Flash Filesystem

NAND structure

The Switch's eMMC storage features a large user area, two smaller boot partitions, and a replay-protected memory block which is unused (no authentication key is programmed).

Boot Partitions

Boot Partition 0 (0 of 1)

Offset	Size	Description
0x000000	0x4000	Title 0100000000000819 BCT
0x004000	0x4000	Title 010000000000081A BCT
0x008000	0x4000	Title 0100000000000819 BCT
0x00C000	0x4000	Title 010000000000081A BCT
0x100000	0x40000	Title 0100000000000819 "package1"
0x140000	0x40000	Title 0100000000000819 "package1" (Backup)
0x180000	0x4000	Keyblob area
0x184000	0x20	Unknown pseudorandom data, often changes on reboot. All zero on 1.0.
0x184020	0x8?	Increments on every boot until hitting a certain number? Bottom 10 bits (0x3FF) are always zero. All zero on 1.0.

Boot Partition 1 (1 of 1)

Offset	Size	Description
0x000000	0x40000	Title 010000000000081A "package1"
0x040000	0x40000	Title 010000000000081A "package1" (Backup)
0x080000	0x40000
0x0C0000	0x40000

Keyblob

Offset	Size	Description
0x0	0x10	Keyblob AES-CMAC over the remaining 0xA0-bytes (Checked with a mem-diff function which is safe against timing attacks, calls the general panic() func on failure)
0x10	0x10	Keyblob AES CTR
0x20	0x90	Keyblob encrypted payload
0xB0	0x150	Unused, all-zero.

Decrypted Keydata format:

Offset	Size	Description
0x0	0x80	Array of master static key encryption keys
0x80	0x10	Stage 2 key

Starting at 0x180000 is an array of 0x200-byte entries, for a total of 32 keyblobs. Each one is unique compared to the others. They are all console unique.

The 0xB0-byte keyblob is installed to the "customer data" section in BCTs (BCT+0x450).

BCT offset 0x2330 is the field controlling which keyblob gets used. NS uses this to inject the appropriate keyblob on system update. Boot also uses this index for repairing corrupt sectors.

With [ 3.0.0 + ] index 2 is used instead of index 1.

The Tegra 210 BCT format can be found in nvidia's cbootimage [1]

User Partitions

Partition name	Offset	Size	Bis Partition ID	Description
N/A	0x0		20	GPT header, Bis-storage also allows raw access to the entire NAND eMMC sectors starting at sector0.
PRODINFO	0x00004400	0x003FBC00	27	"CAL0" raw partition containing set:cal data.
PRODINFOF	0x00400000	0x00400000	28	FAT12 filesystem, additional calibration.
BCPKG2-1-Normal-Main	0x00800000	0x00800000	21	For all these packages, data starts at offset 0x4000 and is not console-unique. This is installed from "package2" in firmware package A (0100000000000819) by default. With the exFAT update installed, this is switched to firmware package C (010000000000081B). The data stored here matches the raw /nx/package2 file stored in the 81[9AB] data archives -- there is no additional encryption.
BCPKG2-2-Normal-Sub	0x01000000	0x00800000	22	Identical to BCPKG2-1-Normal-Main, probably used as a backup partition.
BCPKG2-3-SafeMode-Main	0x01800000	0x00800000	23	This is installed from "package2" in firmware package B (010000000000081A).
BCPKG2-4-SafeMode-Sub	0x02000000	0x00800000	24	Identical to BCPKG2-3-SafeMode-Main.
BCPKG2-5-Repair-Main	0x02800000	0x00800000	25	Installed at the factory.
BCPKG2-6-Repair-Sub	0x03000000	0x00800000	26	Identical to BCPKG2-5-Repair-Main.
SAFE	0x03800000	0x04000000	29	FAT32 filesystem.
SYSTEM	0x07800000	0xA0000000	31 (and 32?)	FAT32 filesystem.
USER	0xA7800000	0x680000000	30	FAT32 filesystem.
	0x747BFFE00	0x200		This is the backup GPT header specified by the main GPT header. This is also the last sector readable with Bis-storage paritionID 20.

If the client process lacks the relevant permission for any of the above partition IDs, error 0x2EE202 is returned.

NCAs stored in NAND are raw, identical to the data readable with Content_Manager_services#ReadEntryRaw.

The filenames for saveimages is just "<lower-case hex u64 saveID>". SYSTEM-partition saveIDs are specified by FS commands, while USER-partition saveIDs are determined by FS-module internally. The high u32 of the saveID is normally either 0x00000000 or 0x80000000.

PRODINFOF

PRODINFOF
├── Certifications
│   └── WirelessCertification.png
└── ptd
    ├── DeviceIdWithEmsBit.dat
    ├── Ecid.dat
    ├── prodCode.dat
    └── log
        ├── Process_asm1.log
        ├── Process_board1.log
        ├── TestFlagLine.log
        ├── TestFlagQc.log
        ├── AGING
        │   └── Sequence.log
        ├── BOARD_TEST
        │   └── Sequence.log
        ├── BOARD_WIRELESS
        │   └── Sequence.log
        ├── FINAL_CHECK
        │   └── Sequence.log
        ├── LCD_AND_KEY
        │   └── Sequence.log
        └── USB_AND_HP
            └── Sequence.log

DeviceIdWithEmsBit.dat

Contains a 0x10-byte uppercase hex string, identical to the DeviceId in the DeviceCert.

SYSTEM

SYSTEM
├── PRF2SAFE.RCV
├── Contents
│   ├── registered
│   │   └── ... NCA
│   └── placehld
│       └── ... NCA
├── save
│   └── ...
└── saveMeta
    └── ... (empty?)

The saves stored under this partition are only for system-titles / etc.

USER

USER
├── PRF2SAFE.RCV
├── Album (Same layout as SD)
├── Contents
│   ├── registered
│   │   └── ... NCA
│   └── placehld
│       └── ... NCA
├── save
│   └── ...
├── saveMeta
│   └── ... 
└── temp 

The saves for all non-system applications, regardless of where the application is located(storageID), is stored here. Each user account which has savedata has a separate saveimage. Save-common for an application is presumably a separate saveimage too. Every saveimage here is only for applications.

SAFE

SAFE
├── PRF2SAFE.RCV
├── Contents
│   ├── registered
│   │   └── ... NCA (nothing installed?)
│   └── placehld
│       └── ... NCA
└── save
    ├── 8000000000000000
    └── 8000000000000120

On a v2.1 system with MountBis, the only thing under here is "PRF2SAFE.RCV".

System Savegames

This is a listing of known System Savedata and what titles they correspond to.

SaveID	Owner	Notes
0x80000000000000d1	erpt	Contains "/journal" report listing + actual crash reports ("/%08x-%04x-%04x-%02x%02x-%04x%08x"), which are serialized via MsgPack.