什么是“ dist-upgrade”，为什么它比“ upgrade”更多升级？

我想知道为什么upgrade有时不希望升级系统的某些部分，而有时却想要dist-upgrade。这是运行后的示例apt-get upgrade：

apt-get upgrade：

rimmer@rimmer-Lenovo-IdeaPad-S10-2:~$ sudo apt-get upgrade
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages have been kept back:
  linux-generic linux-headers-generic linux-image-generic
0 upgraded, 0 newly installed, 0 to remove and 3 not upgraded.

与apt-get dist-upgrade：

rimmer@rimmer-Lenovo-IdeaPad-S10-2:~$ sudo apt-get dist-upgrade
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Calculating upgrade... Done
The following NEW packages will be installed:
  linux-headers-3.0.0-13 linux-headers-3.0.0-13-generic
  linux-image-3.0.0-13-generic
The following packages will be upgraded:
  linux-generic linux-headers-generic linux-image-generic
3 upgraded, 3 newly installed, 0 to remove and 0 not upgraded.
Need to get 48.5 MB of archives.
After this operation, 215 MB of additional disk space will be used.
Do you want to continue [Y/n]?

换句话说，为什么不能执行此操作upgrade？

从apt-get手册：

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.

dist-upgrade
   dist-upgrade in addition to performing the function of upgrade,
   also intelligently handles changing dependencies with new versions
   of packages; apt-get has a "smart" conflict resolution system, and
   it will attempt to upgrade the most important packages at the
   expense of less important ones if necessary. So, dist-upgrade
   command may remove some packages. The /etc/apt/sources.list file
   contains a list of locations from which to retrieve desired package
   files. See also apt_preferences(5) for a mechanism for overriding
   the general settings for individual packages.

并apt从14.04开始使用更新的工具：

full-upgrade
   full-upgrade performs the function of upgrade but may also remove
   installed packages if that is required in order to resolve a
   package conflict.

你的具体情况，我明白了，例如，linux-headers是由双方提供了一个虚拟包linux-headers-3.0.0-12，并linux-headers-3.0.0-13和这听起来像那种软件包安装和删除所处理的dist-upgrade，而不是通过upgrade。

apt-get upgrade仅限于将软件包替换为较新版本的情况，但无需添加或删除软件包。例如，新版本的Firefox应该可以通过安装apt-get upgrade。

但是apt-get upgrade，当更新版本需要添加或删除时，它将拒绝工作。例如，当您linux-image-3.2.0-10-generic安装并linux-image-3.2.0-11-generic出现内核时，该linux-image-generic软件包将更新为依赖于较新的版本。为了安装新内核，您需要运行apt-get dist-upgrade。

请注意，如何apt-get upgrade表示内核软件包已经存在held back。这就是使用的提示apt-get dist-upgrade。

基本上，升级只会将现有软件包从一个版本升级到另一个版本。即使升级其他软件包，也不会安装或删除软件包。对于内核更新，升级linux-generic软件包需要安装新的linux-3.0.0-13-generic软件包，并且由于upgrade拒绝安装或删除软件包，因此它拒绝升级linux-generic。

有时，程序包之间的各种不兼容性会要求删除某些程序包以升级其他程序包，而这也需要进行dist-upgrade。内核更新由于其处理方式而始终需要dist-upgrade。每次都会创建一个全新的内核包，而不是更新内核包，并且将内核元包更新为依赖于新的内核包而不是旧的内核包。这样做是为了保留旧的内核版本，以防万一启动新内核时出现问题，可以从启动菜单中选择旧内核并进行恢复。

该apt-get upgrade命令通常只会安装对当前安装的软件包的更新（或修复）。例如，通常会使用此命令安装新版本的Mozilla Firefox。

但是apt-get upgrade将不一般安装新版本，其中的重大变化（包括去除包或GRUB更新是必需的）。例如，当有新的Linux内核（linux-image-3.xx-xx-generic等）可用时，将不会安装该软件包。

为了安装新内核，您需要运行apt-get dist-upgrade。当您运行时apt-get upgrade，系统会通知您，因为它表示某些软件包已被保留。这是您使用的提示：apt-get dist-upgrade。

最好的选择是：

apt full-upgrade

-升级包时自动处理依赖关系；而：

apt upgrade

-升级软件包时不自动处理依赖性。

- duBtrotterS