直接取自apt-get的手册页:
update
update is used to resynchronize the package index files from their
sources. The indexes of available packages are fetched from the
location(s) specified in /etc/apt/sources.list. For example, when
using a Debian archive, this command retrieves and scans the
Packages.gz files, so that information about new and updated
packages is available. An update should always be performed before
an upgrade or dist-upgrade. Please be aware that the overall
progress meter will be incorrect as the size of the package files
cannot be known in advance.
upgrade
upgrade is used to install the newest versions of all packages
currently installed on the system from the sources enumerated in
/etc/apt/sources.list. Packages currently installed with new
versions available are retrieved and upgraded; under no
circumstances are currently installed packages removed, or packages
not already installed retrieved and installed. New versions of
currently installed packages that cannot be upgraded without
changing the install status of another package will be left at
their current version. An update must be performed first so that
apt-get knows that new versions of packages are available.
更新来更新apt-get的软件包列表,升级来安装更新为全部为包。要仅更新一个包,请使用install。
sudo apt-get install firefox
约翰你好,你的问题不是一个编程问题。在StackExchange中尝试超级用户。 – drum 2012-07-15 19:23:06
不是一个编程问题,所以脱离堆栈溢出的话题。 [askubuntu.com](http://askubuntu.com)将是一个更好的地方来问这个问题。 – Oded 2012-07-15 19:23:27