Script to make creating swap easier and quicker

create_swap.sh

#!/bin/bash

# Color Codes
RED='\033[0;31m'       # Red for errors
GREEN='\033[0;32m'     # Green for info
YELLOW='\033[1;33m'    # Yellow for warnings
NC='\033[0m'           # No Color

# Functions for colored output
info() {
    echo -e "${GREEN}[INFO]${NC} $1"
}

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

error() {
    echo -e "${RED}[ERROR]${NC} $1"
}

# Function to display help
show_help() {
    echo "Usage: $0 [-h] [-s SWAPPINESS] [-p CACHE_PRESSURE] SIZE"
    echo ""
    echo "Create a swap file with the specified size and optionally set kernel parameters for swappiness and cache pressure."
    echo ""
    echo "Options:"
    echo "  -h                    Show this help message and exit"
    echo "  -s SWAPPINESS         Set the vm.swappiness kernel parameter (0-100)"
    echo "  -p CACHE_PRESSURE     Set the vm.vfs_cache_pressure kernel parameter (e.g., 50, 100)"
    echo ""
    echo "Arguments:"
    echo "  SIZE                  Size of the swap file (e.g., 1G, 512M, etc.)"
    echo ""
    echo "Examples:"
    echo "  $0 -s 60 -p 50 2G     # Creates a 2GB swap file and sets swappiness to 60 and cache pressure to 50"
    echo "  $0 1G                 # Creates a 1GB swap file without changing kernel parameters"
}

# Function to create swap
create_swap() {
    local size=$1
    local swapfile="/swapfile"

    # Check if swapfile already exists
    if [ -f "$swapfile" ]; then
        warning "Swap file $swapfile already exists."
        read -r -p "Do you want to overwrite it? [y/N]: " choice
        case "$choice" in
            y|Y )
                info "Disabling existing swap..."
                sudo swapoff "$swapfile"
                info "Removing existing swap file..."
                sudo rm "$swapfile"
                ;;
            * )
                info "Exiting without making changes."
                exit 0
                ;;
        esac
    fi

    info "Creating a swap file of size $size at $swapfile..."

    # Create the swap file
    sudo fallocate -l "$size" "$swapfile"
    if [ $? -ne 0 ]; then
        error "Failed to allocate swap file. Ensure you have enough disk space and permissions."
        exit 1
    fi

    # Set correct permissions
    sudo chmod 600 "$swapfile"

    # Set up the swap file
    sudo mkswap "$swapfile"

    # Enable the swap file
    sudo swapon "$swapfile"

    # Add to /etc/fstab for persistence
    if ! grep -q "^/swapfile" /etc/fstab; then
        info "Adding swap file to /etc/fstab..."
        echo "/swapfile none swap sw 0 0" | sudo tee -a /etc/fstab > /dev/null
    fi

    # Verify swap is active
    info "Swap file created and activated."
    info "Swap details:"
    sudo swapon --show
}

# Function to set swappiness
set_swappiness() {
    local swappiness=$1

    info "Setting vm.swappiness to $swappiness..."
    sudo sysctl vm.swappiness="$swappiness"
    if [ $? -ne 0 ]; then
        error "Failed to set vm.swappiness. Ensure you have sufficient permissions."
        exit 1
    fi

    # Make it persistent
    sudo sed -i '/vm.swappiness/d' /etc/sysctl.conf
    echo "vm.swappiness=$swappiness" | sudo tee -a /etc/sysctl.conf > /dev/null
    info "vm.swappiness set to $swappiness."
}

# Function to set vfs_cache_pressure
set_cache_pressure() {
    local cache_pressure=$1

    info "Setting vm.vfs_cache_pressure to $cache_pressure..."
    sudo sysctl vm.vfs_cache_pressure="$cache_pressure"
    if [ $? -ne 0 ]; then
        error "Failed to set vm.vfs_cache_pressure. Ensure you have sufficient permissions."
        exit 1
    fi

    # Make it persistent
    sudo sed -i '/vm.vfs_cache_pressure/d' /etc/sysctl.conf
    echo "vm.vfs_cache_pressure=$cache_pressure" | sudo tee -a /etc/sysctl.conf > /dev/null
    info "vm.vfs_cache_pressure set to $cache_pressure."
}

# Parse command-line arguments
swappiness=""
cache_pressure=""
while getopts "hs:p:" opt; do
    case "$opt" in
        h)
            show_help
            exit 0
            ;;
        s)
            swappiness="$OPTARG"
            ;;
        p)
            cache_pressure="$OPTARG"
            ;;
        *)
            show_help
            exit 1
            ;;
    esac
done

# Shift positional arguments
shift $((OPTIND-1))

# Check if size is provided
if [ -z "$1" ]; then
    error "SIZE argument is required."
    show_help
    exit 1
fi

# Validate swappiness if provided
if [ -n "$swappiness" ]; then
    if ! [[ "$swappiness" =~ ^[0-9]+$ ]] || [ "$swappiness" -lt 0 ] || [ "$swappiness" -gt 100 ]; then
        error "SWAPPINESS must be an integer between 0 and 100."
        show_help
        exit 1
    fi
fi

# Validate cache pressure if provided
if [ -n "$cache_pressure" ]; then
    if ! [[ "$cache_pressure" =~ ^[0-9]+$ ]]; then
        error "CACHE_PRESSURE must be a positive integer."
        show_help
        exit 1
    fi
fi

# Create swap with specified size
create_swap "$1"

# Set swappiness if specified
if [ -n "$swappiness" ]; then
    set_swappiness "$swappiness"
fi

# Set vfs_cache_pressure if specified
if [ -n "$cache_pressure" ]; then
    set_cache_pressure "$cache_pressure"
fi

REAMD.md

What is this?

This is a simple Bash script designed to help easily create and manage swap files on a Linux system. It also allows easily configure kernel parameters vm.swappiness and vm.vfs_cache_pressure.

---

How to Use

1. Basic Usage
   Create a swap file with the specified size:

   ./create_swap.sh SIZE

   Example:

   ./create_swap.sh 2G

2. Set vm.swappiness
   Adjust the kernel parameter for how aggressively the system uses swap:

   ./create_swap.sh -s SWAPPINESS SIZE

   Example:

   ./create_swap.sh -s 60 2G

3. Set vm.vfs_cache_pressure
   Adjust the kernel parameter for how the system prioritizes cache over swap:

   ./create_swap.sh -p CACHE_PRESSURE SIZE

   Example:

   ./create_swap.sh -p 50 2G

4. Set Both Parameters
   Configure both vm.swappiness and vm.vfs_cache_pressure:

   ./create_swap.sh -s SWAPPINESS -p CACHE_PRESSURE SIZE

   Example:

   ./create_swap.sh -s 60 -p 50 2G

5. Check for Existing Swap
   If a swap file already exists, the script will prompt you to overwrite it.

6. Display Help
   To see usage instructions:

   ./create_swap.sh -h

---

Important Notes

• Permissions: The script requires sudo privileges to create swap files and modify kernel parameters.
• Persistence: Swap settings and kernel parameters are automatically made persistent across reboots.
• Validation: After running the script, verify the swap and kernel settings using:

  swapon --show
  sysctl vm.swappiness
  sysctl vm.vfs_cache_pressure