How to mount ubifs filesystem on android emulator?

Question

I want to test the functionality of a custom ubifs filesystem on an android emulator (avd- Nexus 5). I have compiled and deployed a goldfish kernel(3.4) with ubifs support. But not finding the correct steps to mount a ubifs onto the emulator. I have tried using adb's mount command but no use. Any ideas on how to proceed ? or if you have idea on mounting a ubifs onto a real Nexus 5 device, Please do share.

Thanks in advance..

Answer 1

UbiFs requires UBI to work. UBI in turn requires a flash device or MTD (memory technology device). In order to mount it, you can use the nand_sim driver. The following are some commands to setup a UbiFs filesystem,

# nandsim emulating Micron 3.3V 256MiB, 2048 bytes page.
modprobe nandsim first_id_byte=0x2c second_id_byte=0xda third_id_byte=0x90 \
  fourth_id_byte=0x95
flash_erase /dev/mtd0 0 0
ubiformat /dev/mtd0
modprobe ubi mtd=0
ubiupdatevol /dev/ubi0_0 ubi.img
mount -t ubifs -o ro /dev/ubi0_0 /mnt/ubifs

This requires that nand_sim as a module; it is probably helpful to have ubi, ubifs, and mtd as modules. At least the above commands work on Debian/Ubuntu systems to verify UbiFs images as well as to diagnose corrupt images. There will probably be some Android simulator specific way to create modules. Alternatively, you can build nand_sim into the kernel and give it parameters to create a dummy flash device.

See the UBI Wiki entry for more information and resources. At least the concepts given should get you on the correct path.

Note: You ubi.img will have been created with some flash parameters such as erase block size. This is a property of the NAND device. You need to give nand_sim parameters for a device that matches those for your test image. The Linux kernel file nand_ids.c has tables with acceptable values for first_id_byte, second_id_byte, etc. There is a NAND hardware command to id flash which nand_sim will emulate to create the proper NAND geometry. The first byte is the manufacturer id.^{Ref: UbiFs on nand_sim}.