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Executing Remote Commands | Developer Guide | OKD 3.7
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Executing Remote Commands

Overview

You can use the cli to execute remote commands in a container. This allows you to run general Linux commands for routine operations in the container.

For security purposes, the oc exec command does not work when accessing privileged containers except when the command is executed by a cluster-admin user. See the cli operations topic for more information.

Basic Usage

Support for remote container command execution is built into the cli:

$ oc exec <pod> [-c <container>] <command> [<arg_1> ... <arg_n>]

For example:

$ oc exec mypod date
Thu Apr  9 02:21:53 UTC 2015

Protocol

clients initiate the execution of a remote command in a container by issuing a request to the Kubernetes API server:

/proxy/minions/<node_name>/exec/<namespace>/<pod>/<container>?command=<command>

In the above URL:

  • <node_name> is the FQDN of the node.

  • <namespace> is the namespace of the target pod.

  • <pod> is the name of the target pod.

  • <container> is the name of the target container.

  • <command> is the desired command to be executed.

For example:

/proxy/minions/node123.openshift.com/exec/myns/mypod/mycontainer?command=date

Additionally, the client can add parameters to the request to indicate if:

  • the client should send input to the remote container’s command (stdin).

  • the client’s terminal is a TTY.

  • the remote container’s command should send output from stdout to the client.

  • the remote container’s command should send output from stderr to the client.

After sending an exec request to the API server, the client upgrades the connection to one that supports multiplexed streams; the current implementation uses SPDY.

The client creates one stream each for stdin, stdout, and stderr. To distinguish among the streams, the client sets the streamType header on the stream to one of stdin, stdout, or stderr.

The client closes all streams, the upgraded connection, and the underlying connection when it is finished with the remote command execution request.

Administrators can see the Architecture guide for more information.