Rebuilding initramfs

Admins migrating VMs between different hypervisors often forget to rebuild the initramfs, which leads to missing drivers required by the target environment—causing the VM to fail to boot.

Here's a quick summary of how to fix that:

We'll use SystemRescue (sysrescue) instead of a CentOS installation CD for rebuilding initramfs—and in many cases, it’s even better because:

• ✅ It’s lightweight and fast to boot
• ✅ Includes all common tools: chroot, dracut, lvm2, mdadm, etc.
• ✅ Actively maintained and not tied to a specific distro

🛠️ Steps Using SystemRescue to Rebuild initramfs

1. Boot the VM with the SystemRescue ISO
2. Identify and mount your root filesystem

lvm vgchange -ay  # Activate LVM volumes, if needed
lsblk             # Identify root and boot partitions
mount /dev/mapper/centos-root /mnt
mount /dev/sda1 /mnt/boot      # if /boot is separate

3. Chroot into your system

mount --bind /dev /mnt/dev
mount --bind /proc /mnt/proc
mount --bind /sys /mnt/sys
chroot /mnt

4. Rebuild initramfs with needed drivers

dracut -f -v
# Or specify kernel version:
dracut -f -v /boot/initramfs-$(uname -r).img $(uname -r)

5. Exit and reboot

exit
reboot