无法在 Ubuntu 20.04 上安装“libdrm-dev”，因为它需要比我拥有的依赖项更旧的依赖项

[我的建议]通过自动降级安装的依赖项aptitude来安装libdrm-dev

我想通了，这有效：用于aptitude降级依赖项。

只是命令：

sudo aptitude install libdrm-dev
# then choose these options:
n  # do NOT leave things as-is
y  # DO downgrade dependencies
y  # Do continue with the install

运行后sudo aptitude install libdrm-dev，选择no它的提案to Keep the following packages at their current version，并选择yes它说它会的提案Remove the following packages，，Install the following packages和Downgrade the following packages。然后再次选择yes显示： 的位置0 packages upgraded, 2 newly installed, 13 downgraded, 5 to remove and 0 not upgraded. Need to get 33.4 MB of archives. After unpacking 140 MB will be freed. Do you want to continue? [Y/n/?]。就是这样！它（稍微）降级了一些软件包，并且现在安装得很好！

细节：

这是完整的命令和输出（我将在下面解释）。我用一些标记标记了输入n、y、 和 的位置：y<======

$ sudo aptitude install libdrm-dev
The following NEW packages will be installed:
  libdrm-dev{b} 
0 packages upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 126 kB of archives. After unpacking 658 kB will be used.
The following packages have unmet dependencies:
 libdrm-dev : Depends: libdrm2 (= 2.4.101-2) but 2.4.107-8ubuntu1~20.04.2 is installed
              Depends: libdrm-intel1 (= 2.4.101-2) but 2.4.107-8ubuntu1~20.04.2 is installed
              Depends: libdrm-radeon1 (= 2.4.101-2) but 2.4.107-8ubuntu1~20.04.2 is installed
              Depends: libdrm-nouveau2 (= 2.4.101-2) but 2.4.107-8ubuntu1~20.04.2 is installed
              Depends: libdrm-amdgpu1 (= 2.4.101-2) but 2.4.107-8ubuntu1~20.04.2 is installed
The following actions will resolve these dependencies:

     Keep the following packages at their current version:
1)     libdrm-dev [Not Installed]                         



Accept this solution? [Y/n/q/?] n                           <=================
The following actions will resolve these dependencies:

      Remove the following packages:                                                    
1)      mesa-va-drivers [21.2.6-0ubuntu0.1~20.04.2 (now)]                               
2)      va-driver-all [2.7.0-2 (focal, now)]                                            

      Install the following packages:                                                   
3)      libllvm9 [1:9.0.1-12 (focal)]                                                   

      Downgrade the following packages:                                                 
4)      libdrm-amdgpu1 [2.4.107-8ubuntu1~20.04.2 (now) -> 2.4.101-2 (focal)]            
5)      libdrm-intel1 [2.4.107-8ubuntu1~20.04.2 (now) -> 2.4.101-2 (focal)]             
6)      libdrm-nouveau2 [2.4.107-8ubuntu1~20.04.2 (now) -> 2.4.101-2 (focal)]           
7)      libdrm-radeon1 [2.4.107-8ubuntu1~20.04.2 (now) -> 2.4.101-2 (focal)]            
8)      libdrm2 [2.4.107-8ubuntu1~20.04.2 (now) -> 2.4.101-2 (focal)]                   
9)      libegl-mesa0 [21.2.6-0ubuntu0.1~20.04.2 (now) -> 20.0.4-2ubuntu1 (focal)]       
10)     libgbm1 [21.2.6-0ubuntu0.1~20.04.2 (now) -> 20.0.4-2ubuntu1 (focal)]            
11)     libgl1-mesa-dri [21.2.6-0ubuntu0.1~20.04.2 (now) -> 20.0.4-2ubuntu1 (focal)]    
12)     libglapi-mesa [21.2.6-0ubuntu0.1~20.04.2 (now) -> 20.0.4-2ubuntu1 (focal)]      
13)     libglx-mesa0 [21.2.6-0ubuntu0.1~20.04.2 (now) -> 20.0.4-2ubuntu1 (focal)]       
14)     libosmesa6 [21.2.6-0ubuntu0.1~20.04.2 (now) -> 20.0.4-2ubuntu1 (focal)]         
15)     mesa-vdpau-drivers [21.2.6-0ubuntu0.1~20.04.2 (now) -> 20.0.4-2ubuntu1 (focal)] 
16)     mesa-vulkan-drivers [21.2.6-0ubuntu0.1~20.04.2 (now) -> 20.0.4-2ubuntu1 (focal)]



Accept this solution? [Y/n/q/?] y                           <=================
The following packages will be DOWNGRADED:
  libdrm-amdgpu1 libdrm-intel1 libdrm-nouveau2 libdrm-radeon1 libdrm2 libegl-mesa0 libgbm1 libgl1-mesa-dri libglapi-mesa libglx-mesa0 libosmesa6 mesa-vdpau-drivers mesa-vulkan-drivers 
The following NEW packages will be installed:
  libdrm-dev libllvm9{a} 
The following packages will be REMOVED:
  i965-va-driver{u} intel-media-va-driver{u} libigdgmm11{u} mesa-va-drivers{a} va-driver-all{a} 
0 packages upgraded, 2 newly installed, 13 downgraded, 5 to remove and 0 not upgraded.
Need to get 33.4 MB of archives. After unpacking 140 MB will be freed.
Do you want to continue? [Y/n/?] y                          <=================

注意未满足的依赖关系。正如你所看到的，它说它需要 libdrm2 版本 2.4.101-2，但我安装了版本 2.4.107-8ubuntu1~20.04.2 等。奇怪的是，我的版本对它来说太新了。

The following packages have unmet dependencies:
 libdrm-dev : Depends: libdrm2 (= 2.4.101-2) but 2.4.107-8ubuntu1~20.04.2 is installed
              Depends: libdrm-intel1 (= 2.4.101-2) but 2.4.107-8ubuntu1~20.04.2 is installed
              Depends: libdrm-radeon1 (= 2.4.101-2) but 2.4.107-8ubuntu1~20.04.2 is installed
              Depends: libdrm-nouveau2 (= 2.4.101-2) but 2.4.107-8ubuntu1~20.04.2 is installed
              Depends: libdrm-amdgpu1 (= 2.4.101-2) but 2.4.107-8ubuntu1~20.04.2 is installed

因此，aptitude首先提出解决方案：

     Keep the following packages at their current version:
1)     libdrm-dev [Not Installed] 

我强烈要求n拒绝该解决方案。然后它会提出一个更好的解决方案来降级依赖项并执行安装。我选择y该选项。那我y以后还得重新选择。

完成后，您可以看到常规sudo apt install libdrm-dev程序现在也可以正常工作，表明libdrm-dev已经成功安装！：

$ sudo apt install libdrm-dev
[sudo] password for gabriel: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
libdrm-dev is already the newest version (2.4.101-2).
0 upgraded, 0 newly installed, 0 to remove and 5 not upgraded.

完毕！

现在我可以返回到在 Ubuntu 20.04 上安装 displaylink-driver，这样我就可以使用我的新双 4k 60 Hz USB-A 适配器！请参阅我的答案：USB to HDMI adapter that Works with Ubuntu。

替代方案：如何libdrm从源代码构建和安装最新版本

这并不能完全回答我的问题，但以下是如何libdrm从源代码构建的方法：

源代码在这里： https: //gitlab.freedesktop.org/mesa/drm

在此处获取最新的标记版本：https ://gitlab.freedesktop.org/mesa/drm/-/tags

下载并解压。

请参阅自述文件中的“编译”说明： https: //gitlab.freedesktop.org/mesa/drm

跑步：

meson builddir/  # prep a folder
time sudo ninja -C builddir/ install  # build and install

构建和安装只花了 20 秒。它安装到/usr/local/include/libdrm.