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EFS, modemst1, modemst2, fsg, backup partitions - Backup needed and what do they do?

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Question EFS, modemst1, modemst2, fsg, backup partitions - Backup needed and what do they do?

Sorry for posting this in Android Development, but I think this is important information that many other people might want to know as well:

In addition to the EFS partition, there are several partitions on our n9005 devices that do not exist in official odin roms.

This means that they must be unique to your phone, and they might be as important to back up as the EFS folder to prevent IMEI loss or other problems (like those bootloops many people get when flashing kernels, which appear to be tied to corrupted modemst1 partitions).

These partitions are: modemst1, modemst2, fsg, fsc, backup, dbi, ddr, pad

You can see them by executing the following command:

ls -l /dev/block/platform/msm_sdcc.1/by-name/

CWM does not back up EFS at all afaik, and the EFS backup tools usually only take the EFS partition while ignoring the others.

TWRP is the only one which also backs up modemst1 and modemst2 as far as I can tell. (it creates 2 additional efs backup files with 3MB in size - which is exactly the size of these partitions.)


From further research (this was discussed in the S3 forum) it turns out that the "fsg" and the "backup" partitions are meant to take copies of the modemst1 and modemst2 partitions - this can be done/forced by executing "reboot nvbackup" in terminal or with adb. So these partitions are meant to hold the backups of modemst1 and modemst2. But I'm not sure if our devices ship with these backups already made - the S3's apparently did not, so users had to do this backup themselves. (and/or use dd to also create image backups of these partitions)

People in the S3 forum reported that when they had corrupted modemst1 and/or modemst2 partitions (and no backup available) that while they still had their imei through EFS backup (or written to the phone with qualcomm tool) that they could only use the phone on roaming with these partitions corrupted.


So does anyone actually know more about this? Please lets use this thread to figure out (and then create some sort of sticky with the info) what these partitions actually do and if they need backup.

The "bootloop" fix goes as far as formatting modemst1 and modemst2 (I done it myself too in terminal before) to fix the bootloop issue. And its said that the partitions contents are just recreated then. But from which source? EFS or the fsg / backup partitions? etc.

This really needs some further investigation I think.


What I also did was to compare all the backups I had and see if they were the same or if they did differ.... and the weird thing is that EVERY single backup I have of my EFS folder or the modemst1 and modemst2 partitions do differ in checksum and also in binary diff.

Even the EFS folder did change over the time it seems. (partially this is caused by me editing the wifi mac ... but even before I did that the efs backups did differ from backup to backup).

But nonetheless, it seems that my phone is actually working alright. I have my imei, and I can just normally log in to my carrier network (can only test hsdpa+ though) and wifi is alright too.

So it appears that modemst1 and modemst2 indeed get recreated if they are formatted, but what about those other partitions. Unfortunately (since I only have one backup of these, made by hand) I cannot compare them to see if they also changed over the time.


Last but not least: modemst1, modemst2, fsg (meant to have copy of modemst1) and backup (meant to hve copy of modemst2) also differ on my device..... (can you guys who are fit in the terminal maybe also test if the partitions differ on your phones or if they are indeed copies?)


Would really like to understand these partitions more...
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Thank you so much, always wondered what all those things meant and what they did...very informative
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thanks you for making this thread.
so we can understand it.
i edited and made a windows efs backup tool for making backup and restore EFS, modemst1, modemst2.
and i will edit aroma method too.
... if we need more backup of more partitions, i will edit EFS Tool for them (dd backup/restore method)
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(Last edited by zroice; 20th January 2014 at 07:14 PM.)
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so I got some more infos:

I checked the "fsg" and "backup" partition, and they did not change over the course of all my actions. Even the partitions on the system are exactly the same as they were when I took backups. (remember: EFS and modemst1 and modemst2 constantly changed, and I could not find 2 exact copies in my backups).

So this means fsg and backup are indeed left untouched.


Since they are meant to hold backups of modemst1 and modemst2 which can be restored with "reboot nvrestore" I tried that as well.

But apparently they do not contain valid backups when you first get your phone (just like in the S3 case).

When I tried nvrestore the device rebooted and showed a message like "no nvbackup found" in red letters. (phone was stuck in this mode, even with forced reboot by holding down power - only pulling the battery got my device back to normal life... man was I scared when this message kept reappearing on hard reset)..


So in turn this means, the best thing to do when you get a new N3 (and didnt mess up modemst1 and modemst2 yet by flashing) that you should run "reboot nvbackup" in terminal.

This will fill the fsg and backup partition with valid copies of modemst1 and modemst2 which later can be restored with "reboot nvrestore".


Still not sure what these partitions are really about - they seem to be the "nvram" of the device (whatever that is lol) ... and I *think* there are things stored like carrier specific settings from what I understood. So simlock and netlock etc is stored there apparently. But since the note3's are all simlock free as far as I know (at least our n9005s) this should not really be important to us.

But when they are corrupted we get the bootloops.

These can be fixed by simply formatting the partitions, but I'm not 100% sure if this has any downsides yet. (aka if we need our original modemst1 and modemst2, or if it does not matter....)

ADD: I read in another post that someone lost his imei when his modemst1 got corrupted/formatted. But I can just say that I manually formatted modemst1 and modemst2 before (if you try this, back them up first though!!!!!!!) and I kept my imei and could connect phone to carrier etc. So the imei does not seem to be stored there really.


Someone has to know more about this, please enlighten us.....
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Interesting subject...

To add bits, pit file dump:

PIT dump v1.0 by LeTama

 - 30 partitions in PIT file
 - Format string = [COM_TAR2MSM8974]

01|APNHLOS             | 0x00002000 | 0x00007800 |     8192 |    30720 |    15360 KB | NON-HLOS.bin
02|MODEM               | 0x00009800 | 0x0001CB80 |    38912 |   117632 |    58816 KB | modem.bin
03|SBL1                | 0x00026380 | 0x00000400 |   156544 |     1024 |      512 KB | sbl1.mbn
04|DBI                 | 0x00026780 | 0x00000040 |   157568 |       64 |       32 KB | sdi.mbn
05|DDR                 | 0x000267C0 | 0x00000040 |   157632 |       64 |       32 KB |
06|ABOOT               | 0x00026800 | 0x00001000 |   157696 |     4096 |     2048 KB | aboot.mbn
07|RPM                 | 0x00027800 | 0x00000400 |   161792 |     1024 |      512 KB | rpm.mbn
08|TZ                  | 0x00027C00 | 0x00000400 |   162816 |     1024 |      512 KB | tz.mbn
09|PAD                 | 0x00028000 | 0x00005000 |   163840 |    20480 |    10240 KB |
10|PARAM               | 0x0002D000 | 0x00005000 |   184320 |    20480 |    10240 KB | param.bin
11|EFS                 | 0x00032000 | 0x00007000 |   204800 |    28672 |    14336 KB | efs.img.ext4
12|MODEMST1            | 0x00039000 | 0x00001800 |   233472 |     6144 |     3072 KB | nvrebuild1.bin
13|MODEMST2            | 0x0003A800 | 0x00001800 |   239616 |     6144 |     3072 KB | nvrebuild2.bin
14|BOOT                | 0x0003C000 | 0x00005800 |   245760 |    22528 |    11264 KB | boot.img
15|RECOVERY            | 0x00041800 | 0x00006800 |   268288 |    26624 |    13312 KB | recovery.img
16|FOTA                | 0x00048000 | 0x00006800 |   294912 |    26624 |    13312 KB |
17|BACKUP              | 0x0004E800 | 0x000037EE |   321536 |    14318 |     7159 KB |
18|FSG                 | 0x00051FEE | 0x00001800 |   335854 |     6144 |     3072 KB |
19|FSC                 | 0x000537EE | 0x00000002 |   341998 |        2 |        1 KB |
20|SSD                 | 0x000537F0 | 0x00000010 |   342000 |       16 |        8 KB |
21|PERSIST             | 0x00053800 | 0x00004000 |   342016 |    16384 |     8192 KB | persist.img.ext4
22|PERSDATA            | 0x00057800 | 0x00004800 |   358400 |    18432 |     9216 KB | persdata.img.ext4
23|SYSTEM              | 0x0005C000 | 0x00480000 |   376832 |  4718592 |  2359296 KB | system.img.ext4
24|CACHE               | 0x004DC000 | 0x00096000 |  5095424 |   614400 |   307200 KB | cache.img.ext4
25|HIDDEN              | 0x00572000 | 0x0000F000 |  5709824 |    61440 |    30720 KB | hidden.img.ext4
26|USERDATA            | 0x00581000 | 0x00000000 |  5771264 |        0 |        0 KB | userdata.img.ext4
70|PGPT                | 0x00000000 | 0x00000022 |        0 |       34 |       17 KB | pgpt.img
71|PIT                 | 0x00000022 | 0x00000010 |       34 |       16 |        8 KB | MSM8974.pit
72|MD5                 | 0x00000032 | 0x00000020 |       50 |       32 |       16 KB | md5.img
73|SGPT                | 0x03A3DFDF | 0x00000021 | 61071327 |       33 |       16 KB | sgpt.img
 - signature /trailer size = [4204]
It's showing more locations than the one exposed by kernel like pgpt /sgpt (primary/secondary gpt partition table), pit table, md5 (?).

Last, there is the rpmb partition that we can't see without knowing the access key.
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Originally Posted by genius.lizard2 View Post
thanks you for making this thread.
so we can understand it.
i edited and made a windows efs backup tool for making backup and restore EFS, modemst1, modemst2.
and i will edit aroma method too.
... if we need more backup of more partitions, i will edit EFS Tool for them (dd backup/restore method)
Thank you, worked perfectly.
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