--- layout: "docs" page_title: "client Stanza - Agent Configuration" sidebar_current: "docs-agent-configuration-client" description: |- The "client" stanza configures the Nomad agent to accept jobs as assigned by the Nomad server, join the cluster, and specify driver-specific configuration. --- # `client` Stanza
Placement **client**
The `client` stanza configures the Nomad agent to accept jobs as assigned by the Nomad server, join the cluster, and specify driver-specific configuration. ```hcl client { enabled = true servers = ["1.2.3.4:4647", "5.6.7.8:4647"] } ``` ## `client` Parameters - `alloc_dir` `(string: "[data_dir]/alloc")` - Specifies the directory to use for allocation data. By default, this is the top-level [data_dir](/docs/agent/configuration/index.html#data_dir) suffixed with "alloc", like `"/opt/nomad/alloc"`. This must be an absolute path - `chroot_env` ([ChrootEnv](#chroot_env-parameters): nil) - Specifies a key-value mapping that defines the chroot environment for jobs using the Exec and Java drivers. - `enabled` `(bool: false)` - Specifies if client mode is enabled. All other client configuration options depend on this value. - `max_kill_timeout` `(string: "30s")` - Specifies the maximum amount of time a job is allowed to wait to exit. Individual jobs may customize their own kill timeout, but it may not exceed this value. - `meta` ([Meta][]: nil) - Specifies a key-value map that annotates with user-defined metadata. - `network_interface` `(string: "lo | lo0")` - Specifies the name of the interface to force network fingerprinting on. This defaults to the loopback interface. - `network_speed` `(int: 0)` - Specifies an override for the network link speed. This value, if set, overrides any detected or defaulted link speed. Most clients can determine their speed automatically, and thus in most cases this should be left unset. - `node_class` `(string: "")` - Specifies an arbitrary string used to logically group client nodes by user-defined class. This can be used during job placement as a filter. - `options` ([Options](#options-parameters): nil) - Specifies a key-value mapping of internal configuration for clients, such as for driver configuration. - `reserved` ([Reserved](#reserved-parameters): nil) - Specifies that Nomad should reserve a portion of the node's resources from receiving tasks. This can be used to target a certain capacity usage for the node. For example, 20% of the node's CPU could be reserved to target a CPU utilization of 80%. - `servers` `(array: [])` - Specifies an array of addresses to the Nomad servers this client should join. This list is used to register the client with the server nodes and advertise the available resources so that the agent can receive work. This may be specified as an IP address or DNS, with or without the port. If the port is omitted, the default port of `4647` is used. - `state_dir` `(string: "[data_dir]/client")` - Specifies the directory to use to store client state. By default, this is - the top-level [data_dir](/docs/agent/configuration/index.html#data_dir) suffixed with "client", like `"/opt/nomad/client"`. This must be an absolute path. ### `chroot_env` Parameters Drivers based on [isolated fork/exec](/docs/drivers/exec.html) implement file system isolation using chroot on Linux. The `chroot_env` map allows the chroot environment to be configured using source paths on the host operating system. The mapping format is: ```text source_path -> dest_path ``` The following example specifies a chroot which contains just enough to run the `ls` utility: ```hcl client { chroot_env { "/bin/ls" = "/bin/ls" "/etc/ld.so.cache" = "/etc/ld.so.cache" "/etc/ld.so.conf" = "/etc/ld.so.conf" "/etc/ld.so.conf.d" = "/etc/ld.so.conf.d" "/lib" = "/lib" "/lib64" = "/lib64" } } ``` When `chroot_env` is unspecified, the `exec` driver will use a default chroot environment with the most commonly used parts of the operating system. Please see the [Nomad `exec` driver documentation](/docs/drivers/exec.html#chroot) for the full list. ### `options` Parameters The following is not an exhaustive list of options for only the Nomad client. To find the options supported by each individual Nomad driver, please see the [drivers documentation](/docs/drivers/index.html). - `"driver.whitelist"` `(string: "")` - Specifies a comma-separated list of whitelisted drivers . If specified, drivers not in the whitelist will be disabled. If the whitelist is empty, all drivers are fingerprinted and enabled where applicable. ```hcl client { options = { "driver.whitelist" = "docker,qemu" } } ``` - `"driver.blacklist"` `(string: "")` - Specifies a comma-separated list of blacklisted drivers . If specified, drivers in the blacklist will be disabled. ```hcl client { options = { "driver.blacklist" = "docker,qemu" } } ``` - `"env.blacklist"` `(string: see below)` - Specifies a comma-separated list of environment variable keys not to pass to these tasks. Nomad passes the host environment variables to `exec`, `raw_exec` and `java` tasks. If specified, the defaults are overridden. If a value is provided, **all** defaults are overridden (they are not merged). ```hcl client { options = { "env.blacklist" = "MY_CUSTOM_ENVVAR" } } ``` The default list is: ```text CONSUL_TOKEN VAULT_TOKEN ATLAS_TOKEN AWS_ACCESS_KEY_ID AWS_SECRET_ACCESS_KEY AWS_SESSION_TOKEN GOOGLE_APPLICATION_CREDENTIALS ``` - `"user.blacklist"` `(string: see below)` - Specifies a comma-separated blacklist of usernames for which a task is not allowed to run. This only applies if the driver is included in `"user.checked_drivers"`. If a value is provided, **all** defaults are overridden (they are not merged). ```hcl client { options = { "user.blacklist" = "root,ubuntu" } } ``` The default list is: ```text root Administrator ``` - `"user.checked_drivers"` `(string: see below)` - Specifies a comma-separated list of drivers for which to enforce the `"user.blacklist"`. For drivers using containers, this enforcement is usually unnecessary. If a value is provided, **all** defaults are overridden (they are not merged). ```hcl client { options = { "user.checked_drivers" = "exec,raw_exec" } } ``` The default list is: ```text exec qemu java ``` - `"fingerprint.whitelist"` `(string: "")` - Specifies a comma-separated list of whitelisted fingerprinters. If specified, any fingerprinters not in the whitelist will be disabled. If the whitelist is empty, all fingerprinters are used. ```hcl client { options = { "fingerprint.whitelist" = "network" } } ``` - `"fingerprint.blacklist"` `(string: "")` - Specifies a comma-separated list of blacklisted fingerprinters. If specified, any fingerprinters in the blacklist will be disabled. ```hcl client { options = { "fingerprint.blacklist" = "network" } } ``` ### `reserved` Parameters - `cpu` `(int: 0)` - Specifies the amount of CPU to reserve, in MHz. - `memory` `(int: 0)` - Specifies the amount of memory to reserve, in MB. - `disk` `(int: 0)` - Specifies the amount of disk to reserve, in MB. - `reserved_ports` `(string: "")` - Specifies a comma-separated list of ports to reserve on all fingerprinted network devices. Ranges can be specified by using a hyphen separated the two inclusive ends. ## `client` Examples ### Common Setup This example shows the most basic configuration for a Nomad client joined to a cluster. ```hcl client { enabled = true servers = ["1.2.3.4:4647", "5.6.7.8:4647"] } ``` ### Reserved Resources This example shows a sample configuration for reserving resources to the client. This is useful if you want to allocate only a portion of the client's resources to jobs. ```hcl client { enabled = true reserved { cpu = 500 memory = 512 disk = 1024 reserved_ports = "22,80,8500-8600" } } ``` ### Custom Metadata, Network Speed, and Node Class This example shows a client configuration which customizes the metadata, network speed, and node class. ```hcl client { enabled = true network_speed = 500 node_class = "prod" meta { "owner" = "ops" } } ``` [meta]: /docs/job-specification/meta.html "Nomad meta Job Specification"