Install Logstash on Ubuntu

Add ELK repository to apt.

Add GPG key of ELK's repository via apt-key.

$ wget --quiet --output-document=- https://artifacts.elastic.co/GPG-KEY-elasticsearch | sudo apt-key add -
[sudo] password for user:
OK

Add ELK's repository to apt's repository list.

$ echo "deb https://artifacts.elastic.co/packages/6.x/apt stable main" | sudo tee -a /etc/apt/sources.list.d/elastic-6.x.list
deb https://artifacts.elastic.co/packages/6.x/apt stable main

Update list of available packages from the newly added repository.
```
$ sudo apt update
```
Install latest Java Runtime Environment.
```
$ sudo apt install -y openjdk-11-jre
```
Install logstash package.
```
$ sudo apt install -y logstash
```
Configure logstash options located in /etc/logstash/logstash.yml.
1. Allow connection from remote host.
```
xxx: 0.0.0.0
```
Configure logstash to automatically start during boot.
```
$ sudo systemctl enable logstash
```
Start logstash service.
```
 $ sudo systemctl start logstash
```