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Detailed Nomad Pack Usage
This guide will go into detail on Nomad Pack usage and commands.
For an overview on basic use, see the repository README.
For more information on writing custom packs and registries, see the Writing Packs Guide in the repository or in the HashiCorp Learn Guides.
When first using Nomad Pack, a directory at ./.nomad/packs will be created to store information about available packs and packs in use.
During initializing, Nomad Pack downloads a default registry of packs from https://github.com/hashicorp/nomad-pack-community- registry.
The directory structure is as follows:
.nomad
└── packs
├── <REGISTRY>
├── <PACK-NAME>
├── <PACK-REF>
├── ...files containing pack contents...
The contents of the .nomad/pack directory are needed for Nomad Pack to work properly,
but users must not manually manage or change these files. Instead, use the registry
commands.
The registry list command lists the packs available to deploy.
nomad-pack registry list
This command reads from the .nomad/packs directory explained above.
The registry command includes several sub-commands for interacting with registries.
Custom registries can be added using the registry add command. Any git based
registry supported by go-getter should
work.
For instance, if you wanted to add the entire Nomad Pack Community Registry, you would run the following command to download the registry.
nomad-pack registry add community github.com/hashicorp/nomad-pack-community-registry
To add a single pack from the registry, use the --target flag.
nomad-pack registry add community github.com/hashicorp/nomad-pack-community-registry --target=nginx
To download single pack or an entire registry at a specific version/SHA, use the --ref flag.
nomad-pack registry add community github.com/hashicorp/nomad-pack-community-registry --ref=v0.0.1
To remove a registry or pack from your local cache. Use the registry delete command.
This command also supports the --target and --ref flags.
nomad-pack registry delete community
At times, you may wish to use Nomad Pack to render jobspecs, but you will not want to immediately deploy these to Nomad.
This can be useful when writing a pack, debugging deployments, integrating Nomad Pack into a CI/CD environment, or if you have another mechanism for handlign Nomad deploys.
The render command takes the --var and --var-file flags that run takes.
The --to-dir flag determines the directory where the rendered templates will be written.
The --render-output-template can be passed to additionally render the output template. Some output templates rely on a deployment for information. In these cases, the output template may not be rendered with all necessary information.
nomad-pack render hello-world --to-dir ./tmp --var greeting=hola --render-output-template
To deploy the resources in a pack to Nomad, use the run command.
nomad-pack run hello-world
By passing a --name value into run, Nomad Pack deploys each resource in the
pack with a metadata value for "pack name". If no name is given, the pack name
is used by default.
This allows Nomad Pack to manage multiple deployments of the same pack.
nomad-pack run hello-world --name hola-mundo
It is also possible to run a local pack directly from the pack directory by passing in the directory instead of the pack name.
nomad pack run .
Each pack defines a set of variables that can be provided by the user. Values for variables can be passed into the run command using the --var flag.
nomad-pack run hello-world --var greeting=hola
Values can also be provided by passing in a variables file.
nomad-pack run hello-world -f ./my-variables.hcl
These files can define overrides to the variables defined in the pack.
docker_image = "hashicorp/hello-world"
app_count = 3
datacenters = [
"us-east-1",
"us-west-2",
]
app_resources = {
memory = 512
cpu = 256
}
To see the type and description of each variable, run the info command.
nomad-pack info hello-world
If you do not want to immediately deploy the pack, but instead want details on how it will be deployed, run the plan command.
This invokes Nomad in a dry-run mode using the Nomad Plan API endpoint.
nomad-pack plan hello-world
By passing a --name value into plan, Nomad Pack will look for packs deployed with that name. If no name is provided, Nomad Pack uses the pack name by default.
nomad-pack plan hello-world --name hola-mundo
The plan command takes the --var and -f flags like the run command.
nomad-pack plan hello-world --var greeting=hallo
nomad-pack plan hello-world -f ./my-variables.hcl
If you want to see a list of the packs currently deployed (this may include packs that are stopped but not yet removed), run the status command.
nomad-pack status
To see the status of jobs running in a specific pack, use the status command with the pack name.
nomad-pack status hello-world
If you want to remove the resources deployed by a pack, run the destroy command with the pack name.
nomad-pack destroy hello-world
If you deployed the pack with a --name value, pass in the name you gave the pack. For instance, if you deployed with the command:
nomad-pack run hello-world --name hola-mundo
You would destroy the contents of that pack with the command;
nomad-pack destroy hello-world --name hola-mundo
If you deployed the pack with variable overrides that override the job name in a pack, pass in those same overrides. For example, if you deployed with the command:
nomad-pack run hello-world --name hola-mundo --var job_name=spanish
You would destroy the contents of that pack with the command:
nomad-pack destroy hello-world --name hola-mundo --var job_name=spanish
It's possible to deploy multiple instances of a pack using the same --name value but with different job names using variable
overrides. For example, you can run the following commands, which will create two jobs,
one named "spanish" and one named "hola":
nomad-pack run hello-world --name hola-mundo --var job_name=spanish
nomad-pack run hello-world --name hola-mundo --var job_name=hola
If you run the destroy command without including the variable overrides, the command will destroy both jobs, since by default nomad pack will target all jobs belonging to the specified pack and deployment name.
# This destroys both jobs: "spanish" and "hola"
nomad-pack destroy hello-world --name hola-mundo
If you only want to destroy one of the jobs, you need to include the variable overrides so nomad pack knows which job to target:
# This destroys the job named "spanish"
nomad-pack destroy hello-world --name hola-mundo --var job_name=spanish
To stop the jobs without completely removing them from Nomad completely, use the stop command:
nomad-pack stop hola-mundo
N.B. The destroy command is an alias for stop --purge.