nvidia is not in the sudoers file. This incident will be reported.

Hello. I have a trouble with sudo command. Everythingh was ok, but today i restarted ubuntu on my jetson tx2 and now it gives me an error: “nvidia is not in the sudoers file. This incident will be reported” when i try to use sudo command. How can i fix this?
UPD: I found out that i can make an image of my system to host computer, then mount it and change sudoers file, but commands from this https://elinux.org/Jetson/Cloning guide don’t work because there is no nvflash on my host computer.

getent group gives me:
adm:x:4:ubuntu,syslog,nvidia
sudo:x:27:

Which release is this (see “head -n 1 /etc/nv_tegra_release”)? FYI, in later releases user “nvidia” is not added by default, so I am wondering if you had to add this account, and if so, what command you used.

Note that the URL you quoted is for the 32-bit TK1 (from many years ago). The clone content there has some validity in how it works, but actual clone has changed. Clone method may depend on release. This may be of interest, but even this may be out of date for some details:
https://devtalk.nvidia.com/default/topic/1000105/jetson-tx2/tx2-cloning/