我的机器是CUDA16.04的，之前装过CUDA10.0，因为一些原因，现在需要安转CUDA9.0。
下载run版本的（如果之前没装过CUDA，可以下载deb版本的）
2.按照上面的教程
sudo chmod +x cuda_9..176_384.81_linux.run # 为 cuda_9..176_384.81_linux.run 添加可执行权限
./cuda_9..176_384.81_linux.run # 安装 cuda_9..176_384.81_linux.run
3.相关参数的设置
Install NVIDIA Accelerated Graphics Driver for Linux-x86_64 384.81?(y)es/(n)o/(q)uit: n #我已经装过CUDA10了，所以不需要安转9.0的显卡驱动Install the CUDA 9.0 Toolkit?
(y)es/(n)o/(q)uit: y/usr/local/cuda-9.0 is not writable.
Do you wish to run the installation with 'sudo'? (y)es/(n)o: y #使用超级用户权限Please enter your password: Do you want to install a symbolic link at /usr/local/cuda? # 是否将安装目录通过软连接的方式 link 到 /usr/local/cuda，yes or no 都可以，取决于你是否使用 /usr/local/cuda 为默认的 cuda 目录。
(y)es/(n)o/(q)uit: y #我目前需要使用9.Enter Toolkit Location
[ default is /usr/local/cuda-9.0 ]:#直接回车
4.安转结束后相关环境变量的设置
Finished copying samples.===========
= Summary =
===========Driver: Not Selected
Toolkit: Installed in /usr/local/cuda-9.0
Samples: Installed in /usr/local/cuda-9.0/SamplesPlease make sure that
- PATH includes /usr/local/cuda-9.0/bin
- LD_LIBRARY_PATH includes /usr/local/cuda-9.0/lib64, or, add /usr/local/cuda-9.0/lib64 to /etc/ld.so.conf and run ldconfig as rootTo uninstall the CUDA Toolkit, run the uninstall script in /usr/local/cuda-9.0/binPlease see CUDA_Installation_Guide_Linux.pdf in /usr/local/cuda-9.0/doc/pdf for detailed information on setting up CUDA.***WARNING: Incomplete installation! This installation did not install the CUDA Driver. A driver of version at least 384.00 is required for CUDA 9.0 functionality to work.
To install the driver using this installer, run the following command, replacing <CudaInstaller> with the name of this run file:
sudo <CudaInstaller>.run -silent -driverLogfile is /tmp/cuda_install_11003.log
如上，需要设置PATH和LD_LIBRARY_PATH两个变量，在./bashrc文件中修改即可，记得要source一些./bashrc，让其生效。
完成上面这些步骤后，就可以进行多个版本的切换了，直接修改/usr/local/cuda即可，使其指向不同版本的CUDA。
