I have uploaded EasyOS version 4.2.1, but only the "delta" file, which is just 338KB.
I wanted to test updating from 4.2 using the new small delta-file system, and it works great. You do need the latest scripts:
/usr/sbin/mount-img
/usr/local/easy_version/easy-update
...attached, with false ".gz" appended.
If you have Easy 4.2 installed, you can update. It sure is a pleasure the 338KB download, compared with the full 'easy-4.2.1-amd64.img' at 825MB!
Probably work also with earlier installed versions, though they might be setup with 'vmlinuz' and 'initrd' not in the working-partition. Whatever boot-manager is used now has to have the "wkg_uuid" (or wkg_dev or wkg_label) and "wkg_dir" kernel parameters. In other words, there might be some pain involved with updating.
Also, updating earlier versions, the update will download the full-size image file, as only have a 4.2-to-4.2.1 difference-file online. So might as well wait for 4.2.2.
Even with 4.2, the if you have /mnt/wkg/easy-4.2-amd64.img, it might not have the correct checksum. The 'mount-img' script changed the file checksum. The latest mount-img doesn't.
Have a few things to do, expect 4.2.2 as the official next release, in a day or two.
I have rewritten the updating instructions:
https://easyos.org/user/how-to-update-easyos.html
...might require a browser page refresh.