I guess I have to format my disc on cRIO NI 9038 with operating system NI Linux Real-Time x64 4.1.15-rt17-4.0.0f0.
I'm not sure if It is possible to install back just from MAX like Update firmware or I need to build Linux RT kernel some different way. I don't want to format my disc without knowing how to put my operating system back, but in FAQ i read that reinstall of NI Linux RT OS supposed to take just 5 min and if it is so easy please let me know how exactly I have to do it.
Yes, if you format from MAX, the 9038 will reboot into the read-only "safe" or "install" mode, ready to have a new OS image installed through MAX. If you install any software to the target from MAX, it will get the clean OS image.