How to install what I build from source?

I feel like this must be a really obvious question, because I see people here who have built from source, but when I install OpenWRT on other routers, I do it from the web UI. I don’t see a way to do this on the Omnia–there’s nothing in the LUCI UI that lets me do it. Is there a way to use sysupgrade from the command line?

Well your question is very unclear what you want to archieve and how. You don’t need to install OpenWRT on omnia as it is actually preinstalled on it. If you want install additional package or kernel module you can do it in LUCI or login to turris directly via SSH and pray for opkg package manager to function and not crash with segmentation fault. But this problem will be fixed soon as everybody here got same issue now but it is just temporary. If you want reinstall Turris OS you can do by following official documentation by flashing from SD card.

As Twinkie said, OpenWRT is already installed, it’s the OS the Omnia already runs. You won’t update OpenWRT as you do with other routers, you use Turris’ update page in the “easy” web interface (not LuCI) or from a shell on your router using the script.

Basically the Omnia is custom hardware designed by Turris which runs a branch of OpenWRT that has customizations, mainly to support the hardware and some software enhancements added by Turris. Turris is submitting some of these customizations back to OpenWRT to be accepted back into mainstream.

Right now it is very difficult to build your own copy of the OpenWRT binaries from the source shared by Turris because of a complicated build process and requirements. Turris has stated they are attempting to simplify the process as time goes on.

I’ve already built the stable branch from github. The question is how do I get it onto my Turris.

Stable branch of what? OpenWRT? You can enter reset mode and re-flash it.

If you created from sources there should be sdcard.img created in some folder (sdcard-rescue folder), to install it just put on sdcard and flash into turris clear NAND and press button to return to factory settings, that will use software from NOR and copy it into NAND memory. Then reboot again it is described in official documentation.

There are scripts that look like they could be used to build something like that, but it wasn’t built. What I got as output of the build were these files, plus the package tree: openwrt-mvebu-turris-omnia-rootfs.ext4 openwrt-mvebu-Turris-Omnia-rootfs.tar.gz

I’m curious, how does your build differ from the official release?

At the moment it doesn’t. Once I’m able to build and install, then I can work on customizing.