In the context of the Samsung Galaxy S6 (SM-G920F) NV (Non-Volatile) data file
No Redundancy – Unlike newer Samsung devices that mirror NV data, the G920F stores critical parameters in a single location. One bad write = permanent damage without a backup. sm-g920f nv data file
su
dd if=/dev/block/platform/155a0000.ufs/by-name/EFS of=/sdcard/efs.img
“It’s the NV Data file,” said Malik, the wiry repairman in the back of a dusty electronics shop. He spoke like a pathologist delivering a verdict. “Your phone’s lost its memory of who it is.” In the context of the Samsung Galaxy S6
Or copy entire /efs:
“How did it happen?” Lena asked.