External Ext4 card mounted only for root (!) on Android 5.1 64 bits

**In short**: if I mount my Ext4 8GB SD card, **only root (SU) can see** it. The rest of users (so, the rest of apps) don't detect it. As long as my **Ext4 SD** card is not correctly mounted (Android always yields Damaged SD card. Format it... blah blah blah), I followed this guide to mount it. And it works: SD Card is at /dev/block/mmcblk1, so first partition is at /dev/block/mmcblk1p1. I performed the (not very clear for me) prior ADB process: su setprop service.adb.tcp.port 5555 adb kill-server stop adbd start adbd HOME=/sdcard adb start-server adb connect localhost adb -s localhost:5555 shell exit stop adbd cat /sdcard/.android/adbkey.pub >> /data/misc/adb/adb_keys start adbd And then the card is **correctly mounted** by doing (as root): # mount -t ext4 /dev/block/mmcblk1p1 /storage/extSdCard && sleep 5 && /system/bin/vold Note how it works as SU but **not as normal user**: root@unknown:/ # ls /storage/sdcard1 lost+found root@unknown:/ # exit u0_a98@unknown:/ $ ls /storage/sdcard1 ls: can't open '/storage/sdcard1': Permission denied I have tested the above steps via *SSH* (remote shell). The SD Card has been formatted from Windows using *Minitool Partition Wizard*. I have tested too: - Editing the /system/etc/permissions/platform.xml file manually (adding `) to WRITE_EXTERNAL_STORAGE` section, as referred here. - SDFix . - Using Xposed framework with HandleExternalStorage module. But the apps (Total Commander, Ghost Commander, or any other program) have no access to the Ext4 SDCard. What else could I try? **Workarounds** to make apps read (and write) SD Card accepted too. Extra data 1: Note the output of the mount command for both users: root@unknown:/ # mount | grep "sdcard" -i /dev/block/mmcblk1p1 /storage/sdcard1 ext4 rw,seclabel,relatime,data=ordered 0 0 root@unknown:/ # exit u0_a98@unknown:/ $ mount | grep "sdcard" u0_a98@unknown:/ $ mount | grep "mmcblk" As can be seen, the root user has a mounted device that the normal user has not (!). I did not know this could happen on Linux.