# class_cmds: Class Commands

This section describes the Class Commands hooks library, which exposes several control commands for manipulating client classes, being a part of the Kea DHCP servers' configurations, without the need to restart those servers. Using these commands it is possible to add, update, delete and list client classes configured for a given server.

This library may only be loaded by `kea-dhcp4` or `kea-dhcp6` process.

The Class Commands hooks library is available to premium Kea customers only.

## class-add command

The `class-add` command is used to add a new client class to the DHCP server configuration. This class is appended at the end of the list of classes used by the server, i.e. this class may depend on any of the already configured client classes.

The following example demonstrates how to add a new client class to the DHCPv4 server configuration:

    {
        "command": "class-add",
        "arguments": {
            "client-classes": [
                {
                    "name": "ipxe_efi_x64",
                    "test": "option[93].hex == 0x0009",
                    "next-server": "192.0.2.254",
                    "server-hostname": "hal9000",
                    "boot-file-name": "/dev/null"
                }
            ]
        }
    }

Note that the `client-classes` parameter is a JSON list, but it allows only a single client class to be present. In the future this hooks library may be extended to support specification of multiple client classes within a single `class-add` command.

The following is the example response to the `class-add` command:

    {
        "result": 0,
        "text": "Class 'ipxe_efi_x64' added."
    }

## class-update command

The `class-update` command is used to update an existing client class in the DHCP server configuration. If the client class with the given name doesn't exist, the server returns result code of 3. In such case, the server configuration is not modified (client class is not created). The `class-add` command must be used instead to create the new client class.

The `class-update` command has the same arguments structure as `class-add` command:

    {
        "command": "class-update",
        "arguments": {
            "client-classes": [
                {
                    "name": "ipxe_efi_x64",
                    "test": "option[93].hex == 0x0017",
                    "next-server": "0.0.0.0",
                    "server-hostname": "xfce",
                    "boot-file-name": "/dev/null"
                }
            ]
        }
    }

The following is the example response:

    {
        "result": 0,
        "text": "Class 'ipxe_efi_x64' updated."
    }

Any parameter of the client class can be modified with this command, except `name`. There is currently no way to rename the class, because the class name is used as a key for searching the class to be updated. In order to achieve similar effect to renaming the class, an existing class should be removed with `class-del` command and then added again with a different name using `class-add`. Note however, that the class with the new name will be added at the end of the list of configured classes.

## class-del command

The `class-del` is used to remove a particular class from the server configuration. The class to be removed is identified by name. The class won't be removed if there are other classes dependening on it. In order to remove such class, the dependent classes must be removed first.

The following is the example command removing `ipxe_efi_x64` class:

    {
        "command": "class-del",
        "arguments": {
            {
                "name": "ipxe_efi_x64"
            }
        }
    }

The following is the sample response to the `class-del` command when the specified client class has been found:

    {
        "result": 0,
        "text": "Class 'ipxe_efi_x64' deleted."
    }

If the class doesn't exist, the result of 3 is returned.

## class-list command

The `class-list` is used to retrieve a list of all client classes. This command includes no arguments:

    {
        "command": "class-list"
    }

The following is the example response of the server including the list of client classes:

    {
        "result": 0,
        "text": "2 classes found",
        "arguments": {
            "client-classes": [
                {
                    "name": "ipxe_efi_x64"
                },
                {
                    "name": "pxeclient"
                }
            ]
        }
    }

Note that the returned list does not contain full class definitions, but merely class names. In order to retrieve full class information, the `class-get` command should be used.

## class-get command

The `class-get` is used to retrieve detail information about specified class. The command structure is very simple:

    {
        "command": "class-get",
        "arguments": {
            "name": "pxeclient"
        }
    }

If the class with the specified name doesn't exist, the status code of 3 is returned. If the specified client class exists, the class details are returned in the following format:

    {
        "result": 0,
        "text": "Class 'pxeclient' definition returned",
        "arguments": {
            "client-classes": [
                {
                    "name": "pxeclient",
                    "only-if-required": true,
                    "test": "option[vendor-class-identifier].text == 'PXEClient'",
                    "option-def": [
                        {
                            "name": "configfile",
                            "code": 209,
                            "type": "string"
                        }
                    ],
                    "option-data": [ ],
                    "next-server": "0.0.0.0",
                    "server-hostname": "xfce",
                    "boot-file-name": "/dev/null"
                }
            ]
        }
    }

Note that the example above is DHCPv4 specific. The last three parameters are only returned by the DHCPv4 server and never returned by the DHCPv6 server. Also, some of the parameters provided in this example may not be returned if they are not specified for the class. Specifically, `only-if-required`, `test` and the `option-def` are not returned if they are not specified for the class.