Flashing a custom ROM

- Intro -

- Pre-reqs -

- A-only -

- A-only 2SI -

- A / B -

- My opinions regarding GApps -

Intro

Here's a custom ROM flashing guide I've constantly relied on. However, this guide assumes that TWRP recovery is used, as I have 0 experience with other custom recoveries (hopefully they're similar).

This guide will work on most custom ROMs except for the likes of official Calyx & Graphene (and some non-TWRP-flashable ROMs such as LineageOS on Zenfone 6). Also, if you want to follow this guide on any other devices other than the ones listed in this guide, do at your own risk (or just don't & follow the Lineage wiki for your device).

Pre-reqs (especially important when coming from encrypted ROM) :

  1. Backup your data & place the backups in the external storage. You can use Titanium, Migrate, OAndBackupX (these 3 require root), and/or SeedVault (if available).
  2. Remove your SIM card, if it's attached.
  3. Remove lock screen security. This prevents TWRP from asking for decryption password.
  4. Boot to TWRP recovery (or any other TWRP-based recovery of your choice)
  5. If you haven't removed your lock screen security, TWRP will ask for the password to decrypt files.

  6. Enter Wipe > Format Data & type yes when prompted
  7. Reboot to recovery
  8. Skip the 2nd step of the flashing guide found below. Which guide to follow depends on your device.

A-only partitioned devices (Poco F1; LG V30; OnePlus 3T)

  1. Place custom ROM in external storage
  2. For the F1; vendor and/or firmware can also be included.

  3. Boot to recovery - with external storage attached to PDA. If you come from the encrypted pre-reqs, start here.
  4. Go to Wipe > Advanced Wipe. Then, wipe Dalvik, Cache, System, Data. Some TWRP and/or devices (such as official TWRP for F1) has the option of wiping vendor, which is optional (since most F1 ROMs come with prebuilt vendor)
  5. Return to main menu, go to Install. Browse to the external storage where you placed your ROM in, and flash it.
  6. Additional notes for the Poco F1 : If you want and/or need to run encrypted on A11 ROMs that don't encrypt on 1st boot (such as crDroid, Fluid, Havoc), you will need to flash an encryption enabler zip from the crDroid thread. Flash it alongside the ROM.

  7. Head to Wipe > Format Data, and type yes to wipe data. Alternatively, do a factory reset if your PDA isn't encrypted.
  8. Reboot to system, and wait until it boots.

A-only 2SI (Poco X3 [N/P])

  1. Place custom ROM in external storage
  2. Boot to recovery - with external storage attached to PDA. If you come from the encrypted pre-reqs, start here.
  3. Go to Wipe > Advanced Wipe. Then, wipe Dalvik, Cache, Data.
  4. Return to main menu, go to Install. Browse to the external storage where you placed your ROM in, and flash it.
  5. Head to Wipe > Format Data, and type yes to wipe data.
  6. Reboot to system, and wait until it boots.

A/B partitioned devices (Pixel XL [Pie]; Mi A1; Mi A2; Zenfone 6 [Pie, A10])

  1. Place custom ROM (or the full stock ROM for Zenfone 6, if using) & recovery installer zip in external storage
  2. Boot to recovery - with external storage attached to PDA. If you come from the encrypted pre-reqs, start here.
  3. Zenfone 6 users coming from firmware updates will also start here, if using custom ROM.

  4. Go to Wipe > Advanced Wipe. Then, wipe Dalvik, Cache (cache option may not appear, so it's optional), & System (may cause issues, so it's optional). For some device and/or TWRP variants, there may be a "Vendor" option, which generally shouldn't be wiped.
  5. Return to main menu, go to Install. Browse to the external storage where you placed your ROM & recovery installer in, and flash both of them, in the order of ROM > recovery zip (or install recovery .img in Advanced > Install Recovery Ramdisk after flashing ROM if your preferred recovery isn't a flashable zip file).
  6. Some TWRP variants (like this one) have its own TWRP survival script, rendering the recovery zip installation unnecessary.
    Some ROMs have prebuilt TWRP (or other TWRP-based recovery), which allows you to flash only the ROM. In this case, recovery zip flashing is optional, but still possible.
    If you prefer to hotboot TWRP with a PC & ADB commands, you may skip installing the recovery.

  7. Reboot Recovery. (If you installed a recovery zip on the previous step, ignore the first note below)
  8. If you're not flashing TWRP, reboot to bootloader & boot TWRP using fastboot commands (this part requires you to connect your bootloader-booted PDA to a PC with adb/fastboot commands).
  9. Check the partition you're on. If you previously came from A, you should be on B & vice versa. However, if you're still stuck on the previously active partition, manually change partition in Reboot by selecting the other partition.
  10. Head to Wipe > Format Data, and follow instructions to wipe data. Alternatively, do a factory reset if your PDA isn't encrypted.
  11. Reboot to system, and wait until it boots.

My opinions regarding GApps

When it comes to GApps (Google's Play Services, Play Store, etc.), they are :

I don't recommend flashing GApps (unless you absolutely need to use it; but at that point you might as well flash a Pixel ROM), so I won't write a guide on how to flash them - you can search the internet for those guides. However, there are times where I had no choice but to rely on GApps to make apps work, such as in my "phone" PDA, so take that as you wish.

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