scripts/mk_swapfile

   1 #!/bin/bash -e
   2 # This script adds a 1GB swapfile to the system
   3
   4 function do_err() {
   5     code=$?
   6     echo "Command failed with code $code: $BASH_COMMAND"
   7     exit $code
   8
   9 }
  10 trap do_err ERR
  11
  12
  13 function set_swappiness() {
  14   if ! grep -q '^vm.swappiness' /etc/sysctl.conf; then
  15     echo -n 'Setting '
  16     sysctl -w vm.swappiness=10
  17     echo vm.swappiness = 10 >> /etc/sysctl.conf
  18   fi
  19 }
  20
  21 function get_new_swapfile() {
  22   for i in `seq 0 99`; do
  23     if [ ! -e /swapfile.$i ]; then
  24       echo /swapfile.$i
  25       return
  26     fi
  27   done
  28   # Seriously? 100 swapfiles already exist?
  29   echo "too many swapfiles"
  30   exit 1
  31 }
  32
  33 [ `id -u` -eq 0 ] || { echo "You must be root to run this script"; exit 1; }
  34
  35 # how big? default 1GB
  36 declare -i num_gb
  37 num_gb="${1-1}"
  38 [ $num_gb -lt 1 ] && { echo "Please specify an integer >= 1"; exit 1; }
  39 echo "Creating a ${num_gb}GB swapfile..."
  40
  41 set_swappiness
  42
  43 SWAPFILE=$(get_new_swapfile)
  44
  45 umask 077
  46 dd if=/dev/zero of=$SWAPFILE bs=1k count=$(($num_gb * 1024 * 1024)) conv=excl
  47 mkswap $SWAPFILE
  48 swapon $SWAPFILE
  49 echo "$SWAPFILE swap swap auto 0 0" >> /etc/fstab
  50
  51 echo 1GiB swapfile successfully added