opencv c++安装踩坑记录 file cannot create directory: /usr/local/include/opencv2. Maybe need administrative privileges

前言

最近深度学习Ultra-Fast-Lane-Detection/INSTALL.md at master · cfzd/Ultra-Fast-Lane-Detection (github.com)需要安装opencv c++，于是准备安装。于是按照OpenCV: Installation in Linux官网一顿操作，好像是成功了。但是在安装成功，进行软链接的时候

# First you need to install OpenCV C++. 
# After installation, make a soft link of OpenCV include path.

ln -s /usr/local/include/opencv4/opencv2 /usr/local/include/opencv2

失败，提示已经存在文件夹，不会解决。于是删除opencv编译过程中的文件，尝试第二种方式，还是失败。于是百度去安装了。

安装过程

来源：Ubuntu18.04下opencv的安装及应用_风吹麦甜的博客-CSDN博客_ubuntu18.04安装opencv

额外的问题：

1. 在sudo make install提示：

   root@yf407:/home/swx/Desktop/opencv-3.4.14/build# sudo make install
   [  0%] Built target gen-pkgconfig
   [  4%] Built target libtiff
   [ 13%] Built target libwebp
   [ 16%] Built target libjasper
   [ 24%] Built target IlmImf
   [ 30%] Built target libprotobuf
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   [ 39%] Built target opencv_core
   [ 46%] Built target opencv_imgproc
   [ 47%] Built target opencv_imgcodecs
   [ 48%] Built target opencv_videoio
   [ 49%] Built target opencv_highgui
   [ 50%] Built target opencv_ts
   [ 53%] Built target opencv_test_core
   [ 55%] Built target opencv_perf_core
   [ 55%] Built target opencv_flann
   [ 55%] Built target opencv_test_flann
   [ 59%] Built target opencv_perf_imgproc
   [ 63%] Built target opencv_test_imgproc
   [ 64%] Built target opencv_ml
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   [ 67%] Built target opencv_photo
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   [ 69%] Built target opencv_video
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   [ 71%] Built target opencv_test_video
   [ 77%] Built target opencv_dnn
   [ 78%] Built target opencv_perf_dnn
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   [ 81%] Built target opencv_features2d
   [ 81%] Built target opencv_perf_features2d
   [ 83%] Built target opencv_test_features2d
   [ 83%] Built target opencv_perf_imgcodecs
   [ 84%] Built target opencv_test_imgcodecs
   [ 84%] Built target opencv_shape
   [ 84%] Built target opencv_test_shape
   [ 84%] Built target opencv_test_videoio
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   [ 86%] Built target opencv_calib3d
   [ 87%] Built target opencv_perf_calib3d
   [ 90%] Built target opencv_test_calib3d
   [ 90%] Built target opencv_test_highgui
   [ 91%] Built target opencv_objdetect
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   [ 93%] Built target opencv_stitching
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   [ 97%] Built target opencv_videostab
   [ 97%] Built target opencv_test_videostab
   [ 98%] Built target opencv_traincascade
   [ 99%] Built target opencv_createsamples
   [ 99%] Built target opencv_annotation
   [ 99%] Built target opencv_visualisation
   [100%] Built target opencv_interactive-calibration
   [100%] Built target opencv_version
   Install the project...
   -- Install configuration: "Release"
   -- Up-to-date: /usr/local/share/licenses/opencv3/opencl-headers-LICENSE.txt
   CMake Error at cmake_install.cmake:45 (file):
     file cannot create directory: /usr/local/include/opencv2.  Maybe need
     administrative privileges.
   
   
   Makefile:61: recipe for target 'install' failed
   make: *** [install] Error 1
   
   

   提示没有权限，百度之后是加sudo，但是已经是root用户了，而且已经sudo了，行不通。那就自己解决：

   1. 手动创建/usr/local/include/opencv2.，还是如此提示。

   2. 进入/usr/local/include/,看到了一个文件opencv2，目前2022年6月1日，因此这就是前几天创建的，很奇怪，于是索性删掉，神奇的事情发生了，再次执行命令就成功了。之后软链接也成功了！！！个人猜测应该是最开始安装opencv 4.x失败导致产生的遗留文件产生的这个问题。

      (python3.7) swx@yf407:/usr/local/include$ ll
      total 176
      drwxr-xr-x  2 root root  4096 Jun  1 09:58 ./
      drwxr-xr-x 14 root root  4096 Apr 14 18:58 ../
      -rw-r--r--  1 root root  5777 Dec 27  2007 lauxlib.h
      -rw-r--r--  1 root root 22299 Feb 12  2008 luaconf.h
      -rw-r--r--  1 root root 11688 Jan 14  2012 lua.h
      -rw-r--r--  1 root root   191 Dec 23  2004 lua.hpp
      -rw-r--r--  1 root root  1026 Dec 27  2007 lualib.h
      -rw-r--r--  1 root root  1292 Mar  3 10:56 ms-erref.h
      -rw-r--r--  1 root root  1952 Mar  3 10:56 ms-fscc.h
      -rw-r--r--  1 root root 23075 Mar  3 10:56 ms-rdpbcgr.h
      -rw-r--r--  1 root root  3413 Mar  3 10:56 ms-rdpeclip.h
      -rw-r--r--  1 root root  1018 Mar  3 10:56 ms-rdpedisp.h
      -rw-r--r--  1 root root  4620 Mar  3 10:56 ms-rdpefs.h
      -rw-r--r--  1 root root  2174 Mar  3 10:56 ms-rdpegdi.h
      -rw-r--r--  1 root root  1400 Mar  3 10:56 ms-rdpele.h
      -rw-r--r--  1 root root  1029 Mar  3 10:56 ms-rdperp.h
      -rw-r--r--  1 root root  2835 Mar  3 10:56 ms-smb2.h
      lrwxrwxrwx  1 root root    34 May 27 09:07 opencv2 -> /usr/local/include/opencv4/opencv2
      -rw-r--r--  1 root root  4020 Mar  3 10:56 painter.h
      -rw-r--r--  1 root root  1218 Mar  3 10:56 rfxcodec_common.h
      -rw-r--r--  1 root root  1028 Mar  3 10:56 rfxcodec_decode.h
      -rw-r--r--  1 root root  4158 Mar  3 10:56 rfxcodec_encode.h
      -rw-r--r--  1 root root  5400 Mar  3 10:56 xrdp_client_info.h
      -rw-r--r--  1 root root  9108 Mar  3 10:56 xrdp_constants.h
      -rw-r--r--  1 root root  4684 Mar  3 10:56 xrdp_rail.h
      -rw-r--r--  1 root root  1638 Mar  3 10:56 xrdp_sockets.h