Mounting external sd-card on rooted Android 7.1 tablet fails, but only if partition not empty Edit: I have tried mounting the sd-card with an empty ext4-partition, and it worked just fine, but after I ran debootstrap on the sd-card, the problem reappeared with identical symptoms. 



I want to mount an ext4-formatted sd-card, but 

 # mount -t ext4 /dev/block/mmcblk1p1 mountpoint 

returns 

 mount: mounting /dev/block/mmcblk1p1 on mountpoint/ failed: Invalid argument 

So far I have:


made sure the sd-card itself is OK (mounts fine on my debian laptop)
made sure the block device is the right one
replaced mount with busybox mount , which is a different binary, but gives the same error


The mountpoint exists, and the kernel supports ext4. My device is a rooted Samsung Galaxy Tab S2 running a Lineage OS 14.1 ROM (Android 7.1), SELinux is set to permissive. 



Any pointers are appreciated!
Does sdcard mount Android storage setting?

Run blkid command, see what say about partition.

Also what is mountpoint? I.E. /mnt/sd-ext

If you call mount like this

# mount -t ext4 /dev/block/mmcblk1p1 mountpoint


You have to be in same directory as mountpoint