--- layout: docs page_title: artifact Block - Job Specification description: |- The "artifact" block instructs Nomad to fetch and unpack a remote resource, such as a file, tarball, or binary, and permits downloading artifacts from a variety of locations using a URL as the input source. --- # `artifact` Block The `artifact` block instructs Nomad to fetch and unpack a remote resource, such as a file, tarball, or binary. Nomad downloads artifacts using the popular [`go-getter`][go-getter] library, which permits downloading artifacts from a variety of locations using a URL as the input source. ```hcl job "docs" { group "example" { task "server" { artifact { source = "https://example.com/file.tar.gz" destination = "local/some-directory" options { checksum = "md5:df6a4178aec9fbdc1d6d7e3634d1bc33" } } } } } ``` Nomad supports downloading `http`, `https`, `git`, `hg` and `S3` artifacts. If these artifacts are archived (`zip`, `tgz`, `bz2`, `xz`), they are automatically unarchived before the starting the task. ## `artifact` Parameters - `destination` `(string: "local/")` - Specifies the directory path to download the artifact, relative to the root of the [task's working directory]. If omitted, the default value is to place the artifact in `local/`. The destination is treated as a directory unless `mode` is set to `file`. Source files will be downloaded into that directory path. For more details on how the `destination` interacts with task drivers, see the [Filesystem internals] documentation. - `mode` `(string: "any")` - One of `any`, `file`, or `dir`. If set to `file` the `destination` must be a file, not a directory. By default the `destination` will be `local/`. - `options` `(map: nil)` - Specifies configuration parameters to fetch the artifact. The key-value pairs map directly to parameters appended to the supplied `source` URL. Please see the [`go-getter` documentation][go-getter] for a complete list of options and examples. - `headers` `(map: nil)` - Specifies HTTP headers to set when fetching the artifact using `http` or `https` protocol. Please see the [`go-getter` headers documentation][go-getter-headers] for more information. - `source` `(string: )` - Specifies the URL of the artifact to download. See [`go-getter`][go-getter] for details. ## Operation Limits The client [`artifact`][client_artifact] configuration can set limits to specific artifact operations to prevent excessive data download or operation time. If a task's `artifact` retrieval exceeds one of those limits, the task will be interrupted and fail to start. Refer to the task events for more information. ## `artifact` Examples The following examples only show the `artifact` blocks. Remember that the `artifact` block is only valid in the placements listed above. ### Download File This example downloads the artifact from the provided URL and places it in `local/file.txt`. The `local/` path is relative to the [task's working directory]. ```hcl artifact { source = "https://example.com/file.txt" } ``` To set HTTP headers in the request for the source the optional `headers` field can be configured. ```hcl artifact { source = "https://example.com/file.txt" headers { User-Agent = "nomad-[${NOMAD_JOB_ID}]-[${NOMAD_GROUP_NAME}]-[${NOMAD_TASK_NAME}]" X-Nomad-Alloc = "${NOMAD_ALLOC_ID}" } } ``` To use HTTP basic authentication, preprend the username and password to the hostname in the URL. All special characters, including the username and password, must be URL encoded. For example, for a username `exampleUser` and the password `pass/word!`: ```hcl artifact { source = "https://exampleUser:pass%2Fword%21@example.com/file.txt" } ``` ### Download using git This example downloads the artifact from the provided GitHub URL and places it at `local/repo`, as specified by the optional `destination` parameter. ```hcl artifact { source = "git::https://github.com/hashicorp/nomad-guides" destination = "local/repo" } ``` To download from a private repo, sshkey needs to be set. The key must be base64-encoded string. On Linux, you can run `base64 -w0 ` to encode the file. Or use [HCL2](/nomad/docs/job-specification/hcl2) expressions to read and encode the key from a file on your machine: ```hcl artifact { # The git:: prefix forces go-getter's protocol detection to use the git ssh # protocol. It can also automatically detect the protocol from the domain of # some git hosting providers (such as GitHub) without the prefix. source = "git::git@bitbucket.org:example/nomad-examples" destination = "local/repo" options { # Make sure that the system known hosts file is populated: # ssh-keyscan github.com | sudo tee -a /etc/ssh/ssh_known_hosts # https://github.com/hashicorp/go-getter/issues/55 sshkey = "${base64encode(file("/path/to/private-key"))}" } } ``` To clone specific refs or at a specific depth, use the `ref` and `depth` options: ```hcl artifact { source = "git::https://github.com/hashicorp/nomad-guides" destination = "local/repo" options { ref = "main" depth = 1 } } ``` ### Download and Unarchive This example downloads and unarchives the result in `local/file`. Because the source URL is an archive extension, Nomad will automatically decompress it: ```hcl artifact { source = "https://example.com/file.tar.gz" } ``` To disable automatic unarchiving, set the `archive` option to false: ```hcl artifact { source = "https://example.com/file.tar.gz" options { archive = false } } ``` ### Download and Verify Checksums This example downloads an artifact and verifies the resulting artifact's checksum before proceeding. If the checksum is invalid, an error will be returned. ```hcl artifact { source = "https://example.com/file.zip" options { checksum = "md5:df6a4178aec9fbdc1d6d7e3634d1bc33" } } ``` ### Download from an S3-compatible Bucket These examples download artifacts from Amazon S3. There are several different types of [S3 bucket addressing][s3-bucket-addr] and [S3 region-specific endpoints][s3-region-endpoints]. As of Nomad 0.6 non-Amazon S3-compatible endpoints like [Minio] are supported, but you must explicitly set the "s3::" prefix. This example uses path-based notation on a publicly-accessible bucket: ```hcl artifact { source = "s3://my-bucket-example.s3-us-west-2.amazonaws.com/my_app.tar.gz" } ``` If a bucket requires authentication, you can avoid the use of credentials by using [EC2 IAM instance profiles][iam-instance-profiles]. If this is not possible, credentials may be supplied via the `options` parameter: ```hcl artifact { options { aws_access_key_id = "" aws_access_key_secret = "" aws_access_token = "" } } ``` To force the S3-specific syntax, use the `s3::` prefix: ```hcl artifact { source = "s3::https://my-bucket-example.s3-eu-west-1.amazonaws.com/my_app.tar.gz" } ``` Alternatively you can use virtual hosted style: ```hcl artifact { source = "s3://my-bucket-example.s3-eu-west-1.amazonaws.com/my_app.tar.gz" } ``` ## Environment The `artifact` downloader by default does not have access to the environment variables set for the Nomad client. Inheritence of environment variables can be managed through the [`artifact.set_environment_variables`][client_artifact] client configuration. [client_artifact]: /nomad/docs/configuration/client#artifact-parameters [go-getter]: https://github.com/hashicorp/go-getter 'HashiCorp go-getter Library' [go-getter-headers]: https://github.com/hashicorp/go-getter#headers 'HashiCorp go-getter Headers' [minio]: https://www.minio.io/ [s3-bucket-addr]: http://docs.aws.amazon.com/AmazonS3/latest/dev/UsingBucket.html#access-bucket-intro 'Amazon S3 Bucket Addressing' [s3-region-endpoints]: http://docs.aws.amazon.com/general/latest/gr/rande.html#s3_region 'Amazon S3 Region Endpoints' [iam-instance-profiles]: https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_use_switch-role-ec2_instance-profiles.html 'EC2 IAM instance profiles' [task's working directory]: /nomad/docs/runtime/environment#task-directories 'Task Directories' [filesystem internals]: /nomad/docs/concepts/filesystem#templates-artifacts-and-dispatch-payloads