---
layout: docs
page_title: Upgrade Guides
sidebar_title: Specific Version Details
description: |-
  Specific versions of Nomad may have additional information about the upgrade
  process beyond the standard flow.
---

# Upgrade Guides

The [upgrading page](/docs/upgrade) covers the details of doing
a standard upgrade. However, specific versions of Nomad may have more
details provided for their upgrades as a result of new features or changed
behavior. This page is used to document those details separately from the
standard upgrade flow.

## Nomad 1.0.0

### HCL2 for Job specification

Nomad 1.0.0 adopts HCL2 for parsing the job spec. HCL2 extends HCL with more
expression and reuse support, but adds some stricter schema for HCL blocks (a.k.a. stanzas).  Check [HCL](/docs/job-specification/hcl2) for more details.

### Signal used when stopping Docker tasks

When stopping tasks running with the Docker task driver, Nomad documents that a
`SIGTERM` will be issued (unless configured with `kill_signal`). However, recent
versions of Nomad would issue `SIGINT` instead. Starting again with Nomad v1.0.0
`SIGTERM` will be sent by default when stopping Docker tasks.

### Deprecated metrics have been removed

Nomad v0.7.0 added supported for tagged metrics and deprecated untagged metrics.
There was support for configuring backwards-compatible metrics. This support has
been removed with v1.0.0, and all metrics will be emitted with tags.

### Null characters in region, datacenter, job name/ID, task group name, and task names

Starting with Nomad v1.0.0, jobs will fail validation if any of the following
contain null character: the job ID or name, the task group name, or the task name. Any
jobs meeting this requirement should be modified before an update to v1.0.0. Similarly,
client and server config validation will prohibit either the region or the datacenter
from containing null characters.

### EC2 CPU characteristics may be different

Starting with Nomad v1.0.0, the AWS fingerprinter uses data derived from the
official AWS EC2 API to determine default CPU performance characteristics, including
core count and core speed. This data should be accurate for each instance type
per region. Previously, Nomad used a hand-made lookup table that was not region
aware and may have contained inaccurate or incomplete data. As part of this change,
the AWS fingerprinter no longer sets the `cpu.modelname` attribute.

As before, `cpu_total_compute` can be used to override the discovered CPU resources
available to the Nomad client.

### Inclusive language

Starting with Nomad v1.0.0, the terms `blacklist` and `whitelist` have been
deprecated from client configuration and driver configuration. The existing
configuration values are permitted but will be removed in a future version of
Nomad. The specific configuration values replaced are:

* Client `driver.blacklist` is replaced with `driver.denylist`.
* Client `driver.whitelist` is replaced with `driver.allowlist`.
* Client `env.blacklist` is replaced with `env.denylist`.
* Client `fingerprint.blacklist` is replaced with `fingerprint.denylist`.
* Client `fingerprint.whitelist` is replaced with `fingerprint.allowlist`.
* Client `user.blacklist` is replaced with `user.denylist`.
* Client `template.function_blacklist` is replaced with `template.function_denylist`.
* Docker driver `docker.caps.whitelist` is replaced with `docker.caps.allowlist`.

### Envoy proxy versions

Nomad 1.0.0 changes the behavior around the selection of Envoy version used
for Connect sidecar proxies. Previously, Nomad always defaulted to Envoy v1.11.2
if neither the `meta.connect.sidecar_image` parameter or `sidecar_task` stanza
were explicitly configured. Likewise the same version of Envoy would be used for
Connect ingress gateways if `meta.connect.gateway_image` was unset. Starting with
Nomad 1.0.0, each Nomad Client will query Consul for a list of supported Envoy
versions. Nomad will make use of the latest version of Envoy supported by the
Consul agent when launching Envoy as a Connect sidecar proxy. If the version of
the Consul agent is older than v1.7.8, v1.8.4, or v1.9.0, Nomad will fallback to
the v1.11.2 version of Envoy. As before, if the `meta.connect.sidecar_image`,
 `meta.connect.gateway_image`, or `sidecar_task` stanza are set, those settings
take precedence.

When upgrading Nomad Clients from a previous version to v1.0.0 and above, it is
recommended to also upgrade the Consul agents to v1.7.8, 1.8.4, or v1.9.0 or newer.
Upgrading Nomad and Consul to versions that support the new behaviour while also doing a
full [node drain](https://www.nomadproject.io/docs/upgrade#5-upgrade-clients) at
the time of the upgrade for each node will ensure Connect workloads are properly
rescheduled onto nodes in such a way that the Nomad Clients, Consul agents, and
Envoy sidecar tasks maintain compatibility with one another.

## Nomad 0.12.8

### Docker volume mounts

Nomad 0.12.8 includes security fixes for the handling of Docker volume mounts:

- The `docker.volumes.enabled` flag now defaults to `false` as documented.
- Docker driver mounts of type "volume" (but not "bind") were not sandboxed
  and could mount arbitrary locations from the client host. The
  `docker.volumes.enabled` configuration will now disable Docker mounts with
  type "volume" when set to `false` (the default).

This change Docker impacts jobs that use a `mounts` with type "volume", as
shown below. This job will fail when placed unless `docker.volumes.enabled =
true`.

```hcl
mounts = [
  {
    type     = "volume"
    target   = "/path/in/container"
    source   = "docker_volume"
    volume_options = {
      driver_config = {
        name = "local"
        options = [
          {
            device = "/"
            o      = "ro,bind"
            type   = "ext4"
          }
        ]
      }
    }
  }
]
```

## Nomad 0.12.6

### Artifact and Template Paths

Nomad 0.12.6 includes security fixes for privilege escalation vulnerabilities
in handling of job `template` and `artifact` stanzas:

- The `template.source` and `template.destination` fields are now protected by
  the file sandbox introduced in 0.9.6. These paths are now restricted to fall
  inside the task directory by default. An operator can opt-out of this
  protection with the
  [`template.disable_file_sandbox`](/docs/configuration/client#template-parameters)
  field in the client configuration.
- The paths for `template.source`, `template.destination`, and
  `artifact.destination` are validated on job submission to ensure the paths
  do not escape the file sandbox. It was possible to use interpolation to
  bypass this validation. The client now interpolates the paths before
  checking if they are in the file sandbox.

~> **Warning:** Due to a [bug][gh-9148] in Nomad v0.12.6, the
`template.destination` and `artifact.destination` paths do not support
absolute paths, including the interpolated `NOMAD_SECRETS_DIR`,
`NOMAD_TASK_DIR`, and `NOMAD_ALLOC_DIR` variables. This bug is fixed in
v0.12.9. To work around the bug, use a relative path.

## Nomad 0.12.0

### `mbits` and Task Network Resource deprecation

Starting in Nomad 0.12.0 the `mbits` field of the network resource block has
been deprecated and is no longer considered when making scheduling decisions.
This is in part because we felt that `mbits` didn't accurately account network
bandwidth as a resource.

Additionally the use of the `network` block inside of a task's `resource` block is
also deprecated. Users are advised to move their `network` block to the `group`
block. Recent networking features have only been added to group based network
configuration. If any usecase or feature which was available with task network
resource is not fulfilled with group network configuration, please open an issue
detailing the missing capability.

### Enterprise Licensing

Enterprise binaries for Nomad are now publicly available via
[releases.hashicorp.com](https://releases.hashicorp.com/nomad/). By default all
enterprise features are enabled for 6 hours. During that time enterprise users
should apply their license with the [`nomad license put ...`](/docs/commands/license/put) command.

Once the 6 hour demonstration period expires, Nomad will shutdown. If restarted
Nomad will shutdown in a very short amount of time unless a valid license is
applied.

~> **Warning:** Due to a [bug][gh-8457] in Nomad v0.12.0, existing clusters
that are upgraded will **not** have 6 hours to apply a license. The minimal
grace period should be sufficient to apply a valid license, but enterprise
users are encouraged to delay upgrading until Nomad v0.12.1 is released and
fixes the issue.

### Docker access host filesystem

Nomad 0.12.0 disables Docker tasks access to the host filesystem, by default.
Prior to Nomad 0.12, Docker tasks may mount and then manipulate any host file
and may pose a security risk.

Operators now must explicitly allow tasks to access host filesystem. [Host
Volumes](/docs/configuration/client#host_volume-stanza) provide a fine tune
access to individual paths.

To restore pre-0.12.0 behavior, you can enable [Docker
`volume`](/docs/drivers/docker#enabled-1) to allow binding host paths, by adding
the following to the nomad client config file:

```hcl
plugin "docker" {
  config {
    volumes {
      enabled = true
    }
  }
}
```

### Qemu images

Nomad 0.12.0 restricts the paths the Qemu tasks can load an image from. A Qemu
task may download an image to the allocation directory to load. But images
outside the allocation directories must be explicitly allowed by operators in
the client agent configuration file.

For example, you may allow loading Qemu images from `/mnt/qemu-images` by
adding the following to the agent configuration file:

```hcl
plugin "qemu" {
  config {
    image_paths = ["/mnt/qemu-images"]
  }
}
```

## Nomad 0.11.7

### Docker volume mounts

Nomad 0.11.7 includes a security fix for the handling of Docker volume
mounts. Docker driver mounts of type "volume" (but not "bind") were not
sandboxed and could mount arbitrary locations from the client host. The
`docker.volumes.enabled` configuration will now disable Docker mounts with
type "volume" when set to `false`.

This change Docker impacts jobs that use a `mounts` with type "volume", as
shown below. This job will fail when placed unless `docker.volumes.enabled =
true`.

```hcl
mounts = [
  {
    type     = "volume"
    target   = "/path/in/container"
    source   = "docker_volume"
    volume_options = {
      driver_config = {
        name = "local"
        options = [
          {
            device = "/"
            o      = "ro,bind"
            type   = "ext4"
          }
        ]
      }
    }
  }
]
```

## Nomad 0.11.5

### Artifact and Template Paths

Nomad 0.11.5 includes backported security fixes for privilege escalation
vulnerabilities in handling of job `template` and `artifact` stanzas:

- The `template.source` and `template.destination` fields are now protected by
  the file sandbox introduced in 0.9.6. These paths are now restricted to fall
  inside the task directory by default. An operator can opt-out of this
  protection with the
  [`template.disable_file_sandbox`](/docs/configuration/client#template-parameters)
  field in the client configuration.
- The paths for `template.source`, `template.destination`, and
  `artifact.destination` are validated on job submission to ensure the paths
  do not escape the file sandbox. It was possible to use interpolation to
  bypass this validation. The client now interpolates the paths before
  checking if they are in the file sandbox.

~> **Warning:** Due to a [bug][gh-9148] in Nomad v0.11.5, the
`template.destination` and `artifact.destination` paths do not support
absolute paths, including the interpolated `NOMAD_SECRETS_DIR`,
`NOMAD_TASK_DIR`, and `NOMAD_ALLOC_DIR` variables. This bug is fixed in
v0.11.6. To work around the bug, use a relative path.

## Nomad 0.11.3

Nomad 0.11.3 fixes a critical bug causing the nomad agent to become
unresponsive. The issue is due to a [Go 1.14.1 runtime
bug](https://github.com/golang/go/issues/38023) and affects Nomad 0.11.1 and
0.11.2.

## Nomad 0.11.2

### Scheduler Scoring Changes

Prior to Nomad 0.11.2 the scheduler algorithm used a [node's reserved
resources][reserved]
incorrectly during scoring. The result of this bug was that scoring biased in
favor of nodes with reserved resources vs nodes without reserved resources.

Placements will be more correct but slightly different in v0.11.2 vs earlier
versions of Nomad. Operators do _not_ need to take any actions as the impact of
the bug fix will only minimally affect scoring.

Feasability (whether a node is capable of running a job at all) is _not_
affected.

### Periodic Jobs and Daylight Saving Time

Nomad 0.11.2 fixed a long outstanding bug affecting periodic jobs that are
scheduled to run during Daylight Saving Time transitions.

Nomad 0.11.2 provides a more defined behavior: Nomad evaluates the cron
expression with respect to specified time zone during transition. A 2:30am
nightly job with `America/New_York` time zone will not run on the day daylight
saving time starts; similarly, a 1:30am nightly job will run twice on the day
daylight saving time ends. See the [Daylight Saving Time][dst] documentation
for details.

## Nomad 0.11.0

### client.template: `vault_grace` deprecation

Nomad 0.11.0 updates
[consul-template](https://github.com/hashicorp/consul-template) to v0.24.1.
This library deprecates the [`vault_grace`][vault_grace] option for templating
included in Nomad. The feature has been ignored since Vault 0.5 and as long as
you are running a more recent version of Vault, you can safely remove
`vault_grace` from your Nomad jobs.

### Rkt Task Driver Removed

The `rkt` task driver has been deprecated and removed from Nomad. While the
code is available in an external repository,
[https://github.com/hashicorp/nomad-driver-rkt](https://github.com/hashicorp/nomad-driver-rkt),
it will not be maintained as `rkt` is [no longer being developed
upstream](https://github.com/rkt/rkt). We encourage all `rkt` users to find a
new task driver as soon as possible.

## Nomad 0.10.8

### Docker volume mounts

Nomad 0.10.8 includes a security fix for the handling of Docker volume
mounts. Docker driver mounts of type "volume" (but not "bind") were not
sandboxed and could mount arbitrary locations from the client host. The
`docker.volumes.enabled` configuration will now disable Docker mounts with
type "volume" when set to `false`.

This change Docker impacts jobs that use a `mounts` with type "volume", as
shown below. This job will fail when placed unless `docker.volumes.enabled =
true`.

```hcl
mounts = [
  {
    type     = "volume"
    target   = "/path/in/container"
    source   = "docker_volume"
    volume_options = {
      driver_config = {
        name = "local"
        options = [
          {
            device = "/"
            o      = "ro,bind"
            type   = "ext4"
          }
        ]
      }
    }
  }
]
```

## Nomad 0.10.6

### Artifact and Template Paths

Nomad 0.10.6 includes backported security fixes for privilege escalation
vulnerabilities in handling of job `template` and `artifact` stanzas:

- The `template.source` and `template.destination` fields are now protected by
  the file sandbox introduced in 0.9.6. These paths are now restricted to fall
  inside the task directory by default. An operator can opt-out of this
  protection with the
  [`template.disable_file_sandbox`](/docs/configuration/client#template-parameters)
  field in the client configuration.
- The paths for `template.source`, `template.destination`, and
  `artifact.destination` are validated on job submission to ensure the paths
  do not escape the file sandbox. It was possible to use interpolation to
  bypass this validation. The client now interpolates the paths before
  checking if they are in the file sandbox.

~> **Warning:** Due to a [bug][gh-9148] in Nomad v0.10.6, the
`template.destination` and `artifact.destination` paths do not support
absolute paths, including the interpolated `NOMAD_SECRETS_DIR`,
`NOMAD_TASK_DIR`, and `NOMAD_ALLOC_DIR` variables. This bug is fixed in
v0.10.7. To work around the bug, use a relative path.

## Nomad 0.10.4

### Same-Node Scheduling Penalty Removed

Nomad 0.10.4 includes a fix to the scheduler that removes the
same-node penalty for allocations that have not previously failed. In
earlier versions of Nomad, the node where an allocation was running
was penalized from receiving updated versions of that allocation,
resulting in a higher chance of the allocation being placed on a new
node. This was changed so that the penalty only applies to nodes where
the previous allocation has failed or been rescheduled, to reduce the
risk of correlated failures on a host. Scheduling weighs a number of
factors, but this change should reduce movement of allocations that
are being updated from a healthy state. You can view the placement
metrics for an allocation with `nomad alloc status -verbose`.

### Additional Environment Variable Filtering

Nomad will by default prevent certain environment variables set in the client
process from being passed along into launched tasks. The `CONSUL_HTTP_TOKEN`
environment variable has been added to the default list. More information can
be found in the `env.blacklist` [configuration](/docs/configuration/client#env-blacklist) .

## Nomad 0.10.3

### mTLS Certificate Validation

Nomad 0.10.3 includes a fix for a privilege escalation vulnerability in
validating TLS certificates for RPC with mTLS. Nomad RPC endpoints validated
that TLS client certificates had not expired and were signed by the same CA as
the Nomad node, but did not correctly check the certificate's name for the role
and region as described in the [Securing Nomad with TLS][tls-guide] guide. This
allows trusted operators with a client certificate signed by the CA to send RPC
calls as a Nomad client or server node, bypassing access control and accessing
any secrets available to a client.

Nomad clusters configured for mTLS following the [Securing Nomad with TLS][tls-guide]
guide or the [Vault PKI Secrets Engine Integration][tls-vault-guide] guide
should already have certificates that will pass validation. Before upgrading to
Nomad 0.10.3, operators using mTLS with `verify_server_hostname = true` should
confirm that the common name or SAN of all Nomad client node certs is
`client.<region>.nomad`, and that the common name or SAN of all Nomad server
node certs is `server.<region>.nomad`.

### Connection Limits Added

Nomad 0.10.3 introduces the [limits][limits] agent configuration parameters for
mitigating denial of service attacks from users who are not authenticated via
mTLS. The default limits stanza is:

```hcl
limits {
  https_handshake_timeout   = "5s"
  http_max_conns_per_client = 100
  rpc_handshake_timeout     = "5s"
  rpc_max_conns_per_client  = 100
}
```

If your Nomad agent's endpoints are protected from unauthenticated users via
other mechanisms these limits may be safely disabled by setting them to `0`.

However the defaults were chosen to be safe for a wide variety of Nomad
deployments and may protect against accidental abuses of the Nomad API that
could cause unintended resource usage.

## Nomad 0.10.2

### Preemption Panic Fixed

Nomad 0.9.7 and 0.10.2 fix a [server crashing bug][gh-6787] present in
scheduler preemption since 0.9.0. Users unable to immediately upgrade Nomad can
[disable preemption][preemption-api] to avoid the panic.

### Dangling Docker Container Cleanup

Nomad 0.10.2 addresses an issue occurring in heavily loaded clients, where
containers are started without being properly managed by Nomad. Nomad 0.10.2
introduced a reaper that detects and kills such containers.

Operators may opt to run reaper in a dry-mode or disabling it through a client config.

For more information, see [Docker Dangling containers][dangling-containers].

## Nomad 0.10.0

### Deployments

Nomad 0.10 enables rolling deployments for service jobs by default
and adds a default update stanza when a service job is created or updated.
This does not affect jobs with an update stanza.

In pre-0.10 releases, when updating a service job without an update stanza,
all existing allocations are stopped while new allocations start up,
and this may cause a service degradation or an outage.
You can regain this behavior and disable deployments by setting `max_parallel` to 0.

For more information, see [`update` stanza][update].

## Nomad 0.9.5

### Template Rendering

Nomad 0.9.5 includes security fixes for privilege escalation vulnerabilities in handling of job `template` stanzas:

- The client host's environment variables are now cleaned before rendering the template. If a template includes the `env` function, the job should include an [`env`](/docs/job-specification/env) stanza to allow access to the variable in the template.
- The `plugin` function is no longer permitted by default and will raise an error if used in a template. Operator can opt-in to permitting this function with the new [`template.function_blacklist`](/docs/configuration/client#template-parameters) field in the client configuration.
- The `file` function has been changed to restrict paths to fall inside the task directory by default. Paths that used the `NOMAD_TASK_DIR` environment variable to prefix file paths should work unchanged. Relative paths or symlinks that point outside the task directory will raise an error. An operator can opt-out of this protection with the new [`template.disable_file_sandbox`](/docs/configuration/client#template-parameters) field in the client configuration.

## Nomad 0.9.0

### Preemption

Nomad 0.9 adds preemption support for system jobs. If a system job is submitted
that has a higher priority than other running jobs on the node, and the node
does not have capacity remaining, Nomad may preempt those lower priority
allocations to place the system job. See [preemption][preemption] for more
details.

### Task Driver Plugins

All task drivers have become [plugins][plugins] in Nomad 0.9.0. There are two
user visible differences between 0.8 and 0.9 drivers:

- [LXC][lxc] is now community supported and distributed independently.
- Task driver [`config`][task-config] stanzas are no longer validated by
  the [`nomad job validate`][validate] command. This is a regression that will
  be fixed in a future release.

There is a new method for client driver configuration options, but existing
`client.options` settings are supported in 0.9. See [plugin
configuration][plugin-stanza] for details.

#### LXC

LXC is now an external plugin and must be installed separately. See [the LXC
driver's documentation][lxc] for details.

### Structured Logging

Nomad 0.9.0 switches to structured logging. Any log processing on the pre-0.9
log output will need to be updated to match the structured output.

Structured log lines have the format:

```
# <Timestamp> [<Level>] <Component>: <Message>: <KeyN>=<ValueN> ...

2019-01-29T05:52:09.221Z [INFO ] client.plugin: starting plugin manager: plugin-type=device
```

Values containing whitespace will be quoted:

```
... starting plugin: task=redis args="[/opt/gopath/bin/nomad logmon]"
```

### HCL2 Transition

Nomad 0.9.0 begins a transition to [HCL2][hcl2], the next version of the
HashiCorp configuration language. While Nomad has begun integrating HCL2,
users will need to continue to use HCL1 in Nomad 0.9.0 as the transition is
incomplete.

If you interpolate variables in your [`task.config`][task-config] containing
consecutive dots in their name, you will need to change your job specification
to use the `env` map. See the following example:

```hcl
env {
  # Note the multiple consecutive dots
  image...version = "3.2"

  # Valid in both v0.8 and v0.9
  image.version = "3.2"
}

# v0.8 task config stanza:
task {
  driver = "docker"
  config {
    image = "redis:${image...version}"
  }
}

# v0.9 task config stanza:
task {
  driver = "docker"
  config {
    image = "redis:${env["image...version"]}"
  }
}
```

This only affects users who interpolate unusual variables with multiple
consecutive dots in their task `config` stanza. All other interpolation is
unchanged.

Since HCL2 uses dotted object notation for interpolation users should
transition away from variable names with multiple consecutive dots.

### Downgrading clients

Due to the large refactor of the Nomad client in 0.9, downgrading to a
previous version of the client after upgrading it to Nomad 0.9 is not supported.
To downgrade safely, users should erase the Nomad client's data directory.

### `port_map` Environment Variable Changes

Before Nomad 0.9.0 ports mapped via a task driver's `port_map` stanza could be
interpolated via the `NOMAD_PORT_<label>` environment variables.

However, in Nomad 0.9.0 no parameters in a driver's `config` stanza, including
its `port_map`, are available for interpolation. This means `{{ env NOMAD_PORT_<label> }}` in a `template` stanza or `HTTP_PORT = "${NOMAD_PORT_http}"` in an `env` stanza will now interpolate the _host_ ports,
not the container's.

Nomad 0.10 introduced Task Group Networking which natively supports port
mapping without relying on task driver specific `port_map` fields. The
[`to`](/docs/job-specification/network#to) field on group network port stanzas
will be interpolated properly. Please see the
[`network`](/docs/job-specification/network/) stanza documentation for details.

## Nomad 0.8.0

### Raft Protocol Version Compatibility

When upgrading to Nomad 0.8.0 from a version lower than 0.7.0, users will need
to set the
[`raft_protocol`](/docs/configuration/server#raft_protocol) option
in their `server` stanza to 1 in order to maintain backwards compatibility with
the old servers during the upgrade. After the servers have been migrated to
version 0.8.0, `raft_protocol` can be moved up to 2 and the servers restarted
to match the default.

The Raft protocol must be stepped up in this way; only adjacent version numbers are
compatible (for example, version 1 cannot talk to version 3). Here is a table of the
Raft Protocol versions supported by each Nomad version:

<table>
  <thead>
    <tr>
      <th>Version</th>
      <th>Supported Raft Protocols</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>0.6 and earlier</td>
      <td>0</td>
    </tr>
    <tr>
      <td>0.7</td>
      <td>1</td>
    </tr>
    <tr>
      <td>0.8 and later</td>
      <td>1, 2, 3</td>
    </tr>
  </tbody>
</table>

In order to enable all [Autopilot](https://learn.hashicorp.com/tutorials/nomad/autopilot) features, all servers
in a Nomad cluster must be running with Raft protocol version 3 or later.

#### Upgrading to Raft Protocol 3

This section provides details on upgrading to Raft Protocol 3 in Nomad 0.8 and higher. Raft protocol version 3 requires Nomad running 0.8.0 or newer on all servers in order to work. See [Raft Protocol Version Compatibility](/docs/upgrade/upgrade-specific#raft-protocol-version-compatibility) for more details. Also the format of `peers.json` used for outage recovery is different when running with the latest Raft protocol. See [Manual Recovery Using peers.json](https://learn.hashicorp.com/tutorials/nomad/outage-recovery#manual-recovery-using-peersjson) for a description of the required format.

Please note that the Raft protocol is different from Nomad's internal protocol as shown in commands like `nomad server members`. To see the version of the Raft protocol in use on each server, use the `nomad operator raft list-peers` command.

The easiest way to upgrade servers is to have each server leave the cluster, upgrade its `raft_protocol` version in the `server` stanza, and then add it back. Make sure the new server joins successfully and that the cluster is stable before rolling the upgrade forward to the next server. It's also possible to stand up a new set of servers, and then slowly stand down each of the older servers in a similar fashion.

When using Raft protocol version 3, servers are identified by their `node-id` instead of their IP address when Nomad makes changes to its internal Raft quorum configuration. This means that once a cluster has been upgraded with servers all running Raft protocol version 3, it will no longer allow servers running any older Raft protocol versions to be added. If running a single Nomad server, restarting it in-place will result in that server not being able to elect itself as a leader. To avoid this, either set the Raft protocol back to 2, or use [Manual Recovery Using peers.json](https://learn.hashicorp.com/tutorials/nomad/outage-recovery#manual-recovery-using-peersjson) to map the server to its node ID in the Raft quorum configuration.

### Node Draining Improvements

Node draining via the [`node drain`][drain-cli] command or the [drain
API][drain-api] has been substantially changed in Nomad 0.8. In Nomad 0.7.1 and
earlier draining a node would immediately stop all allocations on the node
being drained. Nomad 0.8 now supports a [`migrate`][migrate] stanza in job
specifications to control how many allocations may be migrated at once and the
default will be used for existing jobs.

The `drain` command now blocks until the drain completes. To get the Nomad
0.7.1 and earlier drain behavior use the command: `nomad node drain -enable -force -detach <node-id>`

See the [`migrate` stanza documentation][migrate] and [Decommissioning Nodes
guide](https://learn.hashicorp.com/tutorials/nomad/node-drain) for details.

### Periods in Environment Variable Names No Longer Escaped

_Applications which expect periods in environment variable names to be replaced
with underscores must be updated._

In Nomad 0.7 periods (`.`) in environment variables names were replaced with an
underscore in both the [`env`](/docs/job-specification/env) and
[`template`](/docs/job-specification/template) stanzas.

In Nomad 0.8 periods are _not_ replaced and will be included in environment
variables verbatim.

For example the following stanza:

```text
env {
  registry.consul.addr = "${NOMAD_IP_http}:8500"
}
```

In Nomad 0.7 would be exposed to the task as
`registry_consul_addr=127.0.0.1:8500`. In Nomad 0.8 it will now appear exactly
as specified: `registry.consul.addr=127.0.0.1:8500`.

### Client APIs Unavailable on Older Nodes

Because Nomad 0.8 uses a new RPC mechanism to route node-specific APIs like
[`nomad alloc fs`](/docs/commands/alloc/fs) through servers to the node,
0.8 CLIs are incompatible using these commands on clients older than 0.8.

To access these commands on older clients either continue to use a pre-0.8
version of the CLI, or upgrade all clients to 0.8.

### CLI Command Changes

Nomad 0.8 has changed the organization of CLI commands to be based on
subcommands. An example of this change is the change from `nomad alloc-status`
to `nomad alloc status`. All commands have been made to be backwards compatible,
but operators should update any usage of the old style commands to the new style
as the old style will be deprecated in future versions of Nomad.

### RPC Advertise Address

The behavior of the [advertised RPC
address](/docs/configuration#rpc-1) has changed to be only used
to advertise the RPC address of servers to client nodes. Server to server
communication is done using the advertised Serf address. Existing cluster's
should not be effected but the advertised RPC address may need to be updated to
allow connecting client's over a NAT.

## Nomad 0.6.0

### Default `advertise` address changes

When no `advertise` address was specified and Nomad's `bind_addr` was loopback
or `0.0.0.0`, Nomad attempted to resolve the local hostname to use as an
advertise address.

Many hosts cannot properly resolve their hostname, so Nomad 0.6 defaults
`advertise` to the first private IP on the host (e.g. `10.1.2.3`).

If you manually configure `advertise` addresses no changes are necessary.

## Nomad Clients

The change to the default, advertised IP also effect clients that do not specify
which network_interface to use. If you have several routable IPs, it is advised
to configure the client's [network
interface](/docs/configuration/client#network_interface)
such that tasks bind to the correct address.

## Nomad 0.5.5

### Docker `load` changes

Nomad 0.5.5 has a backward incompatible change in the `docker` driver's
configuration. Prior to 0.5.5 the `load` configuration option accepted a list
images to load, in 0.5.5 it has been changed to a single string. No
functionality was changed. Even if more than one item was specified prior to
0.5.5 only the first item was used.

To do a zero-downtime deploy with jobs that use the `load` option:

- Upgrade servers to version 0.5.5 or later.

- Deploy new client nodes on the same version as the servers.

- Resubmit jobs with the `load` option fixed and a constraint to only run on
  version 0.5.5 or later:

```hcl
    constraint {
      attribute = "${attr.nomad.version}"
      operator  = "version"
      value     = ">= 0.5.5"
    }
```

- Drain and shutdown old client nodes.

### Validation changes

Due to internal job serialization and validation changes you may run into
issues using 0.5.5 command line tools such as `nomad run` and `nomad validate`
with 0.5.4 or earlier agents.

It is recommended you upgrade agents before or alongside your command line
tools.

## Nomad 0.4.0

Nomad 0.4.0 has backward incompatible changes in the logic for Consul
deregistration. When a Task which was started by Nomad v0.3.x is uncleanly shut
down, the Nomad 0.4 Client will no longer clean up any stale services. If an
in-place upgrade of the Nomad client to 0.4 prevents the Task from gracefully
shutting down and deregistering its Consul-registered services, the Nomad Client
will not clean up the remaining Consul services registered with the 0.3
Executor.

We recommend draining a node before upgrading to 0.4.0 and then re-enabling the
node once the upgrade is complete.

## Nomad 0.3.1

Nomad 0.3.1 removes artifact downloading from driver configurations and places them as
a first class element of the task. As such, jobs will have to be rewritten in
the proper format and resubmitted to Nomad. Nomad clients will properly
re-attach to existing tasks but job definitions must be updated before they can
be dispatched to clients running 0.3.1.

## Nomad 0.3.0

Nomad 0.3.0 has made several substantial changes to job files included a new
`log` block and variable interpretation syntax (`${var}`), a modified `restart`
policy syntax, and minimum resources for tasks as well as validation. These
changes require a slight change to the default upgrade flow.

After upgrading the version of the servers, all previously submitted jobs must
be resubmitted with the updated job syntax using a Nomad 0.3.0 binary.

- All instances of `$var` must be converted to the new syntax of `${var}`

- All tasks must provide their required resources for CPU, memory and disk as
  well as required network usage if ports are required by the task.

- Restart policies must be updated to indicate whether it is desired for the
  task to restart on failure or to fail using `mode = "delay"` or `mode = "fail"` respectively.

- Service names that include periods will fail validation. To fix, remove any
  periods from the service name before running the job.

After updating the Servers and job files, Nomad Clients can be upgraded by first
draining the node so no tasks are running on it. This can be verified by running
`nomad node status <node-id>` and verify there are no tasks in the `running`
state. Once that is done the client can be killed, the `data_dir` should be
deleted and then Nomad 0.3.0 can be launched.

[dangling-containers]: /docs/drivers/docker#dangling-containers
[drain-api]: /api-docs/nodes#drain-node
[drain-cli]: /docs/commands/node/drain
[dst]: /docs/job-specification/periodic#daylight-saving-time
[gh-6787]: https://github.com/hashicorp/nomad/issues/6787
[gh-8457]: https://github.com/hashicorp/nomad/issues/8457
[gh-9148]: https://github.com/hashicorp/nomad/issues/9148
[hcl2]: https://github.com/hashicorp/hcl2
[limits]: /docs/configuration#limits
[lxc]: /docs/drivers/external/lxc
[migrate]: /docs/job-specification/migrate
[plugin-stanza]: /docs/configuration/plugin
[plugins]: /docs/drivers/external
[preemption-api]: /api-docs/operator#update-scheduler-configuration
[preemption]: /docs/internals/scheduling/preemption
[reserved]: /docs/configuration/client#reserved-parameters
[task-config]: /docs/job-specification/task#config
[tls-guide]: https://learn.hashicorp.com/tutorials/nomad/security-enable-tls
[tls-vault-guide]: https://learn.hashicorp.com/tutorials/nomad/vault-pki-nomad
[update]: /docs/job-specification/update
[validate]: /docs/commands/job/validate
[vault_grace]: /docs/job-specification/template
