open-consul/website/content/commands/exec.mdx

84 lines
3.2 KiB
Plaintext

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