<a id="install-agent"></a>

# Install ScyllaDB Manager Agent

ScyllaDB Manager Agent is a daemon, that needs to be **installed and started on each ScyllaDB node**.
ScyllaDB Manager Server communicates with nodes in the managed ScyllaDB clusters via the Agents.
The communication is encrypted (HTTPS) and protected by an auth token.
Agent serves as a reverse proxy to ScyllaDB REST API, and provides additional features specific to ScyllaDB Manager.

#### NOTE
Repeat the procedure for **every** ScyllaDB node in the cluster that you want to be managed by ScyllaDB Manager.

> * [Install package](#install-package)
> * [Run the scyllamgr_agent_setup script](#run-the-scyllamgr-agent-setup-script)
> * [Configure an authentication token](#configure-an-authentication-token)
> * [Start ScyllaDB Manager Agent service](#start-scylladb-manager-agent-service)
> * [Next steps](#next-steps)

## Install package

Debian/Ubuntu

1. Import the ScyllaDB GPG signing key. *Note*: If ScyllaDB is already installed on this node, the key was
   imported during ScyllaDB installation.
   > ```console
   > sudo mkdir -p /etc/apt/keyrings
   > sudo gpg --homedir /tmp --no-default-keyring --keyring /etc/apt/keyrings/scylladb.gpg --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys a43e06657bac99e3
   > ```
2. Add the ScyllaDB Manager APT repository to your system.
   > ```console
   > sudo curl -o /etc/apt/sources.list.d/scylla-manager.list -L https://downloads.scylladb.com/deb/debian/scylladb-manager-3.9.list
   > ```
3. Install ScyllaDB Manager Agent.
   > ```console
   > sudo apt update
   > sudo apt install -y scylla-manager-agent
   > ```

Centos/RHEL

> 1. Add the ScyllaDB Manager RPM repository to your system.
>    > ```console
>    > sudo curl -o /etc/yum.repos.d/scylla-manager.repo -L https://downloads.scylladb.com/rpm/centos/scylladb-manager-3.9.repo
>    > ```
1. Install ScyllaDB Manager Agent.
   > ```console
   > sudo yum install scylla-manager-agent
   > ```

## Run the scyllamgr_agent_setup script

The ScyllaDB Manager Agent setup script automates configuration of ScyllaDB Manager Agent by asking you some questions.
It can be run in non-interactive mode by using flags.
You will need to run this command as root or with sudo.

#### NOTE
Make sure you run the ScyllaDB Manager Agent setup script, and enable ScyllaDB helper slice.
The helper slice contains a cgroup definition that governs ScyllaDB Manager Agent resources usage.
Without the slice the node latency during backup upload maybe unpredictable.

```none
scyllamgr_agent_setup -h
Usage: scyllamgr_agent_setup [-y][--no-scylla-helper-slice]

Options:
  -y, --assume-yes          assume that the answer to any question which would be asked is yes
  --no-scylla-helper-slice  skip configuring systemd scylla-helper.slice
  --no-enable-service       skip enabling service
  -h, --help                print this help

Interactive mode is enabled when no flags are provided.
```

Run the `scyllamgr_agent_setup` script to configure the service. You will need to run this command as root or with sudo.

For example:

```none
sudo scyllamgr_agent_setup -y
```

<a id="configure-auth-token"></a>

## Configure an authentication token

Authentication tokens are used to authenticate requests to the Agent.
Unauthenticated requests are rejected.
**Use the same token on all the nodes in a cluster**. Use different tokens in different clusters.

**Procedure**

1. On **one node only** generate an authentication token to be used to authenticate ScyllaDB Manager with the Agent.
   Run the token generator script. For example:
   ```none
   scyllamgr_auth_token_gen
   6Es3dm24U72NzAu9ANWmU3C4ALyVZhwwPZZPWtK10eYGHJ24wMoh9SQxRZEluWMc0qDrsWCCshvfhk9uewOimQS2x5yNTYUEoIkO1VpSmTFu5fsFyoDgEkmNrCJpXtfM
   ```
2. Take the auth token you generated, and place it into `/etc/scylla-manager-agent/scylla-manager-agent.yaml` as the `auth_token` parameter value, remember to uncomment the line. For Example:
   ```none
   cat /etc/scylla-manager-agent/scylla-manager-agent.yaml
   ```

   Results in:
   ```none
   # Scylla Manager Agent config YAML

   # Specify authentication token, the auth_token needs to be the same for all the
   # nodes in a cluster. Use scyllamgr_auth_token_gen to generate the auth_token
   # value.
   auth_token: 6Es3dm24U72NzAu9ANWmU3C4ALyVZhwwPZZPWtK10eYGHJ24wMoh9SQxRZEluWMc0qDrsWCCshvfhk9uewOimQS2x5yNTYUEoIkO1VpSmTFu5fsFyoDgEkmNrCJpXtfM

   ...
   ```

   #### NOTE
   Use the same token on all the nodes in a cluster

## Start ScyllaDB Manager Agent service

**Procedure**

1. Start ScyllaDB Manager Agent service.
   ```none
   sudo systemctl start scylla-manager-agent
   ```
2. Verify the ScyllaDB Manager Agent is running.
   ```none
   sudo systemctl status scylla-manager-agent -l
   ● scylla-manager-agent.service - Scylla Manager Agent
     Loaded: loaded (/usr/lib/systemd/system/scylla-manager-agent.service; disabled; vendor preset: disabled)
     Active: active (running) since Wed 2019-10-30 10:46:51 UTC; 7s ago
       Main PID: 14670 (scylla-manager-)
       CGroup: /system.slice/scylla-manager-agent.service
              └─14670 /usr/bin/scylla-manager-agent
   ```

## Next steps

* [Configure backup location](https://manager.docs.scylladb.com/branch-3.9/backup/index.md#backup-location)
* [Configure native backup](https://manager.docs.scylladb.com/branch-3.9/backup/native-backup.md#configure-native-backup-in-scylla)
* [Add a Cluster](https://manager.docs.scylladb.com/branch-3.9/add-a-cluster.md)