Re: rcd(8) - new service manager daemon

On Sun, Jun 14, 2026 at 1:26 PM Baptiste Daroussin <[email protected]> wrote:
>
> Hello everyone
>
> I have been working for the past years on rcd(8), a new service manager
> daemon for FreeBSD, some of you might recall a presentation in french 15
> years ago or some discussion in BSDcam also that old!
> I would like to start a discussion about its integration into the tree.
>
> What is rcd?
>
> rcd(8) is a service manager daemon called by init(8) (in place of
> /etc/rc).  It reads service definitions from UCL unit files
> (/etc/rcd.d/*.ucl), builds a dependency DAG, and starts services in
> parallel.  After boot completes, it forks to background and stays
> running as a supervision daemon (automatically restarting failed
> services and accepting control commands via a UNIX socket).
>
> Key features:
>
>   - Parallel boot via dependency DAG (no more serial rc.d execution)
>   - Process tracking via pdfork(2) descriptors (no PID file races)
>   - Subreaper via procctl(2) (no orphaned process escape)
>   - Socket activation (pre-bound sockets passed via fd inheritance)
>   - Resource control per service via rctl(2)
>   - Service isolation via native jail(2) integration
>   - OOM protection via procctl(2) PROC_SPROTECT
>   - UCL-based unit files (JSON Schema validated)
>   - Embedded Lua interpreter for inline service hooks
>   - Template units for per-instance services (e.g., dhclient@em0)
>   - Safe in-place binary upgrade (SIGUSR1: save state, re-exec)
>   - Per-service access control on the control socket
>   - Suspend/resume support
>
> User interface: rcctl(8)
>
> Service management is done via rcctl(8):
>
>     rcctl start sshd
>     rcctl enable sshd
>     rcctl restart dhclient@em0 netif@em1
>     rcctl status
>     rcctl show nginx
>
> 100% backward compatibility
>
> This is a hard requirement: rcd must work on existing FreeBSD systems
> without modifying any rc.d scripts or configuration files.  Here is how
> this is achieved:
>
>   1) rcd scans /etc/rc.d/ and /usr/local/etc/rc.d/ for existing
>      rc.d scripts, parses their PROVIDE/REQUIRE/BEFORE/KEYWORD headers
>      (same format as rcorder(8)), reads rc.conf(5) to determine the
>      enabled state, and wraps each script as a virtual "legacy" unit
>      in the dependency graph.
>
>   2) Legacy scripts are auto-classified during loading:
>      - Scripts with pidfile= or command= -> "legacy-forking" units,
>        tracked by rcd-exec(8) sub-reaper without pidfiles.
>      - Scripts with only comments/blank lines -> barrier units.
>      - Scripts without rcvar= are always enabled.
>
>   3) All rcctl(8) commands are passed through to the script directly:
>          rcctl reload sshd -> /bin/sh /etc/rc.d/sshd reload
>
>   4) Template instances preserve the traditional calling convention:
>          rcctl restart netif@em0 netif@em1
>          -> /bin/sh /etc/rc.d/netif restart em0 em1
>
>   5) rcd reads /etc/defaults/rc.conf, /etc/rc.conf and
>      /etc/rc.conf.local to determine legacy service enablement.
>
> The result: you can install rcd on a running system, reboot, and
> everything works exactly as before -- except boot is faster because
> services start in parallel where the dependency graph allows.
>
> Current status and what I need
>
> I would like to commit this to main soon so that people can start
> testing it on their machines.  The initial commit will include:
>
>   - sbin/rcd/   -- the daemon, rcd-exec helper, unit tests
>   - sbin/rcctl/ -- the control utility
>   - Man pages: rcd.8, rcctl.8, rcd.conf.5, rcd.d.5, rcd-lua.3,
>     rcd-exec.8
>
> It will NOT change init(8) or /etc/rc yet.  rcd will be built and
> installed but not activated by default.  To test, you will be able to
> run it manually or configure via kenv(8) to replace /etc/rc.
>
> Migration path
>
> The plan for a smooth transition:
>
> - 1 (now): Commit rcd(8) and rcctl(8) to the tree.  Build by
>   default, but not activated.  Early adopters can test.
>
> - 2 (later): Commit init(8) changes to call rcd when present (falling
>   back to /etc/rc otherwise).  Provide a /etc/rc wrapper that invokes
>   rcd for systems that want to switch.
>
> - In the meantime: convert base system rc.d scripts to native
>   UCL unit files adding the norcd keywords to the rc.d so that they
>   are not read anymore by rcd(8).
>
> - Ultimately: rc.d -> unit files, at the pace each maintainer sees fit.
>   There is no deadline; rc.d scripts are supported as long as needed.
>
> The code lives there:
> https://reviews.freebsd.org/D56835
>
> Baptiste

This sounds turboawesome.  Parallel boot, pdfork, procctl, and UCL, all sound
very exciting to me.  I can't wait to beta-test.  And
backwards-compatibility, too, is super good.  IIRC, the lack of
backwards-compatibility is why the NextBSD experiment failed.  Since
you're the expert, could you tell us how else this rcd differs from
NextBSD/launchd?