Follow the instructions here -> viewtopic.php?f=63&t=212452
(paying particular attention to make a backup of your SD card first AND note the instructions on editing recovery.cmdline to remove 'runinstaller') BUT with the following deviations:
In STEP 3, download pinn-lite as follows:
wget -P /home/pi http://downloads.sourceforge.net/projec ... n-lite.zip
In STEP 6, unzip pinn instead by:
sudo unzip /home/pi/pinn-lite.zip -d /media/pi/MMC_P1
In STEP7, remove `runinstaller` as indicated, but the rest of the recovery.cmdline will look different to that in the tutorial.
After STEP 8 you should be all set to go with PINN.
Note that if you had FULL NOOBS before the upgrade, you will now have the equivalent of NOOBS-lite as you have erased the local copy of the Raspbian install files from the /os folder. They would be out of date for a 3B+ anyway.
If you want to go back to FULL NOOBS you can use PINN to download the latest installation files for Raspbian and copy them back to PINN's recovery partition:
- Get a FAT formatted USB stick and create an 'os' folder in its root directory.
- Insert it into your Pi running PINN.
- Select Raspbian from the list of OSes on the "General" tab.
- Press the "More" icon on the toolbar to go to the 2nd "Archival" menu
- Select "Download" to download Raspbian to your USB stick.
You could leave it at that and install from the USB stick in future, but if you want to copy those files to your SD card, well, just copy the /os folder from the USB stick to PINN's recovery partition. (I don't think I need to detail those steps).