safe-upgrade
Upgrades installed packages to their most recent version. Installed
packages will not be removed unless they are unused (see the
section “Managing Automatically Installed Packages” in the aptitude
reference manual); packages which are not currently installed will
not be installed.
It is sometimes necessary to remove or install one package in order
to upgrade another; this command is not able to upgrade packages in
such situations. Use the full-upgrade command to upgrade as many
packages as possible.
full-upgrade
Upgrades installed packages to their most recent version, removing
or installing packages as necessary. This command is less
conservative than safe-upgrade and thus more likely to perform
unwanted actions. However, it is capable of upgrading packages that
safe-upgrade cannot upgrade.
Note
This command was originally named dist-upgrade for historical
reasons, and aptitude still recognizes dist-upgrade as a synonym
for full-upgrade.