AWS EC2 user_data OS detector pattern prototype

user_data.sh

#!/bin/bash
set -euox pipefail
IFS=$'\n\t'

# https://aws.amazon.com/premiumsupport/knowledge-center/ec2-linux-log-user-data
exec > >(tee /var/log/user-data.log|logger -t user-data -s 2>/dev/console) 2>&1

# Detect OS

if [ -e "/etc/os-release" ]; then
  OS_NAME=$( sed '/^NAME="/!d' < "/etc/os-release" | sed 's/NAME="//' | sed 's/"$//' )
  OS_VERSION=$( sed '/^VERSION="/!d' < "/etc/os-release" | sed 's/VERSION="//' | sed 's/"$//' )

  if [[ ${OS_NAME} = 'Amazon Linux'* ]] ; then
    if [[ ${OS_VERSION} = '2.0 '* ]] ; then
      OS="amazonlinux2"
    else
      OS="amazonlinux1"
    fi
  else
    OS="unknown"
    echo "/etc/os-release file exists but OS does not seem to be Amazon Linux, falling back to unknown OS"
  fi

elif [ -e "/etc/lsb-release" ]; then
  OS_NAME=$( sed '/^DISTRIB_ID="/!d' < "/etc/os-release" | sed 's/DISTRIB_ID="//' | sed 's/"$//' )
  OS_VERSION=$( sed '/^DISTRIB_RELEASE="/!d' < "/etc/os-release" | sed 's/DISTRIB_RELEASE="//' | sed 's/"$//' )

  if [[ ${OS_NAME} = 'Ubuntu' ]] ; then
    OS="ubuntu${OS_VERSION}"
  else
    OS="unknown"
    echo "/etc/lsb-release file exists but OS does not seem to be Ubuntu (...Debian?), falling back to unknown OS"
  fi
fi

# Different actions per-os

case ${OS} in
"amazonlinux2")
  echo "Amazon Linux 2やで"
  # Download and execute phase 2 script for particular OS
  # aws s3 cp s3://bucket-name/amazon-linux-2-setup.sh ./
  # . amazon-linux-2-setup.sh
  ;;
"amazonlinux1")
  echo "Amazon Linux 1やで"
  ;;
"ubuntu16.04")
  echo "Ubuntu 16.04やで"
  ;;
*)
  echo "知らんOSやで"
  ;;
esac