This README list flag files that can be written in /etc/runit/ and their effect:
 
* /etc/runit/verbose
     Start/stop messages from runscripts, when they are written to do so
     Some extra message from maintainerscripts
     Some extra message from cpsv tool

* /etc/runit/debug
     Print the exit code of the run file of services, when finish-exec or similar
     code is used
     May print debug messages from maintainerscripts or cpsv

* /etc/runit/default.runsvdir
     During the boot sequence, when this file contains the basename of a
     directory in /etc/runit/runsvdir/, runsvdir will start monitoring such
     directory instead of 'default'

* /etc/runit/nosync
     Do no invoke 'sync' during the shutdown sequence

* /etc/runit/native.boot.run
      Shipped by runit-init. If this file exists and /etc/runit/boot-run is a
      directory, scripts with .sh extension inside /etc/runit/boot-run/ are
      used for the boot sequence in stage 1 instead of /etc/rcS.d.
      Stage 1 sources each file in lexical order (. /etc/runit/boot-run/*.sh).
      Scripts must use "return", not "exit" (exit aborts the whole of stage 1).

      runit-init installs the base set only:
        00-core-services.sh, 05-boot-oneshots.sh,
        10-writable-runit-logs.sh, 99-prepare-runsvdir.sh

      Other packages may drop additional NN-description.sh files into
      /etc/runit/boot-run/ (same naming convention as boot-oneshots.d:
      two-digit prefix for order). Those files are only present when the
      package is installed — runit does not ship optional integration
      scripts for packages that might be absent (e.g. vdev installs
      15-vdev-env.sh to load /lib/vdev/vdev-env.sh and write /run/vdev/env).

      See /usr/share/doc/runit/boot-oneshots.d.txt for stage-1 oneshots
      under 05-boot-oneshots.sh (/etc/runit/boot-oneshots.d/).

      If the 'bootrun=1' variable is set in the kernel command line it
      has the same effect as the native.boot.run file: this is intended
      for testing new boot set of scripts.
      
      Stage 3 (/etc/runit/3) under native.boot.run:

        - always sources shutdown-run/05- and 85-shutdown-oneshots*.sh
          when present (package *-stop via shutdown-oneshots.d)
        - if shutdown-run has any other *.sh (future umount/halt): source
          those (runit puro)
        - else: run_sysv_scripts on rc0.d/rc6.d (same SysV fallback as
          when shutdown-run is absent) — do not reimplement that inside
          shutdown-run

      runit-init installs only:
        05-shutdown-oneshots.sh, 85-shutdown-oneshots-late.sh

      See /usr/share/doc/runit/shutdown-oneshots.d.txt.

* /etc/runit/no.emulate.sysv
     Shipped by runit-init together with native.boot.run. Skip all sysv
     scripts enabled in rc2.d during the boot sequence, even if there is
     no correspondent native runscript in /etc/sv/

* /etc/runit/runsvdir-waves.enabled
      Enable phased runsvdir boot (01-core, 02-base, default). See
      /usr/share/doc/runit/runsvdir-waves/README. Also enabled when
      /etc/runit/native.boot.run exists.

* /etc/runit/runsvdir/<tier>/.needs
      Optional list of service names that must pass sv check before the
      next tier is enabled via runsvchdir(8).
      
