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
0x010000	0xF0000	60 additional BCTs, normally unused/empty on retail systems.
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

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

From each 0x200-byte entry only the first 0xB0 bytes effectively form the keyblob as below.

Offset	Size	Description
0x0	0x10	Keyblob AES-CMAC over the next 0xA0 bytes (safe against timing attacks)
0x10	0x10	Keyblob AES CTR
0x20	0x90	Keyblob encrypted payload
0xB0	0x150	Unused, all-zero.

The active bootloader's version (offset 0x2330 in the BCT) acts as an index to control which keyblob should be installed into the system. NS uses this during system updates to install the keyblob into the customer data section in BCTs (offset 0x450).

Boot also uses this index for repairing corrupt sectors.

User Partitions

Partition name	Offset	Size	Bis Partition ID	Encrypted	Description
N/A	0x0		20	No	GPT header, Bis-storage also allows raw access to the entire NAND eMMC sectors starting at sector0. The official name for this partitionID from SystemInitializer is "nn::fs::BisPartitionId::UserDataRoot".
PRODINFO	0x00004400	0x003FBC00	27	Yes	"CAL0" raw partition containing set:cal data.
PRODINFOF	0x00400000	0x00400000	28	Yes	FAT12 filesystem, additional calibration.
BCPKG2-1-Normal-Main	0x00800000	0x00800000	21	No	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" is "BootConfigAndPackage2": for example, from SystemInitializer: "BootConfigAndPackage2Part1".
BCPKG2-2-Normal-Sub	0x01000000	0x00800000	22	No	Identical to BCPKG2-1-Normal-Main, probably used as a backup partition.
BCPKG2-3-SafeMode-Main	0x01800000	0x00800000	23	No	This is installed from "package2" in firmware package B (010000000000081A).
BCPKG2-4-SafeMode-Sub	0x02000000	0x00800000	24	No	Identical to BCPKG2-3-SafeMode-Main.
BCPKG2-5-Repair-Main	0x02800000	0x00800000	25	No	Installed at the factory, never written afterwards on retail. In one case this is identical to normal 1.0.0 pkg2, except this has encrypted data at the end padded for 0x1000-byte alignment.
BCPKG2-6-Repair-Sub	0x03000000	0x00800000	26	No	Identical to BCPKG2-5-Repair-Main.
SAFE	0x03800000	0x04000000	29	Yes	FAT32 filesystem.
SYSTEM	0x07800000	0xA0000000	31 and 32	Yes	FAT32 filesystem.
USER	0xA7800000	0x680000000	30	Yes	FAT32 filesystem.
	0x747BFFE00	0x200		No	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.

Encrypted partitions use AES-XTS using the same non-standard (endian-swapped) tweak as other Nintendo AES-XTS code, initial_sector = 0, and sector size 0x4000. All encrypted partitions use console unique keydata.

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	Mount	Notes
0x8000000000000000
0x8000000000000010	account	account:/	Account database.
0x8000000000000011	account	idgen:/
0x8000000000000020	nfc	data:/	NFC data and backups.
0x8000000000000030	ns	mii:/	Mii database.
0x8000000000000031	ns	mii:/	Mii test mode database.
0x8000000000000040	ns	apprecdb:/
0x8000000000000041	ns	nsaccache:/	Home menu icondata/lru list for recently played games.
0x8000000000000043	ns	ns_appman:/
0x8000000000000044	ns	ns_sysup:/	Content update context.
0x8000000000000045	ns	vmdb:/	Version List/Required Version List storage.
0x8000000000000046	ns	dtlman:/
0x8000000000000047	ns	ns_exfat:/
0x8000000000000048	ns	ns_systemseed:/
0x8000000000000050	settings	SystemSettings:/
0x8000000000000051	settings	FwdbgSettingsS:/
0x8000000000000052	settings	PrivateSettings:/
0x8000000000000053	settings	DeviceSettings:/
0x8000000000000054	settings	ApplnSettings:/
0x8000000000000060	ssl	SslSave:/
0x8000000000000070	nim	nim_sys:/
0x8000000000000071	nim	nim_net:/
0x8000000000000072	nim	nim_tmp:/
0x8000000000000073	nim	nim_dac:/
0x8000000000000074	nim	nim_delta:/
0x8000000000000075	nim	nim_vac:/
0x8000000000000080	friends	friends:/
0x8000000000000081	friends	friends-sys:/
0x8000000000000082	friends	friends-image:/
0x8000000000000090	bcat	news:/	Actual news msgpack archives.
0x8000000000000091	bcat	news-sys:/	News metadata, tasklist, history, database, required system version, etc.
0x8000000000000092	bcat	news-dl:/	Storage for newly(?) downloaded news list/data.
0x80000000000000A0	bcat	prepo-sys:/	Play Report system information.
0x80000000000000A1	bcat	prepo:/	Play Report msgpack archives.
0x80000000000000B0	bsdsockets	nsdsave:/	Socket configuration saved data.
0x80000000000000C1	bcat	bcat-sys:/
0x80000000000000C2	bcat	bcat-dl:/
0x80000000000000D1	erpt	save:/	Contains "/journal" report listing + actual crash reports ("/%08x-%04x-%04x-%02x%02x-%04x%08x"), which are serialized via MsgPack.
0x80000000000000E0	es	escertificate:/
0x80000000000000E1	es	escommon:/
0x80000000000000E2	es	espersonalized:/
0x80000000000000F0	ns	pdm:/	Play Data log.
0x8000000000000100	pctl	pctlss:/	Parental Control settings.
0x8000000000000110	npns	npns_save:/	Push notifications persistent storage.
0x8000000000000120	ncm	?	meta/imkvdb.arc for system partition. Cache of data extracted from the .cnmt for installed titles?(Including 816)
0x8000000000000121	ncm	?	meta/imkvdb.arc for sd partition. In some cases this save only contains a "meta/" directory without any file.
0x8000000000000122
0x8000000000001010
0x8000000000001040
0x8000000000001050
0x8000000000001070
0x80000000000010B0
0x0000000000000001
0x0000000000000003
0x0000000000000004
0x0000000000000005
0x0000000000000006
0x0000000000000007
0x0000000000000008
0x0000000000000009
0x000000000000000A
0x8000000000001060
0x000000000000000C
0x000000000000000D