Link2SD: mounting /dev/block/vold/179:66 on /data/sdext2 failed: No such file or directory

Question

I am using a rooted Xperia Z5 Compact E5823 with the latest stock Android 6.0 ROM.

I am trying to use a 2nd partition with Link2SD but so far I always get the same "No such file or directory"-error:

Mount script error

Mount script cannot be created.

mount: mounting /dev/block/vold/179:66 on /data/sdext2 failed: No such file or directory

To format my microSD card I've used GParted under Debian with ext2, 3, and 4, always as primary partition. I've also used TWRP recovery to format this 2nd partition. With this I have only tried ext3, which my Debian recognizes as ext2 and there seems to be no way to choose which type of partition (I suppose they have primary as default). With TWRP I could also try ext4 but preferred to 1st post here.

I do see a /data/sdext2 folder with help of a root file browser. This folder is empty.

The "file" /proc/partitions does show a 179 66 2000000 mmcblk1p2 entrance, which correspond to the second partition of my external SD card.

Link2SD has superuser permissions and its mount script /data/data/com.buak.Link2SD/init-link2sd.sh looks like this:

set +e

echo "$(date) mounting..." > $LOG

sleep 2

mount -t ext2 -o rw /dev/block/vold/179:66 /data/sdext2 1>>$LOG 2>>$LOG

mount -t ext2 -o rw /dev/block/mmcblk1p2 /data/sdext2 1>>$LOG 2>>$LOG

mount >> $LOG

echo "$(date) mount finished" >> $LOG

chmod 773 /data/dalvik-cache

— scjorge | Sources

Answer

This error was very tricky to track! It took me a while to re-address it and here is what I have found out and how to solve it.

A little on mmcblk_p_

SD cards are special about their "block-partition"-suffix, i.e. the -blk*p* part.

For the user, the numbers in the suffix -blk*p* are, on practical matters, determined by the system the card is mounted on.

Link2SD's script is sensitive to the correspondance of the microSD card's "internal" partition-suffix (-p*) and its "external"/"mounted" under some system. (Thus, the No such file or directory).

Solution

For Link2SD's default mount script to succeed, you must delete and re-do the microSD card's partition table (with GParted or similar) and then do its two (or more) partitions, the second one being an ext2-filesystem.
This will yield a correspondance on the suffix-numbers -p* of your "second ext2-partition" both in the card and under the system.

Background

Well, I noticed that each time an SDcad gets a new partition the last index in the suffix -blk*p_ "advances". The microSD card in question has been partitioned more that three times without resetting its partition table. That card has no "internal" -p2 eventhough Android's kernel addresses it as such! (Tricky, huh?!) It seams that Android's kernel only takes the number of existing partitions to create the /proc/partitions-addresses instead of the total count of partitions ever done under an existing partition-table.

Extra-Info

Link2SD guarantees that your second ext2-partition won't be shown on your PC when you plug your device to it via USB. This is true for Windows but unfortunately not true for GNU+Linux! Windows does not recognizes ext2-filesystems. GNU+Linux does. As a consequence some APPs might have trouble retrieving ingormation from /data/sdext2.

Finally

Link2SD latest version at the PlayStore is 4.3.4 from 21.06.2018 and it locates its mount-script at /data/data/com.buak.Link2SD/files.

Also, for more information, visit Link2SD's official site.

— scjorge | Sources

Link2SD: mounting /dev/block/vold/179:66 on /data/sdext2 failed: No such file or directory

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