Why we can't make a folder in Jetson Nano?

Recently, I bought a jetson orin nano and I flashed it using nvidia sdk manager. After all, I tried to make a folder but it is showing an
error. What can I do to overcome this problem?

Terminal output is in the below.

caft@ubuntu:~$ sudo mkdir new_folder
mkdir: cannot create directory ‘new_folder’: Read-only file system

Under what directory are you performing mkdir?

I can’t make a folder in any directory. And also, can’t make a folder in manual as well.

It just does not sound reasonable at all.
Did SDK Manager throw any error during flashing?
Do you have other SD cards/NVMe drives for testing?

What do you see from these (I’ve added a “2>&1 | tee something.txt” to log this; you could remove that if you are not posting log files of the commands, e.g., if using serial console logging):

df -H -T 2>&1 | tee log_df.txt
lsblk -f 2>&1 | tee log_lsblk.txt
mount 2>&1 | tee log_mount.txt

During the flash, was your host PC using ext4 as its filesystem type (which is the default for regular installs of Ubuntu, but perhaps not for a VM)?