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AWS OpsWorks
User Guide (API Version 2013-02-18)

Using the AWS OpsWorks Stacks Agent CLI

Note

The agent CLI is available only on Linux instances.

On every online instance, AWS OpsWorks Stacks installs an agent, which communicates with the service. The AWS OpsWorks Stacks service in turn sends commands to the agent to performs tasks such as initiating Chef runs on the instance when a lifecycle event occurs. On Linux instances, the agent exposes a command line interface (CLI) that is very useful for troubleshooting. To run agent CLI commands, use SSH to connect to an instance. You can then run agent CLI commands to perform a variety of tasks, including the following:

For more information on how to set up an SSH connection to an instance, see Logging In with SSH. You must also have SSH and sudo permissions for the stack.

This section describes how to use the agent CLI for troubleshooting. For more information and a complete command reference, see AWS OpsWorks Stacks Agent CLI.

Executing Recipes

The agent CLI run_command command directs the agent to rerun a command that it performed earlier. The most useful commands for troubleshooting—setup, configure, deploy, and undeploy—each correspond to a lifecycle event. They direct the agent to initiate a Chef run to execute the associated recipes.

Note

The run_command command is limited to executing the group of recipes that is associated with a specified command, typically the recipes that are associated with a lifecycle event. You cannot use it to execute a particular recipe. To execute one or more specified recipes, use the Execute Recipes stack command or the equivalent CLI or API actions (create-deployment and CreateDeployment).

The run_command command is quite useful for debugging custom recipes, especially recipes that are assigned to the Setup and Configure lifecycle events, which you can't trigger directly from the console. By using run_command, you can run a particular event's recipes as often as you need without having to start or stop instances.

Note

AWS OpsWorks Stacks runs recipes from the instance's cookbook cache, not the cookbook repository. AWS OpsWorks Stacks downloads cookbooks to this cache when the instance starts, but does not automatically update the cache on online instances if you subsequently modify your cookbooks. If you have modified your cookbooks since starting the instance, be sure to run the Update Cookbooks stack command stack command to update the cookbook cache with the most recent version from the repository.

The agent caches only the most recent commands. You can list them by running list_commands, which returns a list of cached commands and the time that they were performed.

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sudo opsworks-agent-cli list_commands 2013-02-26T19:08:26 setup 2013-02-26T19:12:01 configure 2013-02-26T19:12:05 configure 2013-02-26T19:22:12 deploy

To rerun the most recent command, run this:

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sudo opsworks-agent-cli run_command

To rerun the most recent instance of a specified command, run this:

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sudo opsworks-agent-cli run_command command

For example, to rerun the Setup recipes, you can run the following command:

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sudo opsworks-agent-cli run_command setup

Each command has an associated stack configuration and deployment JSON that represents stack and deployment state at the time the command was run. Because that data can change from one command to the next, an older instance of a command might use somewhat different data than the most recent one. To rerun a particular instance of a command, copy the time from the list_commands output and run the following:

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sudo opsworks-agent-cli run_command time

The preceding examples all rerun the command using the default JSON, which is the JSON was installed for that command. You can rerun a command against an arbitrary JSON file as follows:

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sudo opsworks-agent-cli run_command /path/to/valid/json.file

Displaying Chef Logs

The agent CLI show_log command displays a specified log. After the command is finished, you will be looking at the end of the file. The show_log command therefore provides a convenient way to tail the log, which is typically where you find error information. You can scroll up to see the earlier parts of the log.

To display the current command's log, run this:

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sudo opsworks-agent-cli show_log

You can also display logs for a particular command, but be aware that the agent caches logs for only the last thirty commands. You can list an instance's commands by running list_commands, which returns a list of cached commands and the time that they were performed. For an example, see Executing Recipes.

To show the log for the most recent execution of a particular command, run the following:

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sudo opsworks-agent-cli show_log command

The command parameter can be set to setup, configure, deploy, undeploy, start, stop, or restart. Most of these commands correspond to lifecycle events and direct the agent to run the associated recipes.

To display the log for a particular command execution, copy the date from the list_commands output and run:

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sudo opsworks-agent-cli show_log date

If a command is still executing, show_log displays the log's current state.

Note

One way to use show_log to troubleshoot errors and out-of-memory issues is to tail a log during execution, as follows:

  1. Use run_command to trigger the appropriate lifecycle event. For more information, see Executing Recipes.

  2. Repeatedly run show_log to see the tail of the log as it is being written.

If Chef runs out of memory or exits unexpectedly, the log will end abruptly. If a recipe fails, the log will end with an exception and a stack trace.

Displaying the Stack Configuration and Deployment JSON

Much of the data used by recipes comes from the stack configuration and deployment JSON, which defines a set of Chef attributes that provide a detailed description of the stack configuration, any deployments, and optional custom attributes that users can add. For each command, AWS OpsWorks Stacks installs a JSON that represents the stack and deployment state at the time of the command . For more information, see Stack Configuration and Deployment Attributes.

If your custom recipes obtain data from the stack configuration and deployment JSON, you can verify the data by examining the JSON. The easiest way to display the stack configuration and deployment JSON is to run the agent CLI get_json command, which displays a formatted version of the JSON object. The following shows the first few lines of some typical output:

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{ "opsworks": { "layers": { "php-app": { "id": "4a2a56c8-f909-4b39-81f8-556536d20648", "instances": { "php-app2": { "elastic_ip": null, "region": "us-west-2", "booted_at": "2013-02-26T20:41:10+00:00", "ip": "10.112.235.192", "aws_instance_id": "i-34037f06", "availability_zone": "us-west-2a", "instance_type": "c1.medium", "private_dns_name": "ip-10-252-0-203.us-west-2.compute.internal", "private_ip": "10.252.0.203", "created_at": "2013-02-26T20:39:39+00:00", "status": "online", "backends": 8, "public_dns_name": "ec2-10-112-235-192.us-west-2.compute.amazonaws.com" ...

You can display the most recent stack configuration and deployment JSON as follows:

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sudo opsworks-agent-cli get_json

You can display the most recent stack configuration and deployment JSON for a specified command by executing the following:

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sudo opsworks-agent-cli get_json command

The command parameter can be set to setup, configure, deploy, undeploy, start, stop, or restart. Most of these commands correspond to lifecycle events and direct the agent to run the associated recipes.

You can display the stack configuration and deployment JSON for a particular command execution by specifying the command's date like this:

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sudo opsworks-agent-cli get_json date

The simplest way to use this command is as follows:

  1. Run list_commands, which returns a list of commands that have been run on the instance, and the date that each command was run.

  2. Copy the date for the appropriate command and use it as the get_json date argument.