System boots into Older kernel due to stale machine-id in /boot/loader/entries

Solution Verified - Updated

Environment

  • Red Hat Enterprise Linux 8 and later

Issue

  • The system unexpectedly boots into an older kernel by default, even though newer kernel versions are installed and available in /boot.

Resolution

Before applying any changes, ensure that the Diagnostics Steps confirm the issue on the system.

  • Clean up stale entries:

    # mkdir /tmp/stale-entries
# mv /boot/loader/entries/<OLD_MACHINE_ID>* /tmp/stale-entries/

  • (Optional) If needed, copy and rename any required entry to match the current machine-id:

    # cp /tmp/stale-entries/<OLD_MACHINE_ID>-<KERNEL>.conf /boot/loader/entries/<CURRENT_MACHINE_ID>-<KERNEL>.conf

  • Make sure the default is now pointing to a valid entry using current machine-id:

    # grubby --default-kernel

Root Cause

  • Each kernel boot entry under /boot/loader/entries/ follows this naming convention:

    <MACHINE-ID>-<KERNEL-VERSION>.conf

If the system has been reinstalled, cloned, or restored from an image, the machine-id found in /etc/machine-id may change. However, older boot entries linked to the previous machine-id may remain in /boot/loader/entries/.

  • Tools like grubby do not prioritize the highest kernel version automatically. Instead, they rely on the order and index of boot entries, even if those entries are from a different (stale) machine-id. This can cause the system to boot into an older kernel by default.

Diagnostic Steps

To determine if this issue applies to your system:

  1. Get current machine-id:

    # cat /etc/machine-id

  2. List all boot entries:

    # ls -l /boot/loader/entries/

  3. Check for multiple sets of entries with different machine-id.

  4. Inspect the output of:

    # grubby --info=ALL

  5. Look for entries associated with stale machine-id showing a lower index or being marked as the default.

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