Installing Lollipop

How to install LX 12.1 (based on CM). It also works for AOSP 5.1.1 which is no longer maintained.

Marshmallow / LX 13 has been released. This is kind of like Lollipop reloaded, so it does not really make sense to install Lollipop anymore.
For good performance with 512MB RAM, KitKat / LX 11 is still the best.

This guide assumes you are familiar with flashing ROMs. If you are new to this, also read the basics here: [Installing LegacyXperia for Dummies](Installing LegacyXperia for Dummies)

Step 1: Prepare SD Card

• speed matters, this will hold the /data partition. UHS-1 / Class 10 strongly recommended. Note that Class10 cards can still differ a lot; the orange Samsung EVO cards seem to be good for this use case.
  See Tuning SD Card Speed
• on Windows, use MiniTool partition wizard and an SD card reader (easy). On Linux, use gparted, or see Partitioning the SD Card using ADB (not easy)
• partition 1: FAT32
• partition 2: ext4 (at least 4GB recommended, this will hold all apps and data)
• both partitions must be primary, and not active
• you will not need tools like link2sd, int2ext. This ROM automatically mounts partition 2 as /data.

Step 2: Copy installer zips onto the SD card (FAT32 partition):

• LX12: https://s.basketbuild.com/devs/LegacyXperia
  (or LX AOSP: http://forum.xda-developers.com/showpost.php?p=59403141&postcount=1 )
• System formatting tool
  download from subfolder /misc
• optional: F2FS data formatter (same folder as formatting tool)
• optional: GAPPS matching the Android version, e.g. Mardon's build for 12.1 (5.1.1) http://forum.xda-developers.com/android/apps-games/hdpi-google-apps-5-1-t3066172 (you can run LX without GAPPS, but then you don't have access to the Google app store)
• optional, only for AOSP: supersu installer (AOSP does not include su)
  https://download.chainfire.eu/696/SuperSU/UPDATE-SuperSU-v2.46.zip?retrieve_file=1

Step 3: Flash all the files

• extract boot.img from ROM and flash it using fastboot
• boot phone into recovery
• flash ("Apply update") the System formatting tool
• optional: flash F2FS data formatter
  Reports on F2FS vs. ext4 are mixed.
  My own comparison showed little real-life difference while testing.
  AndroBench said that read/write is similar, but SQL performance on F2FS is only 1/10 of ext4.
• wipe data
• wipe cache
• Flash ROM
• optional: flash GAPPS 5.1.1
  You should flash this before you boot into Android the first time.
• optional: flash SU (only needed for AOSP)
• Reboot

Common Problems in Lollipop

• AOSP keyboard does not swype. Install the missing lib, or install Google keyboard.

• AOSP does not do MSC ("SDcard looks like USB stick to PC")

• You see "optimizing 1 of 1..." on every boot. This is usually GMSCore.apk from the GAPPS package, or Facebook; it could be any very large app.
  Compiling an apk takes too long (>6 minutes), you have to turn off the timeout temporarily.
  Add this line to /system/build.prop:
  dalvik.vm.dex2oat-flags=--no-watch-dog
  Thanks to bleuxeon http://forum.xda-developers.com/showpost.php?p=60602549&postcount=299
  (Hint: my preferred way to do it is with ES File Explorer. Otherwise, I do adb pull/push via USB. Or search for "tomi build prop editor") Note that this is already done for LX 12.1

• Everything is very slow. Maybe it is caused by the timeout problem above; maybe your SD card is too slow.
  Set Settings > Developer Options > Show CPU usage to see if anything hogs the CPU.
  In my test with two Rays side by side, LX 5.1.1 is similar to LX11 (LX5.1.1 runs @1.4GHz and LX11 @1.0GHz, so basically LX5.1.1 seems about 1/3 slower; this is a very unscientific back-of-the-envelope estimation).