Try (ROOT 6.06/06 with gcc 5.x): [code]# install it into …
ROOT_INSTALL_DIR="${HOME}/ROOT/v6-06-06"
rm -rf ${ROOT_INSTALL_DIR}
mkdir -p ${ROOT_INSTALL_DIR}

download, unpack and build it in /tmp

cd /tmp
rm -rf root-build root-6.06.06 root_v6.06.06.source.tar.gz*
wget https://root.cern.ch/download/root_v6.06.06.source.tar.gz
tar -zxf root_v6.06.06.source.tar.gz
mkdir root-build
cd root-build
unset ROOTSYS
cmake -DCMAKE_INSTALL_PREFIX="${ROOT_INSTALL_DIR}" -DCMAKE_CXX_FLAGS="-D_GLIBCXX_USE_CXX11_ABI=0" -Dcxx14=“ON” -Dall=“ON” -Ddavix=“OFF” -Dr=“OFF” -Dpythia8=“OFF” -Dgeocad=“ON” -Dbuiltin_ftgl=“OFF” -Dbuiltin_glew=“OFF” -Dsoversion=“ON” …/root-6.06.06
make
cmake --build . --target install

final cleanup

cd …/
rm -rf root-build root-6.06.06 root_v6.06.06.source.tar.gz*[/code]
For ROOT 6.06/06 with gcc 4.[89].x see: viewtopic.php?f=3&t=22202&p=97236#p97236

Last, but not least … you will NOT be able to install ROOT 6, if your gcc compiler comes from the RedHat “Software Collections” / “Developer Toolset” (e.g. on Scientific Linux / CentOS 5, 6 and 7 platforms).

BTW. Before you begin, make sure that nothing in your setup points to any existing ROOT installation. In particular, on Ubuntu execute “sudo apt-get purge root-system* root-plugin* libroot*” and then check that the “/usr/lib/i386-linux-gnu/root5.34” and the “/usr/lib/x86_64-linux-gnu/root5.34” subdirectories disappeared completely.