Early versions of Ubuntu (pre-v14) and Ubuntu-based linuxmint distros (pre-v17.03) could be set up with persistence with no problem.
As long as you added the 'persistent' boot parameter, the kernel script would look for either:
1) a 'casper-rw'
file (formatted internally as ext2/3/4)
- OR -
2) a FAT or ext
partition with a volume label of 'casper-rw' which has been formatted as ext2/3/4.
Ubuntu bug!
However, Ubuntu 14.04 and linuxmint 17.03 and (all?) later versions have a
bug in the casper boot script which means that they may fail to boot when a casper-rw
partition is present and if that partition is located after the filesystem partition in the partition table. This bug does not apply if you booted from an ISO file (only from a 'flat-file' partition), so the .mnu files used by E2B which boot from ISOs are not affected by this bug.
Bug report for Ubuntu
here.
So there is no problem if you use a casper-rw
file (except it must be on the same partition and it must be a FAT32 or ext partition). So you can create a very large (>4GB) ext3 file on the E2B NTFS USB drive and use a .mnu file to get persistence - but this only works in MBR\Legacy mode.
For UEFI-booting, we need to create a FAT32 .imgPTN file. However, this issue does affect E2B when using .imgPTN partition images...