upgrade和update的区别

Linux系统中，upgrade和update的区别：

update：更新软件包列表到最新版本，但是他不会去升级软件；

upgrade：升级软件到最新版本。

所以一般是先update软件包列表到最新版本，然后upgrade安装最新版软件。

引用原文如下：

You should first run update, then upgrade. Neither of them automatically runs the other.

• apt-get update updates the list of available packages and their versions, but it does not install or upgrade any packages.
• apt-get upgrade actually installs newer versions of the packages you have. After updating the lists, the package manager knows about available updates for the software you have installed. This is why you first want to update.

Additionally, you can use apt-get update && apt-get upgrade to do both steps after each other.