Toggle kvm - linux

kvm_toggle.sh

#!/bin/bash

KVM_BLACKLIST_FILE="/etc/modprobe.d/blacklist-kvm.conf"
KVM_MODULES=("kvm_intel" "kvm_amd" "kvm")

# Check if the script is run as root
if [[ $EUID -ne 0 ]]; then
   echo "This script must be run as root. Please use 'sudo ./kvm_toggle.sh'."
   exit 1
fi

# Function to enable KVM (remove blacklist and load modules)
enable_kvm() {
    echo "✅ Enabling KVM..."
    # 1. Remove blacklist entries from the configuration file
    for module in "${KVM_MODULES[@]}"; do
        sed -i "/blacklist $module/d" "$KVM_BLACKLIST_FILE"
    done
    echo "  - Modules de-blacklisted from configuration."

    # 2. Attempt to load the modules directly
    for module in "${KVM_MODULES[@]}"; do
        if ! lsmod | grep -q "$module"; then
            echo "  - Loading module '$module'..."
            modprobe "$module"
            if [ $? -eq 0 ]; then
                echo "    OK"
            else
                echo "    Error loading module '$module'. A reboot might still be necessary."
            fi
        else
            echo "  - Module '$module' is already loaded, no action needed."
        fi
    done
    
    # 3. Update initramfs for the next reboot
    update_initramfs

    echo "KVM is now activated for immediate use."
    echo "Note: A system reboot is still recommended for all services to work correctly."
}

# Function to disable KVM (add blacklist and unload modules)
disable_kvm() {
    echo "🚫 Disabling KVM..."
    
    # 1. Add blacklist entries to the configuration file
    touch "$KVM_BLACKLIST_FILE"
    for module in "${KVM_MODULES[@]}"; do
        if ! grep -q "^blacklist $module" "$KVM_BLACKLIST_FILE"; then
            echo "  - Blacklisting module '$module'."
            echo "blacklist $module" >> "$KVM_BLACKLIST_FILE"
        fi
    done

    # 2. Attempt to unload the modules directly
    for module in "${KVM_MODULES[@]}"; do
        if lsmod | grep -q "$module"; then
            echo "  - Unloading module '$module'..."
            modprobe -r "$module"
            if [ $? -eq 0 ]; then
                echo "    OK"
            else
                echo "    Error unloading module '$module'. Services may still be using it. A reboot is required."
            fi
        else
            echo "  - Module '$module' is not loaded, no action needed."
        fi
    done

    # 3. Update initramfs for the next reboot
    update_initramfs

    echo "KVM is now deactivated."
    echo "Note: A system reboot is still highly recommended to prevent KVM from loading on boot."
}

# Function to update initramfs
update_initramfs() {
    echo "⚙️ Updating initramfs..."
    update-initramfs -u > /dev/null 2>&1
    if [ $? -eq 0 ]; then
        echo "   Initramfs updated successfully."
    else
        echo "   Error updating initramfs."
    fi
}

# Main script logic
case "$1" in
    enable)
        enable_kvm
        ;;
    disable)
        disable_kvm
        ;;
    status)
        echo "Checking KVM status..."
        if grep -q "^blacklist kvm" "$KVM_BLACKLIST_FILE" || \
           grep -q "^blacklist kvm_intel" "$KVM_BLACKLIST_FILE" || \
           grep -q "^blacklist kvm_amd" "$KVM_BLACKLIST_FILE"; then
            echo "KVM is currently: 🚫 **DISABLED** (blacklisted in $KVM_BLACKLIST_FILE)"
            echo "Use 'sudo kvm_toggle.sh enable' to enable KVM."
        else
            if modprobe -n kvm &> /dev/null; then
                 if lsmod | grep -q "kvm" || lsmod | grep -q "kvm_intel" || lsmod | grep -q "kvm_amd"; then
                    echo "KVM is currently: ✅ **ENABLED** (modules loaded)"
                 else
                    echo "KVM is currently: ✅ **ENABLED** (modules can be loaded, but are not currently active)"
                 fi
            else
                echo "KVM is currently: ❓ **UNKNOWN/POTENTIALLY DISABLED** (KVM modules not loadable or other issue)"
            fi
            echo "Use 'sudo kvm_toggle.sh disable' to disable KVM."
        fi
        ;;
    *)
        echo "Usage: $0 [enable|disable|status]"
        echo "  enable: Enables KVM (removes blacklist and loads modules)."
        echo "  disable: Disables KVM (adds blacklist and unloads modules)."
        echo "  status: Shows the current KVM status."
        exit 1
        ;;
esac