Ubuntu Swap Configuration Script. Sets swap to recommended amount based on system RAM.

set-swap.sh

#!/bin/bash

# Ubuntu Swap Configuration Script
# Sets swap to recommended amount based on system RAM

set -e

# Check if running as root
if [[ $EUID -ne 0 ]]; then
   echo "This script must be run as root (use sudo)" 
   exit 1
fi

# Get total RAM in GB
TOTAL_RAM_KB=$(grep MemTotal /proc/meminfo | awk '{print $2}')
TOTAL_RAM_GB=$((TOTAL_RAM_KB / 1024 / 1024))

echo "System RAM: ${TOTAL_RAM_GB}GB"

# Determine recommended swap size based on Ubuntu/Red Hat recommendations
if [ $TOTAL_RAM_GB -le 2 ]; then
    SWAP_SIZE="${TOTAL_RAM_GB}G"
    echo "Recommended swap: ${SWAP_SIZE} (equal to RAM for systems ≤2GB)"
elif [ $TOTAL_RAM_GB -le 8 ]; then
    SWAP_SIZE="4G"
    echo "Recommended swap: ${SWAP_SIZE} (minimum 4GB for systems 2-8GB RAM)"
elif [ $TOTAL_RAM_GB -le 64 ]; then
    SWAP_SIZE="8G"
    echo "Recommended swap: ${SWAP_SIZE} (8GB for systems 8-64GB RAM)"
else
    SWAP_SIZE="8G"
    echo "Recommended swap: ${SWAP_SIZE} (8GB minimum for systems >64GB RAM)"
fi

# Allow user to override
read -p "Use recommended swap size (${SWAP_SIZE})? [Y/n] " -n 1 -r
echo
if [[ ! $REPLY =~ ^[Yy]$ ]] && [[ ! -z $REPLY ]]; then
    read -p "Enter desired swap size (e.g., 2G, 4G, 8G): " SWAP_SIZE
fi

SWAPFILE="/swapfile"

# Disable existing swap
echo "Disabling existing swap..."
swapoff -a

# Remove old swapfile if it exists
if [ -f "$SWAPFILE" ]; then
    echo "Removing old swapfile..."
    rm -f "$SWAPFILE"
fi

# Remove swap entries from /etc/fstab
sed -i '/swap/d' /etc/fstab

# Create new swapfile
echo "Creating ${SWAP_SIZE} swapfile..."
fallocate -l "$SWAP_SIZE" "$SWAPFILE" || dd if=/dev/zero of="$SWAPFILE" bs=1M count=$((${SWAP_SIZE%G} * 1024))

# Set proper permissions
chmod 600 "$SWAPFILE"

# Setup swap
echo "Setting up swap..."
mkswap "$SWAPFILE"

# Enable swap
swapon "$SWAPFILE"

# Make swap permanent
echo "$SWAPFILE none swap sw 0 0" >> /etc/fstab

# Optimize swap usage (swappiness)
echo "Configuring swappiness..."
sysctl vm.swappiness=10
echo "vm.swappiness=10" >> /etc/sysctl.conf

echo ""
echo "✓ Swap configuration complete!"
echo ""
swapon --show
free -h