iPadOS 15 beta how to install on 16 GB (NAND eMMC)

[jackluke]

To those who own a limited 16 GB (NAND eMMC) iPad (mini 4 or Air 2) officially supported to iPadOS 15 beta, here is the minimum space requirement that allowed to complete the download and install directly on device also keeping data (without using a Mac as target through iTunes or Finder or an IPSW):

- current iPadOS installed on device : 14.4.2 (system occupies 6,1 GB + installed apps about other 4,2 GB)
- space available before downloading the update : 5,7 GB
- space available after downloaded the iPadOS 15 beta 2 (19A5281h) packages : 1,5 GB
- time to install : about two hours (charger plugged)

- space available after completed iPadOS 15 upgrade : 2,6 GB (but next updates are incremental then smaller, moreover I still have 4,2 GB of installed apps that I could remove to free up more space)

Installation phases include three main stages (automatic reboot) of apple logo with filling progress bar, the second stage progress bar fills very slow, it might take more than one hour.

After the third installer stage, you get a reboot with the apple logo but without progress bar that means update completed successfully and welcomed with "hello" alternates in all the world languages, using my method your data and settings are kept as they were on iPadOS 14.

Consider to make a backup of your important data (or to iCloud) before attempting upgrading iPadOS 15 on any 16 GB device, because after many years on internal NAND a lower wear leveling is expectable, so might encounter a very slow installing time, just keep the charger plugged.

These steps might apply also to iPhone iOS 15 supported devices with just 16 GB , hence the minimum space requirement to upgrade from iOS 14 is 5,7 GB , if lower you should remove eventually big installed apps, for example through this method: https://support.apple.com/en-us/HT203097

Summarising, you can download and install iPadOS 15 directly on target device (more convenient), just having available space ≥ 5,7 GB , I haven't tested upgrading iOS 15 using a Mac as download target, but I guess it's required Monterey to handle the new IPSW (also I guess in some cases data and settings are not kept) , maybe also the current Big Sur version could work, but you need a constant plugged USB cable to the Mac during the downloading and update processing.

 

[jackluke]

Then the newer iPadOS 15 beta updates increased their size OTA updates are currently 4,2 GB , so to update from beta 2 to beta 8 this time I used a Monterey Mac where downloaded the IPSW iPad_64bit_TouchID_15.0_19A5340a_Restore size 5,09 gb

- current iPadOS installed on device : 15 beta 2
- space available : 1,5 GB
- time to install : 60 minutes

after downloaded the IPSW you should plug wired through lightning usb cable the Monterey Mac then Authorise from iPad and Trust from Finder, then on macOS desktop, select from Finder the iPad, wait that it's detected, hold alt option key, while keep holding click "Check for Update"

this trick allows to manually select from Downloads folder the IPSW file to update

keep the Mac plugged to power and also the iPad wired usb plugged to the Mac possibly to an USB 3.0 port, the update process is simple and automatic:

macOS unpack all the IPSW to its internal disk temporary folder (about 6 GB of data so you need on disk 15 GB available) , then automatically restart the iPad in recovery mode to overwrite the system files (that's why 1,5 GB are sufficient even if the entire iPadOS is 6 GB because it's an overwriting of little system files) with apple logo and progress bar, then auto restart and macOS completed its tasks (theoretically here you can unplug from Mac but I advise to still keep usb wired) , so you should wait that iPad auto completes his stage 2 installation phase that will take about 45 minutes to complete.

Of course updated successfully and data are kept, after update available space on iPad is 4,2 GB .