removed, thus we recommend that you stop using...

  - The deprecated `--show-all` flag to `kubectl get` has been removed  ([#69255](https://github.com/kubernetes/kubernetes/pull/69255), [@Pingan2017](https://github.com/Pingan2017))

- kubelet
  - The deprecated `--experimental-fail-swap-on` flag has been removed ([#69552](https://github.com/kubernetes/kubernetes/pull/69552), [@Pingan2017](https://github.com/Pingan2017))

* kubeadm now produces error during preflight checks if swap is enabled. Users, who can setup kubelet to run in unsupported environment with enabled swap, will be able to skip that preflight check. ([#55399](https://github.com/kubernetes/kubernetes/pull/55399), [@kad](https://github.com/kad))