Add SD-Card as internal storage in Android Marshmallow and above
Are you like me, and just got a new Android device whose manufacturer has the device configured to not allow adoptable storage for SD-Cards? Some manufacturers have a bad habit of doing this on all their devices (looking at you, LG, for doing this on both the LG G-Pad X and the LG G6). It is possible to work around this, by turning on Developer mode, enabling USB debugging, and then using adb to do the dirty work. The steps are:
1. BACK UP THE DATA YOU HAVE ON YOUR MICROSD CARD. Your card will be formatted by this process, so make sure you have saved any pictures, videos etc. from your card to your PC before you start.
2. Decide how you want to split your card. You can either commit 100% of the card to internal storage, or split between internal storage and conventional SD. This option is useful if you like to unplug your card and put it in your PC. I would probably recommend committing the whole card.
3. Open your command window / terminal on your computer and type the ‘adb shell‘ command (with your phone connected of course). You will need to enable USB debugging in developer settings (which in turn is displayed by tapping the build number of the device 5 times) in order to see the option.
4. Type ‘sm list-disks‘ to list the disks available for adoption. It’ll look something like below – take note of the disk ID (disk:179:160 in this example).
5. Partition the disk. For this we use the ‘sm partition DISK TYPE RATIO’ command. For example, to partition the disk above as fully adopted storage (aka private) I’d use the command ‘sm partition disk:179:160 private‘. If I wanted a 50/50 split between adopted and regular, I’d use the command ‘sm partition disk:179:160 mixed 50‘. Easy right?
6. This process will take a while, but when it’s done, the Settings -> Additional Settings -> Storage view on your device should show the new Internal Storage.
I am doing something here I almost never do: I’m pasting the full relevant info from the website’s article here. Please go there, so they get the views and clicks, but the tech pages I link to have a habit of disappearing, so I included a full paste of the relevant steps.