升级到 17.04 后无法安装 build-essential/gcc/g++

Question

由于从 Ubuntu 16.04 升级到 17.04，我无法再安装gcc-7或g++-7从http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu存储库安装。事实上，我什至无法安装build-essential.

在Software & Updates > Other Software 下，存储库如下所示：

http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu zesty main

尝试安装build-essential：

$ sudo apt install build-essential
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 build-essential : Depends: gcc (>= 4:5.2) but it is not going to be installed
                   Depends: g++ (>= 4:5.2) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

然而：

$ gcc --version
gcc (Ubuntu 5.4.1-8ubuntu1) 5.4.1 20170304
...
$ g++ --version
g++ (Ubuntu 5.4.1-8ubuntu1) 5.4.1 20170304
...

那么如何build-essential重新安装呢？

Answer 1

所以我可以build-essential按照以下步骤再次安装：

$ sudo apt install build-essential
...
The following packages have unmet dependencies:
 build-essential : Depends: gcc (>= 4:5.2) but it is not going to be installed
                   Depends: g++ (>= 4:5.2) but it is not going to be installed

gcc需要 5.2 以上的版本，所以让我们尝试安装gcc.

$ sudo apt install gcc
...
The following packages have unmet dependencies:
gcc : Depends: cpp (>= 4:6.3.0-2ubuntu1) but it is not going to be installed
      Depends: gcc-6 (>= 6.3.0-9~) but it is not going to be installed

好的。还缺少其他东西。让我们尝试安装它。

$ sudo apt install cpp
...
The following packages have unmet dependencies:
 cpp : Depends: cpp-6 (>= 6.3.0-9~) but it is not going to be installed

依然没有。再试一次。

$ sudo apt install cpp-6
...
The following packages have unmet dependencies:
 cpp-6 : Depends: gcc-6-base (= 6.3.0-12ubuntu2) but 6.3.0-18ubuntu2~16.04 is to be installed

再来一次。

$ sudo apt install gcc-6-base
...
gcc-6-base is already the newest version (6.3.0-18ubuntu2~16.04).

所以在这里我不知道到底出了什么问题。需要注意的是16.04，该版本号末尾有一个字符串。那看起来很奇怪。我删除了那个包。

$ sudo apt remove gcc-6-base

现在我可以build-essential再次安装。这也将重新安装gcc-6-base.

$ sudo apt install build-essential

遗留问题：

$ sudo apt upgrade
...
The following packages have been kept back:
  cpp g++ gcc

问题的根源与上面类似，gcc-7-base是有问题的，但我不能简单地将其删除，因为我得到了这个：

The following packages have unmet dependencies:
 libgcc1 : Depends: gcc-7-base (= 7.1.0-5ubuntu2~16.04) but it is not going to be installed
 va-driver-all : Depends: mesa-va-drivers but it is not going to be installed or
                          vdpau-va-driver but it is not going to be installed
E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.

危险区域：

我设法通过以下步骤解决了这个问题：

$ sudo apt install aptitude
$ sudo dpkg --force-all -P gcc-7-base
$ sudo dpkg --force-all -P gcc-7-base:i386
$ sudo aptitude install gcc-7-base

这是非常危险的，可能会破坏您的安装。执行dpkg --force-all -P将强制删除一个包，忽略对这个包的任何依赖。定期执行此操作apt upgrade可能会从您的安装中删除几乎所有相关软件。

我只能通过 usind 从那里恢复，aptitude这解决了我遇到的每个依赖问题。