container as alternative to virtual machine: systemd-nspawn

[Federico Bruni]

This setup may be interesting for Linux users who want to avoid virtual 
machines.
I started it today so I haven't tested it much yet.

The size of OS is small initially, circa 380MB. But when you install 
the LilyPond dependencies it grows up significantly.


# Instructions

Install the packages `systemd-container` and `debootstrap`.

Run as root the following commands (adapt it to your architecture):
   cd <path/to/dir>
   mkdir LilyDev
   debootstrap --arch=amd64 stable DebianJessie/ 
http://httpredir.debian.org/debian/

Start the container, set the root password

   systemd-nspawn -D LilyDev
   passwd

and add a normal user:

   adduser lilydev
   id lilydev

It's important that the user ID in your guest is the same as the user 
ID in
your host system. This allows to edit the files in the 
LilyDev/home/lilydev
directory either in your host or in your guest.

Now you can boot the container (need to be run as root):

   systemd-nspawn -bD LilyDev

Log in as root and install the dependencies, as described in the 
Contributor Guide.

When you've done, change to the normal user:

   su lilydev

and you are ready to compile lilypond.