Create and enable a swap file on Linux systems.

swap.sh

#!/bin/bash

set -euo pipefail

# Color codes for output
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
BLUE='\033[0;34m'
NC='\033[0m' # No Color

# Logging functions
log_info() {
    echo -e "${BLUE}[INFO]${NC} $1"
}

log_success() {
    echo -e "${GREEN}[SUCCESS]${NC} $1"
}

log_warning() {
    echo -e "${YELLOW}[WARNING]${NC} $1"
}

log_error() {
    echo -e "${RED}[ERROR]${NC} $1" >&2
}

# Show usage
show_usage() {
    cat << EOF
Usage: $0 [OPTIONS] {size}

Create and enable a swap file on Linux systems.

Arguments:
    size                Size of swap file (e.g., 2G, 512M, 4096M)

Options:
    -p, --path PATH     Custom path for swap file (default: /swapfile)
    -s, --swappiness N  Set swappiness value 0-100 (default: 60)
    -r, --remove        Remove existing swap file
    -c, --check         Check current swap status
    -h, --help          Show this help message

Examples:
    $0 4G                           # Create 4GB swap at /swapfile
    $0 2G -p /mnt/swap.img          # Create 2GB swap at custom path
    $0 4G -s 10                     # Create 4GB swap with swappiness 10
    $0 --remove                     # Remove swap file
    $0 --check                      # Check current swap status

EOF
    exit 0
}

# Check current swap status
check_swap_status() {
    log_info "Current swap configuration:"
    echo

    if command -v swapon &> /dev/null; then
        swapon --show
        echo
        free -h | grep -E "Mem:|Swap:"
        echo

        if [ -f /proc/sys/vm/swappiness ]; then
            log_info "Current swappiness: $(cat /proc/sys/vm/swappiness)"
        fi
    else
        log_error "swapon command not found"
        exit 1
    fi

    exit 0
}

# Remove swap file
remove_swap() {
    log_info "Removing swap file at $SWAP_PATH"

    # Check if swap file exists
    if [ ! -f "$SWAP_PATH" ]; then
        log_error "Swap file $SWAP_PATH does not exist"
        exit 1
    fi

    # Turn off swap
    if swapon --show | grep -q "$SWAP_PATH"; then
        log_info "Disabling swap file..."
        $SUDO swapoff "$SWAP_PATH"
        log_success "Swap disabled"
    fi

    # Remove from fstab
    if grep -q "$SWAP_PATH" /etc/fstab; then
        log_info "Removing from /etc/fstab..."
        $SUDO sed -i "\|$SWAP_PATH|d" /etc/fstab
        log_success "Removed from /etc/fstab"
    fi

    # Remove file
    log_info "Removing swap file..."
    $SUDO rm -f "$SWAP_PATH"
    log_success "Swap file removed successfully"

    exit 0
}

# Validate size format
validate_size() {
    local size=$1
    if ! echo "$size" | grep -qE '^[0-9]+[MGT]$'; then
        log_error "Invalid size format: $size"
        log_error "Size must be a number followed by M, G, or T (e.g., 2G, 512M, 1T)"
        exit 1
    fi
}

# Convert size to bytes for validation
size_to_bytes() {
    local size=$1
    local number=$(echo "$size" | sed 's/[^0-9]*//g')
    local unit=$(echo "$size" | sed 's/[0-9]*//g')

    case "$unit" in
        M) echo $((number * 1024 * 1024)) ;;
        G) echo $((number * 1024 * 1024 * 1024)) ;;
        T) echo $((number * 1024 * 1024 * 1024 * 1024)) ;;
        *) echo 0 ;;
    esac
}

# Check available disk space
check_disk_space() {
    local swap_dir=$(dirname "$SWAP_PATH")
    local required_bytes=$(size_to_bytes "$SWAP_SIZE")
    local available_bytes=$(df -B1 "$swap_dir" | awk 'NR==2 {print $4}')

    if [ "$required_bytes" -gt "$available_bytes" ]; then
        log_error "Insufficient disk space"
        log_error "Required: $SWAP_SIZE, Available: $(numfmt --to=iec-i --suffix=B $available_bytes)"
        exit 1
    fi

    log_success "Sufficient disk space available"
}

# Validate swappiness value
validate_swappiness() {
    if [ "$SWAPPINESS" -lt 0 ] || [ "$SWAPPINESS" -gt 100 ]; then
        log_error "Swappiness must be between 0 and 100"
        exit 1
    fi
}

# Parse command line arguments
SWAP_SIZE=""
SWAP_PATH="/swapfile"
SWAPPINESS=60
REMOVE_SWAP=false
CHECK_STATUS=false

while [[ $# -gt 0 ]]; do
    case $1 in
        -h|--help)
            show_usage
            ;;
        -p|--path)
            SWAP_PATH="$2"
            shift 2
            ;;
        -s|--swappiness)
            SWAPPINESS="$2"
            shift 2
            ;;
        -r|--remove)
            REMOVE_SWAP=true
            shift
            ;;
        -c|--check)
            CHECK_STATUS=true
            shift
            ;;
        *)
            if [ -z "$SWAP_SIZE" ]; then
                SWAP_SIZE="$1"
            else
                log_error "Unknown option: $1"
                show_usage
            fi
            shift
            ;;
    esac
done

# Setup sudo if needed
SUDO=''
if [ "$(id -u)" -ne 0 ]; then
    log_warning "Root access required"
    if sudo true; then
        SUDO='sudo'
        log_success "Sudo access granted"
    else
        log_error "Unable to obtain root access"
        exit 1
    fi
fi

# Handle check status
if [ "$CHECK_STATUS" = true ]; then
    check_swap_status
fi

# Handle remove swap
if [ "$REMOVE_SWAP" = true ]; then
    if [ -z "$SWAP_SIZE" ]; then
        SWAP_PATH="/swapfile"
    fi
    remove_swap
fi

# Validate required arguments
if [ -z "$SWAP_SIZE" ]; then
    log_error "Size argument is required"
    show_usage
fi

# Validate inputs
validate_size "$SWAP_SIZE"
validate_swappiness

# Display configuration
echo
log_info "Swap Setup Configuration:"
log_info "========================="
log_info "Size: $SWAP_SIZE"
log_info "Path: $SWAP_PATH"
log_info "Swappiness: $SWAPPINESS"
echo

# Check if swap file already exists
if [ -f "$SWAP_PATH" ]; then
    log_warning "Swap file already exists at $SWAP_PATH"
    read -p "Do you want to remove it and create a new one? (y/N): " -n 1 -r
    echo
    if [[ $REPLY =~ ^[Yy]$ ]]; then
        if swapon --show | grep -q "$SWAP_PATH"; then
            log_info "Disabling existing swap..."
            $SUDO swapoff "$SWAP_PATH"
        fi
        $SUDO rm -f "$SWAP_PATH"
        log_success "Removed existing swap file"
    else
        log_info "Aborted"
        exit 0
    fi
fi

# Check available disk space
check_disk_space

# Create swap file
log_info "Creating swap file..."
if $SUDO fallocate -l "$SWAP_SIZE" "$SWAP_PATH"; then
    log_success "Swap file allocated"
else
    log_warning "fallocate failed, falling back to dd..."
    $SUDO dd if=/dev/zero of="$SWAP_PATH" bs=1M count=$(echo "$SWAP_SIZE" | sed 's/[^0-9]*//g') status=progress
    log_success "Swap file created with dd"
fi

# Set proper permissions
log_info "Setting permissions..."
$SUDO chmod 600 "$SWAP_PATH"
log_success "Permissions set to 600"

# Setup swap
log_info "Setting up swap space..."
$SUDO mkswap "$SWAP_PATH"
log_success "Swap space created"

# Enable swap
log_info "Enabling swap..."
$SUDO swapon "$SWAP_PATH"
log_success "Swap enabled"

# Add to fstab if not already present
if ! grep -q "$SWAP_PATH" /etc/fstab; then
    log_info "Adding to /etc/fstab..."
    echo "$SWAP_PATH   none    swap    sw    0   0" | $SUDO tee -a /etc/fstab > /dev/null
    log_success "Added to /etc/fstab"
else
    log_warning "Entry already exists in /etc/fstab"
fi

# Set swappiness
log_info "Setting swappiness to $SWAPPINESS..."
$SUDO sysctl vm.swappiness="$SWAPPINESS" > /dev/null
echo "vm.swappiness=$SWAPPINESS" | $SUDO tee -a /etc/sysctl.conf > /dev/null
log_success "Swappiness configured"

# Display final status
echo
log_success "Swap setup completed successfully!"
echo
log_info "Final swap status:"
swapon --show
echo
free -h | grep -E "Mem:|Swap:"