[OLD] RECOVERY.fstab

TWRP 2.5 and higher supports some new recovery.fstab features that you can use to extend TWRP's backup/restore capabilities. You do not have to add fstab flags as most partitions are handled automatically.

Note that TWRP does not currently support the "fstab 2" version of fstab files seen in 4.3 or higher. You will still need to use the "old" format of fstab for TWRP (example of that format is below). To maximize TWRP's compatibility with your build tree, you can create a twrp.fstab and use PRODUCT_COPY_FILES to place the file in /etc/twrp.fstab When TWRP boots, if it finds a twrp.fstab in the ramdisk it will rename /etc/recovery.fstab to /etc/recovery.fstab.bak and then rename /etc/twrp.fstab to /etc/recovery.fstab. Effectively this will "replace" the fstab 2 file that your device files are providing with the TWRP fstab allowing you to maintain compatibility within your device files and with other recoveries.

PRODUCT_COPY_FILES += device/lge/hammerhead/twrp.fstab:recovery/root/etc/twrp.fstab

The fstab in TWRP can contain some "flags" for each partition listed in the fstab.

Here's a sample TWRP fstab for the Galaxy S4 that we will use for reference:

/boot       emmc        /dev/block/platform/msm_sdcc.1/by-name/boot
/system     ext4        /dev/block/platform/msm_sdcc.1/by-name/system
/data       ext4        /dev/block/platform/msm_sdcc.1/by-name/userdata length=-16384
/cache      ext4        /dev/block/platform/msm_sdcc.1/by-name/cache
/recovery   emmc        /dev/block/platform/msm_sdcc.1/by-name/recovery
/efs        ext4        /dev/block/platform/msm_sdcc.1/by-name/efs                            flags=display="EFS";backup=1
/external_sd     vfat       /dev/block/mmcblk1p1    /dev/block/mmcblk1   flags=display="Micro SDcard";storage;wipeingui;removable
/usb-otg         vfat       /dev/block/sda1         /dev/block/sda       flags=display="USB-OTG";storage;wipeingui;removable
/preload    ext4        /dev/block/platform/msm_sdcc.1/by-name/hidden                            flags=display="Preload";wipeingui;backup=1
/modem      ext4        /dev/block/platform/msm_sdcc.1/by-name/apnhlos
/mdm		emmc		/dev/block/platform/msm_sdcc.1/by-name/mdm

Flags are added to the end of the partition listing in the fstab separated by white space (spaces or tabs are fine). The flags affect only that partition but not any of the others. Flags are separated by semicolons. If your display name is going to have a space, you must surround the display name with quotes.

/external_sd  vfat  /dev/block/mmcblk1p1  flags=display="Micro SDcard";storage;wipeingui;removable

The flags for this partition give it a display name of "Micro SDcard" which is displayed to the user. wipeingui makes this partition available for wiping in the advanced wipe menu. The removable flag indicates that sometimes this partition may not be present preventing mounting errors from being displayed during startup. Here is a full list of flags:

removable -- indicates that the partition may not be present preventing mounting errors from being displayed during boot

storage -- indicates that the partition can be used as storage which makes the partition available as storage for backup, restore, zip installs, etc.

settingsstorage -- only one partition should be set as settings storage, this partition is used as the location for storing TWRP's settings file

canbewiped -- indicates that the partition can be wiped by the back-end system, but may not be listed in the GUI for wiping by the user

userrmrf -- overrides the normal format type of wiping and only allows the partition to be wiped using the rm -rf command

backup= -- must be succeeded by the equals sign, so backup=1 or backup=0, 1 indicates that the partition can be listed in the backup/restore list while 0 ensures that this partition will not show up in the backup list.

wipeingui -- makes the partition show up in the GUI to allow the user to select it for wiping in the advanced wipe menu

wipeduringfactoryreset -- the partition will be wiped during a factory reset

ignoreblkid -- blkid is used to determine what file system is in use by TWRP, this flag will cause TWRP to skip/ignore the results of blkid and use the file system specified in the fstab only

retainlayoutversion -- causes TWRP to retain the .layoutversion file in /data on devices like Sony Xperia S which sort of uses /data/media but still has a separate /sdcard partition

symlink= -- causes TWRP to run an additional mount command when mounting the partition, generally used with /data/media to create /sdcard

display= -- sets a display name for the partition for listing in the GUI

storagename= -- sets a storage name for the partition for listing in the GUI storage list

backupname= -- sets a backup name for the partition for listing in the GUI backup/restore list

length= -- usually used to reserve empty space at the end of the /data partition for storing the decryption key when Android's full device encryption is present, not setting this may lead to the inability to encrypt the device

canencryptbackup= -- 1 or 0 to enable/disable, makes TWRP encrypt the backup of this partition if the user chooses encryption (only applies to tar backups, not images)

userdataencryptbackup= -- 1 or 0 to enable/disable, makes TWRP encrypt only the userdata portion of this partition, certain subfuldes like /data/app would not be encrypted to save time

subpartitionof= -- must be succeeded by the equals sign and the path of the partition it is a subpartition of. A subpartition is treated as "part" of the main partition so for instance, TWRP automatically makes /datadata a subpartition of /data. This means that /datadata will not show up in the GUI listings, but /datadata would be wiped, backed up, restored, mounted, and unmounted anytime those operations are performed on /data. A good example of the use of subpartitions is the 3x efs partitions on the LG Optimus G:

/efs1         emmc   /dev/block/mmcblk0p12 flags=backup=1;display=EFS
/efs2         emmc   /dev/block/mmcblk0p13 flags=backup=1;subpartitionof=/efs1
/efs3         emmc   /dev/block/mmcblk0p14 flags=backup=1;subpartitionof=/efs1

This lumps all 3 partitions into a single "EFS" entry in the TWRP GUI allowing all three to be backed up and restored together under a single entry.

If you have questions, feel free to stop by #twrp on Freenode. If you post here I may not see it for a while as I have lots of threads out there and there's no way for me to keep track of them all. If you successfully port TWRP to a new device, please let us know! We love to hear success stories!

If you have code changes that you'd like to submit, please submit them through the Omni Gerrit server. Guide is here.

Once you get Omni or CM synced and your TWRP flags set, you should do a source ./build/envsetup.sh. We usually lunch for the device in question, so something like lunch omni_hammerhead-eng.

After lunch finishes successfully for your device this is the command used for most devices:

make clean && make -j# recoveryimage

Replace the # with the core count +1, so if you have a dual core it's -j3 and a quad core becomes -j5, etc. If you're dealing with a "typical" Samsung device, then you'll need to run:

make -j# bootimage

Most Samsung devices have the recovery included as an extra ramdisk in the boot image instead of a separate recovery partition as found on most other devices.

Notes about 4.4 KitKat ROMs and SELinux