step 1 download tar.gz package
step2 unpack tar -zxvf xxx.tar.gz
step3 cd ruby2.1.1.dir
step4 .configure
step5 make
step6 sudo make install
step7 remove 1.8.7 : sudo apt-get remove ruby1.8.7
done
step 1 download tar.gz package
step2 unpack tar -zxvf xxx.tar.gz
step3 cd ruby2.1.1.dir
step4 .configure
step5 make
step6 sudo make install
step7 remove 1.8.7 : sudo apt-get remove ruby1.8.7
done