New versions of MSM contain new features, more reliable code, bug fixes, and contributions from the community. Since version 0.8.0 MSM has an inbuilt command to download and install everything for you automatically. Don’t worry, it will ask for confirmation before overwriting your files.
sudo msm update
If you are upgrading from a version of MSM that does not have the update command, you will have to do one thing by hand. Download and replace your MSM script file with the latest version:
sudo wget https://raw.github.com/msmhq/msm/latest/init/msm -O /etc/init.d/msm
Then just call the sudo msm update command to get all the other files automatically.
sudo msm version
The version command will return the current MSM version you have installed, useful for checking the upgrade was successful.