Pakos:
You're describing a problem common to all Android devices.
You're also doing some good research into the problem.
The second partition has to be mounted in order to access it. Most Android devices will only mount the first partition, recognizing as vfat (FAT32).
You have to install something that runs a script at boot, like Smanager or Universal Init.d, so a script will mount the second partition.
On my LG Optimus F6 the external SD card is known as /dev/mmcblk1. This device name is different on various devices and models. You'll have to look at your mount table (mount command without parameters) to note what device is automatically mounted as the partition 1, the vfat partition, to figure this out.
On my device that reads vold 33,1 (if I remember correctly). I subsequently did:
ls -l /dev/block
Examining the result. In that (long) list, there was a device of major number 33, with two entries following it. It looks like this:
/dev/block/mmcblk1 33, 1
/dev/block/mmcblk1p1 33,2
/dev/block/mmcblk1p2 33,3
Your device names may differ...your devices might not even be in the block directory (this is simply the convention LG used).
Once (and if) if you discover the device name used for your external card, you can probably deduce from my example that mmcblk1 is the BASE of the sd card...BEFORE partitions. That is what you direct attention to for the partitioning of an SD card (if you used the command line fdisk, you may already know this).
On my F6, therefore, I have a script at boot which does:
mount -o rw -t ext4 /dev/block/mmcblk1p2 /storage/ext_part2
Now, every boot the directory /storage is reformed, and ONLY contains two entries, sdcard0 and external_SD (LG conventions).
Before I can mount, therefore, I must ALWAYS create this directory in the script.
Before I can create the directory I must have rw access to /storage, which is owned by the / (root directory) mount.
Therefore, the complete series is:
mount -o rw,remount /
mkdir /storage/ext_part2
mount -o rw -t ext4 /dev/block/mmcblk1p2 /storage/ext_part
mount -o ro,remount /
Now, you'll have to substitute the location of the mount directory (/storage is LG's choice, but it's typical), and name of the directory...plus you'll substitute your device's second partition identity, but the theory is the same.
You're obviously technically inclined enough to find this thread of interest and perhaps some use:
http://androidforums.com/lg-optimus...ernal-sd-storage-solution-f6.html#post6406733
I opened this thread to discuss a thorough solution to the storage problem, and you're already half way there.
Specifically, my F6 has only 1.27 Gbytes of storage in the /data directory. It's tiny. It fills up within a few hours in the hands of my 12 year old son, downloading every free thing he finds interesting.
After the adjustments made described in detail in that thread, my son's F6 has 28 Gbytes available under the /data directory.
That means, I'm sure you recognize, that I have zero consideration for app by app fiddling with storage. The 28Gbytes is real. You probably realize that the app in settings / storage is confused easily, and lies.
In my F6, that 28 Gbytes is available for all storage under /data, including the dalvik-cache, all temporary download locations (you probably recognize the various store apps use different directories under /data/data or /data/media), the /data/app directory...everything. No qualifications.
No move-to-phone. No link2sd. Nothing else.
The PRIMARY storage for all of /data, which is everything we know as Android, is served from the second partition on the external card.
Zero exception. It's the next best thing to desoldering the internal card and replacing it with a large one.
