launch helper exited with unknown return code 127

[Simon McVittie]

On 02/06/16 08:12, Florin Gherendi wrote:
> This is my first message to this list.
> I've compiled and installed dbus 1.10.6

That is not a current version. You probably want the current stable
version, which is currently 1.10.8. (However, 1.10.8 does not contain
any fixes directly related to what you're reporting.)

> on an ARM DD-WRT WiFi router

dbus is typically compiled by operating system integrators, not by end
users. If you are compiling it yourself, you are effectively making your
own operating system variant.

You might have better success by using a software distribution that
already offers dbus as an optional component, such as OpenWRT.

> It will always give me "launch helper exited with unknown return code
> 127" when try to launch manually

127 is traditionally the exit code used by shells when the process to be
executed does not exist.

I suspect that this means that either the setuid-root system activation
helper (dbus-daemon-launch-helper), or the service you are trying to
activate (for example colord), does not exist at its expected location.

> I must say that I modified installation root dir to /opt, since the root
> filesystem is read only; but the config files are all changed
> accordingly, and I've even tried to change the default search dirs in
> the sources, but with no success.

The correct way to configure dbus to install in /opt (or any other
directory of your choice) is to run ./configure with --prefix=/opt (or
whatever directory you want). You can't usually just move compiled Unix
system software around and expect it to work; you should configure with
the same prefix you are going to use.

>From what you've written about colord, it seems you might be trying to
use --prefix=/opt/usr, which is unusual but valid.

> The service
> org.freedesktop.ColorManager (as I was talking about colord) is system
> wide known, cause dbus does not complain about the name (it *does*
> complain if I use an unknown service name), but when I try to list all
> services with "dbus-send --system --dest=org.freedesktop.DBus
> --type=method_call --print-reply /org/freedesktop/DBus
> org.freedesktop.DBus.ListNames" it does not get listed.

If colord isn't running, then this is the expected result. Call
ListActivatableNames instead of ListNames to see whether dbus-daemon
thinks colord is available for activation.

-- 
Simon McVittie
Collabora Ltd. <http://www.collabora.com/>