Common Issues·3 min lezen

/boot Partition Full: Removing Old Kernels

/boot partition full and apt can't update? Safely remove old Linux kernels to free space.

On Ubuntu and Debian, each kernel update leaves the old one in the /boot partition. Over time they accumulate until the partition (typically 500 MB) fills up and apt stops working with errors like:

E: Failed to fetch ... No space left on device
dpkg: error processing package linux-image-...

Diagnosis

bash

# Check space on /boot
df -h /boot

# List installed kernels
dpkg --list | grep linux-image

# Currently running kernel (DO NOT remove this!)
uname -r

Quick solution (Ubuntu)

bash

# Automatically remove unused kernels (safe method)
apt autoremove --purge

apt autoremove removes old kernels no longer needed, keeping current kernel and the previous one. It's the safest method.

Never remove the kernel returned by uname -r. If something goes wrong, you won't be able to boot the server.

If apt can't run due to lack of space

When /boot is completely full, even apt won't work. Solution:

bash

# Find installed kernels
dpkg --list | grep linux-image | awk '{print $2}'

# Example output:
# linux-image-5.15.0-91-generic
# linux-image-5.15.0-94-generic
# linux-image-5.15.0-97-generic   ← this is the current one (uname -r)

# Remove manually the old ones (NOT the current one)
dpkg --purge linux-image-5.15.0-91-generic
dpkg --purge linux-image-5.15.0-94-generic

# Now apt should work again
apt autoremove --purge
apt clean

Remove kernels with script

bash

# List all kernels except the active one
CURRENT=$(uname -r)
dpkg --list | grep linux-image | grep -v "$CURRENT" | grep "^ii" | awk '{print $2}'

# Remove them all at once
dpkg --list | grep linux-image | grep -v "$(uname -r)" | grep "^ii" | awk '{print $2}' | xargs apt-get -y purge

Remove old headers and modules too

bash

# Remove headers corresponding to removed kernels
apt autoremove --purge linux-headers-\*

# Or more precisely
dpkg --list | grep linux-headers | grep -v "$(uname -r | cut -d- -f1,2)" | grep "^ii" | awk '{print $2}' | xargs apt-get -y purge

Clean apt cache

After removing kernels, also free up cache:

bash

apt clean          # empty /var/cache/apt/archives
apt autoclean      # remove only packages no longer downloadable

df -h /boot        # verify freed space

Prevention for the future

Regularly check /boot

bash

# Add alert to cron if /boot exceeds 70%
echo '0 8 * * * root USAGE=$(df /boot | awk "NR==2{print \$5}" | tr -d "%"); if [ $USAGE -gt 70 ]; then echo "/boot at ${USAGE}% on $(hostname)" | mail -s "ALERT: /boot almost full" root; fi' > /etc/cron.d/check-boot

Configure GRUB to keep fewer kernels

bash

nano /etc/default/grub

# Keep only the last 2 kernels (default is unlimited)
GRUB_DEFAULT=0

Then:

bash

echo 'Dpkg::AutoRemove::SuggestsImportant "false";' > /etc/apt/apt.conf.d/99nosuggests

Ubuntu: use unattended-upgrades with purge

bash

# In /etc/apt/apt.conf.d/50unattended-upgrades
# Add:
Unattended-Upgrade::Remove-Unused-Kernel-Packages "true";
Unattended-Upgrade::Remove-New-Unused-Dependencies "true";

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