This page provides reference information for runtime environment settings in your Nomad job specification. Learn about task identifiers, CPU and memory resources, IP addresses, task directories, and host variables. Review job, network, and Consul variables. Supply arbitrary configuration to a job task.
Some settings you specify in your job specification are passed to tasks when they start. Other settings are dynamically allocated when your job is scheduled. Both types of values are made available to your job through environment variables.
Job-related variables Variable DescriptionNOMAD_ALLOC_DIR The path to the shared alloc/ directory. See the Runtime Task Directories documentation for more information. NOMAD_TASK_DIR The path to the task local/ directory. See the Runtime Task Directories documentation for more information. NOMAD_SECRETS_DIR Path to the task's secrets/ directory. See the Runtime Task Directories documentation for more information. NOMAD_MEMORY_LIMIT Memory limit in MB for the task NOMAD_MEMORY_MAX_LIMIT The maximum memory limit the task may use if client has excess memory capacity, in MB. Omitted if task isn't configured with memory oversubscription. NOMAD_CPU_LIMIT CPU limit in MHz for the task NOMAD_CPU_CORES The specific CPU cores reserved for the task in cpuset list notation. Omitted if the task does not request CPU cores. For example, 0-2,7,12-14 NOMAD_ALLOC_ID Allocation ID of the task NOMAD_SHORT_ALLOC_ID The first 8 characters of the allocation ID of the task NOMAD_ALLOC_NAME Allocation name of the task. This is derived from the job name, task group name, and allocation index. NOMAD_ALLOC_INDEX Allocation index; useful to distinguish instances of task groups. From 0 to (count - 1). For system jobs and sysbatch jobs, this value will always be 0. The index is unique within a given version of a job, but canaries or failed tasks in a deployment may reuse the index. NOMAD_TASK_NAME Task's name NOMAD_GROUP_NAME Group's name NOMAD_JOB_ID Job's ID, which is equal to the Job name when submitted through the command-line tool but can be different when using the API NOMAD_JOB_NAME Job's name NOMAD_JOB_PARENT_ID ID of the Job's parent if it has one NOMAD_DC Datacenter in which the allocation is running NOMAD_PARENT_CGROUP The parent cgroup used to contain task cgroups (Linux only) NOMAD_NAMESPACE Namespace in which the allocation is running NOMAD_REGION Region in which the allocation is running NOMAD_UNIX_ADDR Use this value as your NOMAD_ADDR to use nomad CLI with the task API's unix socket. The value is equivalent to "unix://${NOMAD_SECRETS_DIR}/api.sock" NOMAD_META_<key> The metadata value given by key on the task's metadata. Any character in a key other than [A-Za-z0-9_.] will be converted to _.
${meta.<key>} which are keys in the node's metadata. CONSUL_HTTP_TOKEN The tasks' Consul token. See Consul Integration documentation for more details. CONSUL_TOKEN The tasks' Consul token. See Consul Integration documentation for more details. This variable is deprecated and exists only for backwards compatibility. VAULT_TOKEN The task's Vault token. See the Vault Integration documentation for more details Network-related Variables Variable Description NOMAD_IP_<label> Host IP for the given port label. See the network block documentation for more information. NOMAD_PORT_<label> Port for the given port label. Driver-specified port when a port map is used, otherwise the host's static or dynamic port allocation. Services should bind to this port. See the network block documentation for more information. NOMAD_ADDR_<label> Host IP:Port pair for the given port label. NOMAD_ALLOC_INTERFACE_<label> The configured network namespace interface for the given port label when using bridged or CNI networking. NOMAD_ALLOC_IP_<label> The configured network namespace IP for the given port label when using bridged or CNI networking. NOMAD_ALLOC_ADDR_<label> The configured network namespace IP:Port pair for the given port label when using bridged or CNI networking. NOMAD_HOST_PORT_<label> Port on the host for the port label. See the Mapped Ports section of the network block documentation for more information. NOMAD_UPSTREAM_IP_<service> IP for the given service when defined as a Consul service mesh upstream. NOMAD_UPSTREAM_PORT_<service> Port for the given service when defined as a Consul service mesh upstream. NOMAD_UPSTREAM_ADDR_<service> Host IP:Port for the given service when defined as a Consul service mesh upstream. NOMAD_ENVOY_ADMIN_ADDR_<service> Local address 127.0.0.2:Port for the admin port of the envoy sidecar for the given service when defined as a Consul service mesh enabled service. Envoy runs inside the group network namespace unless configured for host networking. NOMAD_ENVOY_READY_ADDR_<service> Local address 127.0.0.1:Port for the ready port of the envoy sidecar for the given service when defined as a Consul service mesh enabled service. Envoy runs inside the group network namespace unless configured for host networking.
Note
Nomad replaces characters that are neither alphanumeric nor underscores in port labels or task names with underscores when generating environment variable names such as NOMAD_ADDR_<task>_<label>
Note
These variables are only set for Consul service mesh native tasks. Variable DescriptionCONSUL_HTTP_ADDR Specifies the address to the local Consul agent. Will be automatically set to a unix domain socket in bridge networking mode, or a TCP address in host networking mode. CONSUL_HTTP_TOKEN Specifies the Consul ACL token used to authorize with Consul. Will be automatically set to a generated Consul service identity token specific to the service instance if Consul ACLs are enabled. CONSUL_HTTP_SSL Specifies whether HTTPS should be used when communicating with Consul. Will be automatically set to true if Nomad is configured to communicate with Consul using TLS. CONSUL_HTTP_SSL_VERIFY Specifies whether the HTTPS connection with Consul should be mutually verified. Will be automatically set to true if Nomad is configured to verify TLS certificates. CONSUL_CACERT Specifies the path to the CA certificate used for Consul communication. Will be automatically set if Nomad is configured with the consul.share_ssl option. CONSUL_CLIENT_CERT Specifies the path to the Client certificate used for Consul communication. Will be automatically set if Nomad is configured with the consul.share_ssl option. CONSUL_CLIENT_KEY Specifies the path to the Client Key certificate used for Consul communication. Will be automatically set if Nomad is configured with the consul.share_ssl option. CONSUL_TLS_SERVER_NAME Specifies the server name to use as the SNI host for Consul communication. Will be automatically set if Consul is configured to use TLS and the task is in a group using bridge networking mode.
Nomad will pass both the allocation ID and name, the deployment ID that created the allocation, the job ID and name, the parent job ID as well as the task and group's names. These are given as NOMAD_ALLOC_ID, NOMAD_ALLOC_NAME, NOMAD_ALLOC_INDEX, NOMAD_JOB_NAME, NOMAD_JOB_ID, NOMAD_JOB_PARENT_ID, NOMAD_GROUP_NAME and NOMAD_TASK_NAME. The allocation ID and index can be useful when the task being run needs a unique identifier or to know its instance count.
When you request resources for a job, Nomad creates a resource offer. The final resources for your job are not determined until it is scheduled. Nomad will tell you which resources have been allocated after evaluation and placement.
CPU and MemoryNomad will pass CPU and memory limits to your job as NOMAD_CPU_LIMIT, NOMAD_MEMORY_LIMIT, and NOMAD_MEMORY_MAX_LIMIT. Your task should use these values to adapt its behavior to fit inside the resource allocation that Nomad provides. For example, you can use the memory limit to inform how large your in-process cache should be, or to decide when to flush buffers to disk.
Both CPU and memory are presented as integers. The unit for CPU limit is 1024 = 1GHz. The unit for memory is 1 = 1 megabyte.
Writing your applications to adjust to these values at runtime provides greater scheduling flexibility since you can adjust the resource allocations in your job specification without needing to change your code. You can also schedule workloads that accept dynamic resource allocations so they can scale up or down as your cluster gets more or less busy.
NetworkingNomad assigns IP addresses and ports to your jobs and exposes them via environment variables. See the Networking page for more details.
Task DirectoriesNomad creates a working directory for each allocation on a client. The allocation working directory contains a task working directory for each task in the allocation.
Nomad makes the following directories available to tasks, relative to the task working directory:
alloc/: This directory is shared across all tasks in a task group and can be used to store data that needs to be used by multiple tasks, such as a log shipper.local/: This directory is private to each task. It can be used to store arbitrary data that should not be shared by tasks in the task group.secrets/: This directory is private to each task, not accessible via the nomad alloc fs command or filesystem APIs. Where possible it is backed by an in-memory filesystem and mounted noexec. It can be used to store secret data that should not be visible outside the task.These directories are persisted until the allocation is removed, which occurs hours after all the tasks in the task group enter terminal states. This gives time to view the data produced by tasks.
Depending on the driver and operating system being targeted, the directories are made available in various ways. For example, on docker the directories are bound to the container, while on exec on Linux the chroot is built in the task working directory, and the directories are mounted into that chroot. Regardless of how the directories are made available, the path to the directories can be read through the NOMAD_ALLOC_DIR, NOMAD_TASK_DIR, and NOMAD_SECRETS_DIR environment variables.
For more details on the task directories, see the Filesystem internals.
The job specification also allows you to specify a meta block to supply arbitrary configuration to a task. This allows you to easily provide job-specific configuration even if you use the same executable unit in multiple jobs. These key-value pairs are passed through to the job as NOMAD_META_<key>=<value> environment variables. Any character in a key other than [A-Za-z0-9_.] will be converted to _. Both the original case and an uppercased version are injected. The uppercased version will be deprecated in a future release.
Currently there is no enforcement that the meta keys be lowercase, but using multiple keys with the same uppercased representation will lead to undefined behavior.
Nomad passes the environment variables defined in the client host to tasks when using the exec, raw_exec, and java task drivers. Nomad also modifies HOME and USER variables for tasks that have the user parameter set, to reflect the set username. The variables that are passed to the tasks can be controlled using the client configuration env.denylist.
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