How to fix dpkg: error processing archive: failed to write to copy of file: No space left on device in APT

Run this command to see all partitions and their usage:

df -h

Look for any partition at 100% usage. Pay special attention to /boot. If /boot shows 100%, you've found the culprit. Run this to see what's consuming space:

du -sh /boot/*

This will show large files (usually old kernels) taking up space.

Before removing kernels, identify which one is currently running:

uname -r

This outputs something like 5.15.0-84-generic. Make a note of this—DO NOT remove this kernel. List all installed kernels:

dpkg -l 'linux-*' | grep '^ii'

You'll see multiple kernel versions. Identify the older ones that differ from your current kernel.

Replace 5.15.0-83-generic with the actual old kernel version from the previous step (one that's NOT your current kernel):

sudo apt-get remove --purge linux-image-5.15.0-83-generic
sudo apt-get remove --purge linux-headers-5.15.0-83-generic

Or use autoremove to remove all unused kernels at once (safe, only removes unused ones):

sudo apt-get autoremove --purge

If you get "No space left on device" even with autoremove, try removing the oldest kernel manually first to create space, then use autoremove.

Once you've freed some space, clean up the apt cache:

sudo apt clean
sudo apt autoclean

apt clean removes all cached .deb files. apt autoclean removes only old cached packages. This can free up several hundred MB.

After freeing space, fix any incomplete package operations:

sudo apt-get -f install

This repairs dependencies and completes any interrupted installations. Then try your original command again:

sudo apt update
sudo apt upgrade