When you power on your Ubuntu Linux machine, the bootloader (GRUB) loads the kernel and an initial RAM filesystem (initramfs) into memory. This initramfs contains the essential drivers needed to mount your actual hard drive. If you update your kernel but the initramfs generation process is interrupted, the file becomes corrupted.
The next time you boot, the screen will turn black and display a kernel panic error stating: Initramfs unpacking failed: Decoding failed, completely halting the boot process and leaving you stranded at a stark initramfs command prompt. To fix this, you must force the system to regenerate a pristine initramfs file.
How to Fix the “Initramfs unpacking failed” Boot Error in Ubuntu
You must boot into Ubuntu’s Recovery Mode to repair the corrupted filesystem files.
- Reboot your computer.
- Immediately after your computer manufacturer’s logo disappears, press and hold the Shift key (or tap the Esc key repeatedly if using UEFI) to force the GRUB boot menu to appear.
- Use the arrow keys to select Advanced options for Ubuntu and press Enter.
- You will see a list of kernels. Select the topmost entry that ends with the word (recovery mode) and press Enter.
- The Recovery Menu will eventually load. Use the arrow keys to select the option labelled root – Drop to root shell prompt and press Enter. (Press Enter a second time when prompted).
- You now have root terminal access. First, you must remount your main hard drive so you have write permissions. Type the following command and press Enter:
mount -o remount,rw / - Now, you must force the system to rebuild the corrupted initramfs for all installed kernels. Type the following command and press Enter:
update-initramfs -u -k all - Wait for the process to complete (it will take a minute or two).
- Once the prompt returns, type
rebootand press Enter.
Your Ubuntu machine will restart, load the freshly generated, uncorrupted initramfs file, and successfully boot straight to your graphical desktop, resolving the kernel panic.