open-nomad/website/content/docs/upgrade/upgrade-specific.mdx

---
layout: docs
page_title: Upgrade Guides
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 1.4.0

#### Raft Protocol Version 2 Unsupported

Raft protocol version 2 was deprecated in Nomad v1.3.0, and is being removed
in Nomad v1.4.0. In Nomad 1.3.0, the default raft protocol version was updated
to version 3, and in Nomad 1.4.0 Nomad requires the use of raft protocol version
3. If [`raft_protocol`] version is explicitly set, it must now be set to `3`.
For more information see the [Upgrading to Raft Protocol 3] guide.

#### Audit logs filtering logic changed

Audit Log filtering in previous versions of Nomad handled `stages` and
`operations` filters as `OR` filters. If _either_ condition was met, the logs
would be filtered. As of 1.4.0, `stages` and `operations` are treated as `AND
filters`. Logs will only be filtered if all filter conditions match.

#### Prevent Overlapping New Allocations with Stopping Allocations

Prior to Nomad 1.4.0 the scheduler would consider the resources used by
allocations that are in the process of stopping to be free for new allocations
to use. This could cause newer allocations to crash when they try to use TCP
ports or memory used by an allocation in the process of stopping. The new and
stopping [allocations would "overlap" improperly.][alloc_overlap]

[Nomad 1.4.0 fixes this behavior][gh_10446] so that an allocation's resources
are only considered free for reuse once the client node the allocation was
running on reports it has stopped. Technically speaking: only once the
`Allocation.ClientStatus` has reached a terminal state (`complete`, `failed`,
or `lost`).

Despite this being a bug fix, it is considered a significant enough change in
behavior to reserve for a major Nomad release and *not* be backported. Please
report any negative side effects encountered as [new
issues.][gh_issue]

## Nomad 1.3.3

Environments that don't support the use of [`uid`][template_uid] and
[`gid`][template_gid] in `template` blocks, such as Windows clients, may
experience task failures with the following message after upgrading to Nomad
1.3.3:

```
Template failed: error rendering "(dynamic)" => "...": failed looking up user: managing file ownership is not supported on Windows
```

It is recommended to avoid this version of Nomad in such environments.

## Nomad 1.3.2, 1.2.9, 1.1.15

#### Client `max_kill_timeout` now enforced

Nomad versions since v0.9 have incorrectly ignored the Client [`max_kill_timeout`][max_kill_timeout]
configuration option. This bug has been fixed in Nomad versions v.1.3.2,
v1.2.9, and v1.1.15. Job submitters should be aware that a Task's [`kill_timeout`][kill_timeout]
will be reduced to the Client's `max_kill_timeout` if the value exceeds the maximum.

## Nomad 1.3.1, 1.2.8, 1.1.14

#### Default `artifact` limits

Nomad 1.3.1, 1.2.8, and 1.1.14 introduced mechanisms to limit the size of
`artifact` downloads and how long these operations can take. The limits are
defined in the new [`artifact`client configuration][client_artifact] and have
predefined default values.

While the defaults set are fairly large, it is recommended to double-check them
prior to upgrading your Nomad clients to make sure they fit your needs.

## Nomad 1.3.0

#### Raft Protocol Version 2 Deprecation

Raft protocol version 2 will be removed from Nomad in the next major
release of Nomad, 1.4.0.

In Nomad 1.3.0, the default raft protocol version has been updated to
3. If the [`raft_protocol`] version is not explicitly set, upgrading a
server will automatically upgrade that server's raft protocol. See the
[Upgrading to Raft Protocol 3] guide.

#### Client State Store

The client state store will be automatically migrated to a new schema
version when upgrading a client.

Downgrading to a previous version of the client after upgrading it to
Nomad 1.3 is not supported. To downgrade safely, users should drain
all tasks from the Nomad client and erase its data directory.

#### CSI Plugins

The client filesystem layout for CSI plugins has been updated to
correctly handle the lifecycle of multiple allocations serving the
same plugin. Running plugin tasks will not be updated after upgrading
the client, but it is recommended to redeploy CSI plugin jobs after
upgrading the cluster.

The directory for plugin control sockets will be mounted from a new
per-allocation directory in the client data dir. This will still be
bind-mounted to `csi_plugin.mount_config` as in versions of Nomad
prior to 1.3.0.

The volume staging directory for new CSI plugin tasks will now be
mounted to the task's `NOMAD_TASK_DIR` instead of the
`csi_plugin.mount_config`.

#### Raft leadership transfer on error

Starting with Nomad 1.3.0, when a Nomad server is elected the Raft leader but
fails to complete the process to start acting as the Nomad leader it will
attempt to gracefully transfer its Raft leadership status to another eligible
server in the cluster. This operation is only supported when using Raft
Protocol Version 3.

#### Server Raft Database

The server raft database in `raft.db` will be automatically migrated to a new
underlying implementation provided by `go.etcd.io/bbolt`. Downgrading to a previous
version of the server after upgrading it to Nomad 1.3 is not supported. Like with
any Nomad upgrade it is recommended to take a snapshot of your database prior to
upgrading in case a downgrade becomes necessary.

The new database implementation enables a new server configuration option for
controlling the underlying freelist-sync behavior. Clusters experiencing extreme
disk IO on servers may want to consider disabling freelist-sync to reduce load.
The tradeoff is longer server startup times, as the database must be completely
scanned to re-build the freelist from scratch.

```hcl
server {
  raft_boltdb {
    no_freelist_sync = true
  }
}
```

#### Changes to the `nomad server members` command

The standard output of the `nomad server members` command replaces the previous
`Protocol` column that indicated the Serf protocol version with a new column
named `Raft Version` which outputs the Raft protocol version defined in each
server.

The `-detailed` flag is now called `-verbose` and outputs the standard values
in addition to extra information. The previous name is still supported but may
be removed in future releases.

The previous `Protocol` value can be viewed using the `-verbose` flag.

#### Changes to `client.template.function_denylist` configuration

consul-template v0.28 added a new function
[`writeToFile`](https://github.com/hashicorp/consul-template/blob/v0.28.0/docs/templating-language.md#writeToFile)
which can write to arbitrary files on the host.

Nomad 1.3.0 disables this function by default in its
[`function_denylist`](/docs/configuration/client#function_denylist).

However *if you have overridden the default `template.function_denylist` in
your client configuration, you must add `writeToFile` to your denylist.*
Failing to do so allows templates to write to arbitrary paths on the host.

#### Changes to Envoy metrics labels

When using Envoy as a sidecar proxy for Connect enabled services, Nomad will now
automatically inject the unique allocation ID into Envoy's stats tags configuration.
Users who wish to set the tag values themselves may do so using the [`proxy.config`](/docs/job-specification/proxy#config)
block.

```hcl
connect {
  sidecar_service {
    proxy {
      config {
        envoy_stats_tags = ["nomad.alloc_id=<allocID>"]
      }
    }
  }
}
```

#### Changes to Consul Connect Service Identity Tokens

Starting with Nomad 1.3.0, Consul Service Identity Tokens created automatically
by Nomad on behalf of Connect services will now be created as [`Local`] tokens. These
tokens will no longer be replicated globally. To facilitate cross-Consul datacenter
requests of Connect services registered by Nomad, Consul agents will need to be
configured with [default anonymous][anon_token] ACL tokens with ACL policies of
sufficient permissions to read service and node metadata pertaining to those
requests. This mechanism is described in Consul [#7414][consul_acl].
A typical Consul agent anonymous token may contain an ACL policy such as:

```hcl
service_prefix "" { policy = "read" }
node_prefix    "" { policy = "read" }
```

The minimum version of Consul supported by Nomad's Connect integration is now Consul v1.8.0.

#### Changes to task groups that utilise Consul services and checks

Starting with Nomad 1.3.0, services and checks that utilise Consul will have an
automatic constraint placed upon the task group. This ensures they are placed
on a client with a Consul agent running that meets a minimum version
requirement. The minimum version of Consul supported by Nomad's service and
check stanzas is now Consul v1.7.0.

#### Linux Control Groups Version 2

Starting with Nomad 1.3.0, Linux systems configured to use [cgroups v2][cgroups2]
are now supported. A Nomad client will only activate its v2 control groups manager
if the system is configured with the cgroups2 controller mounted at `/sys/fs/cgroup`.
  * Systems that do not support cgroups v2 are not affected.
  * Systems configured in hybrid mode typically mount the cgroups2
    controller at `/sys/fs/cgroup/unified`, so Nomad will continue to
    use cgroups v1 for these hosts.
  * Systems configured with only cgroups v2 now correctly support setting cpu [cores].

Nomad will preserve the existing cgroup for tasks when a client is
upgraded, so there will be no disruption to tasks. A new client
attribute `unique.cgroup.version` indicates which version of control
groups Nomad is using.

When cgroups v2 are in use, Nomad uses `nomad.slice` as the [default parent][cgroup_parent] for cgroups
created on behalf of tasks. The cgroup created for a task is named in the form `<allocID>.<task>.scope`.
These cgroups are created by Nomad before a task starts. External task drivers that support
containerization should be updated to make use of the new cgroup locations.

The new cgroup file system layout will look like the following:

```shell-session
➜ tree -d /sys/fs/cgroup/nomad.slice
/sys/fs/cgroup/nomad.slice
├── 8b8da4cf-8ebf-b578-0bcf-77190749abf3.redis.scope
└── a8c8e495-83c8-311b-4657-e6e3127e98bc.example.scope
```
#### Support for pre-0.9 Tasks Removed

Running tasks that were created on clusters from Nomad version 0.9 or
earlier will fail to restore after upgrading a cluster to Nomad
1.3.0. To safely upgrade without unplanned interruptions, force these
tasks to be rescheduled by `nomad alloc stop` before upgrading. Note
this only applies to tasks that have been running continuously from
before 0.9 without rescheduling. Jobs that were created before 0.9 but
have had tasks replaced over time after 0.9 will operate normally
during the upgrade.

## Nomad 1.2.6, 1.1.12, and 1.0.18

#### ACL requirement for the job parse endpoint

Nomad 1.2.6, 1.1.12, and 1.0.18 require ACL authentication for the
[job parse][api_jobs_parse] API endpoint. The `parse-job` capability has been
created to allow access to this endpoint. The `submit-job`, `read`, and `write`
policies include this capability.


The capability must be enabled for the namespace used in the API request.

## Nomad 1.2.4

#### `nomad eval status -json` deprecated

Nomad 1.2.4 includes a new `nomad eval list` command that has the
option to display the results in JSON format with the `-json`
flag. This replaces the existing `nomad eval status -json` option. In
Nomad 1.4.0, `nomad eval status -json` will be changed to display only
the selected evaluation in JSON format.

## Nomad 1.2.2

### Panic on node class filtering for system and sysbatch jobs fixed

Nomad 1.2.2 fixes a [server crashing bug][gh-11563] present in the scheduler
node class filtering since 1.2.0. Users should upgrade to Nomad 1.2.2 to avoid
this problem.

## Nomad 1.2.0

#### Nvidia device plugin

The Nvidia device is now an external plugin and must be installed separately.
Refer to [the Nvidia device plugin's documentation][nvidia] for details.

#### ACL requirements for accessing the job details page in the Nomad UI

Nomad 1.2.0 introduced a new UI component to display the status of `system` and
`sysbatch` jobs in each client where they are running. This feature makes an
API call to an endpoint that requires `node:read` ACL permission. Tokens used
to access the Nomad UI will need to be updated to include this permission in
order to access a job details page.

This was an unintended change fixed in Nomad 1.2.4.

#### HCLv2 Job Specification Parsing

In previous versions of Nomad, when rendering a job specification using override
variables, a warning would be returned if a variable within an override file
was declared that was not found within the job specification. This behaviour
differed from passing variables via the `-var` flag, which would always cause an
error in the same situation.

Nomad 1.2.0 fixed the behaviour consistency to always return an error by default,
where an override variable was specified which was not a known variable within the
job specification. In order to mitigate this change for users who wish to only
be warned when this situation arises, the `-hcl-strict=false` flag can be
specified.

## Nomad 1.0.11 and 1.1.5 Enterprise

#### Audit log file names

Audit log file naming now matches the standard log file naming introduced in
1.0.10 and 1.1.4. The audit log currently being written will no longer have a
timestamp appended.

## Nomad 1.0.10 and 1.1.4

#### Log file names

The [`log_file`] configuration option was not being fully respected, as the
generated filename would include a timestamp. After upgrade, the active log
file will always be the value defined in `log_file`, with timestamped files
being created during log rotation.

## Nomad 1.0.9 and 1.1.3

#### Namespace in Job Run and Plan APIs

The Job Run and Plan APIs now respect the `?namespace=...` query parameter over
the namespace specified in the job itself. This matches the precedence of
region and [fixes a bug where the `-namespace` flag was not respected for the
`nomad run` and `nomad apply` commands.][gh-10875]

For users of [`api.Client`][go-client] who want their job namespace respected,
you must ensure the `Config.Namespace` field is unset.

#### Docker Driver

**1.1.3 only**

Starting in Nomad 1.1.2, task groups with `network.mode = "bridge"` generated a
hosts file in Docker containers. This generated hosts file was bind-mounted
from the task directory to `/etc/hosts` within the task. In Nomad 1.1.3 the
source for the bind mount was moved to the allocation directory so that it is
shared between all tasks in an allocation.

Please note that this change may prevent [`extra_hosts`] values from being
properly set in each task when there are multiple tasks within the same group.
When using `extra_hosts` with Consul Connect in `bridge` network mode, you
should set the hosts values in the [`sidecar_task.config`] block instead.

## Nomad 1.1.0

#### Enterprise licenses

Nomad Enterprise licenses are no longer stored in raft or synced between
servers. Nomad Enterprise servers will not start without a license. There is
no longer a six hour evaluation period when running Nomad Enterprise. Before
upgrading, you must provide each server with a license on disk or in its
environment (see the [Enterprise licensing] documentation for details).

The `nomad license put` command has been removed.

The `nomad license get` command is no longer forwarded to the Nomad leader,
and will return the license from the specific server being contacted.

Click [here](https://www.hashicorp.com/products/nomad/trial) to get a trial license for Nomad Enterprise.

#### Agent Metrics API

The Nomad agent metrics API now respects the
[`prometheus_metrics`](https://www.nomadproject.io/docs/configuration/telemetry#prometheus_metrics)
configuration value. If this value is set to `false`, which is the default value,
calling `/v1/metrics?format=prometheus` will now result in a response error.

#### CSI volumes

The volume specification for CSI volumes has been updated to support volume
creation. The `access_mode` and `attachment_mode` fields have been moved to a
`capability` block that can be repeated. Existing registered volumes will be
automatically modified the next time that a volume claim is updated. Volume
specification files for new volumes should be updated to the format described
in the [`volume create`] and [`volume register`] commands.

The [`volume`] block has an `access_mode` and `attachment_mode` field that are
required for CSI volumes. Jobs that use CSI volumes should be updated with
these fields.

#### Connect native tasks

Connect native tasks running in host networking mode will now have `CONSUL_HTTP_ADDR`
set automatically. Before this was only the case for bridge networking. If an operator
already explicitly set `CONSUL_HTTP_ADDR` then it will not get overridden.

#### Linux capabilities in exec/java

Following the security [remediation][no_net_raw] in Nomad versions 0.12.12, 1.0.5,
and 1.1.0-rc1, the `exec` and `java` task drivers will additionally no longer enable
the following linux capabilities by default.

```
AUDIT_CONTROL  AUDIT_READ  BLOCK_SUSPEND  DAC_READ_SEARCH  IPC_LOCK  IPC_OWNER  LEASE
LINUX_IMMUTABLE  MAC_ADMIN  MAC_OVERRIDE  NET_ADMIN  NET_BROADCAST  NET_RAW  SYS_ADMIN
SYS_BOOT  SYSLOG  SYS_MODULE  SYS_NICE  SYS_PACCT  SYS_PTRACE  SYS_RAWIO  SYS_RESOURCE
SYS_TIME  SYS_TTY_CONFIG  WAKE_ALARM
```

The capabilities now enabled by default are modeled after Docker default
[`linux capabilities`] (excluding `NET_RAW`).

```
AUDIT_WRITE  CHOWN  DAC_OVERRIDE  FOWNER  FSETID  KILL  MKNOD  NET_BIND_SERVICE
SETFCAP  SETGID  SETPCAP  SETUID  SYS_CHROOT
```

A new `allow_caps` plugin configuration parameter for [`exec`][allow_caps_exec]
and [`java`][allow_caps_java] task drivers can be used to restrict the set of
capabilities allowed for use by tasks.

Tasks using the `exec` or `java` task drivers can add or remove desired linux
capabilities using the [`cap_add`][cap_add_exec] and [`cap_drop`][cap_drop_exec]
task configuration options.

#### iptables

Nomad now appends its iptables rules to the `NOMAD-ADMIN` chain instead of
inserting them as the first rule. This allows better control for user-defined
iptables rules but users who append rules currently should verify that their
rules are being appended in the correct order.

## Nomad 1.1.0-rc1, 1.0.5, 0.12.12

Nomad versions 1.1.0-rc1, 1.0.5 and 0.12.12 change the behavior of the `docker`, `exec`,
and `java` task drivers so that the [`CAP_NET_RAW`] linux capability is disabled
by default. This is one of the [`linux capabilities`] that Docker itself enables
by default, as this capability enables the generation of ICMP packets - used by
the common `ping` utility for performing network diagnostics. When used by groups in
`bridge` networking mode, the `CAP_NET_RAW` capability also exposes tasks to ARP spoofing,
enabling DoS and MITM attacks against other tasks running in `bridge` networking
on the same host. Operators should weigh potential impact of an upgrade on their
applications against the security consequences inherit with `CAP_NET_RAW`. Typical
applications using `tcp` or `udp` based networking should not be affected.

This is the sole change for Nomad 1.0.5 and 0.12.12, intended to provide better
task network isolation by default.

Users of the `docker` driver can restore the previous behavior by configuring the
[`allow_caps`] driver configuration option to explicitly enable the `CAP_NET_RAW`
capability.

```hcl
plugin "docker" {
  config {
    allow_caps = [
      "CHOWN", "DAC_OVERRIDE", "FSETID", "FOWNER", "MKNOD",
      "SETGID", "SETUID", "SETFCAP", "SETPCAP", "NET_BIND_SERVICE",
      "SYS_CHROOT", "KILL", "AUDIT_WRITE", "NET_RAW",
    ]
  }
}
```

An upcoming version of Nomad will include similar configuration options for the
`exec` and `java` task drivers.

This change is limited to `docker`, `exec`, and `java` driver plugins. It does
not affect the Nomad server. This only affects Nomad clients running Linux, with
tasks using `bridge` networking and one of these task drivers, or third-party
plugins which relied on the shared Nomad executor library.

Upgrading a Nomad client to 1.0.5 or 0.12.12 will not restart existing tasks. As
such, processes from existing `docker`, `exec`, or `java` tasks will need to be
manually restarted (using `alloc stop` or another mechanism) in order to be
fully isolated.

## Nomad 1.0.3, 0.12.10

Nomad versions 1.0.3 and 0.12.10 change the behavior of the `exec` and `java` drivers so that
tasks are isolated in their own PID and IPC namespaces. As a result, the
process launched by these drivers will be PID 1 in the namespace. This has
[significant impact](https://man7.org/linux/man-pages/man7/pid_namespaces.7.html)
on the treatment of a process by the Linux kernel. Furthermore, tasks in the
same allocation will no longer be able to coordinate using signals, SystemV IPC
objects, or POSIX message queues. Operators should weigh potential impact of an
upgrade on their applications against the security consequences inherent in using
the host namespaces.

This is the sole change for Nomad 1.0.3, intended to provide better process
isolation by default. An upcoming version of Nomad will include options for
configuring this behavior.

This change is limited to the `exec` and `java` driver plugins. It does not affect
the Nomad server. This only affect Nomad clients running on Linux, using the
`exec` or `java` drivers or third-party driver plugins which relied on the shared
Nomad executor library.

Upgrading a Nomad client to 1.0.3 or 0.12.10 will not restart existing tasks.
As such, processes from existing `exec`/`java` tasks will need to be manually restarted
(using `alloc stop` or another mechanism) in order to be fully isolated.

## Nomad 1.0.2

#### Dynamic secrets trigger template changes on client restart

Nomad 1.0.2 changed the behavior of template `change_mode` triggers when a
client node restarts. In Nomad 1.0.1 and earlier, the first rendering of a
template after a client restart would not trigger the `change_mode`. For
dynamic secrets such as the Vault PKI secrets engine, this resulted in the
secret being updated but not restarting or signalling the task. When the
secret's lease expired at some later time, the task workload might fail
because of the stale secret. For example, a web server's SSL certificate would
be expired and browsers would be unable to connect.

In Nomad 1.0.2, when a client node is restarted any task with Vault secrets
that are generated or have expired will have its `change_mode` triggered. If
`change_mode = "restart"` this will result in the task being restarted, to
avoid the task failing unexpectedly at some point in the future. This change
only impacts tasks using dynamic Vault secrets engines such as [PKI][pki], or
when secrets are rotated. Secrets that don't change in Vault will not trigger
a `change_mode` on client restart.

## Nomad 1.0.1

#### Envoy worker threads

Nomad v1.0.0 changed the default behavior around the number of worker threads
created by the Envoy when being used as a sidecar for Consul Connect. In Nomad
v1.0.1, the same default setting of [`--concurrency=1`][envoy_concurrency] is set for Envoy when used
as a Connect gateway. As before, the [`meta.connect.proxy_concurrency`][proxy_concurrency]
property can be set in client configuration to override the default value.

## Nomad 1.0.0

### HCL2 for Job specification

Nomad v1.0.0 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`.

### Consul Connect

Nomad 1.0's Consul Connect integration works best with Consul 1.9 or later. The
ideal upgrade path is:

1. Create a new Nomad client image with Nomad 1.0 and Consul 1.9 or later.
2. Add new hosts based on the image.
3. [Drain][drain-cli] and shutdown old Nomad client nodes.

While inplace upgrades and older versions of Consul are supported by Nomad 1.0,
Envoy proxies will drop and stop accepting connections while the Nomad agent is
restarting. Nomad 1.0 with Consul 1.9 do not have this limitation.

#### Envoy proxy versions

Nomad v1.0.0 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 v1.0.0, 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 behavior
while also doing a full [node drain][] 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.

#### Envoy worker threads

Nomad v1.0.0 changes the default behavior around the number of worker threads
created by the Envoy sidecar proxy when using Consul Connect. Previously, the
Envoy [`--concurrency`][envoy_concurrency] argument was left unset, which caused
Envoy to spawn as many worker threads as logical cores available on the CPU. The
`--concurrency` value now defaults to `1` and can be configured by setting the
[`meta.connect.proxy_concurrency`][proxy_concurrency] property in client
configuration.

## 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`][] 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.

Additionally, the `docker` driver's `port_map` configuration is deprecated in
lieu of the `ports` field.

### 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.

Feasibility (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>, 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][] 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`] 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.

### 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.

[api_jobs_parse]: /api-docs/jobs#parse-job
[cgroups2]: https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html
[cgroup_parent]: /docs/configuration/client#cgroup_parent
[client_artifact]: /docs/configuration/client#artifact-parameters
[cores]: /docs/job-specification/resources#cores
[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
[envoy_concurrency]: https://www.envoyproxy.io/docs/envoy/latest/operations/cli#cmdoption-concurrency
[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
[gh-10875]: https://github.com/hashicorp/nomad/pull/10875
[gh-11563]: https://github.com/hashicorp/nomad/issues/11563
[go-client]: https://pkg.go.dev/github.com/hashicorp/nomad/api#Client
[hcl2]: https://github.com/hashicorp/hcl2
[limits]: /docs/configuration#limits
[lxc]: /plugins/drivers/community/lxc
[migrate]: /docs/job-specification/migrate
[nvidia]: /plugins/devices/nvidia
[plugin-stanza]: /docs/configuration/plugin
[plugins]: /plugins/drivers/community
[preemption-api]: /api-docs/operator#update-scheduler-configuration
[preemption]: /docs/concepts/scheduling/preemption
[proxy_concurrency]: /docs/job-specification/sidecar_task#proxy_concurrency
[`sidecar_task.config`]: /docs/job-specification/sidecar_task#config
[`raft_protocol`]: /docs/configuration/server#raft_protocol
[`raft protocol`]: /docs/configuration/server#raft_protocol
[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
[node drain]: https://www.nomadproject.io/docs/upgrade#5-upgrade-clients
[`template.disable_file_sandbox`]: /docs/configuration/client#template-parameters
[template_gid]: /docs/job-specification/template#gid
[template_uid]: /docs/job-specification/template#uid
[pki]: https://www.vaultproject.io/docs/secrets/pki
[`volume create`]: /docs/commands/volume/create
[`volume register`]: /docs/commands/volume/register
[`volume`]: /docs/job-specification/volume
[enterprise licensing]: /docs/enterprise/license
[`cap_net_raw`]: https://security.stackexchange.com/a/128988
[`linux capabilities`]: https://docs.docker.com/engine/reference/run/#runtime-privilege-and-linux-capabilities
[`allow_caps`]: /docs/drivers/docker#allow_caps
[`extra_hosts`]: /docs/drivers/docker#extra_hosts
[no_net_raw]: /docs/upgrade/upgrade-specific#nomad-1-1-0-rc1-1-0-5-0-12-12
[allow_caps_exec]: /docs/drivers/exec#allow_caps
[allow_caps_java]: /docs/drivers/java#allow_caps
[cap_add_exec]: /docs/drivers/exec#cap_add
[cap_drop_exec]: /docs/drivers/exec#cap_drop
[`log_file`]: /docs/configuration#log_file
[Upgrading to Raft Protocol 3]: /docs/upgrade#upgrading-to-raft-protocol-3
[`Local`]: https://www.consul.io/docs/security/acl/acl-tokens#token-attributes
[anon_token]: https://www.consul.io/docs/security/acl/acl-tokens#special-purpose-tokens
[consul_acl]: https://github.com/hashicorp/consul/issues/7414
[kill_timeout]: /docs/job-specification/task#kill_timeout
[max_kill_timeout]: /docs/configuration/client#max_kill_timeout
[alloc_overlap]: https://github.com/hashicorp/nomad/issues/10440
[gh_10446]: https://github.com/hashicorp/nomad/pull/10446#issuecomment-1224833906
[gh_issue]: https://github.com/hashicorp/nomad/issues/new/choose