Update 'README.md'

README.md

@@ -13,7 +13,26 @@ rmdir easyconfigs; git clone ssh://egit/pbarriat/easyconfigs.git
 ## Requirements
 
 * openSUSE : `gcc-c++ patch libopenssl-devel gperf`
-* ubuntu : `gfortran libibverbs-dev`
+* ubuntu :
+
+```bash
+sudo apt install gcc-4.8 g++-4.8 gfortran-4.8 libibverbs-dev
+
+sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.8 10
+sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-7 20
+sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.8 10
+sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-7 20
+sudo update-alternatives --install /usr/bin/gfortran gfortran /usr/bin/gfortran-4.8 10
+sudo update-alternatives --install /usr/bin/gfortran gfortran /usr/bin/gfortran-7 20
+
+sudo update-alternatives --set cc /usr/bin/gcc
+sudo update-alternatives --set c++ /usr/bin/g++
+sudo update-alternatives --set cc /usr/bin/gfortran
+
+sudo update-alternatives --config gcc
+sudo update-alternatives --config g++
+sudo update-alternatives --config gfortran
+```
 
 ## Getting started