Puppy ISOs can be booted using a .iso file extension, but some versions require a special kernel parameter when booting from a USB drive because the boot menu assumes it is booting from a CD\DVD.
Most Puppy versions allow you to create a 'Save File' when you exit from Linux. You can thus save the OS settings onto a file on the E2B USB drive.
If you have problems booting from the ISO, try using an alternative file extension:
.isoPUP - use for Puppy linux and other similar linux ISOs
.isomacpup - use for Macpup ISOs (modifies the ISO to remove (cd) in menu.lst)
BugFix note: A bug had crept into grub4dos which prevented .isopup files from booting, please use E2B v2.09c or later.
Once a save file has been created (e.g. Ptn1: \slacko64save.3fs), Puppy will automatically find and load the file on boot (and save on exit).
Installing Puppy from an ISO
How to install Puppy to an HDD using Easy2Boot
You can boot directly from the ISO to a 'LiveCD' version of Puppy and get to the Desktop.
But if you then try to install Puppy to a hard disk, you may get an error because it cannot find the 'CDROM'.
First, if you have a CD drive, ensure it is empty.
Then use these commands in a terminal shell session before you start the Install process:
mount /dev/sdX4 /cdrom
where X is the letter for your E2B USB drive (in my case it was 'a' because I was using VBOX+VMUB).
The first command will probably fail if you have a CD-ROM drive fitted (make sure it's empty), but you can ignore the error.
The second command should cause the USB partition, which contains the ISO file, to be mounted as a read-only device.
This mounts the ISO as the CD-ROM so it can be found by the installer.
After installation, do not create a Save file and do not copy the .sfs file from CD-ROM when requested on shutdown.
Once you have booted to Puppy on the hard disk, you can create a save file on the hard disk.