One very good method is to encrypt your Hard Drive. This can be done at the beginning of installing Ubuntu on a machine. Setting a strong password will make it near impossible for your data to get compromised if your laptop is ever stolen.
As for accessing your data if your laptop gets stolen, they will not be able to log into your machine if it is password protected. But if your hard drive or data are not encrypted, they can remove the hard drive and access it as external memory on a separate machine. That is why it is always a good idea to both encrypt your data and your hard drive.
One very good method is to encrypt your Hard Drive. This can be done at the beginning of installing Ubuntu on a machine. Setting a strong password will make it near impossible for your data to get compromised if your laptop is ever stolen.
Here are some good resource to get you started:
As for accessing your data if your laptop gets stolen, they will not be able to log into your machine if it is password protected. But if your hard drive or data are not encrypted, they can remove the hard drive and access it as external memory on a separate machine. That is why it is always a good idea to both encrypt your data and your hard drive.