Database Info

[Guide] Step by Step Installation of Android Pie Custom Roms

Step by Step Installation of/Upgrade to Android Pie Custom Roms
Following this guide, you will lose all your data if haven't backed it up yet!!
Also NO USING GSI PIE!!!
Requirements:
- Twrp is already installed.
What you need:
- LineageosTWRP (Attached to thread)
- Custom Rom (can be found here)
- Open Gapps (Pico or Nano)
Only if Root is wanted: Chose either of them
Magisk(Recommended) or SuperSU
- A brain and a body
- The Knowledge that you will wipe your phone by doing this. Be Warned.
Installation:
1. Backup all the files that you have either by copying them to a usb drive ,a micro SD or your computer.
2. Check that all files are copied successfully and can be opened or viewed.
( Some apps have a cloud synchonisation feature, use it if you have it as an option since it is really helpful!)
3. Now, get your preferred rom, gapps and if wanted, your root method ready, also unzip the twrp file aswell.
Copy them to your micro SD.
4. Boot into twrp via adb or by using some app(root needed).
In Twrp, go into wipe option, then select change file system. Change file System to ext4.
4.1 Now use Twrp Reboot-Menu Option to reboot into recovery(twrp) again.
4.2 Wipe system, data, cache and dalvik-cache partitions using the Wipe option
5. Go into Install Option and Press on "Install IMG" , select pietwrp image and flash it. (The name should be lineagerecovery.img or something if downloaded via telegram)
(If you don't have it yet and are in the Lenovo P2 Telegram group, type #pietwrp in chat and make sure to safe it to your download folder. Otherwise it's also attached to this thread.)
6. Reboot back to recovery like you did in step 4.1.
7. Now install your rom and gapps.
8. Wipe cache and then reboot .
9. Setup your phone and Enjoy.
( For Root, reboot to recovery. Flash your Root Method, wipe cache and reboot)
Enjoy and thank your Devs
FAQ
Q: Instructions unclear, phone stuck in bootloop
A: Either do this:
Download this folder and use one of the two ".bat" files. Boot into Bootloader via Volume Down and Power Button. --
It will flash S048 Firmware of our Lenovo P2, after the flash-process is finished it will boot up on its own. Recommended: Do all the ota updates via ota app.
Or: Boot into bootloader, via adb cmd prompt use: fastboot boot lineagerecovery.img , then use reboot menu to reboot into twrp. Clean Wipe phone(Wipe system,data, cache and dalvik-cache Partitions) and try flashing your Rom etc. again.
Q: Instructions unclear, hardbricked my phone!!
A: Thaat shouldn't have happened. Did you screw up somewhere?...
Luckily you backed up your most important files!

GSI for the Galaxy A20 (Android 10)

What is GSI?
GSI stands for Generic System Image and will allow you to install an alternative ROM on your Galaxy A20?
No longer will we be restricted to the Samsung ROM.
These ones worked for me. If they don't work for you, go to the list of all GSIs. There are plenty to choose from. Select arm64 ab files.
Q GSIs
1. AOSP 10
https://github.com/phhusson/treble_experimentations/releases
2. Pixel Experience, EvolutionX & Havoc
https://forum.xda-developers.com/pr...iscussion/gsi-expressluke-built-gsis-t4003457
3. Crdroid
https://sourceforge.net/projects/amber-gsi/files/crDroid v6.1/crDroidAndroid-10.0-20200104--v6.1-arm64-ab-vanilla.img.xz/download
Custom Android 10 boot screens
https://forum.xda-developers.com/galaxy-a20/themes/a20-custom-splash-screen-android-10-gsi-t4019693
List of all GSIs
https://github.com/phhusson/treble_experimentations/wiki/Generic-System-Image-(GSI)-list
physwizz collection
A collection of guides, kernels and ROMs. Guides Complete Guide to the A20 GSIs for the A20 Quick Root and TWRP for the A20 Making my First Kernel for the A20 A20 Rooting Guide Making Your Own ROM Making Your Own Version of QwizzROM-a20...
forum.xda-developers.com

Before you Start
1. Make sure your phone is rooted
For A20: https://forum.xda-developers.com/galaxy-a20/how-to/root-samsung-galaxy-a20-rooting-guide-t3954872
For A30: https://forum.xda-developers.com/galaxy-a30/how-to/root-galaxy-a30-magisk-canary-relaese-t3936481
2. Install TWRP and remove data encryption.
For A20: https://forum.xda-developers.com/ga...p-samsung-galaxy-a20-custom-recovery-t3955271
For A30: https://forum.xda-developers.com/galaxy-a30/development/recovery-twrp-galaxy-a30-t3968085
Quick root and TWRP together for the A20: https://forum.xda-developers.com/galaxy-a20/how-to/guide-quick-root-twrp-galaxy-a20-t4069423
3. Backup only 3 parts: boot, data & system (not system image) onto external SD or usb-otg. If something goes wrong you should be able to restore the phone using TWRP.
4. Also use SMS Backup and Restore so you don't lose your messages or calls.
5. Make sure your Ext SD card is Fat32. I've noticed that GSIs don't recognise ExFat.
Android 10 (Q)
1. Installation
1. Begin with stock ROM
2. Reboot into TWRP ( then mount product - system - vendor)
Back boot data and system
3. Wipe both caches, data & system
4. Install GSI
5. Flash Magisk and physwizz GSI kernel from here https://forum.xda-developers.com/t/kernel-physwizz-kernel-for-the-galaxy-a20.4180107/
6. Reboot.
2. Installing GApps
Some GSIs come with GApps. If you're doesn't and you want to have GApps, then use this method.
a.-Resize system partition so you can install OpenGAPPS, go to wipe, advanced wipe, select system, select repair or change file system and select resize file system. If you get error 1 unmount and mount the system partition and try again
b. Install GApps
3. Fixing Navbar
As soon as you boot up. Run Magisk and install this module.
View attachment navbar-enabler.zip
4. Android 10 Backup
Backup Data only (EvolutionX and Havoc 3.0 will do boot/data/system backup and restore),
5. Android 10 Restore
1. Reinstall GSI (a - h above)
2. Restore Data
3. Install GApps (if needed)
Reboot
To Access larger SD cards
Unzip the file below
Use TWRP file manager to copy this file to
/system/system/bin
Tap on to file
Press chmod755
Reboot system
Android 11 (R)
wIP

Some interesting links.
https://forum.xda-developers.com/showpost.php?p=80177833&postcount=199
phhusson treble releases
https://github.com/phhusson/treble_experimentations/releases
GSIs for A50
https://forum.xda-developers.com/galaxy-a50/how-to/guide-guide-how-to-flash-gsi-t3934005/page1
AOSP GSIs
https://source.android.com/setup/build/gsi
GSI for the A70
https://forum.xda-developers.com/galaxy-a70/how-to/gsi-testing-thread-t3956230
List of all GSIs
https://github.com/phhusson/treble_experimentations/wiki/Generic-System-Image-(GSI)-list
Project Treble
https://forum.xda-developers.com/project-treble
Lolinet mirror
https://mirrors.lolinet.com/firmware/gsi/

Only this one for install? I Will Search another gsi

alexHdz said:
Only this one for install? I Will Search another gsi
Click to expand...
Click to collapse
It looks like this one comes with GApps and su built in.

physwizz said:
It looks like this one comes with GApps and su built in.
Click to expand...
Click to collapse
WiFi not working I guess

alexHdz said:
WiFi not working I guess
Click to expand...
Click to collapse
I thought that problem was only for Android 10

I tried to install GSI today but it didn't work.
Had to do a factory reset.

physwizz said:
Possible Installation Instructions (they will become more precise as more information becomes available)
1. Make sure your A20 is rooted (https://forum.xda-developers.com/showpost.php?p=80021195&postcount=4)
2. Backup with Titanium Backup
3. Install TWRP
https://forum.xda-developers.com/showpost.php?p=80028118&postcount=2
4. Backup system onto external SD or usb-otg (exclude data)
5. Install GSI from TWRP.
a. Download the desired GSI (it MUST be A/B_arm64 Variant)
-One GSI can be found here (https://forum.xda-developers.com/showpost.php?p=80177833&postcount=199)
b. unpack it if it wasn't in .IMG format
c. Go to TWRP , Install , Install IMAGE
d. Pick your GSI and select SYSTEM IMAGE
e. Reboot to TWRP Recovery
f. Flash "GSI_Fix_boot.zip"
View attachment 4815497
If you can't get TWRP you may need to install via Odin.
I'm not sure of any of this at the moment.
Click to expand...
Click to collapse
Hi guys! I try to install android 10 gsi, however when I go into twrp mode not recognizing the rom img what can it be?
I rooted and twrp A205G

physwizz said:
Possible Installation Instructions (they will become more precise as more information becomes available)
1. Make sure your A20 is rooted (https://forum.xda-developers.com/showpost.php?p=80021195&postcount=4)
2. Backup with Titanium Backup
3. Install TWRP
https://forum.xda-developers.com/showpost.php?p=80028118&postcount=2
4. Backup system onto external SD or usb-otg (exclude data)
5. Install GSI from TWRP.
a. Download the desired GSI (it MUST be A/B_arm64 Variant)
-One GSI can be found here (https://forum.xda-developers.com/showpost.php?p=80177833&postcount=199)
b. unpack it if it wasn't in .IMG format
c. Go to TWRP , Install , Install IMAGE
d. Pick your GSI and select SYSTEM IMAGE
e. Reboot to TWRP Recovery
f. Flash "GSI_Fix_boot.zip"
View attachment 4815497
If you can't get TWRP you may need to install via Odin.
I'm not sure of any of this at the moment.
Click to expand...
Click to collapse
i tried install any GSI on my A205F , but it's keeps bootloop , any suggestions to fix ?

hwp_2804 said:
i tried install any GSI on my A205F , but it's keeps bootloop , any suggestions to fix ?
Click to expand...
Click to collapse
I have the same problem on 205yn.
which method did you use to install twrp. there are some 205f users having trouble installing twrp

physwizz said:
I have the same problem on 205yn.
which method did you use to install twrp. there are some 205f users having trouble installing twrp
Click to expand...
Click to collapse
i use methods 1 and 2 , both also the same
twrp is working , but my internal storage seems like corrupted .

hwp_2804 said:
i use methods 1 and 2 , both also the same
twrp is working , but my internal storage seems like corrupted .
Click to expand...
Click to collapse
So method 1 have you the same result as method 2
Can you backup with either method?
Method 1
For the SM-A205YN
Download the A205YN custom recovery from here
https://forum.xda-developers.com/sho...&postcount=169
No need to patch it. Just flash it with Flashify.
If this first method works for a different version, please let me know.
Method 2
For the SM-A205G,
Download the composite recovery from here.
https://forum.xda-developers.com/sho...&postcount=198
Install to ap slot using Odin.

I haven't tested this yet so be wary. I'm going to try it today.
Format data (this is NOT the same as Wipe data) (In TWRP: Wipe -> Format Data)
Reboot back into recovery
Install GSI from TWRP. : Install , Install IMAGE
Pick your GSI and select SYSTEM IMAGE
Reboot to TWRP Recovery
Flash "GSI_Fix_boot.zip"View attachment GSI_Fix_boot.zip
Flash this zipView attachment Disable_Dm-Verity_ForceEncrypt_08.18.2019.zip
Reboot
That didn't work.
Reinstalling now ?

physwizz said:
I haven't tested this yet so be wary. I'm going to try it today.
Format data (this is NOT the same as Wipe data) (In TWRP: Wipe -> Format Data)
Reboot back into recovery
Install GSI from TWRP. : Install , Install IMAGE
Pick your GSI and select SYSTEM IMAGE
Reboot to TWRP Recovery
Flash "GSI_Fix_boot.zip"View attachment 4815771
Flash this zipView attachment 4815767
Reboot
That didn't work.
Reinstalling now
Click to expand...
Click to collapse
Try this:
Links donwload:
ROM: Android 10 GSI Treble (A-Only):
https:// enrt.eu/ FpMD
FixZygote V2 and Permissiver v5
https://androidfilehost.com/?w=files&flid=279429
Instalation:
1- Into TWRP mode
2- Wipe/ advanced wipe/ system. data and cache
3-Install/ select internal storage/ search rom image and install
4-Install/ FixZygote and Permissiver v5
5-reboot
PS: I haven't tested it yet on A205G as my twrp doesn't recognize any img rom!

Theus01 said:
Try this:
Links donwload:
ROM: Android 10 GSI Treble (A-Only):
https:// enrt.eu/ FpMD
FixZygote V2 and Permissiver v5
https://androidfilehost.com/?w=files&flid=279429
Instalation:
1- Into TWRP mode
2- Wipe/ advanced wipe/ system. data and cache
3-Install/ select internal storage/ search rom image and install
4-Install/ FixZygote and Permissiver v5
5-reboot
PS: I haven't tested it yet on A205G as my twrp doesn't recognize any img rom!
Click to expand...
Click to collapse
How did you install your TWRP?

physwizz said:
How did you install your TWRP?
Click to expand...
Click to collapse
I rooted for magisk and twrp used method 2 of the post!

Theus01 said:
I rooted for magisk and twrp used method 2 of the post!
Click to expand...
Click to collapse
I just changed method 2

physwizz said:
I just changed method 2
Click to expand...
Click to collapse
I did the twrp process again by the new method 2 but still the same error, the internal storage is having problems it does not appear the folders or files! and to install a GSI rom it must be the internal memory because the SD card does not work!

Theus01 said:
I did the twrp process again by the new method 2 but still the same error, the internal storage is having problems it does not appear the folders or files! and to install a GSI rom it must be the internal memory because the SD card does not work!
Click to expand...
Click to collapse
did you go to mount and mount everything

I have successfully downgraded from Pie to Oreo G965F (Custom Rom)

Hello, I will try to be very fast & clear with this:
It's a custom 8.0 Oreo rom works with Pie bootloader (U6CSGD) , thanks to @yash92duster for his amazing work.
So how? PLEASE READ THE COMPLETE TOPIC FIRST!!
1- Installed TWRP from here https://forum.xda-developers.com/ga...cross-device-development/twrp-exynos-t3763464 (DO AN EFS BACKUP WITH TWRP JUST INCASE)
2- Installed TeamExyKings' LightRom from here: https://forum.xda-developers.com/ga...ross-device-development/rom-lightrom-t3770243
3- I just downloaded the LightRom (Not AddOns) and flashed it wia TWRP (Read Step 4 before installing!).
Installation instructions from topic:
*In TWRP Recovery Format The Following:
--"Internal, System, Dalvik/ART, Cache"
*Flash ROM Zip
*Reboot And Enjoy The ROM
*** It May Take A While For ROM to Boot, So wait patiently ***​
YOU CAN MOVE THE ROM TO DEVICE AFTER FORMAT OR YOU CAN SIMPLY INSTALL FROM EXT SD CARD
4- Instal TTS if you want to add accessibility services such as (Bixby remapper/Navigation bar gestures)
- If you choose anything about bixby remapping while installing the rom you can't change it after installing even with remapper (or Idk how )
- Choose Samsung keyboard if you want to use UPSM.
- I Chose TGB kernel and have no idea about the stock kernel and how it works but TGB works without problems.
- Choose ''Netflix fix' 'if you want to use Netflix. Then, install this version: https://www.apkmirror.com/apk/netflix-inc/netflix/netflix-6-26-1-build-15-31696-release/
BONUS
Idan's GCam 4.1: https://forum.xda-developers.com/showpost.php?p=78101115&postcount=164

How do you install twrp on a locked bootloader?

revized said:
How do you install twrp on a locked bootloader?
Click to expand...
Click to collapse
He's using the Exynos version. The Exynos variant isn't bootloader locked, only U.S. Snapdragon variants.

Why u did that pie rom better than oreo what's the point of coming back to oreo ????

Adham_android said:
Why u did that pie rom better than oreo what's the point of coming back to oreo ????
Click to expand...
Click to collapse
Better battery life
Call recording (Removed on Pie by Samsung)
Pro video mode (Removed on Pie by Samsung)
perfect camera quality (Better than original camera like 10 times) with Idan's Gcam for rooted rom
So why not?

I did it step by step. Works very well. thanks bro

alimokhtarabadi said:
I did it step by step. Works very well. thanks bro
Click to expand...
Click to collapse
You're welcome

Could someone help me with flashing oreo 8.0 from pie 9.0? I am very confused and I do not want to make any mistake or choose the wrong one. Help me out here. Thank you.

xProudDeafLadyx said:
Could someone help me with flashing oreo 8.0 from pie 9.0? I am very confused and I do not want to make any mistake or choose the wrong one. Help me out here. Thank you.
Click to expand...
Click to collapse
Well, first of all: ''do this at your own risk, your warranty will be voided! and you wont be able to use Samsung pay, Samsung Pass, Knox, Secure Folder (I think there are some ways for this but dont know how)''.
1- BACKUP ALL YOUR FILES (PHOTOS, DOCUMENTS) AND BACKUP THINGS LIKE WHATSAPP TO GOOGLE DRIVE! I MEAN BACKUP EVERYTHING! Because everything in your phone will be deleted!
2- Download this ROM: https://forum.xda-developers.com/ga...ross-device-development/rom-lightrom-t3770243 or just download from this link: https://androidfilehost.com/?fid=6006931924117939052 (Tell me if it's slow, I will try to upload it to my Google Drive)
2- Install TWRP from here but remember to read all steps BEFORE YOU START!! https://forum.xda-developers.com/ga...cross-device-development/twrp-exynos-t3763464
3- Once you installed TWRP turn off your phone and reboot into TWRP by pressing [VOLUME UP] + [BIXBY] + [POWER].
4- Select "Keep /system RO" as usual.
5- Go to "Wipe" menu of TWRP -> Advanced Wipe. Select ''Dalvik / ART Cache, System, Data, Internal Storage, Cache'' and Wipe.
6- Connect your phone to PC and copy the ROM to internal storage (similar to how you transfer files when in system).
7- After copying the ROM to your phone, from TWRP go back to main menu then go to ''Install'' and flash your ROM.
8- Once you press Install Zip, Aroma Installer will be started I mentioned things I did in the post you can check them.
If you didn't get any part feel free to ask and mention which part yo didn't understand or you couldn't do it, from here or DM, wont matter.
Hope this helps you

Piknie działa - perfekt going - BIG THX

Do I have to wipe internal storage for the ROM to work or can I just skip the internal storage ?

Sparko612 said:
Do I have to wipe internal storage for the ROM to work or can I just skip the internal storage ?
Click to expand...
Click to collapse
I'm not sure but it's better to do a clean install. You can give it a try but I don't recommend it.

Download link please
The Rom download link/mirrors are down. you have the drive link handy?

How To Guide GSI Installation Guide for Realme C2

Requirement:
Gsi Download arm64-ab or bvN (on some download page)
For ColorOs Base
Twrp COS
Gsi Flash files
Stockboot.img
For RealmeUi Base
Twrp RMUI
Gsi Flash files
Stockboot.img
Installation
1.Reboot to Twrp
2.Factory reset device from Wipe >> Slide>>>
3.Format data from Wipe >> Format data>> Type Yes
4.Flash RMC2decryption.zip
5.Go to Advance wipe & wipe
dalvik, data, cache, internal storage & system
Do Not Wipe Vendor partion
6. Goto install & select install image from bottom right
7. Flash stockboot.img as boot
8. Flash (gsi filename).img as system image
9.Flash vbmeta.img as vbmeta (Download as per base)
10.Flash Deletebootanimation.zip (Read Note First)
11.Flash keystore.zip
12.Format data from wipe bottom right
13.Flash permissiver.zip (skip for RMUI)
14.Reboot System
Note:
only some gsi boot with bootanimation if device bootloop from bootanimation flash deletebootanimation.zip
if deletebootanimation.zip doesnt work delete file manually
System/system/media or system/system/product/media
Optional
For Root flash Magisk 20.3
(in phh based gsi Normal magisk.zip doesn't works)
Rooting on Android 11
make sbin folder in /system & /system_root/system then flash magisk zip
For discussion join
https://t.me/RealmeC2Community
For Gsi Fix follow #gsifix
For Modified Bootanimation #gsibootanimation

realme c2 color os v9.
what will I press in the last step 'do not install twrp' or 'reboot system' only ??

GSI AOSP Android 10
I've tried to open the GSI list you provided.
And I got confused which one do I have to download/pick and which file.
Do you have any recommendations for Android 10 stock AOSP?
Thanks in advance.
Cheers. :fingers-crossed:

Rj clno said:
what will I press in the last step 'do not install twrp' or 'reboot system' only ??
Click to expand...
Click to collapse
always do not install twrp app
Shinnosuke Nohara said:
I've tried to open the GSI list you provided.
And I got confused which one do I have to download/pick and which file.
Do you have any recommendations for Android 10 stock AOSP?
Thanks in advance.
Cheers. :fingers-crossed:
Click to expand...
Click to collapse
arm64 a/b or arm64 bvn/bgn v=vanilla g=gapps

I’ve downloaded the arm64 a/b gapps and go. I’ll try it later. Then I will tell you if I find any bugs and then upload the logs. Where should I upload it?

I am using :
system-roar-arm64-ab-gapps.img from here
TWRP 3.5.0_9-1 SIDDK
ColorOS GSI
adb version Version 30.0.5-6877874
I can't make it run. It loops in opening screen RealmeME (white logo) not Yellow font..
I still can boot to fast-boot mode and call twrp recovery.
Somebody can help me?
many thanks in advance

hey i am using the stock color os 9 on my rmx1943 it similar to rmx1945 yiu think i could use the old stockboot file for it on sourceforge

i'm getting an error whenever i'm trying to flash keystore for rmui. what should i do @Siddk

patrickbusto081302 said:
i'm getting an error whenever i'm trying to flash keystore for rmui. what should i do @Siddk
Click to expand...
Click to collapse
everything fine with keystore make sure u using latest recovery & using A10 keystore

Ahh...booting into recovery even if i press system

@arksolitude is that because you are trying to install android 10 for realme c2? if yes...
1. download stockrecovery.img (or get the recovery.img from the zip file you've downloaded)
2. reboot to bootloader/fastboot
3. type in your computer "fastboot flash recovery (name of the file).img"
4. reboot (this will take you to stock recovery)
5. wipe data and reboot
this is from my experience but this should work

[SOLVED] 4g Version (perseus) bootloop when trying to flash custom rom

Hi there,
after going through several threads, and trying for 5 days to get it to work I decided to open a new topic on my issue.
My goal is to flash PixelExperience for Xiaomi Mi Mix 3 [Perseus]. (I also tried [ROM] [11.0.0] [perseus] ArrowOS 11.0 [OFFICIAL] [NIGHTLIES] also with no luck) I think I am missing something since every time I try to flash it according to several descriptions (have stopped counting how often) I end up in a bootloop with the mi logo.
Here is what I do step by step in hopes that someone can show me where I am making a mistake / provide a working procedure:
A. Downloads (on my PC) and setup of PC
Magisk-v22.1.apk renamed to Magisk-v22.1.zip
miui_MIMIX3_V12.0.3.0.QEECNXM_b96755549d_10.0.zip from (here)​
since Arrow and PE devs recommend this as a base for flashing their ROM´s. My Phone originally ran 12.0.2 EU. Flashing 12.0.3 works with no issues.
twrp-3.5.2_9-0-perseus.img which I flash
Custom Rom.zip (as described tried Arrow 11 and PE)
B. Step by step guide what I do:
1. Install Flash 12.0.3 Firmware, Enable Dev Mode, fastboot and flash twrp-3.5.2_9-0-perseus.img
2. Boot into TWRP
3. Wipe -> 1. Factory Reset -> 2. Format Data -> yes -> 3. Advanced Wipe (cache, system, vendor, data)
4. ADB-Sideload PixelExperience_perseus-11.0-20210408-0751-UNOFFICIAL.zip - also tried adb push to sd and then install - with same result
5. Wipe Format Data -> yes
6. ADB-Sideload Magisk-v22.1.zip
7. Bootloop - when I select reboot TWRP tells me no OS detected and it loops with the Mi logo.
I am sure I am missing something or messing something up (maybe in TWRP Wipes Step 3 or 5?) since either PE or Arrow work.
Any suggestion / help would be appreciated
Have a nice day

Solved it.

illballer said:
Solved it.
Click to expand...
Click to collapse
Would you please do the following two things:
1) Edit the title and append something like [SOLVED].
2) Please share what you did so others can learn from it and use it if they also need it.

User699 said:
Would you please do the following two things:
1) Edit the title and append something like [SOLVED].
2) Please share what you did so others can learn from it and use it if they also need it.
Click to expand...
Click to collapse
Solution from User p1exer worked after flashing twrp-3.4.0-10-perseus-mauronofrio.img
1. Download the xiaomi.eu ROM.
2. Reboot in TWRP.
3. Flash the xiaomi.eu ROM.
4. Wipe Format Data.
5. Advanced Wipe Cache and System.
6. Flash the ROM
Click to expand...
Click to collapse