CREATE A USER FOR GIT

sudo adduser git

ADD KEY TO ALLOW PASSWORDLESS AUTHENTICATION

sudo su - git
mkdir .ssh
#assuming the public key was uploaded to /temp/ryan_key.pub
cat /tmp/ryan_key.pub >> ~/.ssh/authorized_keys

SET UP AN EMPTY REPO

sudo mkdir /opt/git
sudo chown git:git /opt/git 
mkdir /opt/git/project.git
sudo chown git:git /opt/git/project.git
cd /opt/git/project.git
git --bare init

CLONING THE REPO

git clone git@your.server.example.com:/opt/git/project.git

LIMIT GIT USER TO GIT ACTIVITIES

Git comes with a shell 'git-shell'. We can change the git user to use this shell.

sudo vim /etc/passwd
#change git:x:1000:1000::/home/git:/bin/sh to the following
git:x:1000:1000::/home/git:/usr/bin/git-shell

COMMITTING TO THE REPO

# on Johns computer
cd myproject
git init
git add .
git commit -m 'initial commit'
git remote add origin git@gitserver:/opt/git/project.git
git push origin master