> For the complete documentation index, see [llms.txt](https://daniel-guo.gitbook.io/notebook/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://daniel-guo.gitbook.io/notebook/having-fun-with-docker/customize-fluentd-docker-image.md).

# Customize Fluentd docker image

## What is Fluentd

Briefly speaking, Fluentd is an open source data collector, which lets you unify the data collection and consumption for a better use and understanding of data. Click [here](/notebook/logging-related/logging-tools-or-projects/fluentd.md) for more details.

You could use Fluentd by either installing the Fluentd agent manually as the daemon process or running a docker image. This article will mainly focus on how to build you own Fluentd docker image which fits your use cases.

## Get started

* Create folder with the following skeleton

```
#$:~/fluentd-docker$ tree .
.
├── Dockerfile
├── fluent.conf
└── plugins

1 directory, 2 files
```

* Edit the `Dockerfile` 

```
FROM fluent/fluentd:v1.4-debian-onbuild

# Use root account to use apt
USER root

# below RUN includes plugin as examples elasticsearch is not required
# you may customize including plugins as you wish
RUN buildDeps="sudo make gcc g++ libc-dev ruby-dev" \
 && apt-get update \
 && apt-get install -y --no-install-recommends $buildDeps \
 && apt-get install -y libsystemd0 \
 && sudo gem install fluent-plugin-vmware-loginsight \
 && sudo gem install fluent-plugin-systemd -v 1.0.1 \
 && sudo gem sources --clear-all \
 && SUDO_FORCE_REMOVE=yes \
    apt-get purge -y --auto-remove \
                  -o APT::AutoRemove::RecommendsImportant=false \
                  $buildDeps \
 && rm -rf /var/lib/apt/lists/* \
           /home/fluent/.gem/ruby/2.3.0/cache/*.gem

USER fluent
```

{% hint style="info" %}

* `apt-get install -y libsystemd0` and  `sudo gem install fluent-plugin-systemd -v 1.0.1` are specificly for fetching systemd logs

* Refer to the official [doc](https://hub.docker.com/r/fluent/fluentd) for more details

* All available fluentd plugins could be found [here](https://www.fluentd.org/plugins)
  {% endhint %}

* `fluent.conf` is required to build the custom docker image. It could be a default conf file. When you run the docker image the config file could be replaced from the `docker run` command.

The following fluent.conf is just an example for fetching the systemd log:

```
<source>
  @type systemd
  tag pks-mgmt-server
  path /var/log/journal
  matches [{ "_SYSTEMD_UNIT": "pks-mgmt-server.service" }]
  read_from_head true
</source>

<source>
  @type systemd
  tag pks-ui-server
  path /var/log/journal
  matches [{ "_SYSTEMD_UNIT": "pks-ui-server.service" }]
  read_from_head true
</source>

<source>
  @type systemd
  tag nginx
  path /var/log/journal
  matches [{ "_SYSTEMD_UNIT": "nginx.service" }]
  read_from_head true
</source>

<filter **>
  @type systemd_entry
  fields_lowercase true
  fields_strip_underscores true
</filter>

<match **>
  @type vmware_loginsight
  host <log-server-ip>
  port 9543
  scheme https
    ssl_verify false
  path api/v1/events/ingest
  agent_id xxxxxx
  http_method post
  serializer json
  rate_limit_msec 0
  raise_on_error false
  flush_mode interval
  flush_interval 20
  include_tag_key true
  tag_key tag
</match>
```

* You could leave plugins folder empty in this example
* Build the new image by using `docker build` command
* Refer to the official [doc](https://hub.docker.com/r/fluent/fluentd) for running the container with your own configuration files and other additional options.