Most of the software in the distribution has been updated: over 28492 software packages (this is 66% of all packages in jessie).Also, a significant number of packages (over 7268, 17% of the packages in jessie) have for various reasons been removed from the distribution.It is important to point out that nothing is bulletproof and proper failover procedure should be discussed before the upgrade takes place.The rule of thumb is, the less software is installed on your system the higher chance for a successful upgrade.When you run a server then you should include the databases (My SQL, Postgresql, etc), web and email data in the backup as well.The backup should be stored on a external harddisk, on an external server e.g. Here are a few examples on how to create backups with tar.now also installs recommended packages as default, and thanks to its robustness it's the preferred program for package management from console to perform system installation and major system upgrades.The apt tool suite also includes the tool to query the package lists.
It provides commandline tools for searching and managing packages, and for querying information about them, as well as low-level access to all features of the libapt-pkg library.
The recommended strategy is to do manual restart as it provides more flexibility.
If you are running SSH service you will be also given an option to disable SSH root access.
For more information, see the User's Guide in tool merges functionality of apt-get and apt-cache and by default has a fancier colored output format, making it more pleasant for humans.
For usage in scripts or advanced use cases, apt-get is still preferable or needed.