第1个回答 2017-10-17
update
update 是同步 /etc/apt/sources.list 和 /etc/apt/sources.list.d 中列出的源的索引,这样才能获取到最新的软件包。
upgrade
upgrade 是升级已安装的所有软件包,升级之后的版本就是本地索引里的,因此,在执行 upgrade 之前一定要执行 update, 这样才能是最新的。
An update should always be performed before an upgrade or dist-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.