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#Photon on GCE

Google Compute Engine (GCE) Image background

GCE is a service that lets user run virtual machines on Google's infrastructure. User can customize the virtual machine as much as they want, even can install their custom OS imsage apart from the publicly provided images. For any OS to be useable on GCE, it must match the Google's infrastructure needs. Following are Google provided tools used for VM instances to behave properly.

  • Google startup scripts: User can provide some startup script to configure their instances at startup.
  • Google Daemon: Google Daemon creates new accounts and configures ssh to accept public keys using the metadata server.
  • Google Cloud SDK: Command line tools to manage your images, instances and other objects on GCE.

Following is the list (extracted from this link) of items must be done to make Photon work on GCE.

  • Install Google Compute Engine Image Packages
  • Install Google Cloud SDK
  • Change GPT partition table to MBR
  • Update Grub config for new MBR and serial console output
  • Update ssh configuration
  • Delete ssh host keys
  • Set the time zone to UTC
  • Use the Google NTP server
  • Delete the hostname file.
  • Add Google hosts /etc/hosts
  • Set MTU to 1460. SSH will not work without it.
  • Create /etc/ssh/sshd_not_to_be_run with just the contents “GOOGLE\n”.

Creating Photon image for GCE

1. Prepare Photon Disk
Install Photon Minimal on Fusion/Workstation and install some required packages.
  mount /dev/cdrom /media/cdrom
  tdnf install yum
  tdnf install python2-libs
  yum install ntp sudo wget tar which gptfdisk sed findutils grep gzip --nogpgcheck -y
Photon installer installs GPT partition table by default but GCE only accepts MBR(msdos) type partition table. We need to convert GPT to MBR and update the grub. Following are commands to do that.
  # Change partition table to MBR from GPT
  sgdisk -m 1:2 /dev/sda
  grub-install /dev/sda
  
  # Enable serial console on grub for GCE.
  cat << EOF >> /etc/default/grub
  GRUB_CMDLINE_LINUX="console=ttyS0,38400n8"
  GRUB_TERMINAL=serial
  GRUB_SERIAL_COMMAND="serial --speed=38400 --unit=0 --word=8 --parity=no --stop=1"
  EOF
  
  # Create new grub.cfg based on the settings in /etc/default/grub
  grub-mkconfig -o /boot/grub/grub.cfg
2. Install Google Cloud SDK and GCE Packages
  yum install google-daemon google-startup-scripts
  cp /usr/lib/systemd/system/google* /lib/systemd/system/
  cd /lib/systemd/system/multi-user.target.wants/
  
  # Create links in multi-user.target to auto-start these scripts and services.
  for i in ../google*; do  ln -s $i `basename $i`; done
  
  cd /tmp/; wget https://dl.google.com/dl/cloudsdk/release/google-cloud-sdk.tar.gz --no-check-certificate
  tar -xf google-cloud-sdk.tar.gz
  cd google-cloud-sdk
  ./install.sh
3. Update /etc/hosts file with GCE values
  echo "169.254.169.254 metadata.google.internal metadata" >> /etc/hosts
4. Remove all servers from ntp.conf and add Google's ntp server.
  sed -i -e "/server/d" /etc/ntp.conf
  cat /etc/ntp.conf
  echo "server 169.254.169.254" >> /etc/ntp.conf
  # Create ntpd.service to auto starting ntp server.
  cat << EOF >> /lib/systemd/system/ntpd.service
  [Unit]
  Description=Network Time Service
  After=network.target nss-lookup.target

  [Service]
  Type=forking
  PrivateTmp=true
  ExecStart=/usr/sbin/ntpd -g -u ntp:ntp
  Restart=always
  
  [Install]
  WantedBy=multi-user.target
  EOF
  
  # Add link in multi-user.target.wants to auto start this service.
  cd /lib/systemd/system/multi-user.target.wants/
  ln -s ../ntpd.service ntpd.service
5. Set UTC timezone
  ln -sf /usr/share/zoneinfo/UTC /etc/localtime
6. Update /etc/resolv.conf
  echo "nameserver 8.8.8.8" >> /etc/resolv.conf
7. Remove ssh host keys and add script to regenerate them at boot time.
  rm /etc/ssh/ssh_host_*
  # Depending on the installation, you may need to purge the following keys
  rm /etc/ssh/ssh_host_rsa_key*
  rm /etc/ssh/ssh_host_dsa_key*
  rm /etc/ssh/ssh_host_ecdsa_key*

  sed -i -e "/exit 0/d" /etc/rc.local
  echo "[ -f /etc/ssh/ssh_host_key ] && echo 'Keys found.' || ssh-keygen -A" >> /etc/rc.local
  echo "exit 0" >> /etc/rc.local
  printf "GOOGLE\n" > /etc/ssh/sshd_not_to_be_run
  
  # Edit sshd_config and ssh_config as per instructions on [this link](https://cloud.google.com/compute/docs/tutorials/building-images ).
8. Change MTU to 1460 for network interface.
  # Create a startup service in systemd that will change MTU and exits
  cat << EOF >> /lib/systemd/system/eth0.service
  [Unit]
  Description=Network interface initialization
  After=local-fs.target network-online.target network.target
  Wants=local-fs.target network-online.target network.target

  [Service]
  ExecStart=/bin/ifconfig eth0 mtu 1460 up
  Type=oneshot

  [Install]
  WantedBy=multi-user.target
  EOF
  # Make this service auto-start at boot.
  cd /lib/systemd/system/multi-user.target.wants/
  ln -s ../eth0.service eth0.service
9. Pack and Upload to GCE.
Shutdown the Photon VM and copy its disk to tmp folder.
  # You will need to install Google Cloud SDK on host machine to upload the image and play with GCE.
  cp Virtual\ Machines.localized/photon.vmwarevm/Virtual\ Disk.vmdk /tmp/disk.vmdk
  cd /tmp
  # GCE needs disk to be named as disk.raw with raw format.
  qemu-img convert -f vmdk -O raw disk.vmdk disk.raw
  
  # ONLY GNU tar will work to create acceptable tar.gz file for GCE. MAC's default tar is BSDTar which will not work. 
  # On Mac OS X ensure that you have gtar "GNU Tar" installed. exmaple: gtar -Szcf photon.tar.gz disk.raw 

  gtar -Szcf photon.tar.gz disk.raw 
  
  # Upload
  gsutil cp photon.tar.gz gs://photon-bucket
  
  # Create image
  gcloud compute --project "<project name>" images create "photon-beta-vYYYYMMDD" --description "Photon Beta" --source-uri https://storage.googleapis.com/photon-bucket/photon032315.tar.gz
  
  # Create instance on GCE of photon image
  gcloud compute --project "photon" instances create "photon" --zone "us-central1-f" --machine-type "n1-standard-1" --network "default" --maintenance-policy "MIGRATE" --scopes "https://www.googleapis.com/auth/devstorage.read_only" "https://www.googleapis.com/auth/logging.write" --image "https://www.googleapis.com/compute/v1/projects/photon/global/images/photon" --boot-disk-type "pd-standard" --boot-disk-device-name "photon"