The ISO image

assemble.sh builds a hybrid ISO/GPT installer/maintenance-mode medium, booted as a disk: dd’d to a USB stick, presented as a removable disk by a BMC, or attached to a VM as a disk. Its UKI names its root partitions by GPT label (PARTLABEL=JANUS-ISO-DATA/-HASH, set with sgdisk after xorriso, which can’t name the partitions it appends) - so it boots whatever the disk is called (/dev/sdb as a USB stick), and never confuses its own partitions with the BOOT-A-* ones of a disk it has just installed. Not from an optical drive: the root is a partition of the image, which a CD/DVD drive doesn’t expose. make iso-image builds one; make qemu-iso-boot-test proves it boots under real OVMF (see hack/qemu-iso-boot-test.sh), and make qemu-baremetal-test boots it from an emulated USB stick and installs a virtio-scsi disk.

Deliberately ephemeral (no A/B slots, no persistent STATE partition) - this is a throwaway live environment, not a final installed system. It boots straight to a running janusd (mTLS, prints its bootstrap CA/ admin creds to the console once, same as every other first boot in this project), which an operator then drives remotely - e.g. janusctl lifecycle install <target-disk> <bundle-dir> - to actually install Janus onto a real, separate target disk.

assemble.sh takes an optional [release-bundle-dir] argument (image/release/assemble.sh’s own output) that gets embedded directly onto the medium’s own ISO9660 partition, mounted read-only at /etc/janus/release by rootfs/init’s mountReleaseBundle - so <bundle-dir> above can just be /etc/janus/release, needing nothing else reachable from the operator’s own machine. make iso-image-with-bundle builds this variant (the one actually meant for distribution - iso-image itself stays bundle-free, for a faster plain boot test); make qemu-iso-install-test proves a node booted this way can genuinely install a real disk using only what’s already on the medium (see hack/qemu-iso-install-test.sh).

The operator’s procedure - from booting the ISO to approving the installed node on the Controller - is docs/provisioning-a-node.md, method 4. PXE: see ../pxe/README.md.