<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-3.11.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-3.11.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.
The helper slice is provided by ScyllaDB packages. If helper slice configuration is enabled and the ScyllaDB-provided
`scylla-helper.slice` unit is missing, the setup script fails and asks you to install or upgrade the ScyllaDB package
that provides it. If a legacy local `/etc/systemd/system/scylla-helper.slice` override or
`/etc/systemd/system/scylla-helper.slice.d` drop-in directory exists, the setup script moves it to a backup path so
the ScyllaDB-provided configuration can take effect without deleting local changes.

```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.
When run with `--no-scylla-helper-slice`, the script skips helper slice configuration and leaves any existing
`scylla-helper.slice` files untouched.

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