Debugging an immutable OS

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Temporarily install debugging tools on a IBM Storage Ceph Provisioner node running an immutable RHEL Image Mode OS to diagnose complex issues.

About this task

IBM Storage Ceph Provisioner images are immutable RHEL Image Mode images. You cannot add or remove software by using dnf in normal operation. In special cases, you can use the bootc usr-overlay feature to temporarily install debugging tools. Any tools installed this way are discarded on the next reboot.

Important: This procedure must only be performed under the supervision of IBM support.

A valid Red Hat user account with RHEL subscription entitlement is required to install tools from Red Hat repositories.

Procedure

  1. Log in to the node as the root user and enable the writable overlay: 
    bootc usr-overlay

    The command mounts a writable overlayfs on /usr. All changes are discarded on reboot.

  2. Register the node with Red Hat subscription management: 
    subscription-manager register

    Enter your Red Hat user account credentials when prompted.

  3. Install the required debugging tool. For example, to install tcpdump: 
    dnf install tcpdump
  4. Use the debugging tool to collect the required diagnostic information.

Results

The debugging tool is available for use during the current session. All changes are discarded when the node is rebooted.