[Samsung Galaxy S Duos] billysam:
Okay I was facing a weird problem with the latest twrp 2.8.0.1, maybe others would face this as well too. here it is with the problem and solution by myself.

Well I faced issues since the first day.

I tried both the builds of cm11 physical primary and normal build.

Both were performed as a clean flash using 2.8.0.1

The Roms install successfully, and It got booted up.

installed apps set up everything. no worries there like everyone else, the Rom works great.

Now, I tried to push a modified services.jar and framework.jar file(very little modification, no errors there) through a root filemanager.

I restarted the device normally without force. and all my apps stored on the external sdcard was gone.

I tried to restore my nandroid backup and I got the error.

[RESTORE STARTED]

Restore folder: '/external_sd/TWRP/BACKUPS/ab69146c/2016-04-07--20-23-16 cm_kylessopen-userdebug 4.4.4 KTU84Q 4f2c5e'
Skipping MD5 check based on user setting.
Calculating restore details...
I:InfoManager loading from '/external_sd/TWRP/BACKUPS/ab69146c/2016-04-07--20-23-16 cm_kylessopen-userdebug 4.4.4 KTU84Q 4f2c5e/system.info'.
I:Read info file, restore size is 562871089
I:InfoManager loading from '/external_sd/TWRP/BACKUPS/ab69146c/2016-04-07--20-23-16 cm_kylessopen-userdebug 4.4.4 KTU84Q 4f2c5e/data.info'.
I:Read info file, restore size is 292470324
I:InfoManager file '/external_sd/TWRP/BACKUPS/ab69146c/2016-04-07--20-23-16 cm_kylessopen-userdebug 4.4.4 KTU84Q 4f2c5e/boot.info' not found.
I:Restore file system is: 'emmc'.
Restoring 3 partitions...
Total restore size is 827MB
I:Restore filename is: system.ext4.win
I:Restore file system is: 'ext4'.
Wiping system...
Formatting system using make_ext4fs function.
Creating filesystem with parameters:
Size: 1258291200
Block size: 4096
Blocks per group: 32768
Inodes per group: 7680
Inode size: 256
Journal blocks: 4800
Label:
Blocks: 307200
Block groups: 10
Reserved block group size: 79
Created filesystem with 11/76800 inodes and 10109/307200 blocks
Restoring System...
I:Single archive
I:Extracting uncompressed tar
prefix: /system
==> tar_extract_all(TAR *t, "/system")
tar_extract_all(): calling th_get_pathname()
tar_extract_all(): calling tar_extract_file(t, "/system//etc/")
item name: '/etc/'
dir
==> extracting: /system//etc/ (mode 40755, directory)
mkdir(): Read-only file system
FAILED RESTORE OF FILE i: /system//etc/
[B]E:Unable to extract tar archive '/external_sd/TWRP/BACKUPS/ab69146c/2016-04-07--20-23-16 cm_kylessopen-userdebug 4.4.4 KTU84Q 4f2c5e/system.ext4.win'
I:extractTarFork() process ended with ERROR=255[/B]
I:Set page: 'action_complete'
I:Set page: 'clear_vars'
I:Set page: 'restore_select'
I:Set page: 'restore'
I:Set page: 'main'
I:Set page: 'clear_vars'
I:Set page: 'main2'
I:Set page: 'advanced'
I:Set page: 'confirm_action'
I:Set page: 'action_page'

I tried restore only data partition, it goes on successfully.

System didn't restored, in every backup I created on twrp 2.8.0.1 this is the problem others will also face maybe.

anyways

I installed the Rom zip again and it boots back up running with my backup data.

it was strange to see, it didn't happen when I pushed the same 2 files from a flashable zip using recovery, it booted up fine without causing any error in the system.

Again I tested with some other modified files and added new files through custom recovery. it would cause me to lose apps stored on the data/app partition(which was on external sdcard. while those modified files would cause no trouble to the system and would work just fine.

Solution

to be able to restore your nandroid backups successfully.

Go to settings- enable use rm-rf instead of formatting.