I'm using SWUpdate. I distribute an image with a [boot, rootfsA, rootfsB, data] partition scheme [1], and subsequent updates target the non-active rootfs partition. You can even theme SwUpdate's CSS [2] - nifty!

When I was assessing options for over-the-air updates, I evaluated everything between Mender.io (completely managed update service) to building a Coreos distro with OsTree-based patch system. So far Swupdate has felt like the right trade-off between customization and ease-of-use - plus the trail I've walked down feels well-traversed.

[1] https://sbabic.github.io/swupdate/overview.html#double-copy [2] https://twitter.com/grepLeigh/status/1545564418502668289