Read the release notes! This can't be emphasized enough. The Debian developers are careful to include all the important details on what has changed between releases, and any special steps required prior to and after the upgrade process.
As mentioned previously, itis simple to update your system. The commands (or menu items) for upgrading your system to the next official release are different from the standard updating commands. The apt-get command dist-upgrade or the aptitude full-upgrade will perform the necessary special calculations to upgrade to the next major distribution release after the package information cache has been updated (either using the normal update command if you have configured the release name as stable, or after changing to the new release name and executing the update command).
Itis also possible to build Debian packages yourself, either from a partial alien conversion (as previously discussed), or from scratch using the original software. The procedure can vary from simple to complex, depending on what the package is to provide, and is well covered in the Debian maintainer's guide and the Debian policy manual, both available online or as installable packages in Debian, and in many other online resources. A good online starting place is the Debian packaging Wiki page at https://wiki. debian. org/HowToPackageForDebian.
If the package exists in some other Unux distribution, it can often be converted to a Debian package. This is done using a package called alien. Alien provides commands to convert between a number of package formats (including Red Hat RPM, Stampede SLP, Slackware TGZ, Solaris PKG, and Debian DEB).
What do you do when a package doesn't exist in Debian? There are several options. One mentioned previously is to add non-Debian repositories to the repository configuration. After a Synaptic refresh, apt-get, or aptitude update, all of the package information in the repository will be available to the Debian package managers.
If, however, the software isn't included in any repository, there are a couple of options available.
Itis possible to perform automatic, unattended updates to a system, but there are some potential problems. Setting it up is quite simple. Just install the unattendedupgrades package. Ifyou aren't asked during installation ifyou want to enable automatic security upgrades, run the command dpkg-reconfigure -plow
unattended-upgrades.
After installing the software you need for your system, it is good practice to check for updates at regular intervals. In particular, security updates are released as soon as possible after a security flaw in any Debian software is identified.
Removing packages is also handled by any of the package managers. Something to be aware of, however, is that apt-get and Synaptic do not automatically remove dependencies after the package that depends on them is removed. The command apt-get autoremove should be used to do this, no matter which package manager was used for installation and removal. aptitude does this automatically.
dselect, APT, aptitude, and Synaptic, all provide some form of automatic dependency resolution. In rare cases, a dependency can't be resolved automatically, and user intervention is required. aptitude will calculate alternatives and ask the user to select from them. APT and Synaptic generally require the user to add packages to the command line or selection list manually.
One of the most useful package types is called meta packages. These are packages that contain no software themselves, but that require other packages to be installed, and thus provide a unified set of software for a particular purpose. This works because, although no actual software is in the meta package, the package manager will select and install all of the required dependent packages, providing a complete set of features in a single, easy installation step.
