CoreOS swap auto-setup

gistfile1.txt

# add this to your cloud config
# or a systemctl unit file on all nodes
# or as a fleetctl global unit (add [X-Fleet]\nglobal=true)
# will auto detect a nodes memory and create a swap file the same size, turn off CoW, mount a loopback device
# (actually, it touches the file first THEN disables COW!)
# fully dynamic and non-interfering, will find the first free loopback & unmount/delete on stop
   - name: swap-auto.service
      command: start
      enabled: true
      content:
      [Unit]
      Description=Setup Swap Service
      Documentation=http://shaped.ca

      [Service]
      Type=oneshot
      Environment="SWAP_PATH=/swap" "SWAP_FILE=swap.fs"
      ExecStartPre=-/usr/bin/rm -rf ${SWAP_PATH}
      ExecStartPre=/usr/bin/mkdir ${SWAP_PATH}
      ExecStartPre=/usr/bin/touch ${SWAP_PATH}/${SWAP_FILE}
      ExecStartPre=/usr/bin/chattr +C ${SWAP_PATH}/${SWAP_FILE}
      ExecStartPre=/bin/bash -c "fallocate -l $(free -h --si|awk '/^Mem:/{print $2}') ${SWAP_PATH}/${SWAP_FILE}"
      ExecStartPre=/usr/bin/chmod 600 ${SWAP_PATH}/${SWAP_FILE}
      ExecStartPre=/usr/sbin/mkswap ${SWAP_PATH}/${SWAP_FILE}
      ExecStartPre=/usr/sbin/losetup -f ${SWAP_PATH}/${SWAP_FILE}
      ExecStart=/usr/bin/sh -c "/sbin/swapon $(/usr/sbin/losetup -j ${SWAP_PATH}/${SWAP_FILE} | /usr/bin/cut -d : -f 1)"
      ExecStop=/usr/bin/sh -c "/sbin/swapoff $(/usr/sbin/losetup -j ${SWAP_PATH}/${SWAP_FILE} | /usr/bin/cut -d : -f 1)"
      ExecStopPost=/usr/bin/sh -c "/usr/sbin/losetup -d $(/usr/sbin/losetup -j ${SWAP_PATH}/${SWAP_FILE} | /usr/bin/cut -d : -f 1)"
      ExecStopPost=-/usr/bin/rm -rf ${SWAP_PATH}
      RemainAfterExit=true