What is Knife?

Knife is a powerful command-line interface (CLI) that comes with Chef.

It is used by administrators to interact with the Chef Server API and the local Chef repository. It provides the capability to manipulate nodes, cookbooks, roles, databags, environments, etc., and can also be used to provision cloud resources and to bootstrap systems.

Overview

As the administrators command line tool for interacting for the chef server, Knife is run from the management workstation, acting as the intersection between the Chef Server and your infrastructure.

Knife interacts with the Chef Server through the same REST API that the Chef Client software uses, authenticating as an API client. Hosted Chef and Private Chef then have the additional role based authentication controls (RBAC) that authorize changes based upon users and organizations. See Authentication and Authorization for more information on this model.

Knife comes with a series of built in subcommands, which provide the functionality and capability for specific actions upon cookbooks, nodes, roles, etc. within your infrastructure. Knife also has the capability to be a container for Knife Plugins - which extend its functionality beyond the built in commands to features including launching cloud instances and bootstrapping systems.

There is a built in contextual help system for obtaining more information on the commands and subcommands, options for their use, or reviewing manpage documentation. When you go through Workstation Setup, one of the actions includes establishing and configuring knife for use. Subsequent modifications can be made through editing the knife.rb configuration file.

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Subcommands built into Knife:

• Bootstrap
• Client
• Cloud Plugins
• Configure
• Cookbook
• Cookbook Site
• Data Bag
• Environment
• Exec
• Node
• Recipe
• Role
• Search
• SSH
• Status
• Tag
• Bash command completion

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If you invoke knife with the --help option at the top level you will see options common to all subcommands.

If you invoke knife with the --help option at a specific subcommand level, knife presents the options specific to that subcommand.

Further, you can directly access manpages with content similar to this page using the help sub-command. Use knife help list.

Knife has a Man Page The man page for knife is the authoritative reference for knife. It is also shipped with the chef gem, rpm and deb. It can be easily accessed using knife's built-in help system:

You can then read individual pages by using a command in the form of:

Configuring Your System For Knife

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Knife's configuration file is named knife.rb. Unless directly passed the configuration file location via the -c command line option, Knife searches for this configuration by searching for .chef/knife.rb, starting at the current working directory and moving upward. If no configuration is found ~/.chef/knife.rb is used if it exists.

The following parameters can be set in knife.rb:

• node_name:
  User or client identity (i.e., name) to use for authenticating requests to the Chef Server.
• client_key:
  Private key file to authenticate to the Chef server. Corresponds to the -k or --key option.
• chef_server_url:
  URL of the Chef server. Corresponds to the -s or --server-url option. This is requested from the user when running this sub-command.
• cache_type:
  The type of cache to use. Default is BasicFile. This can be any type of Cache that moneta supports: BasicFile, Berkeley, Couch, DataMapper, File, LMC, Memcache, Memory, MongoDB, Redis, Rufus, S3, SDBM, Tyrant, Xattr, YAML.
• cache_option:
  Specifies various options to use for caching. These options are dependent on the cache_type.
• validation_client_name:
  Specifies the name of the client used to validate new clients.
• validation_key:
  Specifies the private key file to use when bootstrapping new hosts. See knife-client(1) for more information about the validation client.
• cookbook_copyright, cookbook_email, cookbook_license:
  Used by knife cookbook create sub-command to specify the copyright holder, maintainer email and license (respectively) for new cookbooks. The copyright holder is listed as the maintainer in the cookbook's metadata and as the Copyright in the comments of the default recipe. The maintainer email is used in the cookbook metadata. The license determines what preamble to put in the comment of the default recipe, and is listed as the license in the cookbook metadata. Currently supported licenses are "apachev2" and "none". Any other values will result in an empty license in the metadata (needs to be filled in by the author), and no comment preamble in the default recipe.

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With Chef 0.10, knife will load commands from the following locations:

• The core set of knife commands shipped with Chef
• Commands in your home chef directory: ~/.chef/plugins/knife/
• Commands in a .chef/plugins/knife/ directory in your cookbook repo
• Commands located in a chef/knife/ directory in a Ruby Gem you have installed.

See Knife Plugins for details on creating and installing plugins, and Community Plugins for a listing of plugins that have been made available by Chef community members.

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You can set this variable when issuing the command.

Alternatively you can set the variable for the rest of your shell's session.

See your shell's documentation for information on how to ensure that EDITOR is always set when you start a new shell.

Command and Output Options

Common Options

The following options can be passed to any subcommand. For sub-command specific options, see the section of Knife Built In Subcommands for the relevant subcommand.

• -s, --server-url URL:
  Chef Server URL
• -k, --key KEY:
  API Client Key
• --color:
  Use colored output
• -c, --config CONFIG:
  The configuration file to use
• --defaults:
  Accept default values for all questions
• -e, --editor EDITOR:
  Set the editor to use for interactive commands
• -E, --environment ENVIRONMENT:
  Set the Chef environment
• -F, --format FORMAT:
  Which format to use for output. See the Output Formats section below.
• --no-color:
  Don't use colors in the output
• -n, --no-editor:
  Do not open EDITOR, just accept the data as is
• -u, --user USER:
  API Client Username
• --print-after:
  Show the data after a destructive operation
• -V, --verbose:
  More verbose output. Use twice for max verbosity
• -v, --version:
  Show chef version
• -y, --yes:
  Say yes to all prompts for confirmation
• -h, --help:
  Show this message

Knife Output Change The default knife output changed with version 0.10. Previous version of knife output JSON while 0.10 formats its output for human consumption. Knife will still output JSON if passed the option -Fj at the command line.

Output Formats

The amount of content displayed and the output format can be modified by the `--format` option. If no alternate format is selected, the default is summary.

Valid formats are:

• summary:
  displays the node in a custom, summarized format (default)
• text:
  displays the node data in its entirety using the colorized tree display
• json:
  displays the node in JSON format
• yaml:
  displays the node in YAML format
• pp:
  displays the node using Ruby's pretty printer.

For brevity, only the first character of the format is required, for example, -Fj will produce JSON format output.

Managing Chef

Knife Built In Subcommands