Kernel panic - VFS: Unable to mount root fs 🐧 Linux

Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

The kernel booted but couldn’t mount the root filesystem — usually a missing or broken initramfs after a kernel update.

Seen on: Linux

Meaning

The initramfs contains the drivers needed to reach the root disk. If an update was interrupted (e.g. /boot full), the new kernel has no initramfs. Wrong root= UUID or a changed disk controller also cause it.

Common causes

  • initramfs missing or not generated (full /boot during update)
  • Wrong root= parameter / changed disk UUID
  • Disk controller driver missing from initramfs
  • Root disk failed or not attached (cloud)

⚡ Quick fix

  1. Boot an older kernel from the GRUB menu (Advanced options)
  2. Regenerate initramfs and GRUB
  3. Free space in /boot by removing old kernels

Detailed fix by platform

Ubuntu

  1. bash
    # after booting an older kernel or from a live/rescue system (chroot):
sudo update-initramfs -c -k all
sudo update-grub
sudo apt autoremove --purge   # remove old kernels to free /boot

How to diagnose

  1. initramfs — ls /boot/initrd.img-* matches every vmlinuz?
  2. /boot — df -h /boot
  3. root= — Matches blkid UUID?

🔧 Still not fixed?

Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:

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