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Many a time when I watch YouTube videos regarding people rooting and flashing custom ROMs on their Android smartphones, they show you how to carry out the procedure both in their respective videos and perhaps also in written dialogue on their main website.

However, as far as I'm aware, most custom ROMs do not include OTA updates, therefore one would generally have to check the XDA website, for example, to be notified of a newer version to whichever custom ROM for the particular device you are using becomes available. (I believe however that the CyanogenMod Installer recently introduced may be an exception to that general rule).

It is also the case as outlined in my first paragraph that those people who have YouTube videos about rooting and flashing custom ROMs fail to do a follow-up video showing how you can install the latest version of a custom ROM they are showcasing from a previous version.

For a beginner, this may be very daunting if you would like the latest version. I would therefore like to know: what are the necessary steps that one must undertake to update a Custom Rom to its latest version from a previous version?

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    Assuming there isn't an OTA it is usually the same process as the last one. Use something like Titanium Backup for your User Apps. Make a nandroid backup. Wipe data / cache etc. Flash new zip file. Restore apps through Titanium Backup. I usually suscribe to the topic on XDA and check in every now and then to see if the version has gone up on the particular thread. SOMETIMES you don't need to wipe data, but they will tell you that on the thread. I find in Android as in life, a thorough wipe is always a good idea!!
    – RossC
    Dec 17, 2013 at 11:20
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    @RossC So its basically the same procedure as with how a custom rom was flashed initially from the default rom on the handset/tablet ?
    – Simon
    Dec 17, 2013 at 12:18
  • That's correct. At least, that way it works for all ROMs (and of course some of the initial steps might be skipped; e.g. you won't need to re-install a custom recovery). Some ROMs might provide "patch updates", but again, they are mostly installed the same way.
    – Izzy ♦
    Dec 17, 2013 at 12:21
  • Yeah exactly. As an example MiUi ROMs update via OTA, but CyanogenMod nightlies must be flashed from scratch! Just to say this again: BACKUPS!! I have forgotten many times and it is a pain!
    – RossC
    Dec 17, 2013 at 12:25
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    Depends on the update. If it's a full ROM, yes. If it's a "patch update", probably not. Easy to find out: If they're missing, you need to install them :) And as RossC wrote: BACKUPS!!! You have no ideas how many cases pop up here (and on other places) from people having forgotten those. Being "a pain" is an understatement! Though with flashing, troubles are rare, it never hurts to have a cold beer in the fridge :)
    – Izzy ♦
    Dec 17, 2013 at 13:19

1 Answer 1

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Summing up from the comments:

This very much depends on...

  • the ROM used
  • the update format chosen for a specific update

Some ROMs (e.g. CyanogenMod) come with their own "updaters", where special rules might apply. Specifically, they might deliver "patch updates", where only some files will be replaced. In those cases, no further action is required (except for, maybe, a reboot).

Some other ROMs ship in specific formats, and might require special tools to be flashed (e.g. or for Samsung devices).

Again other ROMs are delivered using the update.zip principle, where a custom recovery is needed to install them. This update.zip may be a complete ROM, or also just a patch. Instructions usually are to be found where the updates are offered for download.

In all above cases, some "initial steps" required for the first ROM install can be skipped and must not be repeated, including...

  • rooting your device (custom ROMs usually come pre-rooted)
  • unlocking the (unless you've re-locked it)
  • installing a custom recovery (when it's already there, no re-install is required; though there might be updates to this as well, and a newer custom ROM might require a minimum version here as well. Again, instructions should say so)

It's always a good idea to perform a backup before installing updates (or tampering with system stuff in any other way). Points to check for include:

  • backup: a full "sector-wise" copy of all the important partitions. If things go wrong altogether, this enables you to revert to the exact state of when these backups were created
  • logical full-backup: this is performed by tools like , and usually includes all your apps and data. So if something is missing after the ROM update, you can substitute the necessary parts. (note that Titanium Backup also can do that with Nandroid-Backups)
  • backup: quite similar to the previous one (see the wiki for details and differences).

Note also that an is quite unlikely to happen with custom ROMs. Some even include an app named fota-kill to "silence" the related update check. They either bring their own updater, or none altogether. In the latter case, the user has to check himself whether and when updates are available; often a "reminder" can be setup by subscribing to the corresponding thread on XDA (or wherever the ROM comes from), but actions have to be taken manually (as described above).

As I've shown until here, videos on updating your ROM most likely do not exist as the process already has been described as part of the initial video; though a few words like "for updating, skip to index ab:cd" would be a good idea (and could be suggested in the comments).

A special case are the (short: GApps). Whether you have to re-install them or not mainly depends on whether it was a "full update" (complete ROM), or the update just replaced some files. But it's easy to figure: When finished, just check if they are there and working. If not, you obviously have to flash them again. As a full-update replaces the entire partition content, GApps would be gone with that; a "patch-update" would just replace/add some files, and not touch the GApps, so they'd still be there. GApps are never part of a custom ROM (if they are, the "ROM cook" is in trouble due to license issues).

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  • Excellent summation. I've been doing this for years and I still forget certain things, a nandroid, or backup app data for something I need. I've installed the wrong recovery, forgot to check MD5 and so on. It's easy to panic a bit when an expensive piece of hardware goes blank, or into a bootloop. This guide is excellent reference. I would like to add: I've always been able to fix it, so stay calm folks and just start at the very start!
    – RossC
    Dec 17, 2013 at 16:20
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    I may add that my worst case was a "broken copy" (removed SD card a little early, or rather the indicator went off to fast). Result was, the "update" erased all partitions and then found nothing to flash. Unfortunately, I decided to reboot. No life signs (except ADB was able to connect "something"). Even that was recoverable (bootable SD card). Seems hard to really brick a device these days, except when flashing a radio image (maybe :)
    – Izzy ♦
    Dec 17, 2013 at 16:24
  • @Izzy In terms of backing up before flashing to the newest version, would titanium backup suffice, or do people (or yourself) undertake all three of the ways you mentioned ?
    – Simon
    Dec 23, 2013 at 10:14
  • @Simon I usually make a Nandroid backup in addition. Makes a restore-to-previous-state a lot easier in case flashing fails (or the ROM proves "unfitting").
    – Izzy ♦
    Dec 23, 2013 at 10:24
  • @Izzy So the Nandroid backup is undertaken before backing up with Titanium Backup ? (Out of interest what do you make of this App play.google.com/store/apps/… ) ?
    – Simon
    Dec 23, 2013 at 12:20

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