Copied from https://mackerel.io/file/script/setup-apt-v2.sh

setup-apt-v2.sh

#!/bin/sh

set -e

sudo -k

echo "This script requires superuser authority to setup Mackerel agent:"

sudo sh <<'SCRIPT'
  set -x

  if command -v curl; then
    http_get="curl -LfsS"
  elif command -v wget; then
    http_get="wget -q -O -"
  fi
  if [ "$http_get" = "" ]; then
    echo "curl or wget are required to install the mackerel-agent"
    exit 1
  fi

  echo "deb [arch=amd64] http://apt.mackerel.io/v2/ mackerel contrib" > /etc/apt/sources.list.d/mackerel.list
  $http_get https://mackerel.io/file/cert/GPG-KEY-mackerel-v2 | apt-key add -
  apt-get update -qq
SCRIPT

echo 'done'
echo 'To install mackerel-agent type: sudo apt-get install mackerel-agent'