This can be done by first logging to your Ubuntu system via ssh as root or as any user with ‘sudo’ privileges and execute either “apt-get update” as root or “sudo apt-get update” at the command line prompt. Information will be output on your screen showing information associated with accessing the package sources and when complete the message will be displayed as follows:
Reading package lists… Done
After the previous command has successfully completed execute either “apt-get upgrade” as root or “sudo apt-get upgrade” from the command line prompt. to update your Ubuntu OS to the latest available software. The update process may ask you questions for some of the software being upgraded due to significant configuration or OS changes. I some cases you may need to select a appropriate option given in order for updating to proceed.
After all updates have been applied it is recommended that you perform a soft reboot of your server using the command either “shutdown -r now” or “sudo shutdown -r now” from the comand line prompt. This is to ensure you boot into any new kernels that may have been installed during the update.