This is still Cosmic, but I expect as some point it will be disco, so you can use same zsync each time.
http://cdimage.ubuntu.com/daily-live/current/
If you go here you can see the most recent:
http://cdimage.ubuntu.com/daily-live/
Then you can zsync your current ISO with just the changes, as of today it is 20181112, but you have to check each time until it is daily-live:
My first zsync is my last copy of Cosmic ISO, renamed.
zsync http://cdimage.ubuntu.com/daily-live...md64.iso.zsync
I directly boot ISO from grub. But I always forget to update grub, so now use a configfile in my /ISO folder. I have one on each drive, so I can install to the other drive. I do copy from download location into /ISO partition on each drive, so path is /ISO, not /home/fred/ISO.
Code:
menuentry 'Live ISOs on SSD' {
configfile (hd0,3)/ISO/livecdimage.cfg
}
menuentry 'Live ISOs on HDD (boot on SSD)' {
configfile (hd1,3)/ISO/livecdimage.cfg
}
Code:
# livecdimage.cfg
# Add this to 40_custom to load this file:
# menuentry 'Live ISOs' {
# configfile (hd0,3)/iso/livecdimage.cfg
#}
# Add iso names to livecdimage.cfg
#for i in `ls *.iso`;do echo "# "$i>>livecdimage.cfg; done;
menuentry "Ubuntu 19.04 Disco amd64" {
set isofile="/ISO/disco-desktop-amd64.iso"
loopback loop (hd0,3)$isofile
linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=$isofile toram
initrd (loop)/casper/initrd
}