Just in case what I'm seeing is OS specific: I am running the latest OxygenOS on a OnePlus 10 Pro 5G (GLO NE2213_15.0.0.401(EX01)).The phone is rooted via Magisk but I doubt that matters (except for how i can use the phone to format the disk; but the behavior is identical when I format with a PC) I format a USB flash-disk with exFAT, via mkfs.exFAT /dev/sxx1, either from a root termux shell on the phone, or from a root terminal on my (arch) linux PC. Either way, the format succeeds, and I can immediately mount the flash-disk via mount /dev/sxx1 /mnt/. The disk is empty, and I can write and read files on it. But if I then unmount it, unplug it (from the PC or the phone), and then insert it into the phone (which might mean "insert it back into the phone), then the phone automagically both mounts the flash-disk AND writes the following 13 directories/folders onto it:

Alarms   Audiobooks  Documents  LOST.DIR  Music          Pictures  Recordings   
Android  DCIM        Download   Movies    Notifications  Podcasts  Ringtones

I would be grateful to read the explanation of: 1. Just what process/system/thingie in Android is noticing the insertion and reacting in this way? I put "Android udev?" into title of the question as a way of asking how whatever is doing that mount+write compares with udev.... 2. Is there some profound (or even just necessary) reason for or benefit from providing all this structure on EVERY disk one might insert? The fact is that I inserted the flash disk so that I could do a TWRP backup to it. And although there are more annoying things about my phone than just needing to erase some folders whenever i want to use a USB flashdisk, perhaps something "bad" will happen if I do? And in any case, I might well want to retrain it to do something else, once I know what's going on. thanks PS: I note that SE points me to [this and this ; but neither explains what system service is doing this udev-like functionality, nor why it is now MORE invasive than it used to be (in the sense that it now writes 13 directories, and not 2. Perhaps it's a OnePlus/OPPO "improvement" ...)

Connect the usb flash drive with otg to the phone and make it a part of the phone's internal storage without booting the system and without booting the Rom. It is possible or not

Do you know an Android phone that instead of a soldered on flash IC has a removable micro SD card and can boot from it? I imagine how easy backup and unbricking could be if such a thing existed.

Is it possible to use a flash drive encrypted with LUKS and connected to the phone with an USB OTG cable?

I install 128 GB extra storage on my android. The thing is, most of those spaces are empty. I cannot, for example, move my most space hoarding apps over there. I can move files but I have no idea which file I should move. My phone is POCO X3 NFC I am using MKIUI Global 12.0.7 Stable Some says I should integrate the flash card with my normal ssd. However, I do not see such option in settings I installed https://play.google.com/store/apps/details?id=com.a0soft.gphone.app2sd It says I can move app but I need to format SD card as internal by going to Settings > Storage > SD card Well, in settings there is no menu called storage. It seems that in APP there should be a button that say Change. I see no such button. I can go to manage apps and I am supposed to see this I don't. My typical screen shen I click manage apps look like. See. No change button. I should format my SD as internal. I do not see any such option. I can format my SD but there is no option that it's formatted as internal.

I have a OnePlus Nord N20 running android 11. Whenever I plug a flashdrive in, It dumps a bunch of empty folders onto the flashdrive. Alarms, Android, Audiobooks, DCIM, Documents etc. Does anyone know how to get it to stop doing that. Thanks.