Add Reference Architecture and Deployment Guide (#4768)

* Add Nomad RA

* Add deployment guide and nav

* Deployment Guide update

* Minor typo fixes

* Update diagrams

* Fixes for review

* Link fixes and typo fix

* Edits following review

- Update image text from "zone" to "datacenter" to match Nomad terminology
- Clean up text based on Preetha's feedback

* Text updates

Based on feedback from Rob

* Update diagrams

* fixing spelling

* Add suggestions from Preetha and Omar

website/source/guides/operations/deployment-guide.html.md

@@ -0,0 +1,241 @@
+---
+layout: "guides"
+page_title: "Nomad Deployment Guide"
+sidebar_current: "guides-operations-deployment-guide"
+description: |-
+  This deployment guide covers the steps required to install and
+  configure a single HashiCorp Nomad cluster as defined in the
+  Nomad Reference Architecture
+product_version: 0.8
+---
+
+# Nomad Deployment Guide
+
+This deployment guide covers the steps required to install and configure a single HashiCorp Nomad cluster as defined in the [Nomad Reference Architecture](/guides/operations/reference-architecture.html).
+
+These instructions are for installing and configuring Nomad on Linux hosts running the systemd system and service manager.
+
+## Reference Material
+
+This deployment guide is designed to work in combination with the [Nomad Reference Architecture](/guides/operations/reference-architecture.html) and [Consul Deployment Guide](https://www.consul.io/docs/guides/deployment-guide.html). Although it is not a strict requirement to follow the Nomad Reference Architecture, please ensure you are familiar with the overall architecture design. For example, installing Nomad server agents on multiple physical or virtual (with correct anti-affinity) hosts for high-availability.
+
+## Overview
+
+To provide a highly-available single cluster architecture, we recommend Nomad server agents be deployed to more than one host, as shown in the [Nomad Reference Architecture](/guides/operations/reference-architecture.html).
+
+![Reference diagram](/assets/images/nomad_reference_diagram.png)
+
+These setup steps should be completed on all Nomad hosts:
+
+- [Download Nomad](#download-nomad)
+- [Install Nomad](#install-nomad)
+- [Configure systemd](#configure-systemd)
+- [Configure Nomad](#configure-nomad)
+- [Start Nomad](#start-nomad)
+
+## Download Nomad
+
+Precompiled Nomad binaries are available for download at [https://releases.hashicorp.com/nomad/](https://releases.hashicorp.com/nomad/) and Nomad Enterprise binaries are available for download by following the instructions made available to HashiCorp Enterprise customers.
+
+You should perform checksum verification of the zip packages using the SHA256SUMS and SHA256SUMS.sig files available for the specific release version. HashiCorp provides [a guide on checksum verification](https://www.hashicorp.com/security.html) for precompiled binaries.
+
+```text
+NOMAD_VERSION="0.8.4"
+curl --silent --remote-name https://releases.hashicorp.com/nomad/${NOMAD_VERSION}/nomad_${NOMAD_VERSION}_linux_amd64.zip
+curl --silent --remote-name https://releases.hashicorp.com/nomad/${NOMAD_VERSION}/nomad_${NOMAD_VERSION}_SHA256SUMS
+curl --silent --remote-name https://releases.hashicorp.com/nomad/${NOMAD_VERSION}/nomad_${NOMAD_VERSION}_SHA256SUMS.sig
+```
+
+## Install Nomad
+
+Unzip the downloaded package and move the `nomad` binary to `/usr/local/bin/`. Check `nomad` is available on the system path.
+
+```text
+unzip nomad_${NOMAD_VERSION}_linux_amd64.zip
+sudo chown root:root nomad
+sudo mv nomad /usr/local/bin/
+nomad --version
+```
+
+The `nomad` command features opt-in autocompletion for flags, subcommands, and arguments (where supported). Enable autocompletion.
+
+```text
+nomad -autocomplete-install
+complete -C /usr/local/bin/nomad nomad
+```
+
+Create a unique, non-privileged system user to run Nomad and create its data directory.
+
+```text
+sudo useradd --system --home /etc/nomad.d --shell /bin/false nomad
+sudo mkdir --parents /opt/nomad
+sudo chown --recursive nomad:nomad /opt/nomad
+```
+
+## Configure systemd
+
+Systemd uses [documented sane defaults](https://www.freedesktop.org/software/systemd/man/systemd.directives.html) so only non-default values must be set in the configuration file.
+
+Create a Nomad service file at /etc/systemd/system/nomad.service.
+
+```text
+sudo touch /etc/systemd/system/nomad.service
+```
+
+Add this configuration to the Nomad service file:
+
+```text
+[Unit]
+Description="HashiCorp Nomad - An application and service scheduler"
+Documentation=https://www.nomad.io/docs/
+Requires=network-online.target
+After=network-online.target
+ConditionFileNotEmpty=/etc/nomad.d/nomad.hcl
+
+[Service]
+User=nomad
+Group=nomad
+ExecStart=/usr/local/bin/nomad agent -config=/etc/nomad.d/
+ExecReload=/bin/kill --signal HUP $MAINPID
+KillMode=process
+Restart=on-failure
+RestartSec=2
+StartLimitBurst=3
+StartLimitIntervalSec=10
+LimitNOFILE=65536
+
+[Install]
+WantedBy=multi-user.target
+```
+
+The following parameters are set for the `[Unit]` stanza:
+
+- [`Description`](https://www.freedesktop.org/software/systemd/man/systemd.unit.html#Description=) - Free-form string describing the nomad service
+- [`Documentation`](https://www.freedesktop.org/software/systemd/man/systemd.unit.html#Documentation=) - Link to the nomad documentation
+- [`Requires`](https://www.freedesktop.org/software/systemd/man/systemd.unit.html#Requires=) - Configure a requirement dependency on the network service
+- [`After`](https://www.freedesktop.org/software/systemd/man/systemd.unit.html#Before=) - Configure an ordering dependency on the network service being started before the nomad service
+- [`ConditionFileNotEmpty`](https://www.freedesktop.org/software/systemd/man/systemd.unit.html#ConditionArchitecture=) - Check for a non-zero sized configuration file before nomad is started
+
+The following parameters are set for the `[Service]` stanza:
+
+- [`User`, `Group`](https://www.freedesktop.org/software/systemd/man/systemd.exec.html#User=) - Run nomad as the nomad user
+- [`ExecStart`](https://www.freedesktop.org/software/systemd/man/systemd.service.html#ExecStart=) - Start nomad with the `agent` argument and path to the configuration file
+- [`ExecReload`](https://www.freedesktop.org/software/systemd/man/systemd.service.html#ExecReload=) - Send nomad a SIGHUP signal to trigger a configuration reload in nomad
+- [`KillMode`](https://www.freedesktop.org/software/systemd/man/systemd.kill.html#KillMode=) - Treat nomad as a single process
+- [`Restart`](https://www.freedesktop.org/software/systemd/man/systemd.service.html#Restart=) - Restart nomad unless it returned a clean exit code
+- [`RestartSec`](https://www.freedesktop.org/software/systemd/man/systemd.service.html#RestartSec=) - Restart nomad after 2 seconds of it being considered 'failed'
+- [`StartLimitBurst`, `StartLimitIntervalSec`](https://www.freedesktop.org/software/systemd/man/systemd.unit.html#StartLimitIntervalSec=interval) - Configure unit start rate limiting
+- [`LimitNOFILE`](https://www.freedesktop.org/software/systemd/man/systemd.exec.html#Process%20Properties) - Set an increased Limit for File Descriptors
+
+The following parameters are set for the `[Install]` stanza:
+
+- [`WantedBy`](https://www.freedesktop.org/software/systemd/man/systemd.unit.html#WantedBy=) - Creates a weak dependency on nomad being started by the multi-user run level
+
+## Configure Nomad
+
+Nomad uses [documented sane defaults](/docs/configuration/index.html) so only non-default values must be set in the configuration file. Configuration can be read from multiple files and is loaded in lexical order. See the [full description](/docs/configuration/index.html) for more information about configuration loading and merge semantics.
+
+Some configuration settings are common to both server and client Nomad agents, while some configuration settings must only exist on one or the other. Follow the [common configuration](#common-configuration) guidance on all hosts and then the specific guidance depending on whether you are configuring a Nomad [server](#server-configuration) or [client](#client-configuration).
+
+- [Common Nomad configuration](#common-configuration)
+- [Configure a Nomad server](#server-configuration)
+- [Configure a Nomad client](#client-configuration)
+
+### Common configuration
+
+Create a configuration file at `/etc/nomad.d/nomad.hcl`:
+
+```text
+sudo mkdir --parents /etc/nomad.d
+sudo touch /etc/nomad.d/nomad.hcl
+sudo chown --recursive nomad:nomad /etc/nomad.d
+sudo chmod 640 /etc/nomad.d/nomad.hcl
+```
+
+Add this configuration to the `nomad.hcl` configuration file:
+
+~> **Note:** Replace the `datacenter` parameter value with the identifier you will use for the datacenter this Nomad cluster is deployed in.
+
+```hcl
+datacenter = "dc1"
+data_dir = "/opt/nomad"
+```
+
+- [`datacenter`](/docs/configuration/index.html#datacenter) - The datacenter in which the agent is running.
+- [`data_dir`](/docs/configuration/index.html#data_dir) - The data directory for the agent to store state.
+
+### Server configuration
+
+Create a configuration file at `/etc/nomad.d/server.hcl`:
+
+```text
+sudo mkdir --parents /etc/nomad.d
+sudo touch /etc/nomad.d/server.hcl
+sudo chown --recursive nomad:nomad /etc/nomad.d
+sudo chmod 640 /etc/nomad.d/server.hcl
+```
+
+Add this configuration to the `server.hcl` configuration file:
+
+~> **NOTE** Replace the `bootstrap_expect` value with the number of Nomad servers you will use; three or five [is recommended](/docs/internals/consensus.html#deployment-table).
+
+```hcl
+server {
+  enabled = true
+  bootstrap_expect = 3
+}
+```
+
+- [`server`](/docs/configuration/server.html#enabled) - Specifies if this agent should run in server mode. All other server options depend on this value being set.
+- [`bootstrap-expect`](/docs/configuration/server.html#bootstrap_expect) - This flag provides the number of expected servers in the datacenter. Either this value should not be provided or the value must agree with other servers in the cluster.
+
+### Client configuration
+
+Create a configuration file at `/etc/nomad.d/client.hcl`:
+
+```text
+sudo mkdir --parents /etc/nomad.d
+sudo touch /etc/nomad.d/client.hcl
+sudo chown --recursive nomad:nomad /etc/nomad.d
+sudo chmod 640 /etc/nomad.d/client.hcl
+```
+
+Add this configuration to the `client.hcl` configuration file:
+
+```hcl
+client {
+  enabled = true
+}
+```
+
+- [`client`](/docs/configuration/client.html#enabled) - Specifies if this agent should run in client mode. All other client options depend on this value being set.
+
+~> **NOTE** The [`options`](/docs/configuration/client.html#options-parameters) parameter can be used to enable or disable specific configurations on Nomad clients, unique to your use case requirements.
+
+### ACL configuration
+
+The [Access Control](/guides/security/acl.html) guide provides instructions on configuring and enabling ACLs.
+
+### TLS configuration
+
+Securing Nomad's cluster communication with mutual TLS (mTLS) is recommended for production deployments and can even ease operations by preventing mistakes and misconfigurations. Nomad clients and servers should not be publicly accessible without mTLS enabled.
+
+The [Securing Nomad with TLS](/guides/security/securing-nomad.html) guide provides instructions on configuring and enabling TLS.
+
+## Start Nomad
+
+Enable and start Nomad using the systemctl command responsible for controlling systemd managed services. Check the status of the nomad service using systemctl.
+
+```text
+sudo systemctl enable nomad
+sudo systemctl start nomad
+sudo systemctl status nomad
+```
+
+## Next Steps
+
+- Read [Outage Recovery](/guides/operations/outage.html) to learn
+  the steps required to recover from a Nomad cluster outage.
+- Read [Autopilot](/guides/operations/autopilot.html) to learn about
+  features in Nomad 0.8 to allow for automatic operator-friendly
+  management of Nomad servers.