From 7deb49e3a60b7b6e04a21decd1803fa51db6a6ba Mon Sep 17 00:00:00 2001 From: Rodrigo Campos Date: Tue, 18 Feb 2025 17:15:22 +0100 Subject: [PATCH] Revert "Enforce the Minimum Kernel Version 6.3 for UserNamespacesSupport feature" This reverts commit 8597b343fa49dcb491282eaa5e5887221a985905. I wrote in the Kubernetes documentation: In practice this means you need at least Linux 6.3, as tmpfs started supporting idmap mounts in that version. This is usually needed as several Kubernetes features use tmpfs (the service account token that is mounted by default uses a tmpfs, Secrets use a tmpfs, etc.) The check is wrong for several reasons: * Pods can use userns before 6.3, they will just need to be careful to not use a tmpfs (like a serviceaccount). MOST users will probably need 6.3, but it is possible to use earlier kernel versions. 5.19 probably works fine and with improvements in the runtime 5.12 can probably be supported too. * Several distros backport changes and the recommended way is usually to try the syscall instead of testing kernel versions. I expect support for simple fs like tmpfs will be backported in several distros, but with this check it can generate confusion. * Today a clear error is shown when the pod is created, so it's unlikely a user will not understand why it fails. * Returning an error if utilkernel fails to understand what kernel version is running is also too strict (as we are logging a warning even if it is not the expected version) * We are switching to enabled by default, which will log a warning on every user that runs on an older than 6.3 kernel, adding noise to the logs. For there reasons, let's just remove the hardcoded kernel version check. Signed-off-by: Rodrigo Campos --- pkg/kubelet/kubelet_pods.go | 13 ------------- pkg/util/kernel/constants.go | 4 ---- 2 files changed, 17 deletions(-) diff --git a/pkg/kubelet/kubelet_pods.go b/pkg/kubelet/kubelet_pods.go index ad3ce43abd4..77d7266bea9 100644 --- a/pkg/kubelet/kubelet_pods.go +++ b/pkg/kubelet/kubelet_pods.go @@ -40,7 +40,6 @@ import ( "k8s.io/apimachinery/pkg/types" "k8s.io/apimachinery/pkg/util/sets" utilvalidation "k8s.io/apimachinery/pkg/util/validation" - "k8s.io/apimachinery/pkg/util/version" utilfeature "k8s.io/apiserver/pkg/util/feature" runtimeapi "k8s.io/cri-api/pkg/apis/runtime/v1" "k8s.io/klog/v2" @@ -62,7 +61,6 @@ import ( kubetypes "k8s.io/kubernetes/pkg/kubelet/types" "k8s.io/kubernetes/pkg/kubelet/util/format" utilfs "k8s.io/kubernetes/pkg/util/filesystem" - utilkernel "k8s.io/kubernetes/pkg/util/kernel" utilpod "k8s.io/kubernetes/pkg/util/pod" volumeutil "k8s.io/kubernetes/pkg/volume/util" "k8s.io/kubernetes/pkg/volume/util/hostutil" @@ -131,17 +129,6 @@ func (kl *Kubelet) getKubeletMappings() (uint32, uint32, error) { if !utilfeature.DefaultFeatureGate.Enabled(features.UserNamespacesSupport) { return defaultFirstID, defaultLen, nil - } else { - kernelVersion, err := utilkernel.GetVersion() - if err != nil { - return 0, 0, fmt.Errorf("failed to get kernel version, unable to determine if feature %s can be supported : %w", - features.UserNamespacesSupport, err) - } - if kernelVersion != nil && !kernelVersion.AtLeast(version.MustParseGeneric(utilkernel.UserNamespacesSupportKernelVersion)) { - return 0, 0, fmt.Errorf( - "the kernel version (%s) is incompatible with the %s feature gate, which needs %s as a minimum kernel version", - kernelVersion, features.UserNamespacesSupport, utilkernel.UserNamespacesSupportKernelVersion) - } } _, err := user.Lookup(kubeletUser) diff --git a/pkg/util/kernel/constants.go b/pkg/util/kernel/constants.go index ea46d46cbe7..1467f6c229d 100644 --- a/pkg/util/kernel/constants.go +++ b/pkg/util/kernel/constants.go @@ -44,10 +44,6 @@ const TCPFinTimeoutNamespacedKernelVersion = "4.6" // (ref: https://github.com/torvalds/linux/commit/35dfb013149f74c2be1ff9c78f14e6a3cd1539d1) const IPVSConnReuseModeFixedKernelVersion = "5.9" -// UserNamespacesSupportKernelVersion is the kernel version where idmap for tmpfs support was added -// (ref: https://github.com/torvalds/linux/commit/05e6295f7b5e05f09e369a3eb2882ec5b40fff20) -const UserNamespacesSupportKernelVersion = "6.3" - const TmpfsNoswapSupportKernelVersion = "6.4" // NFTablesKubeProxyKernelVersion is the lowest kernel version kube-proxy supports using