diff --git a/src/backends.cr b/src/backends.cr
index 4944d3d..a71b71b 100644
--- a/src/backends.cr
+++ b/src/backends.cr
@@ -1,4 +1,27 @@
 
+enum Package::BuildStatus
+	Success
+	Failed
+	Pass
+end
+
+# Building instructions
+#   phases: src-split, (pre-)(configure|build|install) and post-install
+#   name examples: autotools, cmake, make
+#   build(context, recipe)
+
+class Package::Backend::Building
+	getter phase : String
+	getter name : String
+	getter callback : Proc(Context, Recipe, BuildStatus)
+	def initialize(@phase, @name, &block : Proc(Context, Recipe, BuildStatus))
+		@callback = block
+	end
+	def build(context : Context, recipe : Recipe)
+		@callback.call context, recipe
+	end
+end
+
 abstract class Package::Backend::Packaging
 	getter name : String
 
diff --git a/src/backends/baguette.cr b/src/backends/baguette.cr
index 6bb31bd..018d6b1 100644
--- a/src/backends/baguette.cr
+++ b/src/backends/baguette.cr
@@ -2,13 +2,21 @@ require "openssl"
 
 require "../backends.cr"
 
+# Baguette package backend
+#
+# Packages contain:
+# - data.tar.zst: compressed tarball containing all installed data
+# - manifest: list of directories, files and their checksum
+# - control.spec: meta data about the package
+#
+# TODO:
+# - security: add a signature file
 
 class Package::Backend::Packaging::Baguette < Package::Backend::Packaging
 	def initialize
 		@name = "package"
 	end
 
-	# TODO: checksums + security
 	def package(pkgdir : String, architecture : String, package : ::Package::Package) : Bool
 		# Fake root example: /tmp/packages/<uuid>/root-xz-dev
 		fake_root = package.fake_root_directory
@@ -23,7 +31,7 @@ class Package::Backend::Packaging::Baguette < Package::Backend::Packaging
 		package_target = "#{pkgdir}/"
 		package_target += "#{architecture}/"
 		package_target += "#{package.name}-#{package.version}-#{package.release}.baguette"
-		Dir.mkdir_p File.dirname package_target
+		Do.mkdir_p File.dirname package_target
 
 		::Baguette::Log.detail "Archiving package content"
 		Do.run fake_root, "tar", ["cvf", data_archive_path, "."]
@@ -75,7 +83,7 @@ class Package::Backend::Packaging::Baguette < Package::Backend::Packaging
 
 		manifest = File.open(file_name, "w").not_nil!
 
-		Dir.cd package.fake_root_directory
+		Do.cd package.fake_root_directory
 
 		FileUtils.find "." do |path|
 			file = path.lchop
@@ -94,7 +102,7 @@ class Package::Backend::Packaging::Baguette < Package::Backend::Packaging
 
 		manifest.close
 	ensure
-		Dir.cd old_pwd.not_nil!
+		Do.cd old_pwd.not_nil!
 	end
 
 	def self.install(packages : Array(String))
diff --git a/src/backends/build.cr b/src/backends/build.cr
index 3242937..e94a760 100644
--- a/src/backends/build.cr
+++ b/src/backends/build.cr
@@ -1,16 +1,33 @@
 
+# Actual compilation instructions
+#
+# Backends:
+# - make
+#   pass if no Makefile
+
 class Package::Backend::Build
 
 	def self.make : Backend::Building
 		Backend::Building.new "build", "make" do |context, recipe|
-			next BuildStatus::Pass unless Dir.exists? recipe.dirname
-			Dir.cd recipe.dirname
+			unless Dir.exists? recipe.dirname
+				Baguette::Log.detail "no '#{recipe.dirname}' directory: pass"
+				next BuildStatus::Pass
+			end
+			Do.cd recipe.dirname
 
 			unless File.exists? "Makefile"
+				Baguette::Log.detail "no Makefile: pass"
 				next BuildStatus::Pass
 			end
 
-			child = Do.sh "make -j#{context.build_cores} #{recipe.options["make"]? || ""}"
+			ncores = recipe.options["build-cores"]? || context.build_cores
+
+			options = [
+				"-j#{ncores}",
+				recipe.options["make"]? || ""
+			]
+
+			child = Do.sh "make #{options.join " "}"
 
 			if child.exit_status == 0
 				BuildStatus::Success
diff --git a/src/backends/configure.cr b/src/backends/configure.cr
index 99ff575..71656b2 100644
--- a/src/backends/configure.cr
+++ b/src/backends/configure.cr
@@ -1,18 +1,35 @@
 
+# Configuration phase
+#
+# Backends:
+# - autotools
+#   pass if no "configure" file
+# - cmake
+#   pass if no "CMakeLists.txt" file
+# Both backends quit if recipe.dirname doesn't exist.
+
 class Package::Backend::Configure
 
 	def self.autotools : Backend::Building
 		Backend::Building.new "configure", "autotools" do |context, recipe|
-			next BuildStatus::Pass unless Dir.exists? recipe.dirname
-
-			Dir.cd recipe.dirname
-
-			unless File.exists? "configure"
+			unless Dir.exists? recipe.dirname
+				Baguette::Log.detail "no '#{recipe.dirname}' directory: pass"
 				next BuildStatus::Pass
 			end
 
-			child = Do.sh "./configure --prefix=#{recipe.prefix} #{recipe.options["configure"]? || ""}"
+			Do.cd recipe.dirname
 
+			unless File.exists? "configure"
+				Baguette::Log.detail "no 'configure' file: pass"
+				next BuildStatus::Pass
+			end
+
+			options = [
+				"--prefix=#{recipe.prefix}",
+				recipe.options["configure"]? || ""
+			]
+
+			child = Do.sh "./configure #{options.join " "}"
 			if child.exit_status == 0
 				BuildStatus::Success
 			else
@@ -23,16 +40,23 @@ class Package::Backend::Configure
 
 	def self.cmake : Backend::Building
 		Backend::Building.new "configure", "cmake" do |context, recipe|
-			next BuildStatus::Pass unless Dir.exists? recipe.dirname
+			unless Dir.exists? recipe.dirname
+				Baguette::Log.detail "no '#{recipe.dirname}' directory: pass"
+				next BuildStatus::Pass
+			end
 
-			Dir.cd recipe.dirname
+			Do.cd recipe.dirname
 
-			next BuildStatus::Pass unless File.exists? "CMakeLists.txt"
+			unless File.exists? "CMakeLists.txt"
+				Baguette::Log.detail "no 'CMakeLists.txt' file: pass"
+				next BuildStatus::Pass
+			end
 
+			ncores = recipe.options["build-cores"]? || context.build_cores
 			options = [
 				"-DCMAKE_INSTALL_PREFIX='#{recipe.prefix}'",
 				"-DCMAKE_BUILD_TYPE=Release #{recipe.options["cmake"]}",
-				"-- -j#{context.build_cores}"
+				"-- -j#{ncores}"
 			]
 
 			child = Do.sh "cmake . #{options.join " "}"
diff --git a/src/backends/install.cr b/src/backends/install.cr
index 4b812e5..fb64286 100644
--- a/src/backends/install.cr
+++ b/src/backends/install.cr
@@ -1,15 +1,30 @@
 
+# Installation process
+# Files to package are put in recipe.fake_root_directory
+#
+# Backends:
+# - make
+#   pass if no Makefile
+
 class Package::Backend::Install
 	def self.make : Backend::Building
 		Backend::Building.new "install", "make" do |context, recipe|
-			next BuildStatus::Pass unless Dir.exists? recipe.dirname
-			Dir.cd recipe.dirname
+			unless Dir.exists? recipe.dirname
+				Baguette::Log.detail "no '#{recipe.dirname}' directory: pass"
+				next BuildStatus::Pass
+			end
+			Do.cd recipe.dirname
 
 			unless File.exists? "Makefile"
 				next BuildStatus::Pass
 			end
 
-			child = Do.sh "make install 'DESTDIR=#{recipe.fake_root_directory}' #{recipe.options["make install"]? || ""}"
+			options = [
+				"'DESTDIR=#{recipe.fake_root_directory}'",
+				recipe.options["make install"]? || ""
+			]
+
+			child = Do.sh "make install #{options.join " "}"
 
 			if child.exit_status == 0
 				BuildStatus::Success
diff --git a/src/backends/splitter.cr b/src/backends/splitter.cr
index dfb32c0..ba6fad9 100644
--- a/src/backends/splitter.cr
+++ b/src/backends/splitter.cr
@@ -53,23 +53,23 @@ class Package::Backend::Splitter
 		end
 	end
 
-	# Source files: prefix containing "src".
+	# NOTE: src is not a regular split, _all_ files should be included,
+	#       as well as the patches used for the build.
+	#       Files are copied before build.
+
 	def self.src(prefixes : Array(String)) : Splitter
 		Backend::Splitter.new do |recipe|
 			Package.new(recipe, true).tap do |split|
 				prefixes = (prefixes + [recipe.prefix]).uniq
 
 				split.name = "#{recipe.name}-src"
-				split.files = prefixes.map do |prefix|
-					[
-						"#{prefix}/lib/share/src",
-						"#{prefix}/src",
-						"#{prefix}/usr/src",
-						"#{prefix}/usr/local/src"
-					]
-				end.flatten
+				# No need, files are already in the package fake root.
+				# split.files = prefixes.map do |prefix|
+				# 	[ "#{prefix}/src" ]
+				# end.flatten
 				split.recipe.require_stripping = false
 			end
 		end
 	end
+
 end
diff --git a/src/context.cr b/src/context.cr
index b5e3dd3..58cfb35 100644
--- a/src/context.cr
+++ b/src/context.cr
@@ -28,9 +28,6 @@ class Package::Context
 	# By default, building a package only uses one core
 	property build_cores = 1
 
-	# list of environment variables we want to have when building
-	#property environment = {} of String => String
-
 	property recipe : Recipe? = nil
 
 
@@ -53,6 +50,7 @@ class Package::Context
 		# Split = new package from a recipe, each one with different files being included.
 		@splitter_backends << Backend::Splitter.man @prefixes
 		@splitter_backends << Backend::Splitter.dev @prefixes
+		# src isn't really a split, files already are copied before build.
 		@splitter_backends << Backend::Splitter.src @prefixes
 	end
 
diff --git a/src/do.cr b/src/do.cr
index 84477c5..d14efad 100644
--- a/src/do.cr
+++ b/src/do.cr
@@ -5,6 +5,7 @@ class Baguette::Context
 end
 
 class Do < Process
+	# list of environment variables we want to have when building
 	class_property environment = {} of String => String
 
 	def self.require_cmd(cmd : String)
@@ -14,6 +15,11 @@ class Do < Process
 		end
 	end
 
+	def self.cd(chdir)
+		Baguette::Log.detail "cd " + chdir.colorize(:light_magenta).to_s
+		Dir.cd chdir
+	end
+
 	def self.run(chdir, command, args)
 		output = Process::Redirect::Inherit
 
@@ -21,9 +27,9 @@ class Do < Process
 			output = Process::Redirect::Close
 		else
 			# log sub-commands outputs
-			STDOUT.puts "logging command " +
+			Baguette::Log.info "logging command " +
 				"#{command} #{args}".colorize(:light_magenta).to_s
-			STDOUT.puts "in " + Baguette::Context.logfile_path.colorize(:blue).mode(:bright).to_s
+			Baguette::Log.info "in " + Baguette::Context.logfile_path.colorize(:blue).mode(:bright).to_s
 
 			File.open Baguette::Context.logfile_path, "a" do |file|
 				file.puts ""
diff --git a/src/instructions.cr b/src/instructions.cr
index 4de3ace..b9912a1 100644
--- a/src/instructions.cr
+++ b/src/instructions.cr
@@ -1,21 +1,11 @@
 
-enum Package::BuildStatus
-	Success
-	Failed
-	Pass
-end
-
-class Package::Backend::Building
-	getter phase : String
-	getter name : String
-	getter callback : Proc(Context, Recipe, BuildStatus)
-	def initialize(@phase, @name, &block : Proc(Context, Recipe, BuildStatus))
-		@callback = block
-	end
-	def build(context : Context, recipe : Recipe)
-		@callback.call context, recipe
-	end
-end
+# Instructions for src-split, [pre-](configure|build|install) and post-install
+# Simple array of strings with a name.
+#
+# Methods:
+# - run(context, recipe) : BuildStatus
+#   execute each instruction
+#   instructions are provided by the recipe or by a backend if not specified
 
 class Package::Instructions
 	class Set < Array(String)
@@ -26,6 +16,7 @@ class Package::Instructions
 		# FIXME: def execute
 
 		def run(context : Context, recipe : Recipe) : BuildStatus
+			# Does the recipe provided instructions for this phase?
 			if size > 0
 				each do |command|
 					child = Do.run recipe.building_directory, "sh", ["-x", "-c", command]
@@ -38,8 +29,14 @@ class Package::Instructions
 				return BuildStatus::Success
 			end
 
+			last_backend = "not-known"
+			# In case the recipe didn't provide instructions: checking backends.
 			context.building_backends.select(&.phase.==(@phase)).each do |backend|
-				Dir.cd recipe.building_directory
+				last_backend = backend.name
+				Baguette::Log.info "Doing phase '#{@phase}' :: '" +
+					backend.name.colorize(:light_magenta).to_s +
+					"'"
+				Do.cd recipe.building_directory
 
 				rvalue = backend.build context, recipe
 
@@ -53,18 +50,29 @@ class Package::Instructions
 			BuildStatus::Pass
 		rescue e
 			# Possible TODO: print the origin of the exception (backend, user-provided code, other/unknown).
-			STDERR << "Exception caught: " << e.message << "\n"
+			Baguette::Log.error "Exception during phase '#{@phase}', backend '#{last_backend}'"
+			Baguette::Log.error "Exception caught: #{e.message}"
 			BuildStatus::Failed
 		end
 	end
 
 	# FIXME: Switch to an enum at some point?
-	getter configure  = Set.new "configure"
-	getter build      = Set.new "build"
-	getter install    = Set.new "install"
+	getter src_split     = Set.new "src-split"
+	getter configure     = Set.new "configure"
+	getter pre_configure = Set.new "pre-configure"
+	getter build         = Set.new "build"
+	getter pre_build     = Set.new "pre-build"
+	getter install       = Set.new "install"
+	getter pre_install   = Set.new "pre-install"
+	getter post_install  = Set.new "post-install"
 
 	def to_a
-		[configure, build, install]
+		[
+			src_split,
+			pre_configure, configure,
+			pre_build, build,
+			pre_install, install, post_install
+		]
 	end
 end
 
diff --git a/src/package.cr b/src/package.cr
index d52bfa7..9b66678 100644
--- a/src/package.cr
+++ b/src/package.cr
@@ -2,7 +2,13 @@ require "specparser"
 
 class Package::Package
 	getter recipe : Recipe
-	getter automatic : Bool
+	getter automatic : Bool  # Was the package created by automatic splitting?
+
+	# Reference for splits. Recipe#packages[0] should keep this set to `nil`.
+	property files       : Array(String)?
+	property file_patterns : Array(Regex)?
+
+	property fake_root_directory : String?
 
 	def initialize(@recipe, @automatic = false, @fake_root_directory = nil)
 	end
@@ -38,6 +44,8 @@ class Package::Package
 		end
 	end
 
+	# Most of the attributes are inherited from recipe.
+
 	macro inherit(attribute)
 		@{{attribute.var.id}} : {{attribute.type.id}}?
 
@@ -61,14 +69,8 @@ class Package::Package
 	inherit conflicts    : Array(String)
 	inherit provides     : Array(String)
 
-	# Reference for splits. Recipe#packages[0] should keep this set to `nil`.
-	property files       : Array(String)?
-	property file_patterns : Array(Regex)?
-
 	inherit prefix       : String
 
-	property fake_root_directory : String?
-
 	def dependencies
 		@dependencies || @recipe.run_dependencies
 	end
diff --git a/src/recipe.cr b/src/recipe.cr
index 0bb4f8c..60e61fb 100644
--- a/src/recipe.cr
+++ b/src/recipe.cr
@@ -182,6 +182,9 @@ class Package::Recipe
 		# Packages can only be created once @name and @version exist!
 		@packages << Package.new self, false, fake_root_directory
 
+		# Spec sections are like this:
+		#   %split my-application
+		# split = name of the section
 		specs.sections.each do |section|
 			case section.name
 			when "split"
@@ -275,12 +278,9 @@ class Package::Recipe
 	end
 
 	# TODO:
-	#   - Export packaging directory in $PKG.
-	#   - Add (pre|post)-(configure|build|install) instructions.
-	#   - Have some instructions be non-critical, like the (pre|post] ones.
+	#   - Have some instructions be non-critical, like the (pre|post) ones.
 	#   - Be careful about return values, flee from everything if something
 	#     goes somehow wrong.
-	#   - Make things thread-safe. (those ENV[]= calls are definitely not)
 	def build
 		Do.mkdir_p fake_root_directory
 
@@ -289,8 +289,13 @@ class Package::Recipe
 		# Safety precautions.
 		old_dir = Dir.current
 
+		# TODO: skip sequences
 		instructions.to_a.each do |instruction|
 			Baguette::Log.info "Building ('#{instruction.phase}' phase)"
+			# TODO: finish this following lines
+			#if Package::Context.any? &.phase==instruction.phase
+			#	next
+			#end
 
 			if instruction.run(@context, self).failed?
 				raise BuildError.new self, "Building (#{instruction.phase} phase) failed."
@@ -298,7 +303,7 @@ class Package::Recipe
 			end
 		end
 
-		Dir.cd old_dir
+		Do.cd old_dir
 
 		ENV["PKG"] = nil
 
@@ -493,4 +498,3 @@ class Package::Recipe
 		spec
 	end
 end
-