What is captured

A snapshot captures five domains that together constitute the node's
configuration:

Domain Source If missing
qt_settings The QuantumTouch settings document {}
controller_config The controller's full configuration Capture aborts
vpp_startup_conf The VPP startup configuration ""
grub_cmdline The kernel command line, including drop-ins ""
sysctl_hugepages The hugepages sysctl drop-in ""

The asymmetry is load-bearing. A missing sysctl drop-in is normal on a
freshly-installed box and captures as empty. An unreachable controller aborts
the capture with 503
, because a snapshot missing the controller's
configuration would, on a later merge-mode restore, silently appear to contain no
plans and no pools.

Secrets are captured in full, by design — RADIUS shared secrets and captive
portal credentials included. This matches the behaviour of configuration archives
on established carrier platforms, where a restored archive must actually restore
service. Every snapshot therefore carries a warning to that effect in its
warnings array, and snapshot endpoints are admin_only throughout.