# Dependency installation steps for Debian GNU/Linux 9.x (stretch)

This document assumes you are starting from a fresh install of Debian in the 9.x series.

Most recently tested 2019-03-21 with the following debian release:

```
$ lsb_release --description
Description:	Debian GNU/Linux 9.8 (stretch)
```



# Install VirtualBox

Virtualbox is the configured VM provider in this project's Vagrantfile.

First, check whether virtualbox is installed. Some systems may have it already:

```
$ virtualbox --help
Oracle VM VirtualBox VM Selector v6.0.4
[...]
```

(If it is installed, you can probably skip this step. Note that virtualbox installs linux kernel
modules which need to be kept in sync with the virtualbox apt package, so if you decide to change to
a different version, be sure to uninstall completely (including the kernel modules) before
reinstalling.)

Add Oracle's VirtualBox apt repository to your system's apt sources:

```
sudo apt-add-repository "deb http://download.virtualbox.org/virtualbox/debian $(lsb_release -sc) contrib"
```

Verify that the source was added:

```
$ grep -iR virtualbox /etc/apt/sources.list*
/etc/apt/sources.list:deb http://download.virtualbox.org/virtualbox/debian stretch contrib
/etc/apt/sources.list:# deb-src http://download.virtualbox.org/virtualbox/debian stretch contrib
```

Download and register the public gpg key used by Oracle to secure the above
repository:

```
$ wget -q https://www.virtualbox.org/download/oracle_vbox_2016.asc -O- | sudo apt-key add -
OK
```

Verify that the key was added

```
$ apt-key list "B9F8 D658 297A F3EF C18D  5CDF A2F6 83C5 2980 AECF"
pub   rsa4096 2016-04-22 [SC]
      B9F8 D658 297A F3EF C18D  5CDF A2F6 83C5 2980 AECF
uid           [ unknown] Oracle Corporation (VirtualBox archive signing key) <info@virtualbox.org>
sub   rsa4096 2016-04-22 [E]
```

Update your local apt package metadata

```
$ sudo apt update
[...]
```

This command will show the available versions of virtualbox from the apt
repository:

```
$ sudo apt install virtualbox
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Package virtualbox is a virtual package provided by:
  virtualbox-6.0 6.0.4-128413~Debian~stretch
  virtualbox-5.2 5.2.26-128414~Debian~stretch
  virtualbox-5.1 5.1.38-122592~Debian~stretch
  virtualbox-5.0 5.0.40-115130~Debian~stretch
You should explicitly select one to install.

E: Package 'virtualbox' has no installation candidate
```

Decide on the version you want and specify the version number to install it:

```
$ sudo apt install virtualbox-6.0 -y
[...]
```

Source: https://www.virtualbox.org/wiki/Linux_Downloads#Debian-basedLinuxdistributions

Most recently tested 2019-03-21 with the following virtualbox release:

```
$ virtualbox --help
Oracle VM VirtualBox VM Selector v6.0.4
[...]
```



## Install git

```
$ sudo apt install git
```

Most recently tested 2019-03-21 with the following git release:

```
$ git --version
git version 2.11.0
```



# Install Vagrant 2.0.3 or higher

As of this writing, the Vagrant version that Debian uses in its "stretch" release is 1.9.x so we
suggest getting a package from Vagrant's web site:

```
wget -c https://releases.hashicorp.com/vagrant/2.2.4/vagrant_2.2.4_x86_64.deb
sudo dpkg -i vagrant_2.2.4_x86_64.deb
rm vagrant_2.2.4_x86_64.deb
```

Most recently tested 2019-03-21 with the following vagrant release:

```
$ vagrant --version
Vagrant 2.2.4
```



# Install venv support

`venv` is a python module used to create isolated project-specific environments, so that projects on
the same computer can each use their own version of the python executable and their own set of
installed python modules.

`python3-venv` is an `apt` package that includes support for using the `venv` python module.

```
sudo apt install python3-venv
```

Most recently tested 2019-03-05 with the following python3-venv release:

```
$ dpkg --status python3-venv | grep Version
Version: 3.5.3-1
```



# Install direnv (Optional/Recommended)

This tool sets and unsets environment variables as you change directories in a shell session,
providing a convenient facility for setting up project-specific configuration.

```
sudo apt install direnv
```

To activate direnv when starting bash (the default shell on Debian 9), add the following line to the
end of `~/.bashrc`:

```
eval "$(direnv hook bash)"
```

direnv works by incorporating a call to `_direnv_hook` in the `PROMPT_COMMAND` shell variable. You
can check that this was done by starting a new bash session and checking whether that value is
present:

```
$ echo $PROMPT_COMMAND
_direnv_hook;
```

direnv also supports several other shells -- zsh, fish, tcsh, and elvish as of this writing. Its
website includes instructions for enabling each of the shells it supports.

Most recently tested 2019-03-21 with the following direnv release:

```
$ direnv --help
direnv v2.10.0
[...]
```