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[Q] How does a custom recovery works?

Ok, so i'm new to all this stuff about custom recoverys and ROMs. How exactly do they work?
Let's say i make a custom recovery image of my current ROM, wich is stock, does it just backup the OS or my personal files (music, photos, apps, etc.) too?
I'm asking this primarly because i want to upgrade my phone, but to do so i have to flash the stock firmware because i've modified some system files. Wich bring to my other question, flashing ROMs wipe user data? i've read some split responses to this, some people say it does some say it doesn't.
And my final question, let's say i made a backup, wiped my phone flashed stock firmware and updated, now how i recover my data from the
backed up ROM, i mean it is a different version, does it have an option to just restore user data?
Thanks in advance, and sorry if these are too much questions.

it'll back up system, data, boot.img and dalvik cache.
your sd partition isn't backed up, but all the stuff on it will be readable by whatever new rom you put on it (unless you wipe EVERYTHING [not a good idea]).
when you're changing roms/etc, you want to place the rom.zip + gapps.zip (and custom kernel.zip if you're going to use one) on your sd partition. you do this because usb storage mostly doesn't work with custom recoveries as of yet on this device meaning once you've wiped, if you don't have a rom on your sd partition you're mildly screwed in that you'd have to reflash everything from a stock image (meaning you will lose root, all your personal files and whatever rom was on the phone - basically everything goes back to stock bar the bootloader).
e: as for restoring all apps data, use something like titanium backup. i always have a backup on my sd partition of all my current apps (plus wifi passwords, accounts info, sms messages etc to save time/effort when restoring after putting a new rom on). i also always set TB to backup all modified/new data every night at about 3am, then upload the backup to google drive so that if i either brick my phone or accidentally wipe everything, at least i can get back to where i left off.

If you forget to place the ROM zip, and have formatted the device, it is not necessary to flash stock. You use adb side load which is present in every recovery.

in that case i need to remember that for future use - i hardly ever use my pc with my phone now as you can pretty much do anything (update recovery etc) on the phone alone.
that, and i'm on windows 8.1 which afaik doesn't play nicely with fastboot or adb.

twist3d0n3 said:
....and i'm on windows 8.1 which afaik doesn't play nicely with fastboot or adb.
Click to expand...
Click to collapse
....i think this is a rumor. Never ever had any problems on W8.1

^ good to know, thanks

[TWRP]extractTarFork() process ended with ERROR: 255

Hi, 2 days ago with the help of App Inspector and MiXplorer i was debloating my phone from all those useless apps like Huawei ID, HiCare, Swiftkey, ecc. and while I was doing it i took the chance to remove some other service packages that I'm sure I'd never used in future, like Geofence, Mapcon, Fido client, ecc. Everything worked nice in the phone, overall because obviously i paid an extreme caution while removing packages since that we're talking about system files, and i fact i didn't noticed incompatibilities or other issues while using the phone in these 48h.
The only problem that i encountered is that now my TWRP isn't able to restore a nandroid backup without getting a failure accompanied by the error mentioned in thread title.
Code:
[COLOR="red"]extractTarFork() process ended with ERROR: 255[/COLOR]
When i reboot to system however, everything is fine except the theme that i have to set again, the list of previous SMS empty (but i have contacts, system settings, apps, notes, everything else) and a leftover of Swiftkey app that i have to remove again. I tried with 2 different backups: one made before debloating the phone 2 days ago, and the second is a backup took today on the phone already debloated. Anyway making some searches around i found this topic https://github.com/TeamWin/Team-Win-Recovery-Project/issues/964 in which i read that a possible cause could be the amount of free space on the phone, but i have more than 17GB free and I'm restoring the backup from external SD, so i can exclude for sure this cause... Another solution standing by what i read elsewhere could be to unmount the "data" partition on the phone before restoring the backup, but neither that changed a single thing and i keep getting the same error. I think that what could provoke this issue is related to some files linked to missing apks, like data of an app removed but it's the only clue i have about now.
I hope that someone can really help me out on this because TWRP backups for me are essential. Looking forward for your answers guys! Any help will be extremely appreciated!!
EDIT: i can provide logs obviously if someone could be able to detect the error by reading them, i can't so let me know if someone would like to dedicate some minute on reading a log

Other things noticed: i had to reflash again Magisk Modules and even Magisk V14.3 zip to being able to flash modules stored on my SD, even if Magisk was still installed. This is surely due the fact that the restore of data partition started and then it got stopped by fault of error 255, so data partition wasn't fully restored. The thing that i just can't understand is why even the older backup isn't working, maybe I'll have to format data dalvik and cache to get the older backup working..? Damn

Bump. C'mon guys, really no one??

RedSkull23 said:
Bump. C'mon guys, really no one??
Click to expand...
Click to collapse
Haven't seen yet bro

shashank1320 said:
Haven't seen yet bro
Click to expand...
Click to collapse
Dammit that's bad, i known from beginning that it's a complex issue but i thought that someone here could help...

RedSkull23 said:
Other things noticed: i had to reflash again Magisk Modules and even Magisk V14.3 zip to being able to flash modules stored on my SD, even if Magisk was still installed. This is surely due the fact that the restore of data partition started and then it got stopped by fault of error 255, so data partition wasn't fully restored. The thing that i just can't understand is why even the older backup isn't working, maybe I'll have to format data dalvik and cache to get the older backup working..? Damn
Click to expand...
Click to collapse
May be you need to format data, dalvik and cache and then reboot to recovery again from recovery.
I am facing such issue these days and had to opt for this to mount data again. Never understood this concept with huawei phones. my old Yu Yureka was hell easier to flash all these.

shashank1320 said:
May be you need to format data, dalvik and cache and then reboot to recovery again from recovery.
I am facing such issue these days and had to opt for this to mount data again. Never understood this concept with huawei phones. my old Yu Yureka was hell easier to flash all these.
Click to expand...
Click to collapse
The only thing that stops me from trying to solve this by wiping data, dalvik and cache is that if after wiping the issue will persist, other than not being able to restore my backup I'd find myself with a phone where i have to restart from scratch too. And so it could be even worse... I really don't know what to do at the moment, but i must fix this.

RedSkull23 said:
The only thing that stops me from trying to solve this by wiping data, dalvik and cache is that if after wiping the issue will persist, other than not being able to restore my backup I'd find myself with a phone where i have to restart from scratch too. And so it could be even worse... I really don't know what to do at the moment, but i must fix this.
Click to expand...
Click to collapse
May be a twrp backup... once all restored then restore data

So, some day ago i managed to solve my problem trying once again to restoring a copy of a TWRP backup, this time an older one dated 2 weeks ago other than 1 like the previous backup... (for safety reasons i always keep 2 backups, and i overwrite these weekly one after another, by the most recent) and this time it worked. I seriously can't understand why this error happened only on the 1st and more recent backup, since that i started to debloat some system apks and packages only 1 week after the latest backup, and so without system modifications the error shouldn't have to be already present on the backup took exactly 1 week before starting to remove files... but i'm out of this now

[QUESTION] Correct way go backup/restore the Pixel 2?

This is the second time that I have tried to restore a backup from TWRP only to find myself stuck in the bootloader with the "AuthFailed" yellow banner on the bottom. What am I doing wrong? When I created the backup, I had selected every checkbox that I could to back up everything and that is what I restored, but that obviously didn't work. Which are the correct checkmarks to check to get the system to backup/restore correctly without tripping this authentification bootloop?
Any guidance would be greatly appreciated!

JGoldz75 said:
This is the second time that I have tried to restore a backup from TWRP only to find myself stuck in the bootloader with the "AuthFailed" yellow banner on the bottom. What am I doing wrong? When I created the backup, I had selected every checkbox that I could to back up everything and that is what I restored, but that obviously didn't work. Which are the correct checkmarks to check to get the system to backup/restore correctly without tripping this authentification bootloop?
Any guidance would be greatly appreciated!
Click to expand...
Click to collapse
When I make my backups I leave the three things that are automatically checked off boot, system and data. I haven't had any problem restoring backups. Hope this helps

Another backup-restore question. All my other phones had sd cards so my backups and titanium backups we're all stored there.
If I wipe and flash a new rom won't I wipe the backup when reformatting? Where should I store the backup?

SS823 said:
Another backup-restore question. All my other phones had sd cards so my backups and titanium backups we're all stored there.
If I wipe and flash a new rom won't I wipe the backup when reformatting? Where should I store the backup?
Click to expand...
Click to collapse
The phone has a partition that acts like an SD card and won't be wiped unless you perform a full data erase.

PuffDaddy_d said:
The phone has a partition that acts like an SD card and won't be wiped unless you perform a full data erase.
Click to expand...
Click to collapse
What if I need to do a full system wipe? I've been backing up and then transferring the folder to Google drive and then uploading the backup when needed. Seems like extra work, I miss the convenience of sd cards, is there a way to partition just backups?

SS823 said:
What if I need to do a full system wipe? I've been backing up and then transferring the folder to Google drive and then uploading the backup when needed. Seems like extra work, I miss the convenience of sd cards, is there a way to partition just backups?
Click to expand...
Click to collapse
You can backup to a computer. If that isn't feasible or you just don't want to do that, you can use a USB flash drive. Plug the drive into the USB B-USB C adapter that came with the phone and then plug it into your phone. I use a USB flash drive for Titanium Backup backups. TWRP backups too. Works great.

The yellow authfailed at bootloader error. I had to deal with that the other day where even an install of the factory image couldn't fix. I had to use dueces script to get my phone working again. I'm not sure what it does that Google's flash_all.bat doesn't.
https://forum.xda-developers.com/pixel-2/development/tool-deuces-bootloop-recovery-flashing-t3725778

New ROM from LineageOS to RROS --> *sadface*

So I made an oops, *sadface*. Though I'm glad I backed up the important stuff before I went from OOS to LineageOS. I decided to see how RROS was with Q, So I downloaded needed files, and I proceeded with what I thought was necessary. RROS 8.1.0, proper gapps. Had Magisk and TWRP on phone already, so I did factory reset, install RROS, TWRP -> reboot TWRP -> flash GApps, flash magisk... Clearly something went wrong as my phone went default encrypted with no way to decrypt it. Apparently I had to wipe the data and start out freshy fresh. So, what did I do wrong? How could I have avoided this? I've done some research and it seems that with the A/B partition, format data is required? If that is so, so be it. I'd just like to know if there was an alternative way to switch ROMs without having to backup all data and restore it after formatting data. Way more hassle than I anticipated.

Imo, there is no way to change custom rom without formating data, otherwise your storage will end up encrypted. I am just using automatic google backup for apps, settings, wifi, call logs and sms and google photos for images and it works great. You dont need to take care of it at all, just set it and it will automatically backup all your data periodically and when you swith to the new rom you will have choice to restore all of the above from your backup during initial setup.

Full(!) backup via ADB

Is there a way to perform a full backup via ADB?
Like a script or a line which creates a flashable full copy of one or all of the phones filesystems to PC.
Not(!)
adb backup -all
which backups merely system settings and not a migrate app which a) does not perform a full backup as it omits random files and b) works internal and neither TWRP backup-tool which only works internal.

andy01q said:
Is there a way to perform a full backup via ADB?
Like a script or a line which creates a flashable full copy of one or all of the phones filesystems to PC.
Not(!)
adb backup -all
which backups merely system settings and not a migrate app which a) does not perform a full backup as it omits random files and b) works internal and neither TWRP backup-tool which only works internal.
Click to expand...
Click to collapse
It can backup/restore your data, it can not backup your ROM/firmware, if you are not rooted, you will only be able to backup/restore user data, you will not be able to backup/restore any of your system apps/system app data, or any other part of system data and system settings, that will require rooting the device.
If you want a complete backup of the operating system and everything else on the device, you will need TWRP.
Sent from my SM-S767VL using Tapatalk

I am rooted. I am running TWRP.
I can't copy large amounts of data from inside the phone because something is buggy; this includes TWRPs backup-function. Copying works fine if and only if controlled by connected PC.

andy01q said:
I am rooted. I am running TWRP.
I can't copy large amounts of data from inside the phone because something is buggy; this includes TWRPs backup-function. Copying works fine if and only if controlled by connected PC.
Click to expand...
Click to collapse
Try flashing a newer or slightly older version of TWRP, it might fix the bugs that you are experiencing in TWRP. Is TWRP set to store your backups on external? Or is it set to store backups on your internal storage? Storing backups in internal takes up too much space, it's best to store backups on external.
As for adb...
https://forum.xda-developers.com/galaxy-nexus/guide-phone-backup-unlock-root-t1420351
There are several switches that can be used to be specific about what you want backed up and what you don't.
Sent from my SM-S767VL using Tapatalk

I updated to TWRP 3.4.0-0 (newest version) and backup from within TWRP still always fails between 20% and 30%. The last 30 to 40 backups failed and the only one that did finish to 100% is still broken and can't be read.
I would be thinking hardware-failure if not for the thing that copying anything from within the phone is super buggy, but copying when controlled from a PC works completely fine.
I guess I'll try the simple adb backup with some more parameters and then move on.

andy01q said:
I updated to TWRP 3.4.0-0 (newest version) and backup from within TWRP still always fails between 20% and 30%. The last 30 to 40 backups failed and the only one that did finish to 100% is still broken and can't be read.
I would be thinking hardware-failure if not for the thing that copying anything from within the phone is super buggy, but copying when controlled from a PC works completely fine.
I guess I'll try the simple adb backup with some more parameters and then move on.
Click to expand...
Click to collapse
How much free space do you have on internal storage? If there is less free space than your system, data and cache partitions combined, that may be why it is failing. Clear some space. I say this because when the backup is being created, the data that you want included in your backup is being read bit by bit from their partitions and then written into cache bit by bit and then it is read from cache bit for bit then it is written to its final storage location bit for bit. If there is not enough space to write it all into cache before writing it to its final location, it will fail.
The same rule applies when you move files from internal to external or vice versa, the same rule also applies when you are extracting files. It requires enough free space to write that data into cache before it goes where it is actually going.
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Oh come on, I appreciate your efforts, but I felt being treated like a little child from your first answer and this tops it very much. Backup fails at 20-30% with 45GB of free internal space, external MicroSD removed and <10GB of data to backup. Aside from that I doubt that if a lack of free space causes the backup to fail, that this will not cause an error message to tell me what caused the fail.
By now I did the backups that I could backup:
That is I manually pulled all folders I deemed important.
Then I used "adb backup -apk -shared -all -system" which created a 7GB backup.
I also used the buggy migrate-app and ticked all boxes to get a 3GB backup.
And I used Googles cloud-service-backup.
In the end plenty of data and configurations were lost; worst is probably the Corona Warn App data as this can't be remedied.

andy01q said:
Oh come on, I appreciate your efforts, but I felt being treated like a little child from your first answer and this tops it very much. Backup fails at 20-30% with 45GB of free internal space, external MicroSD removed and <10GB of data to backup. Aside from that I doubt that if a lack of free space causes the backup to fail, that this will not cause an error message to tell me what caused the fail.
By now I did the backups that I could backup:
That is I manually pulled all folders I deemed important.
Then I used "adb backup -apk -shared -all -system" which created a 7GB backup.
I also used the buggy migrate-app and ticked all boxes to get a 3GB backup.
And I used Googles cloud-service-backup.
In the end plenty of data and configurations were lost; worst is probably the Corona Warn App data as this can't be remedied.
Click to expand...
Click to collapse
I can't help how you feel and you are entitled to feel however you wantl, but, at the end of the day, it is still only how you "feel", that doesn't make anything true or false. Just saying.
I didn't post anything to make you feel any kind of way, I was merely attempting to be as informative as I could because one can never gauge what someone else knows or understands before your interaction with them.
I've seen some other issues with TWRP backups failing and/or being unreadable, the solution is not a singular solution, there are several reasons why it fails and several fixes to solve it. Have you tried doing some google searches for:
"TWRP backups fail at 40%"
That pulls up some information that might apply or may not, you'll just have to peruse what you find to see if any of seems like it might be what you are experiencing and then try some of the solutions that others have tried. You might get lucky, you might not.
I'm more interested in helping you "find" an answer than whether I "know" the answer or "tell" you the answer.
Sent from my SM-S767VL using Tapatalk

Droidriven said:
Have you tried doing some google searches for:
"TWRP backups fail at 40%"
Click to expand...
Click to collapse
Yeah, I've done that for an hour or so before starting a thread - obviously b/c that has the chance for much quicker solutions and seems less work for me.
Also I did try several solutions like update TWRP, try smaller backups (the small ones do usually work) and so on. I think I did mention that I tried this over 40 times.
Some of the solutions suggest installing another ROM first, (apparently the ROM can cause Read-errors within TWRP?) but obviously I want the full backup before I try another ROM so I tried other methods to backup my data.
Also moving data via adb has worked completely without fail so far, so I wanted to try that path.
By now I can tell that TWRP full backup doesn't work on other ROMs either.

andy01q said:
Yeah, I've done that for an hour or so before starting a thread - obviously b/c that has the chance for much quicker solutions and seems less work for me.
Also I did try several solutions like update TWRP, try smaller backups (the small ones do usually work) and so on. I think I did mention that I tried this over 40 times.
Some of the solutions suggest installing another ROM first, (apparently the ROM can cause Read-errors within TWRP?) but obviously I want the full backup before I try another ROM so I tried other methods to backup my data.
Also moving data via adb has worked completely without fail so far, so I wanted to try that path.
By now I can tell that TWRP full backup doesn't work on other ROMs either.
Click to expand...
Click to collapse
Flash an older version or newer version of the exact same ROM as what you have but not doing any of the wipes, just flash ROM and that's it. This is called a "dirty flash", it will not wipe any of your data unless you specifically tell it to.
Alternatively, you could just do a backup via TWRP without including system and boot, just data and maybe cache(cache isn't necessary and might even cause issues if you restore it). Then, if you need to restore, flash the ROM the backup was created from then reboot to system, then boot back into TWRP then use "advanced restore" in TWRP to restore data and cache, this "should" give the same result as including system and boot in the TWRP backup along with data then restoring everything from that backup.
Also, can you post a copy of your recovery logs to some hosting site then link it here, someone here might be able to see something in the log that needs addressing, preferably the logs from the failed backup processes, if they errored in different ways, post the differences also. You should be able to find your logs if you haven't wiped the device.
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