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fix(bootstrap): support cgroup v1 hosts by disabling kubelet failCgroupV1 check #360

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Merged
drew merged 1 commit into from
Mar 16, 2026
Merged

fix(bootstrap): support cgroup v1 hosts by disabling kubelet failCgroupV1 check #360

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17 changes: 16 additions & 1 deletion deploy/docker/cluster-entrypoint.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -482,10 +482,25 @@ fi
# Pre-creating the directory eliminates this failure mode.
mkdir -p /run/flannel

# ---------------------------------------------------------------------------
# Detect cgroup version and set kubelet compatibility flags
# ---------------------------------------------------------------------------
# Kubernetes 1.35+ (k3s v1.35.x) rejects cgroup v1 by default. Hosts running
# older distros (e.g. Rocky Linux 8, CentOS 7/8, Ubuntu 18.04) still use
# cgroup v1. When we detect cgroup v1, pass --kubelet-arg=fail-cgroupv1=false
# so kubelet warns instead of refusing to start. This flag can be removed once
# cgroup v1 support is no longer needed.
EXTRA_KUBELET_ARGS=""
if [ ! -f /sys/fs/cgroup/cgroup.controllers ]; then
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@pimlock pimlock Mar 16, 2026

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FYI in docs this is how they document checking the version:

stat -fc %T /sys/fs/cgroup/
For cgroup v2, the output is cgroup2fs.
For cgroup v1, the output is tmpfs.

echo "Detected cgroup v1 — adding kubelet compatibility flag (fail-cgroupv1=false)"
EXTRA_KUBELET_ARGS="--kubelet-arg=fail-cgroupv1=false"
fi

# Docker Desktop can briefly start the container before its bridge default route
# is fully installed. k3s exits immediately in that state, so wait briefly for
# routing to settle first.
wait_for_default_route

# Execute k3s with explicit resolv-conf.
exec /bin/k3s "$@" --resolv-conf="$RESOLV_CONF"
# shellcheck disable=SC2086
exec /bin/k3s "$@" --resolv-conf="$RESOLV_CONF" $EXTRA_KUBELET_ARGS
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