#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](https://cloud.google.com/compute/docs/operating-systems/). 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](https://cloud.google.com/compute/docs/startupscript)__: User can provide some startup script to configure their instances at startup.
  *   __[Google Daemon](https://cloud.google.com/compute/docs/metadata)__: Google Daemon creates new accounts and configures ssh to accept public keys using the metadata server.
  *   __[Google Cloud SDK](https://cloud.google.com/sdk/)__: Command line tools to manage your images, instances and other objects on GCE.
 
 Following is the list (extracted from [this link](https://cloud.google.com/compute/docs/tutorials/building-images )) 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

       grub2-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

       grub2-mkconfig -o /boot/grub2/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"