open-nomad/website/source/docs/upgrade/index.html.md

---
layout: "docs"
page_title: "Upgrading Nomad"
sidebar_current: "docs-upgrade-upgrading"
description: |-
  Learn how to upgrade Nomad.
---

# Upgrading Nomad

This page documents how to upgrade Nomad when a new version is released.

~> **Upgrade Warning!** Both Nomad Clients and Servers are meant to be 
long-running processes that maintain communication with each other. Nomad 
Servers maintain quorum with other Servers and Clients are in constant 
communication with Servers. As such, care should be taken to properly 
upgrade Nomad to ensure minimal service disruption. Unsafe upgrades can
cause a service outage.

## Upgrade Process

For upgrades we strive to ensure backwards compatibility. For most upgrades, the
process is as simple as upgrading the binary and restarting the service.

Prior to starting the upgrade please check the 
[specific version details](/docs/upgrade/upgrade-specific.html) page as some 
version differences may require specific steps.

At a high level we complete the following steps to upgrade Nomad:

* **Add the new version**
* **Check cluster health**
* **Remove the old version**
* **Check cluster health**
* **Upgrade clients**

### 1. Add the new version to the existing cluster

Whether you are replacing the software in place on existing systems or bringing
up new hosts you should make changes incrementally, verifying cluster health at
each step of the upgrade  

On a single server, install the new version of Nomad.  You can do this by
joining a new server to the cluster or by replacing or upgrading the binary
locally and restarting the service.

### 2. Check cluster health

Monitor the Nomad logs on the remaining nodes to check the new node has entered
the cluster correctly.

Run `nomad agent-info` on the new server and check that the `last_log_index` is
of a similar value to the other nodes.  This step ensures that changes have been
replicated to the new node.

```
ubuntu@nomad-server-10-1-1-4:~$ nomad agent-info
nomad
  bootstrap = false
  known_regions = 1
  leader = false
  server = true
raft
  applied_index = 53460
  commit_index = 53460
  fsm_pending = 0
  last_contact = 54.512216ms
  last_log_index = 53460
  last_log_term = 1
  last_snapshot_index = 49511
  last_snapshot_term = 1
  num_peers = 2
...
```

Continue with the upgrades across the Server fleet making sure to do a single Nomad
server at a time.  You can check state of the servers and clients with the
`nomad server-members` and `nomad node-status` commands which indicate state of the
nodes.

### 3. Remove the old versions from servers

If you are doing an in place upgrade on existing servers this step is not
necessary as the version was changed in place.

If you are doing an upgrade by adding new servers and removing old servers
from the fleet you need to ensure that the server has left the fleet safely.

1. Stop the service on the existing host
2. On another server issue a `nomad server-members` and check the status, if 
the server is now in a left state you are safe to continue.
3. If the server is not in a left state, issue a `nomad server-force-leave <server id>`
to remove the server from the cluster.

Monitor the logs of the other hosts in the Nomad cluster over this period.

### 4. Check cluster health

Use the same actions in step #2 above to confirm cluster health.

### 5. Upgrade clients

Following the successful upgrade of the servers you can now update your
clients using a similar process as the servers.  If you wish to gracefully
move tasks on a client use the `nomad node-drain <node-id>` command to 
gracefully migrate jobs to another client in the cluster.  The `node-drain` 
command prevents new tasks from being allocated to the client and begins 
migrating existing allocations to another client.

## Done! 

You are now running the latest Nomad version. You can verify all
Clients joined by running `nomad node-status` and checking all the clients
are in a `ready` state.