diff --git a/.gitignore b/.gitignore
index e585969..a7cfb2d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,7 +15,7 @@ mkmf.log
 /vendor/
 .pc/
 debian/*.log
-app/config/hieraviz.yml
+config/hieraviz.yml
 .env.production
 .ruby-version
 .ruby-gemset
diff --git a/CHANGELOG.md b/CHANGELOG.md
index d1396fc..86c8832 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,8 @@ Hieraviz Changelog
 ========================
 
 ### v0.0.2 - wip
+- add oauth2 auth method against gitlab server
+- add session persistence on disk
 
 ### v0.0.1 - 2015-12-30
 - still pretty alpha at this stage, more to come soon
diff --git a/app/common.rb b/app/common.rb
index 8bb5330..447566e 100644
--- a/app/common.rb
+++ b/app/common.rb
@@ -1,18 +1,13 @@
 require 'sinatra/base'
 require 'dotenv'
-require 'hieracles'
-require 'hieraviz'
 
 module HieravizApp
   class Common < Sinatra::Base
 
     configure do
       set :app_name, 'HieraViz'
-      configfile = ENV['HIERAVIZ_CONFIG_FILE'] || File.join("config", "hieraviz.yml")
-      configfile = File.join(root, configfile) unless configfile[0] == '/'
-      set :configfile, configfile
-      set :configdata, YAML.load_file(configfile)
-      set :config, Hieracles::Config.new({ config: configfile })
+      set :configdata, Hieraviz::Config.load
+      set :config, Hieracles::Config.new({ config: Hieraviz::Config.configfile })
       enable :session
       enable :logging
     end
diff --git a/app/main.rb b/app/main.rb
index 6fd81f7..52c7388 100644
--- a/app/main.rb
+++ b/app/main.rb
@@ -1,3 +1,6 @@
+require 'hieracles'
+require 'hieraviz'
+
 require File.expand_path '../web.rb', __FILE__
 require File.expand_path '../apiv1.rb', __FILE__
 
diff --git a/app/config/hieraviz.default.yml b/config/hieraviz.default.yml
similarity index 100%
rename from app/config/hieraviz.default.yml
rename to config/hieraviz.default.yml
diff --git a/lib/hieraviz.rb b/lib/hieraviz.rb
index c716072..f3770d2 100644
--- a/lib/hieraviz.rb
+++ b/lib/hieraviz.rb
@@ -1,4 +1,5 @@
 require "hieraviz/version"
+require "hieraviz/config"
 require "hieraviz/store"
 require "hieraviz/auth_gitlab"
 
diff --git a/lib/hieraviz/store.rb b/lib/hieraviz/store.rb
index 52bdbb0..34a4cbf 100644
--- a/lib/hieraviz/store.rb
+++ b/lib/hieraviz/store.rb
@@ -30,9 +30,7 @@ def tmpdir
     end
 
     def init_tmpdir
-      configfile = ENV['HIERAVIZ_CONFIG_FILE'] || File.join("config", "hieraviz.yml")
-      configfile = File.expand_path(File.join('../../../app', configfile), __FILE__) unless configfile[0] == '/'
-      config = YAML.load_file(configfile)
+      config = Hieraviz::Config.load
       tmp = config['tmpdir'] || '/tmp'
       begin
         FileUtils.mkdir_p(tmp) unless Dir.exist?(tmp)
diff --git a/spec/files/config.yml b/spec/files/config.yml
index 6078775..38dcb7a 100644
--- a/spec/files/config.yml
+++ b/spec/files/config.yml
@@ -3,6 +3,7 @@ basepath: "spec/files/puppet"
 classpath: "farm_modules/%s/manifests/init.pp"
 hierafile: "hiera.yml"
 session_seed: "toto"
+tmpdir: "spec/files/tmp"
 usedb: false
 puppetdb:
   usessl: false
diff --git a/spec/lib/store_spec.rb b/spec/lib/store_spec.rb
index dd95cc2..ddbba41 100644
--- a/spec/lib/store_spec.rb
+++ b/spec/lib/store_spec.rb
@@ -1,4 +1,5 @@
 require 'spec_helper'
+require 'fileutils'
 
 describe Hieraviz::Store do
 
@@ -6,4 +7,64 @@
     it { expect(Hieraviz::Store.data).to eq Hash.new }
   end
 
+  describe '.set' do
+    let(:name) { '123456' }
+    let(:value) { { a: 1 } }
+    let(:tmpfile) { 'spec/files/tmp/123456' }
+    after do
+      File.unlink(tmpfile) if File.exist?(tmpfile)
+    end
+    it {
+      Hieraviz::Store.set name, value
+      expect(File).to exist tmpfile
+      expect(Hieraviz::Store.data[name]).to eq value
+    }
+  end
+
+  describe '.tmpfile' do
+    context "when the filename has weird chars" do
+      let(:name) { 'gdahsj#@!(scg78ud' }
+      let(:expected) { 'spec/files/tmp/gdahsjscg78ud' }
+      it { expect(Hieraviz::Store.tmpfile(name)).to eq expected }
+    end
+    context "when the filename is a normal hash" do
+      let(:name) { 'gdahsjscg78ud' }
+      let(:expected) { 'spec/files/tmp/gdahsjscg78ud' }
+      it { expect(Hieraviz::Store.tmpfile(name)).to eq expected }
+    end
+  end
+
+  describe '.tmpdir' do
+    let(:tmpdir_ok) { 'spec/files/tmp' }
+    before do
+      allow(Hieraviz::Config).to receive(:load).and_return({ 'tmpdir' => tmpdir_ok })
+    end
+    it { expect(Hieraviz::Store.tmpdir).to eq tmpdir_ok }
+  end
+
+  describe '.init_tmpdir' do
+    context 'when specified tmp dir is not present, create it' do 
+      let(:tmpdir_nodir) { File.expand_path('../../files/tmp_tmp', __FILE__) }
+      before do
+        allow(Hieraviz::Config).to receive(:load).and_return({ 'tmpdir' => tmpdir_nodir })
+        tmpexpect = Hieraviz::Store.init_tmpdir
+      end
+      after do
+        FileUtils.rm_rf(tmpdir_nodir) if Dir.exist?(tmpdir_nodir)
+      end
+      it { expect(File).to exist tmpdir_nodir }
+    end
+    context 'when tmp dir is present, returns its value' do
+      let(:tmpdir_ok) { 'spec/files/tmp' }
+      it { expect(Hieraviz::Store.init_tmpdir).to eq tmpdir_ok }
+    end
+    context 'when tmp dir is absent and cannot be created, returns /tmp' do
+      let(:tmpdir_nowrite) { '/diuyao' }
+      before do
+        allow(Hieraviz::Config).to receive(:load).and_return({ 'tmpdir' => tmpdir_nowrite })
+      end
+      it { expect(Hieraviz::Store.init_tmpdir).to eq '/tmp' }
+    end
+  end
+
 end