# Install By Gem

This article explains how to install Fluentd using Ruby gem.

## Step0: Before Installation

Please follow the [Preinstallation Guide](https://docs.fluentd.org/0.12/articles/before-install) to configure your OS properly. This will prevent many unnecessary problems.

## Step1: Install Ruby interpreter

Please install Ruby >= 1.9.3 on your local environment. In addition, install ruby-dev package via package manager to build native extension gems.

## Step2: Install Fluentd gem

Fetch and install the `fluentd` Ruby gem using the `gem` command. The official ruby gem page is [here](https://rubygems.org/gems/fluentd).

```
$ gem install fluentd -v "~> 0.12.0" --no-ri --no-rdoc
```

`-v "~> 0.12.0"` is needed for v0.12 installation. Without it, you install v0.14 series.

## Step3: Run

Run the following commands to confirm that Fluentd was installed successfully:

```
$ fluentd --setup ./fluent
$ fluentd -c ./fluent/fluent.conf -vv & # -vv enables trace level logs. You can omit -vv option.
$ echo '{"json":"message"}' | fluent-cat debug.test
```

The last command sends Fluentd a message '{"json":"message"}' with a "debug.test" tag. If the installation was successful, Fluentd will output the following message:

```
2011-07-10 16:49:50 +0900 debug.test: {"json":"message"}
```

It's HIGHLY recommended that you set up **ntpd** on the node to prevent invalid timestamps in your logs.

For large deployments, you must use [jemalloc](http://www.canonware.com/jemalloc/) to avoid memory fragmentation. This is already included in the [rpm](https://docs.fluentd.org/0.12/articles/install-by-rpm) and [deb](https://docs.fluentd.org/0.12/articles/install-by-deb) packages.

The Fluentd gem doesn't come with /etc/init.d/ scripts. You should use process management tools such as [daemontools](http://cr.yp.to/daemontools.html), [runit](http://smarden.org/runit/), [supervisord](http://supervisord.org/), or [upstart](http://upstart.ubuntu.com/).

## Next Steps

You're now ready to collect your real logs using Fluentd. Please see the following tutorials to learn how to collect your data from various data sources.

* Basic Configuration
  * [Config File](https://docs.fluentd.org/0.12/configuration/config-file)
* Application Logs
  * [Ruby](https://docs.fluentd.org/0.12/articles/ruby), [Java](https://docs.fluentd.org/0.12/articles/java), [Python](https://docs.fluentd.org/0.12/articles/python), [PHP](https://docs.fluentd.org/0.12/articles/php),

    [Perl](https://docs.fluentd.org/0.12/articles/perl), [Node.js](https://docs.fluentd.org/0.12/articles/nodejs), [Scala](https://docs.fluentd.org/0.12/articles/scala)
* Examples
  * [Store Apache Log into Amazon S3](https://docs.fluentd.org/0.12/articles/apache-to-s3)
  * [Store Apache Log into MongoDB](https://docs.fluentd.org/0.12/articles/apache-to-mongodb)
  * [Data Collection into HDFS](https://docs.fluentd.org/0.12/articles/http-to-hdfs)

If this article is incorrect or outdated, or omits critical information, please [let us know](https://github.com/fluent/fluentd-docs-gitbook/issues?state=open). [Fluentd](http://www.fluentd.org/) is a open source project under [Cloud Native Computing Foundation (CNCF)](https://cncf.io/). All components are available under the Apache 2 License.