Scheduler Kubeconfig File Ownership Should Be root:root

More Info:

Verifies that the scheduler.conf kubeconfig file is owned by root:root so only privileged users can read the schedulers client credentials.

Risk Level

Medium

Address

Security

Compliance Standards

• CIS Kubernetes

Triage and Remediation

Remediation

Remediation

Manual Steps

1. Log in to each control plane node over SSH as a user with sudo privileges.

2. On each control plane node, set the correct ownership on the scheduler kubeconfig file:

   sudo chown root:root /etc/kubernetes/scheduler.conf

3. (Optional) Confirm the permissions look reasonable (typically 600 or 644, adjust only if required by your hardening policy):

   stat -c '%a %n' /etc/kubernetes/scheduler.conf

4. Verify the ownership is now set to root:root using the audit command on each control plane node:

   /bin/sh -c 'if test -e /etc/kubernetes/scheduler.conf; then stat -c %U:%G /etc/kubernetes/scheduler.conf; fi'

   The output must be:

   root:root

Using kubectl

kubectl cannot modify host-level file ownership, including /etc/kubernetes/scheduler.conf on control plane nodes. This must be fixed directly on each control plane node’s filesystem; see the Manual Steps section for the exact commands to run over SSH.

Automation

#!/usr/bin/env bash
#
# Fix ownership of /etc/kubernetes/scheduler.conf to root:root
# Scope: run on every control plane node
# Safe to re-run (idempotent)

set -euo pipefail

SCHED_CONF="/etc/kubernetes/scheduler.conf"

echo "==> Checking for ${SCHED_CONF}"

if [ ! -e "${SCHED_CONF}" ]; then
  echo "File ${SCHED_CONF} does not exist on this node. Nothing to do."
  exit 0
fi

current_owner_group="$(stat -c '%U:%G' "${SCHED_CONF}")"

echo "Current ownership: ${current_owner_group}"

if [ "${current_owner_group}" != "root:root" ]; then
  echo "Updating ownership of ${SCHED_CONF} to root:root"
  chown root:root "${SCHED_CONF}"
else
  echo "Ownership already set to root:root; no change needed."
fi

echo "==> Verifying ownership"

verify_owner_group="$(stat -c '%U:%G' "${SCHED_CONF}")"
echo "Verified ownership: ${verify_owner_group}"

if [ "${verify_owner_group}" != "root:root" ]; then
  echo "ERROR: Failed to set ownership of ${SCHED_CONF} to root:root" >&2
  exit 1
fi

echo "Ownership of ${SCHED_CONF} is correctly set to root:root"

Usage (run on every control plane node):

1. Copy the script to each control plane node, for example:

   scp fix-scheduler-kubeconfig-ownership.sh <control-plane-node>:/root/

2. SSH to each control plane node and run:

   chmod +x /root/fix-scheduler-kubeconfig-ownership.sh
   sudo /root/fix-scheduler-kubeconfig-ownership.sh

3. Optional explicit verification on each control plane node:

   /bin/sh -c 'if test -e /etc/kubernetes/scheduler.conf; then stat -c %U:%G /etc/kubernetes/scheduler.conf; fi'