# LinuxConfigurator Operator

The **LinuxConfigurator** operator allows configuring systems tuned by Akamas by applying parameters related to the Linux kernel using different strategies.

The operator can configure provided Components or can configure every Component which has parameters related to the Linux kernel.

The parameters are applied via SSH protocol.

## Using <a href="#using" id="using"></a>

In the most basic use of the Operator, it is sufficient to add a task of type LinuxConfigurator in the workflow.

```yaml
- name: LinuxConf
  operator: LinuxConfigurator
  arguments:
    component: ComponentName
```

The operator makes use of properties specified in the component to identify which instance should be configured, how to access it, and any other information required to apply the configuration.

## Operator arguments <a href="#operator-arguments" id="operator-arguments"></a>

<table data-header-hidden><thead><tr><th></th><th width="187"></th><th></th><th></th><th></th><th></th></tr></thead><tbody><tr><td><strong>Name</strong></td><td><strong>Type</strong></td><td><strong>Value restrictions</strong></td><td><strong>Required</strong></td><td><strong>Default</strong></td><td><strong>Description</strong></td></tr><tr><td><code>component</code></td><td>String</td><td>It should match the name of an existing Component of the System under test</td><td>No</td><td></td><td>The name of the Component for which available Linux kernel parameters will be configured</td></tr></tbody></table>

If no `component` is provided, this operator will try to configure every parameter defined for the Components of the System under test

## Supported Component Properties <a href="#required-component-properties" id="required-component-properties"></a>

The following table highlights the properties that can be specified on components and are used by this operator.

| **Name**         | **Type**         | **Value restrictions**                                                                                                | **Required**                       | **Default** | **Description**                                                                                                           |
| ---------------- | ---------------- | --------------------------------------------------------------------------------------------------------------------- | ---------------------------------- | ----------- | ------------------------------------------------------------------------------------------------------------------------- |
| `hostname`       | String           | It should be a valid SSH host address                                                                                 | Yes                                |             | SSH host address                                                                                                          |
| `sshPort`        | Integer          | 1≤`sshPort`≤65532                                                                                                     | Yes                                | 22          | SSH port                                                                                                                  |
| `username`       | String           |                                                                                                                       | Yes                                |             | SSH login username                                                                                                        |
| `key`            | Multiline string |                                                                                                                       | Either key or password is required |             | SSH login key, provided directly its value or the path of the file to import from. The operator supports RSA and DSA Keys |
| `password`       | String           |                                                                                                                       | Either key or password is required |             |                                                                                                                           |
| `blockDevices`   | List of objects  | It should have a structure like the one described in the [next section](#filter-parameters-and-block-network-devices) | No                                 |             | Allows the user to restrict and specify to which block-device apply block-device-related parameters                       |
| `networkDevices` | List of objects  | It should have a structure like the one described in the [next section](#filter-parameters-and-block-network-devices) | No                                 |             | Allows the user to restrict and specify to which network-device apply network-device-related parameters                   |

### Filter parameters and block/network devices <a href="#filter-parameters-and-block-network-devices" id="filter-parameters-and-block-network-devices"></a>

The properties `blockDevices` and `networkDevices` allow specifying which parameters to apply to each block/network-device associated with the Component, as well as which block/network-device should be left untouched by the *LinuxConfigurator.*

If the properties are omitted, then all block/network-devices associated with the Component will be configured will all the available related parameters.

All block-devices called *loopN* (where *N* is an integer number greater or equal to 0) are automatically excluded from the Component’s block-devices

The properties `blockDevices` and `networkDevices` are lists of objects with the following structure:

| **Name**     | **Type**        | **Value restrictions**                                                 | **Required** | **Default** | **Description**                                                                                                                                                                          |
| ------------ | --------------- | ---------------------------------------------------------------------- | ------------ | ----------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `name`       | String          | It should be a valid regular expression to match block/network-devices | Yes          |             | A regular expression that matches block/network-devices to configure with related parameters of the Component                                                                            |
| `parameters` | List of strings | It should contain the names of matching parameters of the Component    | No           |             | The list of parameters to be configured for the specified block/network-devices. If the list is empty, then no parameter will be applied for the block/network-devices matched by `name` |

### Examples <a href="#examples" id="examples"></a>

```yaml
blockDevices:
- name: "xvd[a-z]"
  parameters:
    - os_StorageReadAhead
    - os_StorageQueueScheduler
```

In this example, **only** the parameters *os\_StorageReadAhead* and *os\_StorageQeueuScheduler* are applied to all the devices that match the regex "xvd\[a-z]" (i.e. xvda, xvdb, …, xvdc).

```yaml
blockDevices:
- name: "xvdb|loop0"
  parameters:
    - os_StorageMaxSectorsKb
```

In these examples, **only** the parameter *os\_StorageMaxSectorKb* is applied to block device *xvdb* and *loop0*.

{% hint style="info" %}
Note that the parameter is applied also to the block device *loop0*, since it is specified in the name filter, this overrides the default behavior since *loopN* devices are excluded by the Linux Optimization Pack
{% endhint %}

```yaml
networkDevices:
  - name: wlp4s0
    parameters: []
```

In this example, no parameters are applied to the *wlp4s0* network device, which is therefore excluded from the optimization.

## How are parameters applied to the system? <a href="#requirements" id="requirements"></a>

To support the scenario in which some configuration parameters related to the Linux kernel may be applied using the strategies supported by this operator, while others with other strategies (e.g, using a file to be written on a remote machine), it is necessary to specify which parameters should be applied with the LinuxConfigurator, and this is done at the ComponentType level; moreover, still at the ComponentType level, it is necessary to specify which strategy should be used to configure each parameter. This information is already embedded in the Linux Optimization pack and, usually, no customization is required.

#### Sysctl strategy <a href="#sysctl-strategy" id="sysctl-strategy"></a>

With this strategy, a parameter is configured by leveraging the *sysctl* utility. The *sysctl* variable to map to the parameter that needs to be configured is specified using the `key` argument.

```yaml
name: Component Type 1
description: My Component type
parameters:
  - name: net_forwarding
    domain:
      type: integer
      domain: [0, 1]
    defaultValue: 1
    operators:
      # the parameter is configured using LinuxConfigurator
      LinuxConfigurator:
        sysctl:
          key: net.ipv4.forwarding
```

#### Echo strategy <a href="#echo-strategy" id="echo-strategy"></a>

With this strategy, a parameter is configured by echoing and piping its value into a provided file. The path of the file is specified using the `file` argument.

```yaml
name: Component Type 1
description: My Component type
parameters:
  - name: os_MemoryTransparentHugepageEnabled
    domain:
      type: categorical
      categories: [always, never]
    defaultValue: always
    operators:
      LinuxConfigurator:
        echo:
          file: /sys/kernel/mm/transparent_hugepage/enabled
```

#### Map strategy <a href="#hardbreak-map-strategy" id="hardbreak-map-strategy"></a>

With this strategy, each possible value of a parameter is mapped to a command to be executed on the machine the LinuxConfigurator operates on(this is especially useful for categorical parameters).

```yaml
name: Component Type 1
description: My Component type
parameters:
  - name: os_MemorySwap
    domain:
      type: categorical
      categories: [swapon, swapoff]
    defaultValue: swapon
    operators:
      LinuxConfigurator:
        map:
          swapon: command1
          swapoff: command2
```

#### Command strategy <a href="#command-strategy" id="command-strategy"></a>

With this strategy, a parameter is configured by executing a command into which the parameter value is interpolated.

```yaml
name: Component Type 1
description: My Component type
parameters:
  - name: os_MemorySwap
    domain:
      type: categorical
      categories: [swapon, swapoff]
    defaultValue: swapon
    operators:
      LinuxConfigurator:
        command:
          cmd: sudo ${value} -a
```