Resolving “Symbol ‘grub_calloc’ Not Found” GRUB Boot Errors

Seeing the dreaded “Symbol ‘grub_calloc’ not found” error on boot is a heart-stopping moment for any Linux admin. It means your system’s bootloader, GRUB, is broken, and your machine can’t start.

I’ve wrestled with this issue a few times, and while it’s serious, it’s usually fixable. This guide will walk you through the steps to diagnose and repair your GRUB installation, focusing on Ubuntu systems.

Understanding the Problem: What is GRUB and grub_calloc?

GRUB (GNU GRand Unified Bootloader) loads your operating system kernel when you power on your computer. It’s the crucial link between your hardware and your OS.

The boot process works like this:

1. Your computer’s firmware (BIOS/UEFI) initializes hardware
2. The firmware locates and loads the bootloader (GRUB)
3. GRUB presents a menu and loads your chosen operating system
4. The OS takes over and completes the startup process

grub_calloc is a fundamental function within GRUB, responsible for allocating memory. If GRUB can’t find this function, it means something is seriously wrong with the GRUB installation – files might be corrupted, missing, or the wrong version.

Common Causes

• Failed or Interrupted Updates: A botched system update (especially kernel or GRUB updates) is the most common culprit.
• Disk Errors: Problems with your hard drive or SSD (bad sectors, file system corruption) can damage GRUB files.
• Dual-Booting Issues: Incorrectly configuring a dual-boot setup with another operating system (like Windows) can sometimes overwrite or corrupt GRUB.
• Incorrect Partitioning: Changes to your disk partitions (resizing, deleting, etc.) can disrupt GRUB’s ability to find the necessary files.
• MBR vs. EFI Confusion: Mixing up Master Boot Record (MBR) and Extensible Firmware Interface (EFI) boot modes can lead to problems. Most modern systems use EFI, but older ones use MBR.

Preparation and Data Backup

You’ll need:

• A bootable Ubuntu USB drive or DVD (latest version recommended)
• Basic familiarity with terminal commands
• Patience and careful attention to detail
• An external drive for backups (optional but recommended)

The Fix: Using a Live Environment

1. Boot from Live Media

• Create a bootable Ubuntu USB drive or DVD. You can download the latest Ubuntu ISO from the official website.
• Boot your computer from the live media. You might need to change your BIOS/UEFI settings to boot from USB or DVD. Look for a key like F2, F12, Del, or Esc to enter the boot menu.
• Choose the “Try Ubuntu without installing” option.

2. Identify Your Partitions

Once in the live environment, open a terminal (Ctrl+Alt+T). You need to identify your partitions:

sudo fdisk -l

Or alternatively:

lsblk -f

You need to identify:

• Root partition: Usually the largest Linux partition, typically formatted as ext4
• EFI partition: For EFI systems, this is a small partition (100-500MB) formatted as FAT32, often labeled “EFI System Partition”

3. Mount Your Root Partition

Replace /dev/sdXY with your actual root partition (e.g., /dev/sda2):

sudo mount /dev/sdXY /mnt

4. Verify You’ve Mounted the Correct Partition

Make sure you’ve mounted the correct root partition by checking for expected system directories:

ls -la /mnt

You should see directories like: bin, boot, dev, etc, home, lib, media, mnt, opt, proc, root, run, sbin, srv, sys, tmp, usr, var

5. Mount Essential Filesystems

Mount the special system directories required for the chroot environment:

sudo mount --bind /dev /mnt/dev
sudo mount --bind /dev/pts /mnt/dev/pts
sudo mount --bind /proc /mnt/proc
sudo mount --bind /sys /mnt/sys
sudo mount --bind /run /mnt/run

6. Mount EFI Partition (for EFI systems only)

If your system uses EFI (most modern systems do), you need to mount the EFI partition. Replace /dev/sdXZ with your EFI partition (e.g., /dev/sda1):

sudo mount /dev/sdXZ /mnt/boot/efi

7. Enter Chroot Environment

Now you’ll enter a chroot environment, which makes the mounted system act as if it were the booted system:

sudo chroot /mnt

Your prompt should change, indicating you’re now working within your installed system.

8. Reinstall GRUB

Depending on whether your system uses EFI or MBR, use one of the following approaches:

For EFI Systems (most common):

grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=ubuntu

Explanation:

• grub-install: The main command to install GRUB.
• --target=x86_64-efi: Specifies the architecture and boot mode (64-bit EFI).
• --efi-directory=/boot/efi: Tells GRUB where the EFI System Partition is mounted.
• --bootloader-id=ubuntu: Gives the bootloader entry a recognizable name.

For MBR Systems (older systems):

grub-install --target=i386-pc --recheck /dev/sdX

Explanation:

• grub-install: The main command to install GRUB.
• --target=i386-pc: Specifies the architecture and boot mode (32-bit or 64-bit MBR).
• --recheck: Asks GRUB to double-check the device map.
• /dev/sdX: This is the device (e.g., /dev/sda), not a partition (like /dev/sda1). This is where GRUB will be installed in the Master Boot Record.

Read: How to fix Ubuntu boot issues

9. Update GRUB Configuration

Generate a new GRUB configuration file:

update-grub

10. Verify the Installation

Check that the GRUB installation was successful:

ls -la /boot/grub

You should see numerous files, including grub.cfg.

11. Exit and Unmount

Exit the chroot environment and unmount all mounted filesystems:

exit
sudo umount /mnt/dev/pts
sudo umount /mnt/dev
sudo umount /mnt/proc
sudo umount /mnt/sys
sudo umount /mnt/run
sudo umount /mnt/boot/efi  # Only if you mounted the EFI partition
sudo umount /mnt

12. Reboot

Remove the live media and reboot your system:

sudo reboot

Alternative Solution: Using Boot-Repair (Easier Option)

The boot-repair tool is a lifesaver. It automates many of the steps above and can often fix GRUB issues with a single click.

1. Boot from Live Media

Boot from the live media as explained in the previous section.

2. Install Boot-Repair

Open a terminal in the live environment and run these commands:

sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo apt update
sudo apt install -y boot-repair

3. Run Boot-Repair

boot-repair

A graphical interface will appear. Choose “Recommended repair”. This will attempt to automatically fix the most common GRUB issues.

4. Advanced Options (if needed)

If the recommended repair doesn’t work, you can explore the “Advanced options”. This gives you more control over the repair process, but it’s best to use the recommended repair first.

5. Reboot

After boot-repair finishes, reboot your system without the live USB/DVD.

Read: How to analyze Linux systemd logs using journalctl advanced filtering options

Verifying the Fix

After rebooting, your system should start normally. If you encounter any issues:

• Check if you see the GRUB menu at boot. If yes, that’s a good sign.
• If Linux boots but has issues, you can check the boot logs with: journalctl -b
• If GRUB appears but fails to boot the OS, you can try recovery mode from the GRUB menu.

Common Pitfalls

• Incorrect Partition Identification: Make sure you’ve identified the correct root partition. Mounting the wrong partition won’t fix the problem and could damage data.
• Not Mounting EFI Partition: For EFI systems, forgetting to mount the EFI partition is a common mistake.
• Using grub-install Incorrectly: Using the wrong –target or specifying a partition instead of a device for MBR systems will lead to failure.
• Internet Connection: The boot-repair tool needs internet access to download necessary files.
• Secure Boot Issues: On some systems, Secure Boot in UEFI might need to be disabled temporarily.

Prevention Tips

To avoid this issue in the future:

• Create a Rescue Disk: Keep a bootable USB with boot-repair ready at all times.
• Backup GRUB Configuration: After a successful system setup, back up your GRUB files:

  sudo cp -r /boot/grub /path/to/backup/location

• Be Cautious with Updates: Don’t interrupt system updates, especially kernel or GRUB updates.
• Regular System Backups: Use tools like Timeshift to create system snapshots before major changes.
• Create a Separate /boot Partition: This can contain damage if the root filesystem is corrupted.

Conclusion

The “grub_calloc not found” error is intimidating, but it’s often a sign of a fixable GRUB problem. By carefully following these steps, and understanding why you’re doing each one, you can usually restore your system to a bootable state. Good luck, and remember to back up your data regularly to avoid future headaches!