Ubuntu上安装了cuda driver后不能启动进入界面，只好通过recovery模式进入，然后卸载cuda driver。
参考地址：
How to uninstall the NVIDIA drivers on Ubuntu 20.04 step by step instructions
https://linuxconfig.org/how-to-uninstall-the-nvidia-drivers-on-ubuntu-20-04-focal-fossa-linux
这里列出了两种方法，介绍如下，
方法一: Uninstall the Ubuntu repository and PPA NVIDIA drivers
- The following command will remove the proprietary Nvidia driver: $ sudo dpkg -P $(dpkg -l | grep nvidia-driver | awk '{print $2}')
$ sudo apt autoremove
- Switch back to nouveau driver: $ sudo apt install xserver-xorg-video-nouveau
The above switch from Nvidia to Nouveau driver can also be performed from GNOME GUI Software & Updates application window. - Reboot your system.
- Once your system has rebooted confirm loaded
nouveau modules: $ lsmod | grep nouveau nouveau 1949696 4 mxm_wmi 16384 1 nouveau ttm 106496 1 nouveau drm_kms_helper 184320 1 nouveau drm 491520 7 drm_kms_helper,ttm,nouveau i2c_algo_bit 16384 1 nouveau wmi 32768 3 wmi_bmof,mxm_wmi,nouveau video 49152 1 nouveau
方法二：Uninstall the official NVIDIA drivers
For Nvidia drivers downloaded and installed from the official Nvidia website follow the below steps for Nvidia driver uninstall and to switch back to Nouveau opensource driver.
- Locate the installation script used to install the Nvidia driver. In case you cannot locate the original installation script simply re-download it again. $ ls
NVIDIA-Linux-x86_64-440.44.run
- Uninstall the Nvidia Driver. Update the below Nvidia script name where appropriate : $ sudo bash NVIDIA-Linux-x86_64-XXX.XX.run --uninstall
- If you have not done so yet, restore your
xorg original configuration from backup: $ sudo nvidia-xconfig --restore-original-backup - Enable Nouveau modules. If you followed our guide on how to disable nouveau drivers on Ubuntu 20.04 execute the following command: $ sudo rm /etc/modprobe.d/blacklist-nvidia-nouveau.conf
- Reboot your Ubuntu 20.04 system.
