I have a 4GB SD card which is partitioned into 3GB and 1GB (Well it's not 1GB it's approx. 750 MB) (I used it through my phone 'cause i didn't have a reader and i used mini tool partition wizard) then I put my data back onto the 3GB partition. Link2SD showed me a screen titled :"select the file system of your SD card's second partition" which has 4 options:
The 1GB partition is ext2 so I choose ext2 and restarted my phone. It showed the same message every time and it tells me "If you're getting this message after reboot it means that the second partition cannot be mounted automatically at boot"
My phone is a rooted Vodafone 858 Smart / Huawei 8160 it's running CM7.2
I tried to reformat and repartition but nothing worked.
If unsure, do as root via adb:
df | grep sdext2 should show you a mounted ext2/ext3/... mmcblk0p2 partition
In my case, I had formatted the partition of interest in ext2 and used on a CM 10.2 build.
I rolled back to CM 7.2 and selected the default ext2 but it wouldn't work.
After rebooting and having the same problem, I selected the ext4 file system and voila!
For CM7, you have to choose ext3 (for CM10.1 and 10.2, none of them works for me).
As described by NaraRockingMyAce at an xda forum :
that problem (link2sd unable to properly recognized partition) will and has happened to people who used modified link2sdPLUS. make sure you are using the actual free version or download the free version and pay for actual Link2SD_plus. that's what I've learnt :D
Fat32 partition must be set as first partition, and ext2,ext3,ext4 set as second partition. It is very important that they be in that order.
After, make sure that you have all partitions set as : primary.
Finally, try all ext2,ext3,ext4 - only ext4 worked for me!!
I struggled getting the ext4 partition to mount. I saw the answer from denny mihai above that emphasized the need to have the partitions in the correct order. Mine were ext4 first and fat32 second. I used minitool to delete the ext4 partition, move the fat32 and then create a new ext4 partition (making sure it was a primary) . My partitions were then in the order described by Denny. On the next reboot of the Android tablet, link2sd mounted the ext4 with no further configuration. Thanks goes to Denny.