swapcreate

#!/bin/sh

# Create a swapfile.

if [ "$1" = "" ]; then
  echo "Usage: swapcreate <num> <loc>?"
  echo "  where <num> is the number of GiB to allocate"
  echo "  and <loc> is the folder to put the swapfile in."
  echo "  If no argument is provided for <loc>, it defaults"
  echo "  to whatever mounts at /dev/sda1."
  exit 1
fi

if [ "$2" = "" ]; then
  TARGET=$(findmnt /dev/sda1 | grep '/dev' | awk '{print $1}')
  if [ "$TARGET" = "" ]; then
    echo "Could not find a drive mounted at /dev/sda1."
    exit 1
  fi
  SWAPFILE="$TARGET/.swapfile.img"
else
  SWAPFILE="$2/.swapfile.img"
fi

NUMGI="$1""Gi"
NUMBYTES="$(numfmt $NUMGI --from=auto)"
FREEKILO="$(df /dev/sda | grep '/dev' | awk '{print $4}')K"
FREEBYTES="$(numfmt $FREEKILO --from=auto)"
FREEGI="$(numfmt $FREEKILO --from=auto --to=iec-i)"

ESWAPFILE="$(sudo swapon --show | grep '/.swapfile.img' | awk '{print $1}')"
if test -f "$ESWAPFILE"; then
  echo "Swapfile already exists. Please call swapdestroy before creating another."
  exit 1
fi

ALLOC_BLKSIZE="4096"
ALLOC_BLOCKS="$(expr $NUMBYTES / $ALLOC_BLKSIZE)"

echo "Creating swapfile: $SWAPFILE"
if command -v fallocate >/dev/null; then
  sudo fallocate -l "$NUMGI""B" "$SWAPFILE"
else
  sudo dd "if=/dev/zero" "of=$SWAPFILE" "bs=$ALLOC_BLKSIZE" "count=$ALLOC_BLOCKS"
fi

sudo chmod 600 "$SWAPFILE"

sudo mkswap "$SWAPFILE"

sudo swapon "$SWAPFILE"

echo "Swapfile created."
echo
sudo swapon --show