switching ROMs with a2sd

Last Updated:

  1. Hypo Luxa

    Hypo Luxa Well-Known Member This Topic's Starter

    May 12, 2010
    Likes Received:
    I have EvilEris 3.0 ROM and of course I have a2sd. I have been reading alot of good things about XTR and thought I give that a spin, however, I have a couple concerns:

    1. How will things react when I switch (in regards to a2sd)
    2. Will I need to go through the process after I partitioned the SD all over again with the new ROM
    3. Will I be able to revert back to my nand backup of EE with all the a2sd stuff intact if for some reason I decide to go back?

  2. erisuser1

    erisuser1 Well-Known Member

    Nov 11, 2009
    Likes Received:
    You should not need to partition again. There is nothing about the process of partitioning which is specific to a ROM which supports A2SD. (For best compatibility with the widest range of ROMs though, you should probably have the ext partition of the SD card formatted as an "ext3" partition - avoid ext4).

    As far as "how will it (the new ROM) react", all of your market (or non-system) apps will still be present on the SD card in the ext partition as soon as you boot up in the new ROM if you did not do a "Wipe ext" in Amon_RA. This assumes that the new ROM auto-configures A2SD if a partitioned SD card is present; otherwise, if you need to turn on A2SD in xtr manually through a toggle or a adb command, you should reboot after this step so that Android can properly build the dalvik cache for the newly-discovered apps.

    One thing to be aware of is that some devs pre-install some apps that they think are of general use to their users, and this differs from dev to dev, and ROM to ROM, so... if you customized your first A2SD ROM by adding an app that is pre-installed as a system app in the next A2SD ROM, it will be duplicated in the 2nd ROM. An example might be a replacement keyboard (HTC_ime mod), or SetCPU, or Titanium Backup.... et cetera. I'm not sure how Android resolves problems like this - but it can lead to subtle difficulties.

    One way to avoid subtleties like this is to make a "Nand+ext" backup of the starting ROM, and then "Wipe ext" in Amon_RA before flashing the new ROM - you will have to re-download all your apps in this case, but at least you are sure that you won't have conflicts.

    Absolutely - but only 100% for sure if you do a "Nand+ext" backup. (On a restore, the contents of the SD partition will get "restored" from the "Nand+ext" backup).

    Note that there are a couple of different strategies that you could use when flip-flopping between ROMs, listed in order of safest to most dangerous:

    1) ALWAYS use Nand+ext (for A2SD ROMs), and always "Wipe ext" before flashing the new ROM, and before restoring the old ROM.

    2) ALWAYS use Nand+ext (for A2SD ROMs), and leave your apps on the SD partition (no "Wipe ext") before flashing a new ROM so that the new ROM "inherits" the apps from the prior ROM, but when you restore, you do Wipe ext so that the recovered ROM is identical to the way you left it.

    3) ALWAYS use plain "Nand" backups and never wipe the ext partition (very dangerous - borderline stupid).

    #1 is very conservative, and completely avoids any problems of conflicts because you never carry apps between ROMs. You still have the advantage of more space for apps, but you lose the advantage of having your apps available quickly after a new ROM install.

    #2 is "pretty safe", but you can occasionally run into conflict problems; also, if you update a particular market app when you are running the second ROM, when you restore back to the first ROM, you will need to update that App again - the restore will restore the older version.

    #3 is pretty dangerous - app changes in one ROM could potentially "wreck" all the ROMs you have backed up.

    BTW, I tend to use strategy #2 - but then I'm a little more familiar with the guts of how Nandroid backups work, so...

  3. thetomlin2

    thetomlin2 Guest

    Nov 23, 2009
    Likes Received:
    Awesome answer by eu1 as always. I will just give you one thing to keep in the back of your mind ... I went from PlainJane w/ apps2sd to XTR with apps2sd. The first time I booted up my phone after flashing app2sd it went into a boot cycle and I was not able to get it working. I had to wipe everything including the ext. I then flashed XTR and apps2sd again and it worked fine, but all my apps were gone. Thank God for Titanium Backup, cause it only took about 10 minutes for it to install them all back.
  4. doogald

    doogald Guides Guide

    Jan 7, 2010
    Likes Received:
    I had the exact same experience - I was actually trying to set up XTR from a factory wipe, and having apps in the ext seemed problematic. I now always wipe ext and either restore from Titanium (if I am switching to a different ROM) or wipe ext and to a nand restore from a nand+ext backup.

    With some (most?) a2sd ROMS that use ext partitions, you may have to manually create a directory in /system called /system/sd in order for nand+ext to back up properly. See this post: xda-developers - View Single Post - [ROM]ErisLightningBolt 2.8 CM5.08 build( OC, JIT, Apps2sd, GPS, Stock MMS!!!)6/21/10

Share This Page