How to fix dpkg: error processing package linux-image-X.X.X-generic (--configure): installed linux-image-X.X.X-generic package post-installation script subprocess returned error exit status 1 in APT

First, verify whether you have sufficient space in your /boot directory. A full /boot partition is the most common cause of this error.

df -h /boot

If the output shows less than 100 MB free, proceed to step 2 to remove old kernels. If you have adequate space, skip to step 3.

List all installed kernels on your system:

dpkg --list | grep linux-image

Identify old kernel versions you no longer need (usually keep only the 2 most recent). Remove them with:

sudo apt-get purge linux-image-X.X.X-XX-generic

Replace X.X.X-XX-generic with the actual version number. Repeat for each old kernel. After removing old kernels, verify you've freed space:

df -h /boot

Once you've freed space, use dpkg to retry configuring packages that failed:

sudo dpkg --configure -a

This tells dpkg to configure all packages that are currently installed but not yet fully configured. If this succeeds, the post-installation script will complete.

If the reconfigure step doesn't resolve the issue, try fixing broken package dependencies:

sudo apt --fix-broken install

Or the older syntax:

sudo apt-get install -f

This will attempt to resolve any missing dependencies or broken package installations.

If the above steps don't work, incompatible DKMS modules may be blocking installation. Check for DKMS errors in the output from step 3. Common problematic modules include:

- wireguard: No longer needed in kernels 5.x+
- evdi (DisplayLink): May not support newer kernel versions
- virtualbox-guest-additions: Version mismatch with kernel

For wireguard:

sudo apt purge wireguard-dkms

For evdi/DisplayLink, check the Debian/Ubuntu repositories for a version compatible with your kernel version.

After removing the problematic package, retry:

sudo dpkg --configure -a

Once dpkg finishes, manually update the initramfs to ensure the kernel is fully configured:

sudo update-initramfs -u -k all

Then, verify the kernel installation completed successfully:

sudo apt update
sudo apt install --fix-broken