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What is procd?

procd is the new OpenWrt process management daemon written in C. It keeps track of processes started from init scripts (via ubus calls), and can suppress redundant service start/restart requests when the config/environment has not changed.

procd has replaced … , e.g.

  • hotplug2, a dynamic device management subsystem for embedded systems. Hotplug2 is a trivial replacement of some of the UDev functionality in a tiny pack, intended for Linux early userspace: Init RAM FS and InitRD.
  • busybox-klogd and busybox-syslogd
  • busybox-watchdog

procd is intended to stay compatible with the existing format of /etc/config/; exceptions …

Help with the development of procd

  1. test what has been ported
  2. review of the code

Buttons with procd

Init scripts with procd

Why do we want procd?

One thing that procd does much better then …

It boils down to the fact that the current … are rather constrained and inflexible:

procd will be able to … - and of course all that without adding unnecessary bloat. AFAIK there are no alternatives to procd.

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procd (process management daemon) – Technical Reference

OpenWrt – operating system architecture

Whereas desktop distributions use glib+dbus+udev(part of systemd), OpenWrt uses libubox+ubus+hotplug2. This provides some pretty awesome functionality without requiring huge libraries with huge dependencies (*cough* glib).

Desktop Distributions OpenWrt Android Replicant mer-based
Typical main memory size 128 MiB to 16 GiB (or more) 32 MiB to 512 MiB1) min 92 MiB for Android 2.1
min 340 MiB for Android 4.0
Supported instruction sets almost anything almost anything x86, 86-64, ARM, MIPS32
non-volatile storage space 100 MiB 8 MiB2) 150MiB for Android 2.1
512MiB for Android 4.0
kernel Linux kernel
FOSS and binary drivers FOSS drivers: e.g. 802.11; Iaccess Android binary drivers
C standard library glibc uClibc, musl bionic glibc + libhybris eglibc 2.15
init init
systemd busybox-initd procd Android init-fork systemd
rsyslog / syslog-ng busybox-klogd, busybox-syslogd
watchdog busybox-watchdog
udev hotplug2
cron busybox-crond
atd na
D-Bus ubus Binder ? D-Bus
network configuration NetworkManager + GUI netifd ConnectivityManager
(not ConnMan = ConnectionManager!)
? ConnMan
(GObject, Glib, GModule, GThread, GIO)
libubox ? ? Qt-based?
PulseAudio pulseaudio (optional) PulseAudio PulseAudio PulseAudio
Package management system dpkg/APT
opkg apk ? RPM

What's the difference between ubus vs dbus?

dbus is bloated, its C API is very annoying to use and requires writing large amounts of boilerplate code. In fact, the pure C API is so annoying that its own API documentation states: “If you use this low-level API directly, you're signing up for some pain.”

ubus is tiny and has the advantage of being easy to use from regular C code, as well as automatically making all exported API functionality also available to shell scripts with no extra effort.

“Of course, NetworkManager should be renamed to “unetwork”, dbus to “ubus”, PulseAudio to “usound”, and X.Org-Server/Wayland-Compositor to “udisplay”; and then indescribable happiness would come down to all people of this world.” – Lennart Poettering


Package history is available at:

yes, heavily stripped OpenWrt can run on 16 or even 8MiB
yes, 4MiB and 2MiB possible
docs/techref/procd.txt · Last modified: 2018/03/04 11:42 by