84 lines
3.3 KiB
Plaintext
84 lines
3.3 KiB
Plaintext
---
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layout: commands
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page_title: 'Commands: Exec'
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description: >-
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The exec command provides a mechanism for remote execution. For example, this
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can be used to run the `uptime` command across all machines providing the
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`web` service.
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---
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# Consul Exec
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Command: `consul exec`
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The `exec` command provides a mechanism for remote execution. For example,
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this can be used to run the `uptime` command across all machines providing
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the `web` service.
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Remote execution works by specifying a job, which is stored in the KV store.
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Agents are informed about the new job using the [event system](/consul/commands/event),
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which propagates messages via the [gossip protocol](/consul/docs/architecture/gossip).
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As a result, delivery is best-effort, and there is **no guarantee** of execution.
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While events are purely gossip driven, remote execution relies on the KV store
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as a message broker. As a result, the `exec` command will not be able to
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properly function during a Consul outage.
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**Verbose output warning:** use care to make sure that your command does not
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produce a large volume of output. Writes to the KV store for this output go
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through the Consul servers and the Raft consensus algorithm, so having a large
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number of nodes in the cluster flow a large amount of data through the KV store
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could make the cluster unavailable.
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The table below shows the [required ACLs](/consul/api-docs/api-structure#authentication) in order to
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execute this command.
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| ACL Required | Scope |
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| --------------- | ----------------- |
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| `agent:read` | local agent |
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| `session:write` | local agent |
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| `key:write` | `"_rexec"` prefix |
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| `event:write` | `"_rexec"` prefix |
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In addition to the above, the policy associated with the [agent token](/consul/docs/security/acl/tokens#acl-agent-token) should have `write` on `"_rexec"` key prefix. This policy permits agents to read the `exec` command and write its output back to the KV store.
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## Usage
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Usage: `consul exec [options] [-|command...]`
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The only required option is a command to execute. This is either given
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as trailing arguments, or by specifying `-`; STDIN will be read to
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completion as a script to evaluate.
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#### Command Options
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- `-prefix` - Key prefix in the KV store to use for storing request data.
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Defaults to `_rexec`.
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- `-node` - Regular expression to filter nodes which should evaluate the event.
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- `-service` - Regular expression to filter to only nodes with matching services.
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- `-shell` - Optional, use a shell to run the command. The default value is true.
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- `-tag` - Regular expression to filter to only nodes with a service that has
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a matching tag. This must be used with `-service`. As an example, you may
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do `-service mysql -tag secondary`.
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- `-wait` - Specifies the period of time in which no agent's respond before considering
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the job finished. This is basically the quiescent time required to assume completion.
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This period is not a hard deadline, and the command will wait longer depending on
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various heuristics.
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- `-wait-repl` - Period to wait after writing the job specification for replication.
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This is a heuristic value and enables agents to do a stale read of the job. Defaults
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to 200 msec.
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- `-verbose` - Enables verbose output.
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#### API Options
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@include 'http_api_options_client.mdx'
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@include 'http_api_options_server.mdx'
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