Add docs on how to install GitLab on GCP

[ci skip]

doc/install/README.md

 # Installation
-- [Installation](installation.md)
-- [Requirements](requirements.md)
-- [Structure](structure.md)
-- [Database MySQL](database_mysql.md)
-- [Digital Ocean and Docker](digitaloceandocker.md)
-- [Docker](https://gitlab.com/gitlab-org/gitlab-ce/tree/master/docker)
-- [All installation methods](https://about.gitlab.com/installation/)
+GitLab can be installed via various ways. Check the [installation methods][methods]
+for an overview.
+
+## Requirements
+
+Before installing GitLab, make sure to check the [requirements documentation](requirements.md)
+which includes useful information on the supported Operating Systems as well as
+the hardware requirements.
+
+## Installation methods
+
+- [Installation using the Omnibus packages](https://about.gitlab.com/downloads/) -
+  Install GitLab using our official deb/rpm repositories. This is the
+  recommended way.
+- [Installation from source](installation.md) - Install GitLab from source.
+  Useful for unsupported systems like *BSD. For an overview of the directory
+  structure, read the [structure documentation](structure.md).
+- [Docker](https://docs.gitlab.com/omnibus/docker/) - Install GitLab using Docker.
+- [Installation on Google Cloud Platform](google_cloud_platform/index.md) - Install
+  GitLab on Google Cloud Platform using our official image.
+- [Digital Ocean and Docker](digitaloceandocker.md) - Install GitLab quickly
+  on DigitalOcean using Docker.
+
+## Database
+
+While the recommended database is PostgreSQL, we provide information to install
+GitLab using MySQL. Check the [MySQL documentation](database_mysql.md) for more
+information.
+
+[methods]: https://about.gitlab.com/installation/

doc/install/google_cloud_platform/index.md

+# Installing GitLab on Google Cloud Platform
+
+![GCP landing page](img/gcp_landing.png)
+
+The fastest way to get started on [Google Cloud Platform (GCP)][gcp] is through
+the [Google Cloud Launcher][launcher] program.
+
+## Prerequisites
+
+There are only two prerequisites in order to install GitLab on GCP:
+
+1. You need to have a Google account.
+1. You need to sign up for the GCP program. If this is your first time, Google
+   gives you [$300 credit for free][freetrial] to consume over a 60-day period.
+
+Once you have performed those two steps, you can visit the
+[GCP launcher console][console] which has a list of all the things you can
+deploy on GCP.
+
+![GCP launcher console](img/gcp_launcher_console_home_page.png)
+
+The next step is to find and install GitLab.
+
+## Configuring and deploying the VM
+
+To deploy GitLab on GCP you need to follow five simple steps:
+
+1. Go to https://cloud.google.com/launcher and login with your Google credentials
+1. Search for GitLab from GitLab Inc. (not the same as Bitnami) and click on
+   the tile.
+
+    ![Search for GitLab](img/gcp_search_for_gitlab.png)
+
+1. In the next page, you can see an overview of the GitLab VM as well as some
+   estimated costs. Click the **Launch on Compute Engine** button to choose the
+   hardware and network settings.
+
+    ![Launch on Compute Engine](img/gcp_gitlab_overview.png)
+
+1. In the settings page you can choose things like the datacenter where your GitLab
+   server will be hosted, the number of CPUs and amount of RAM, the disk size
+   and type, etc. Read GitLab's [requirements documentation][req] for more
+   details on what to choose depending on your needs.
+
+    ![Deploy settings](img/new_gitlab_deployment_settings.png)
+
+1. As a last step, hit **Deploy** when ready. The process will finish in a few
+   seconds.
+
+    ![Deploy in progress](img/gcp_gitlab_being_deployed.png)
+
+
+## Visiting GitLab for the first time
+
+After a few seconds, GitLab will be successfully deployed and you should be
+able to see the IP address that Google assigned to the VM, as well as the
+credentials to the GitLab admin account.
+
+![Deploy settings](img/gitlab_deployed_page.png)
+
+1. Click on the IP under **Site address** to visit GitLab.
+1. Accept the self-signed certificate that Google automatically deployed in
+   order to securely reach GitLab's login page.
+1. Use the username and password that are present in the Google console page
+   to login into GitLab and click **Sign in**.
+
+      ![GitLab first sign in](img/gitlab_first_sign_in.png)
+
+Congratulations! GitLab is now installed and you can access it via your browser,
+but we're not done yet. There are some steps you need to take in order to have
+a fully functional GitLab installation.
+
+## Next steps
+
+These are the most important next steps to take after you installed GitLab for
+the first time.
+
+### Changing the admin password and email
+
+Google assigned a random password for the GitLab admin account and you should
+change it ASAP:
+
+1. Visit the GitLab admin page through the link in the Google console under
+   **Admin URL**.
+1. Find the Administrator user under the **Users** page and hit **Edit**.
+1. Change the email address to a real one and enter a new password.
+
+    ![Change GitLab admin password](img/change_admin_passwd_email.png)
+
+1. Hit **Save changes** for the changes to take effect.
+1. After changing the password, you will be signed out from GitLab. Use the
+   new credentials to login again.
+
+### Assigning a static IP
+
+By default, Google assigns an ephemeral IP to your instance. It is strongly
+recommended to assign a static IP if you are going to use GitLab in production
+and use a domain name as we'll see below.
+
+Read Google's documentation on how to [promote an ephemeral IP address][ip].
+
+### Using a domain name
+
+Assuming you have a domain name in your possession and you have correctly
+set up DNS to point to the static IP you configured in the previous step,
+here's how you configure GitLab to be aware of the change:
+
+1. SSH into the VM. You can easily use the **SSH** button in the Google console
+   and a new window will pop up.
+
+    ![SSH button](img/ssh_via_button.png)
+
+     In the future you might want to set up [connecting with an SSH key][ssh]
+     instead.
+
+1. Edit the config file of Omnibus GitLab using your favorite text editor:
+
+    ```
+    sudo vim /etc/gitlab/gitlab.rb
+    ```
+
+1. Set the `external_url` value to the domain name you wish GitLab to have
+   **without** `https`:
+
+    ```
+    external_url 'http://gitlab.example.com'
+    ```
+
+    We will set up HTTPS in the next step, no need to do this now.
+
+1. Reconfigure GitLab for the changes to take effect:
+
+    ```
+    sudo gitlab-ctl reconfigure
+    ```
+
+1. You can now visit GitLab using the domain name.
+
+### Configuring HTTPS with the domain name
+
+Although not needed, it's strongly recommended to secure GitLab with a TLS
+certificate. Follow the steps in the [Omnibus documentation][omni-ssl].
+
+### Configuring the email SMTP settings
+
+You need to configure the email SMTP settings correctly otherwise GitLab will
+not be able to send notification emails, like comments, and password changes.
+Check the [Omnibus documentation][omni-smtp] how to do so.
+
+## Further reading
+
+GitLab can be configured to authenticate with other OAuth providers, LDAP, SAML,
+Kerberos, etc. Here are some documents you might be interested in reading:
+
+- [Omnibus GitLab documentation](https://docs.gitlab.com/omnibus/)
+- [Integration documentation](https://docs.gitlab.com/ce/integration/)
+- [GitLab Pages configuration](https://docs.gitlab.com/ce/administration/pages/index.html)
+- [GitLab Container Registry configuration](https://docs.gitlab.com/ce/administration/container_registry.html)
+
+[console]: https://console.cloud.google.com/launcher "GCP launcher console"
+[freetrial]: https://console.cloud.google.com/freetrial "GCP free trial"
+[ip]: https://cloud.google.com/compute/docs/configure-instance-ip-addresses#promote_ephemeral_ip "Configuring an Instance's IP Addresses"
+[gcp]: https://cloud.google.com/ "Google Cloud Platform"
+[launcher]: https://cloud.google.com/launcher/ "Google Cloud Launcher home page"
+[req]: ../requirements.md "GitLab hardware and software requirements"
+[ssh]: https://cloud.google.com/compute/docs/instances/connecting-to-instance "Connecting to Linux Instances"
+[omni-smtp]: https://docs.gitlab.com/omnibus/settings/smtp.html#smtp-settings "Omnibus GitLab SMTP settings"
+[omni-ssl]: https://docs.gitlab.com/omnibus/settings/nginx.html#enable-https "Omnibus GitLab enable HTTPS"