Guest: DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #0: Thu Jul  2 06:02:54 UTC 2026  root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC  x86_64
 uptime at check: 3:44PM  up 10 mins, 0 users, load averages: 0.00, 0.00, 0.00
 kldstat: kernel + ehci.ko + xhci.ko (no KTR/KLD-loaded ktr modules)

Live introspection (root):
  $ sysctl debug.ktr
  sysctl: unknown oid 'debug.ktr'          # KTR facility NOT compiled into stock kernel
  $ sysctl debug.ktr.version
  sysctl: unknown oid 'debug.ktr.version'
  $ sysctl -a | grep -c "debug.ktr"
  0                                        # zero debug.ktr OIDs kernel-wide

Live introspection (unprivileged user):
  $ sysctl debug.ktr.version
  sysctl: unknown oid 'debug.ktr.version'  # no unpriv exposure of the ring
  $ sysctl -w debug.ktr.resynchronize=1
  sysctl: unknown oid 'debug.ktr.resynchronize'  # (OID absent; RW ktr knobs are
                                                 #  SYSCAP_NOSYSCTL_WR-gated anyway,
                                                 #  sys/kern/kern_sysctl.c:1445-1448)

Ring dump device permissions:
  crw-r-----  1 root kmem  13, 0x00000001 Oct  9 15:34 /dev/kmem
  crw-r-----  1 root kmem  13, 0x00000000 Oct  9 15:34 /dev/mem
  # ktrdump(1) reads the ring via kvm -> /dev/mem|/dev/kmem: root/kmem group only.

Compilation gating (source tree):
  sys/platform/pc64/conf/files:110:  cpu/x86_64/misc/ktr.c   optional ktr
  sys/conf/files:1377:               kern/kern_ktr.c         optional ktr
  sys/config/X86_64_GENERIC:         (no 'options KTR'; only 'options KTRACE' = ktrace(1), a different facility)

Guest left up and clean: no kernel build, no crash, no filesystem writes.