resize_swap

#!/usr/bin/env bash
# This script resizes the swap file to a specified size in GB.
# Usage: bash resize_swap.sh <size_in_GB>

set -eo pipefail

if [[ "$GITHUB_ACTIONS" != "true" || "$RUNNER_ENVIRONMENT" != "github-hosted" || "$RUNNER_OS" != "Linux" ]]; then
    echo "Warning: This script is intended to run only in GitHub-hosted Linux runners. Skip execution." >&2
    exit 0
fi

if [[ $# -ne 1 || ! $1 =~ ^[0-9]+$ ]]; then
    echo "ERROR: Missing or invalid size argument. Usage: $0 <size_in_GB>" >&2
    exit 1
fi
total_swap=$1
(( total_swap <= 96 && total_swap >= 1 )) || { echo "Warning: Refusing to create <1 or >96 GiB swap" >&2; exit 0; }

# Show the swap size
echo "Swap size before resizing:"
swapon --show
echo "This will resize the swap to $total_swap GB."

# Record current active swap files (full paths) in the Bash array $old_swap_files
mapfile -t old_swap_files < <(awk 'NR>1 && $2=="file"{print $1}' /proc/swaps)

# Create new swap file
# First try to create it under /mnt, if that fails, use the root directory.
new_swap_file="/mnt/swapfile.new"
if  [[ ! -d /mnt ]] || ! sudo dd if=/dev/zero of="$new_swap_file" bs=1G count="$total_swap" oflag=direct status=progress; then
    new_swap_file="/swapfile.new"
    sudo dd if=/dev/zero of="$new_swap_file" bs=1G count="$total_swap" oflag=direct status=progress
fi
echo "Created swap file at $new_swap_file with size $total_swap GB."

# Set up permissions
sudo chmod 600 "$new_swap_file"

# Make the file usable as swap
sudo mkswap "$new_swap_file"

# Activate the swap file with a high priority
sudo swapon -p 32767 "$new_swap_file" || { echo "Warning: swapon failed for $new_swap_file. Swap resizing failed!!!" >&2; exit 0; }

# If there exist old swap files, disable and remove them
if ((${#old_swap_files[@]} == 0)); then
    echo "No old swap files found."
else
    echo "Old swap files to disable and remove: ${old_swap_files[*]}"
    for f in "${old_swap_files[@]}"; do
      sudo swapoff -- "$f" || echo "Warning: swapoff failed for $f (continuing)" >&2
      sudo rm -f -- "$f" || echo "Warning: rm failed for $f (continuing)" >&2
    done
    sudo sync
fi

# Show the swap size
echo "Swap size after resizing:"
swapon --show