Clean up old linux kernels

remove-old-kernels.sh

#!/bin/bash
# Run this script without any param for a dry run
# Run the script with root and with exec param for removing old kernels after checking
# the list printed in the dry run

# bash <(curl -Ls "https://gist.github.com/jpaulickcz/721ad60ad28bb7875a5689defe005305/raw/?clean-kernels-$(date +%s)")


# Function to get disk usage in MB
get_disk_usage() {
    df --output=used / | tail -n 1 | awk '{print int($1/1024)}'
}

# Check for old kernels not in use
check_old_kernels() {
    local in_use_kernel=$(uname -r)

    local old_kernels=($(dpkg --list | grep -E 'linux-image-[0-9]+|linux-headers-[0-9]+|linux-modules-[0-9]+' | grep -v "$in_use_kernel" | awk '{print $2}'))
    local old_kernel_count=${#old_kernels[@]}

    if [ "$old_kernel_count" -eq 0 ]; then
        echo -e "\e[32m[OK] There are no old kernels on the system.\e[0m"
    else
        local old_kernels_size=$(dpkg-query -W -f='${Installed-Size}\t${Package}\n' "${old_kernels[@]}" | awk '{total += $1} END {print total / 1024}')
        echo -e "\e[33m[INFO] There are $old_kernel_count old kernels, taking up approximately $old_kernels_size MB.\e[0m"
    fi
}

# Display kernel version
uname -a
IN_USE=$(uname -a | awk '{ print $3 }')
echo "Your in use kernel is $IN_USE"

# Find old kernels and calculate expected freed space
check_old_kernels

# Check disk space before cleanup
DISK_USAGE_BEFORE=$(get_disk_usage)

if [ "$1" == "exec" ]; then
    for PACKAGE in $OLD_KERNELS; do
        yes | apt purge "$PACKAGE"
    done
    apt autoremove -y

    # Check disk space after cleanup
    DISK_USAGE_AFTER=$(get_disk_usage)

    # Calculate and display the freed space
    SPACE_FREED=$(($DISK_USAGE_BEFORE - $DISK_USAGE_AFTER))

    # Display comparison with expected freed space
    echo -e "\e[34m[INFO] Expected to free up approximately $old_kernels_size MB, actually freed $SPACE_FREED MB.\e[0m"
fi