When GRUB (GRand Unified Bootloader) throws "Disk Filter writing not supported" (error:) during the installation or update process When the "disk filter writes are not supported" error occurs, it usually means that the boot program cannot handle specific disk configurations correctly (such as advanced features of LVM, RAID, encrypted volumes, or NVMe drives). The complete solution for addressing the root cause of this error is compiled in the following text, mainly covering the processing strategies in both BIOS and UEFI boot modes.

First, let's analyze the cause of the error. This error mostly occurs in the following scenarios: Incorrect selection of the GRUB installation target, attempting to install GRUB to a logical volume (LV) instead of a physical disk or partition; Disk filter conflicts. When using LVM, dmcrypt encryption or RAID, GRUB fails to correctly identify the physical storage layer. The UEFI and BIOS modes are confused. In a UEFI system, the BIOS mode is mistakenly used to install GRUB, or vice versa. File system compatibility issue: GRUB has insufficient support for certain file systems (such as subvolumes of Btrfs).

Basic investigation and repair steps

Step 1: Confirm the disk layout and the GRUB installation target

Use lsblk and fdisk to check the disk structure and ensure that GRUB is installed on a physical device (such as /dev/sda), rather than a logical volume (such as /dev/mapper/vg0root) :

sudo lsblk o NAME,FSTYPE,MOUNTPOINT  
sudo fdisk l  

Correct example:

NAME        FSTYPE      MOUNTPOINT  
sda                      
├─sda1      vfat        /boot/efi  
├─sda2      ext4        /boot  
└─sda3      LVM2_member  
├─vg0root ext4        /  
└─vg0swap swap        [SWAP]  

Here, GRUB should be installed on sda (the entire disk) or sda2 (independent /boot partition), rather than sda3 or vg0root.

Step 2: Reinstall GRUB to the correct location

Mount the key partition and execute grubinstall, mount the root partition and /boot (if independent)

sudo mount /dev/vg0root /mnt  
sudo mount /dev/sda2 /mnt/boot  
sudo mount /dev/sda1 /mnt/boot/efi UEFI system required

Bind the system directory

sudo mount bind /dev /mnt/dev  
sudo mount bind /proc /mnt/proc  
sudo mount bind /sys /mnt/sys  

Chroot to the target system

sudo chroot /mnt  

Install GRUB (select based on the boot mode) and the UEFI system

grubinstall target=x86_64efi efidirectory=/boot/efi bootloaderid=GRUB  

BIOS system

grubinstall target=i386pc /dev/sda  

Generate the configuration file

grubmkconfig o /boot/grub/grub.cfg  

Step 3: Verify the installation result

Check the contents and logs of the /boot/grub directory:

The.mod module should exist in the ls /boot/grub/x86_64efi UEFI mode

cat /var/log/grubinstall.log | grep error  

Advanced repair: Complex storage configuration processing

Scene 1: LVM logical Volume environment

If the root partition is located in LVM, it is necessary to ensure that /boot is an independent physical partition (not LVM), otherwise GRUB cannot read the boot file.

1. Create an independent /boot partition (at least 1GB, formatted as ext4);

2. Reinstall GRUB to the disk (such as /dev/sda);

3. Update /etc/fstab to ensure that /boot is mounted correctly.

Scene 2: Full Disk Encryption (LUKS)

GRUB 2.06+ supports LUKS2 encryption, but additional modules need to be enabled:

1. Edit /etc/default/grub and add:

GRUB_ENABLE_CRYPTODISK=y  

2. Regenerate the GRUB configuration:

grubmkconfig o /boot/grub/grub.cfg  

3. Ensure that initramfs contains the drivers required for decryption:

updateinitramfs u  

Scene 3: RAID array

For software RAID (such as mdadm), RAID support needs to be enabled in GRUB. The grubpc (BIOS) or grubefiamd64 (UEFI) package needs to be installed. Confirm that /boot is located in a non-RAID partition or RAID1 array when executing grubinstall to specify the RAID member disk:

grubinstall /dev/sda  
The grubinstall /dev/sdb multi-disk RAID needs to be installed one by one

Special processing in UEFI mode

Question 1: The ESP partition is not configured correctly

The EFI system partition (ESP) needs to be formatted as FAT32. Mount to /boot/efi; Size ≥100MB (512MB is recommended).

Fix the command and format the partition

sudo mkfs.vfat F32 /dev/sda1  

Mount and reinstall GRUB

sudo mount /dev/sda1 /mnt/boot/efi  
grubinstall target=x86_64efi efidirectory=/boot/efi removable 

Question 2: Secure Boot conflict

Disable Secure Boot or sign GRUB:

Enter the BIOS Settings and turn off Secure Boot; Or use the shimsigned package to generate the signature:

sudo apt install shimsigned  
sudo cp /usr/lib/shim/shimx64.efi.signed /boot/efi/EFI/ubuntu/grubx64.efi  

Fault prevention and debugging tools

The first one, in the GRUB Rescue mode, manually load the module and start the system:

"ls" lists all partitions
set root=(hd0,gpt2) specifies the /boot partition
linux /vmlinuz5.15.078generic root=/dev/mapper/vg0root
The initrd/initrd img5.15.078 generic
boot  

The second type is log collection and analysis. View the installation log:

journalctl u grubinstall  

Enable GRUB debugging output:

grubinstall verbose debug /dev/sda  

The third type is backup and recovery. Regularly back up the boot sectors and configuration files:

dd if=/dev/sda of=/boot/grub/grub_backup.bin bs=512 count=1 Back up MBR
cp /boot/grub/grub.cfg /boot/grub/grub.cfg.bak  

Although the error "Disk filter writing is not supported" is rather troublesome, it is mostly due to a mismatch between the storage configuration and the GRUB installation target. By accurately identifying the disk topology structure, reasonably dividing the /boot partition, and strictly distinguishing the BIOS/UEFI installation mode, such problems can be completely avoided.