Re: rcd(8) - new service manager daemon

Baptiste,
	Would this rcd(8) work as a supervisor alleviate the issues described 
here with regard to invocations of daemon(8) :
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=287384

Thanks,

Anish

On 6/14/26 3:26 PM, Baptiste Daroussin 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
> 

-- 
Anish