Already tried with sudo apt-get install gitolite command but now sure is it installed. How to verify it?
A better way is to follow the doc:
su - git
mkdir -p ~/bin
git clone git://github.com/sitaramc/gitolite
gitolite/install -ln ~/bin # please use absolute path here
gitolite setup -pk yourname.pub
By cloning the gitolite repo, you ensure to install the very latest version of gitolite (3.6.1+)