Warn against using a custom --data-dir for K3s with SELinux

Author: catherineluse

content/k3s/latest/en/advanced/_index.md

@@ -316,6 +316,8 @@ To force the install script to log a warning rather than fail, you can set the f
 
 The way that SELinux enforcement is enabled or disabled depends on the K3s version. Prior to v1.19.x, SELinux enablement for the builtin containerd was automatic but could be disabled by passing `--disable-selinux`. With v1.19.x and beyond, enabling SELinux must be affirmatively configured via the `--selinux` flag or config file entry. Servers and agents that specify both the `--selinux` and (deprecated) `--disable-selinux` flags will fail to start.
 
+Using a custom `--data-dir` under SELinux is not supported. To customize it, you would most likely need to write your own custom policy. For guidance, you could refer to the [containers/container-selinux](https://github.com/containers/container-selinux) repository, which contains the SELinux policy files for Container Runtimes, and the [rancher/k3s-selinux](https://github.com/rancher/k3s-selinux) repository, which contains the SELinux policy for K3s .
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