To keep the system up to date with the latest fixes and security advisories, upgrades should be done regularly. System upgrade is a two steps process: update the list of available software and, if necessary, upgrade the system. Both operation can be achieved with aptitude, with different options.

Get the latest list of available packages on the repositories:

root@server:~# aptitude update
Hit http://ftp.pt.debian.org wheezy Release.gpg
Hit http://ftp.pt.debian.org wheezy-updates Release.gpg
Hit http://ftp.pt.debian.org wheezy Release
Hit http://ftp.pt.debian.org wheezy-updates Release
Hit http://ftp.pt.debian.org wheezy/main Sources
Hit http://ftp.pt.debian.org wheezy/main i386 Packages
Hit http://ftp.pt.debian.org wheezy/main Translation-en
Hit http://ftp.pt.debian.org wheezy-updates/main Sources
Hit http://ftp.pt.debian.org wheezy-updates/main i386 Packages
Hit http://ftp.pt.debian.org wheezy-updates/main Translation-en
Hit http://security.debian.org wheezy/updates Release.gpg
Hit http://security.debian.org wheezy/updates Release
Hit http://security.debian.org wheezy/updates/main Sources
Hit http://security.debian.org wheezy/updates/main i386 Packages
Hit http://security.debian.org wheezy/updates/main Translation-en

There are no updates available for our system installation.

Upgrading our system is also very easy:

root@server:~# aptitude upgrade
No packages will be installed, upgraded, or removed.
0 packages upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 0 B of archives. After unpacking 0 B will be used.

No packages upgraded, the system is up to date.

• Debian Reference, 2.2. Basic package management operations (http://www.debian.org/doc/manuals/reference/ch02.en.html#_basic_package_management_operations)