A corrupted EFS, NVRAM, or modem partition can kill your IMEI, break Wi-Fi/Bluetooth MAC addresses, or dead-lock your SIM slot. The fix is simple: dump these partitions to your PC before flashing anything.

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Critical partitions to back up

  • modem / NON-HLOS — Baseband firmware (Qualcomm)
  • persist — MAC addresses, serial, calibration (Qualcomm, MTK)
  • nvram — IMEI, Bluetooth MAC, Wi-Fi MAC (MTK)
  • nvdata — Modem NV data (MTK)
  • protect1 / protect2 — Protected calibration (MTK)
  • EFS — Encrypted modem FS (Samsung Qualcomm)
  • oeminfo — OEM calibration, SN (Huawei)
  • boot — Kernel + ramdisk (all)
  • preloader — BROM-validated first-stage (MTK)

Minimum backup set

If you only back up three partitions, pick: persist, nvram (MTK) or modemst1/modemst2 (Qualcomm), and boot. These three cover 95% of recovery scenarios.

Difficulty: Intermediate • Reading time: 15 min