A method of ‘masking’ an OpenRC service (NetworkManager, in this case)

A Gentoo Linux user with an installation using OpenRC recently asked in the Gentoo Forums how to either a) disable NetworkManager so that it would not interfere with his netifrc configuration to give his installation a static IP address, or b) configure NetworkManager to use a static IP address (see the thread NetworkManager and static IP [SOLVED! THANKYOU]). In the end he solved the problem by uninstalling NetworkManager, the cleanest solution in his case given that his desktop machine is always in the same location and he does not need the features NetworkManager provides.

Now, although I use NetworkManager instead of netifrc, what intrigued me is that disabling the NetworkManager service using the standard command below does not stop the NetworkManager init script from running at boot-up:

root # rc-update delete NetworkManager default

Despite using the above command, following a reboot the NetworkManager service is still started and becomes active, and the NetworkManager daemon is running. Web browsers and other applications requiring network access still work. In order to stop the service running immediately so that his netifrc static IP address configuration could work, the aforementioned Gentoo user had to stop the NetworkManager service as follows:

root # /etc/init.d/NetworkManager stop

(The command ‘rc-service NetworkManager stop‘ does the same thing.)

The behaviour is the same on my laptop running Gentoo with OpenRC 0.22.4 and NetworkManager installed by networkmanager-1.4.0-r1 ebuild (with the upstream patch and necessary edit to the init script mentioned in Gentoo Bug Report No. 595806 – net-misc/networkmanager-1.4.0-r1[consolekit]: doesn’t automatically activate connections marked with "Automatically connect to this network when it’s available").

So two questions arose: What launches the NetworkManager init script when it has not been added to a runlevel? What needs to be done to stop this from happening? My curiosity was piqued.

As it happens, a somewhat similar situation exists when using systemd rather than OpenRC, as explained in Arch Linux Forums thread [SOLVED] NetworkManager auto restart even though I stop it. and Red Hat Bugzilla Report No. 815243 – Even though NetworkManager was manually stopped, it gets restarted automatically via D-Bus, although those were primarily concerned with how to prevent NetworkManager being restarted during the same session, i.e. without having rebooted.

The following systemd commands are needed to stop immediately the NetworkManager service and keep it from being restarted subsequently during the current session and after rebooting:

root # systemctl mask NetworkManager
root # systemctl stop NetworkManager
root # systemctl disable NetworkManager

Unfortunately there is no equivalent mask command for an OpenRC service. The equivalent OpenRC commands for the second and third commands above are:

root # rc-service NetworkManager stop
root # rc-update delete NetworkManager default

However, as I pointed out earlier, for some reason the latter command does not stop OpenRC running the NetworkManager init script at boot.

I wondered how I could ‘mask’ the NetworkManager service in OpenRC. I asked myself what the systemd mask command actually does. Well, it simply creates a symlink from /etc/systemd/system/NetworkManager.service to /dev/null so that there is no longer a real unit file for systemd to use, and therefore systemd can no longer launch the service. So why not do something similar in OpenRC. I hit upon the idea of telling the NetworkManager init script it needs a non-existent service in order to start, thus preventing OpenRC from starting the NetworkManager service:

root # echo 'rc_need="non-existent_service"' >> /etc/conf.d/NetworkManager # (Or just edit the file manually.)

That is all there is to it. When booting, OpenRC now displays the messages shown below:

* ERROR: NetworkManager needs service(s) non-existent_service
* ERROR: cannot start netmount as NetworkManager would not start
* ERROR: cannot start samba as NetworkManager would not start

As shown below, now the service is not started, so the NetworkManager daemon is never launched:

root # rc-status
Runlevel: default
 dbus                                                  [  started  ]
 syslog-ng                                             [  started  ]
 consolekit                                            [  started  ]
 netmount                                              [  stopped  ]
 cupsd                                                 [  started  ]
 samba                                                 [  stopped  ]
 cronie                                                [  started  ]
 clamd                                                 [  started  ]
 bluetooth                                             [  started  ]
 xdm                                                   [  started  ]
 cups-browsed                                          [  started  ]
 sshd                                                  [  started  ]
 local                                                 [  started  ]
Dynamic Runlevel: hotplugged
Dynamic Runlevel: needed/wanted
 modules-load                                          [  started  ]
 xdm-setup                                             [  started  ]
 avahi-daemon                                          [  started  ]
Dynamic Runlevel: manual
root # ps -ef | grep -v grep | grep -i network
root #

As expected, given that the netmount service and samba service depend on the NetworkManager service starting, neither of those services were able to start either.

Furthermore, because I masked the service, if I attempt to start it manually:

root # rc-service NetworkManager restart
 * ERROR: NetworkManager needs service(s) non-existent_service

To unmask the service in OpenRC, all that is needed is:

root # sed -i '/rc_need="non-existent_service"/d' /etc/conf.d/NetworkManager # (Or just edit the file manually.)

Note that, instead of “non-existent_service” I could have written “fubar”, “null” or any other string that is not the name of an actual service. But “non-existent_service” is more meaningful and less likely to confuse me when viewing system messages and contents of the service configuration file.

In summary…

Why does OpenRC run the NetworkManager service init script when it is not in any runlevel?

I have no idea!

I wondered if the D-Bus service does it. The Arch Wiki article on NetworkManager claims this is the case (see the section titled Disable NetworkManager). However, my attempts at preventing D-Bus doing anything to NetworkManager did not stop the NetworkManager init script from being run at boot. I deleted /etc/dbus-1/system.d/org.freedesktop.NetworkManager.conf and /etc/dbus-1/system.d/nm-dispatcher.conf but that did not help. Neither did creating an appropriate /etc/dbus-1/system.d/org.freedesktop.NetworkManager.conf or /etc/dbus-1/system-local.conf. There is no /usr/share/dbus-1/system-services/org.freedesktop.NetworkManager.service file in my Gentoo installation using OpenRC, but creating one did not help either. So, if you know what runs the OpenRC NetworkManager init script when it is not in any runlevel, please post a comment.

Anyway, I now know how to prevent it happening, so I have satisfied my curiosity. Below I list the commands I actually used in a Gentoo Linux installation (amd64, OpenRC) and a Sabayon Linux installation (~amd64, systemd) to check the functionality.

OpenRC

The following two (optionally three) commands are needed to stop immediately the NetworkManager service and prevent it being restarted subsequently during this session and after rebooting:

root # rc-service NetworkManager stop
root # echo 'rc_need="non-existent_service"' >> /etc/conf.d/NetworkManager
root # rc-update del NetworkManager default # (Optional.)

The following two (optionally three) commands are needed to unmask the NetworkManager service and start it immediately, and make it start automatically after rebooting:

root # sed -i '/rc_need="non-existent_service"/d' /etc/conf.d/NetworkManager
root # rc-service NetworkManager restart
root # rc-update add NetworkManager default # Only needed if I earlier deleted the service from the default runlevel.

systemd

The following three commands are needed to stop immediately the NetworkManager service and prevent it being restarted subsequently during this session and after rebooting:

root # systemctl mask NetworkManager
root # systemctl stop NetworkManager
root # systemctl disable NetworkManager

The following three systemd commands are needed to unmask the NetworkManager service and start it immediately, and also make it start automatically after rebooting:

root # systemctl unmask NetworkManager
root # systemctl enable NetworkManager
root # systemctl start NetworkManager

About Fitzcarraldo
A Linux user with an interest in all things technical.

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