If your LiveCD ISO is based on Ubuntu and it contains a \casper folder and recognises a persistent volume name of casper-rw, you can use the .isopersist file extension together with an ext file to boot from the iso file with persistence. No extra .mnu file is required.
Typical Ubuntu-based ISOs that you can use with a .isopersist file extension are: ubuntu, lubuntu, xbmcbuntu, linuxMint, peppermint, cublinux (+Chromixium), elementaryos, linuxlite, zorin, StartOS, bitdefender, BackTrack5, lxle and DrWeb.
For Debian and other LiveCD ISOs, if you want persistence you must use a .mnu file.
When using .isopersist with Ubuntu ISOs, you do not need to copy and modify a .mnu file. You just need these files:
1. (optional) Open the .ISO file (e.g. using 7Zip) and ensure it has a /isolinux folder and a /casper folder.
2. Copy the .ISO file to any suitable E2B menu folder (e.g. \_ISO\LINUX).
3. Change the file extension of the .iso file to .isopersist.
4. Use RMPrepUSB.exe - Create ext2/3/4 or \_ISO\docs\Make_Ext\Make_Ext.exe (E2B v1.A3+) to create a -rw file with exactly the same name as the ISO file but with -rw added, the volume name must be casper-rw for Ubuntu-based ISOs, e.g.
File Name = Ubuntu64-rw - Note: no spaces or dots (full-stops) in filename
Volume Name = casper-rw - must be casper-rw
Type = ext3 - or ext4 (ext2 is not recommended as it is prone to corruption)
Size = 300 - as large as you like (note: some OSs require at least 300MB)
Note that the persistence file must end in -rw but must start with the identical filename as teh ISO file.
Also note that RMPrepUSB cannot create ext files with spaces in the filename, but you can change the filename after it has been created.
5. (optional) Move the -rw persistence file to the same folder as the ISO file (or leave it in the root folder of the E2B drive).
Make sure it does not contain any dots in the filename. If it contains a dot then the persistence file will be listed in the E2B menu if you place it in a menu folder instead of the root. For example, if you use \_ISO\LINUX\linuxmint-18.3-cinnamon-64bit-rw, then an erroneous 'linuxmint-18' menu item will also appear in the Linux sub-menu as well as the linuxmint-18.3-cinnamon-64bit.isopersist file.
When you first boot, E2B will modify the ISO file permanently. If it fails to work, delete the ISO file in case it is corrupted - do not use the modified .iso file with a .mnu file or for any other purpose.
You can also add a .txt file if you want to change the menu entry text and menu entry help text under the menu.
Note: The 'quiet splash' menu keywords, which are in a file inside the iso, are replaced with the cheat code word 'persistent' by E2B, so you will now see all the linux messages as the ISO boots. If you don't wish to see these lines displayed as it boots, then you must use a .mnu file instead of using the .isopersist file extension.
Run the ISO without persistence
If you sometimes wish to run the same ISO without persistence, use the original ISO file and a persistence .mnu file