Dual Booting Ubuntu and Manjaro: Resolving Manjaro’s Initramfs Fallback Kernel Boot Issue #

Dual-booting Ubuntu and Manjaro can offer the best of both worlds: Ubuntu’s robust ecosystem and Manjaro’s cutting-edge, rolling-release model. However, encountering issues during the setup, particularly when Manjaro only boots into the initramfs fallback kernel, is a common hurdle. This comprehensive guide, brought to you by revWhiteShadow, aims to provide a detailed walkthrough to diagnose and resolve this problem, ensuring a smooth dual-booting experience.

Understanding the Problem: Why Manjaro Boots into Initramfs Fallback #

The initramfs (initial RAM filesystem) is a minimal root filesystem loaded into memory before the actual root filesystem. It contains essential drivers and utilities needed to mount the real root partition and boot the operating system. When Manjaro boots into the initramfs fallback kernel, it indicates that the system failed to locate or mount the root filesystem during the normal boot process. This failure can stem from several factors, including:

• Incorrect GRUB configuration: The GRUB bootloader might have incorrect paths or UUIDs for the Manjaro partition.
• Missing or corrupted kernel modules: Essential modules required to access the root filesystem might be absent or damaged.
• Filesystem errors: The Manjaro root partition could contain errors preventing it from being mounted correctly.
• Kernel incompatibility: The installed kernel might not be compatible with the hardware or the filesystem.
• RAID/LVM issues: If Manjaro is installed on a RAID or LVM volume, misconfiguration can lead to boot failures.
• Encryption Issues: If Manjaro’s root partition is encrypted, incorrect decryption parameters will cause this error.

Step-by-Step Troubleshooting and Solutions #

Before attempting any solutions, it’s crucial to gather information about your system. Boot into the initramfs fallback shell and run the following commands:

blkid
lsblk -f
cat /etc/fstab

These commands will display the block device information (including UUIDs), the filesystem layout, and the contents of the /etc/fstab file, which contains mount point definitions. Save this information, as it will be vital for diagnosing the issue.

1. Verifying and Correcting GRUB Configuration #

The most common cause of this problem is an incorrect GRUB configuration. The update-grub command run from Ubuntu might not have correctly identified the Manjaro installation or generated the correct boot entries.

Booting into Manjaro Using the Initramfs Shell #

First, we need to manually boot into Manjaro from the initramfs shell. Identify your root partition using the output of blkid or lsblk -f. The Manjaro root partition will typically be formatted as ext4, btrfs, or xfs.

Once you’ve identified the root partition, mount it:

mount /dev/sdXY /mnt  # Replace sdXY with your Manjaro root partition (e.g., sda3)

If you have a separate /boot partition, mount it as well:

mount /dev/sdZZ /mnt/boot # Replace sdZZ with your /boot partition if applicable

Now, exit the initramfs shell:

exit

This should boot into Manjaro. If not, continue with the following steps. Alternatively, use a Manjaro live USB to boot into Manjaro.

Reinstalling GRUB from Manjaro #

Once you are logged into Manjaro (either from the initramfs workaround or from a live USB), reinstall GRUB. This is the most reliable way to ensure a correct GRUB configuration.

First, identify the EFI system partition (ESP). This is typically mounted at /boot/efi. Verify its mount point using:

findmnt /boot/efi

If the ESP is not mounted at /boot/efi, mount it:

mount /dev/sdXX /boot/efi  # Replace sdXX with your EFI system partition (e.g., sda1)

Now, reinstall GRUB:

sudo grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=manjaro --recheck
sudo update-grub

• --target=x86_64-efi: Specifies that we’re installing GRUB for a UEFI system.
• --efi-directory=/boot/efi: Specifies the location of the EFI system partition.
• --bootloader-id=manjaro: Sets the name of the boot entry in the UEFI firmware.
• --recheck: Checks for available drives before installing.

After reinstalling GRUB, reboot your system and check if Manjaro boots correctly.

2. Addressing Missing or Corrupted Kernel Modules #

If reinstalling GRUB doesn’t resolve the issue, the problem might lie in missing or corrupted kernel modules. This can happen due to incomplete updates or filesystem errors.

Reinstalling the Kernel #

Reinstalling the kernel can replace any missing or corrupted modules. Use the following command:

sudo pacman -S linux

This will reinstall the latest stable kernel. If you’re using a different kernel (e.g., linux-lts), replace linux with the appropriate package name.

Regenerating the Initramfs Image #

After reinstalling the kernel, regenerate the initramfs image:

sudo mkinitcpio -P

This command will create new initramfs images for all installed kernels, ensuring they contain the necessary modules.

3. Resolving Filesystem Errors #

Filesystem errors on the Manjaro root partition can prevent the system from booting correctly.

Running a Filesystem Check #

Boot into Manjaro using the initramfs workaround or a live USB and run a filesystem check on the root partition. First, unmount the partition:

sudo umount /mnt #If the root partition is mounted

Then, run the filesystem check:

sudo fsck -y /dev/sdXY  # Replace sdXY with your Manjaro root partition

The -y option automatically answers “yes” to any prompts to fix errors. Be cautious when using this option, as it can potentially cause data loss if the errors are severe. If you’re unsure, omit the -y option and carefully review each prompt before proceeding.

If your filesystem is Btrfs, the command will be different. Run:

sudo btrfs check --repair /dev/sdXY # Replace sdXY with your Manjaro root partition

Be extremely careful when using the --repair option, as it can cause data loss if used incorrectly. Consult the Btrfs documentation for more information.

4. Dealing with Kernel Incompatibility #

In rare cases, the installed kernel might not be fully compatible with your hardware, leading to boot issues.

Trying a Different Kernel #

Manjaro offers different kernel options, such as the LTS (Long Term Support) kernel. Installing and booting into a different kernel can sometimes resolve compatibility issues.

First, list the available kernels:

pacman -Ss linux | grep ^linux

Install the LTS kernel:

sudo pacman -S linux-lts

After installing the LTS kernel, regenerate the GRUB configuration:

sudo update-grub

Reboot your system and select the LTS kernel from the GRUB menu.

5. Addressing RAID/LVM Misconfiguration #

If Manjaro is installed on a RAID or LVM volume, ensure that the RAID or LVM volumes are correctly activated before attempting to mount the root partition.

Activating RAID/LVM Volumes #

In the initramfs shell, use the following commands to activate the RAID/LVM volumes:

mdadm --assemble --scan #For RAID
vgscan #For LVM
vgchange -ay #For LVM

After activating the volumes, try mounting the root partition again and exiting the initramfs shell as described earlier.

6. Resolving Encryption Issues #

If Manjaro’s root partition is encrypted using LUKS, ensure that the encryption key is correctly entered during the boot process.

Verifying LUKS Configuration #

In the initramfs shell, verify that the LUKS volume is correctly identified and unlocked. First, identify the LUKS volume using blkid or lsblk -f. Then, try unlocking the volume manually:

cryptsetup luksOpen /dev/sdXY cryptroot  # Replace sdXY with your LUKS volume

If the command prompts for a passphrase and you enter it correctly, the volume should be unlocked. Then, mount the unlocked volume:

mount /dev/mapper/cryptroot /mnt

If these steps fail, there might be an issue with the LUKS configuration or the passphrase. Ensure you are entering the correct passphrase and that the LUKS volume is not corrupted.

If unlocking it fails, try adding encrypt and lvm2 hooks to /etc/mkinitcpio.conf.

sudo nano /etc/mkinitcpio.conf

Locate the HOOKS= line and ensure that encrypt and lvm2 are present and in the correct order, like this:

HOOKS="base udev autodetect modconf block keyboard keymap encrypt lvm2 filesystems fsck"

Save the file and exit the editor. Then regenerate the initramfs images:

sudo mkinitcpio -P

Finally, update GRUB to apply the changes.

sudo update-grub

7. Inspecting fstab for Errors #

The /etc/fstab file defines how the system mounts filesystems at boot. Incorrect entries in this file can cause boot failures.

Correcting fstab Entries #

Boot into Manjaro and examine the /etc/fstab file:

sudo nano /etc/fstab

Ensure that the entries for the Manjaro root partition and other partitions (e.g., /boot, /home) are correct. Pay close attention to the UUIDs and mount points. The UUIDs in /etc/fstab should match the UUIDs displayed by blkid.

For example, a typical /etc/fstab entry for the root partition might look like this:

UUID=a1b2c3d4-e5f6-7890-1234-567890abcdef / ext4 defaults 0 1

If you find any errors, correct them and save the file. Then, reboot your system.

8. Disabling Quiet Splash to See Boot Messages #

Sometimes, the boot process happens too quickly to see any error messages. Disabling the “quiet splash” options in GRUB can help diagnose the issue.

Editing GRUB Configuration #

Edit the /etc/default/grub file:

sudo nano /etc/default/grub

Remove the quiet and splash options from the GRUB_CMDLINE_LINUX_DEFAULT line:

GRUB_CMDLINE_LINUX_DEFAULT=""

Save the file and update GRUB:

sudo update-grub

Now, when you boot, you’ll see detailed boot messages, which can provide clues about what’s causing the boot failure.

Preventative Measures for a Smooth Dual-Booting Experience #

To minimize the risk of encountering boot issues when dual-booting Ubuntu and Manjaro, consider the following preventative measures:

• Install Ubuntu First: Always install Ubuntu before Manjaro. Ubuntu’s GRUB is generally more reliable at detecting other operating systems.
• Use Separate Partitions: Allocate separate partitions for the Manjaro root, /boot, and /home directories. This simplifies the boot process and reduces the risk of conflicts.
• Keep Systems Updated: Regularly update both Ubuntu and Manjaro to ensure you have the latest kernel and drivers.
• Backup Your Data: Before making any changes to your partitions or bootloader, back up your important data.
• Disable Secure Boot: If you’re encountering issues with GRUB, try disabling Secure Boot in your UEFI firmware settings. However, be aware of the security implications of disabling Secure Boot.

Conclusion #

Resolving boot issues when dual-booting Ubuntu and Manjaro can be challenging, but by systematically working through the troubleshooting steps outlined in this guide, you can identify and fix the root cause of the problem. Remember to gather information about your system, proceed cautiously when making changes, and back up your data regularly. By following these guidelines, you can enjoy the benefits of a dual-booting setup without the frustration of boot failures. For more guides and tips, visit revWhiteShadow.