Steps Necessary To Update A Custom Rom To Its latest Version? 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 maybe 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 maybe 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 ?
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. odin or heimdall 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 bootloader (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:


nandroid 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 titanium-backup, 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)
adb backup: quite similar to the previous one (see the backup wiki for details and differences).




Note also that an ota-update 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 google-apps (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).