# Jenkins

How to install and administrate Jenkins.

## Install

### Java

You need Java 8 or 11 if you have Jenkins above 2.164.

```
sudo apt install openjdk-8-jre
```

### Raspberry Pi

[Jenkins doc : installation](https://jenkins.io/doc/book/installing/#debianubuntu)

To execute on debian server

```
wget -q -O - https://pkg.jenkins.io/debian/jenkins.io.key | sudo apt-key add - ;
sudo sh -c 'echo deb https://pkg.jenkins.io/debian-stable binary/ > /etc/apt/sources.list.d/jenkins.list' ;
sudo apt-get update ;
sudo apt-get install jenkins ;
```

Jenkins is now installed as a daemon and you should connect locally to it with a browser to complete installation.

`192.168.0.40:8080`

### HTTPS

The best way to secure _Jenkins_ is to use the proxy with _Apache_.

[Jenkins wiki : running Jenkins behind Apache](https://wiki.jenkins.io/display/JENKINS/Running+Jenkins+behind+Apache)

See the _JovianHttpd_ repository to see the template for configuration.

## Integration

Integrate Jenkins with other tools

### Gogs

#### Plugin

Install `gogs-webhook` plugin.

Documentation on [plugins.jenkins.io](https://plugins.jenkins.io/gogs-webhook).

#### Add webhook on Gogs side

In the Gogs repository settings, add the _webhook_

`https://jenkins.jovian-hersemeule.eu/gogs-webhook/?job=experiments/connect`

Adapt job name.

#### Private communication

- Create a Jenkins account on Gogs
- Generate an SSH key with `ssh-keygen`
- Create credentials under Jenkins and store private key and passphrase
- Put SSH public key in Jenkins account on Gogs
- On Gogs : Add Jenkins user with _read_ rights to any repository Jenkins has to build

### Apache2 http server

How to deploy on a Httpd server.

#### Grant _jenkins_ user

You have to set _jenkins_ user owner of the targeted folder.

## Trouble shooting

### Logs

In file `/var/log/jenkins/jenkins.log` 

### Git describe

To allow the command `git describe` to work, go to your job configuration and add an **Advanced Cloned Behoviours** and tick the _tags_ checkbox.

## Configure

Configuration parameters can be found at `/etc/default/jenkins`

## Useful plugins

### Basic Branch strategy

Useful to build tags.