Kernel panic on s390x after manual initramfs regeneration without zipl execution

Environment

• Red Hat Enterprise Linux 8
• Red Hat Enterprise Linux 9
• Red Hat Enterprise Linux 10
• IBM Z(s390x)
• zipl

Issue

• After regenerating the initramfs using dracut -f without executing the zipl command, the system fails to boot and encounters a kernel panic with error:

  No filesystem could mount root, tried:
  Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
  

Resolution

• zipl immediately after any use of dracut to regenerate the bootmap:

  # zipl
  

• After applying the workaround or manually running zipl, verify timestamps:

  # ls -l /boot/initramfs-*.img /boot/bootmap
  

  Ensure that /boot/bootmap is newer than or equal to the latest initramfs files.

Root Cause

• IBM Z (s390x) systems use zipl to generate a bootmap containing raw block addresses of the kernel and initramfs. When the initramfs is regenerated with dracut -f, the physical layout on disk may change. Since dracut does not automatically call zipl, the bootmap remains stale, leading to a bootloader mismatch and kernel panic.

Diagnostic Steps

• Confirm if the initramfs was regenerated recently:

  # ls -l /boot/initramfs-*.img
  

• Check if /boot/bootmap is older than the initramfs:

  # stat /boot/bootmap
  # stat /boot/initramfs-<kernel-version>.img
  

• Check if zipl was executed recently (not guaranteed to log):

  # journalctl | grep zipl
  

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