more detailed build instructions

Author: ogra1

README.md

@@ -9,16 +9,25 @@ https://bugs.launchpad.net/snapd/+filebug
 
 ## Building
 
-To build the core snap locally you need a chroot or container with
-Ubuntu 16.04. Then run:
+To build the core snap locally you need a clean chroot or container with
+Ubuntu 16.04. Inside this container or chroot run:
 
+    $ sudo apt install git snapcraft
+    $ git clone https://github.com/snapcore/core.git
     $ sudo apt-add-repository ppa:snappy-dev/image
-    $ sudo snapcraft
+    $ cd core
+    $ # now make any modifications of the Makefile you require (see below)
+    $ sudo snapcraft # (if you are not root already)
 
-An easy way to customize the content of the built snap is including additional
+One easy way to customize the content of the built snap is including additional
 PPAs with custom packages in the `EXTRA_PPAS` variable inside the Makefile's
 `ENV` variable.
 
+Another is to add a script snippet to live-build/hooks (where scripts with the
+ending .chroot are executed chrooted inside the resulting rootfs during build, 
+the ones with .binary ending are run in the build environment from outside the
+resulting rootfs).
+
 Launchpad builds should be done against xenial with the
 `~snappy-dev/ubuntu/image` PPA as source archive and `Updates` as the default
 pocket.