It's difficult to use with some odd defaults as I remember, and you have to boot into it which is annoying.
Rescuezilla seems like a good open source option, but you do still have to boot into it.
My go-to is the free Veeam Endpoint, as it just installs on the system and does full system images without needing to reboot. I'm not sure if there is a good easy to use open source equivalent to it, so far I have not found one.