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NetworkManager(8) manual page
Copyright 2005 - 2016 Red Hat, Inc.
Copyright 2005 - 2009 Novell, Inc.
Copyright 2005 Robert Love
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<refentry id="NetworkManager">
<refentryinfo>
<title>NetworkManager</title>
<author>NetworkManager developers</author>
</refentryinfo>
<refmeta>
<refentrytitle>NetworkManager</refentrytitle>
<manvolnum>8</manvolnum>
<refmiscinfo class="source">NetworkManager</refmiscinfo>
<refmiscinfo class="manual">Network management daemons</refmiscinfo>
<refmiscinfo class="version">&NM_VERSION;</refmiscinfo>
</refmeta>
<refnamediv>
<refname>NetworkManager</refname>
<refpurpose>network management daemon</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>NetworkManager <arg choice="opt" rep="repeat">OPTIONS</arg></command>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
The NetworkManager daemon attempts to make networking
configuration and operation as painless and automatic as
possible by managing the primary network connection and other
network interfaces, like Ethernet, Wi-Fi, and Mobile Broadband
devices. NetworkManager will connect any network device when a
connection for that device becomes available, unless that
behavior is disabled. Information about networking is exported
via a D-Bus interface to any interested application, providing a
rich API with which to inspect and control network settings and
operation.
</para>
</refsect1>
<refsect1>
<title>Dispatcher scripts</title>
<para>
NetworkManager-dispatcher service can execute scripts for the user
in response to network events. See
<link linkend='NetworkManager-dispatcher'><citerefentry><refentrytitle>NetworkManager-dispatcher</refentrytitle><manvolnum>8</manvolnum></citerefentry></link> manual.
</para>
</refsect1>
<refsect1>
<title>Options</title>
<para>The following options are understood:</para>
<variablelist>
<varlistentry>
<term><option>--version</option> | <option>-V</option></term>
<listitem><para>Print the NetworkManager software version and exit.
</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--help</option> | <option>-h</option></term>
<listitem><para>Print NetworkManager's available options and exit.
</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--no-daemon</option> | <option>-n</option></term>
<listitem><para>Do not daemonize.
</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--debug</option> | <option>-d</option></term>
<listitem><para>Do not daemonize, and direct log output to the
controlling terminal in addition to syslog.
</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--pid-file</option> | <option>-p</option></term>
<listitem><para>Specify location of a PID file. The PID file
is used for storing PID of the running process and prevents
running multiple instances.
</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--state-file</option></term>
<listitem><para>Specify file for storing state of the
NetworkManager persistently. If not specified, the default
value of <filename>/var/lib/NetworkManager/NetworkManager.state</filename>
is used.
</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--config</option></term>
<listitem><para> Specify configuration file to set up various
settings for NetworkManager. If not specified, the default
value of <filename>/etc/NetworkManager/NetworkManager.conf</filename>
is used with
a fallback to the older 'nm-system-settings.conf' if located
in the same directory. See
<link linkend='NetworkManager.conf'><citerefentry><refentrytitle>NetworkManager.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry></link>
for more information on configuration file.
</para></listitem>
</varlistentry>
<varlistentry>
<term><arg choice='plain'><option>--configure-and-quit</option></arg><arg>initrd</arg></term>
<listitem><para>Quit after all devices reach a stable state.
The optional <literal>initrd</literal> parameter enables mode, where no
processes are left running after NetworkManager stops, which is useful
for running from an initial ramdisk on rearly boot.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--plugins</option></term>
<listitem><para>List plugins used to manage system-wide
connection settings. This list has preference over plugins
specified in the configuration file. See <literal>main.plugins</literal>
setting in <link linkend='NetworkManager.conf'><citerefentry><refentrytitle>NetworkManager.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry></link>
for supported options.
</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--log-level</option></term>
<listitem><para>
Sets how much information NetworkManager sends to the log destination (usually
syslog's "daemon" facility). By default, only informational, warning, and error
messages are logged. See the section on <literal>logging</literal> in
<link linkend='NetworkManager.conf'><citerefentry><refentrytitle>NetworkManager.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry></link>
for more information.
</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--log-domains</option></term>
<listitem><para>
A comma-separated list specifying which operations are logged to the log
destination (usually syslog). By default, most domains are logging-enabled.
See the section on <literal>logging</literal> in
<link linkend='NetworkManager.conf'><citerefentry><refentrytitle>NetworkManager.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry></link>
for more information.
</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--print-config</option></term>
<listitem><para>
Print the NetworkManager configuration to stdout and exit.
</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Udev Properties</title>
<para>
<citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>
device manager is used for the network device discovery. The following
property influences how NetworkManager manages the devices:
</para>
<variablelist>
<varlistentry>
<term><varname>NM_UNMANAGED</varname></term>
<listitem><para>
If set to <literal>"1"</literal> or <literal>"true"</literal>, the device is
configured as unmanaged by NetworkManager. Note that the user still can
explicitly overrule this configuration via means like
<command>nmcli device set "$DEVICE" managed yes</command> or
<literal>"device*.managed=1"</literal> in NetworkManager.conf.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>SIGNALS</title>
<para>
NetworkManager process handles the following signals:
<variablelist>
<varlistentry>
<term><varname>SIGHUP</varname></term>
<listitem><para>
The signal causes a reload of NetworkManager's configuration.
Note that not all configuration parameters can be changed at
runtime and therefore some changes may be applied only after
the next restart of the daemon.
A SIGHUP also involves further reloading actions, like doing
a DNS update and restarting the DNS plugin. The latter can be
useful for example when using the dnsmasq plugin and changing
its configuration in <filename>/etc/NetworkManager/dnsmasq.d</filename>.
However, it also means this will shortly interrupt name resolution.
In the future, there may be further actions added.
A SIGHUP means to update NetworkManager configuration and reload
everything that is supported. Note that this does not reload
connections from disk. For that there is a D-Bus API and
nmcli's reload action
</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>SIGUSR1</varname></term>
<listitem><para>
The signal forces a rewrite of DNS configuration. Contrary to
SIGHUP, this does not restart the DNS plugin and will not interrupt
name resolution.
In the future, further actions may be added. A SIGUSR1
means to write out data like resolv.conf, or refresh a cache.
It is a subset of what is done for SIGHUP without reloading
configuration from disk.
</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>SIGUSR2</varname></term>
<listitem><para>
The signal has no effect at the moment but is reserved for future
use.
</para></listitem>
</varlistentry>
</variablelist>
</para>
<para>
An alternative to a signal to reload configuration is the Reload D-Bus call.
It allows for more fine-grained selection of what to reload, it only returns
after the reload is complete, and it is guarded by PolicyKit.
</para>
</refsect1>
<refsect1>
<title>Debugging</title>
<para>
NetworkManager only configures your system. So when your networking setup doesn't
work as expected, the first step is to look at your system to understand what is actually
configured, and whether that is correct. The second step is to find out how to tell
NetworkManager to do the right thing.
</para>
<para>
You can for example try to <command>ping</command> hosts (by
IP address or DNS name), look at <command>ip link show</command>, <command>ip address show</command> and <command>ip route show</command>,
and look at <filename>/etc/resolv.conf</filename> for name resolution issues.
Also look at the connection profiles that you have configured in NetworkManager (<command>nmcli connection</command>
and <command>nmcli connection show "$PROFILE"</command>)
and the configured interfaces (<command>nmcli device</command>).
</para>
<para>
If that does not suffice, look at the logfiles of NetworkManager. NetworkManager
logs to syslog, so depending on your system configuration you can call <command>journalctl</command>
to get the logs.
By default, NetworkManager logs are not verbose and thus not very helpful for investigating
a problem in detail. You can change the logging level at runtime with <command>nmcli general logging level TRACE domains ALL</command>.
But usually a better way is to collect full logs from the start, by configuring
<literal>level=TRACE</literal> in NetworkManager.conf. See
<link linkend='NetworkManager.conf'><citerefentry><refentrytitle>NetworkManager.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry></link>
manual. Note that trace logs of NetworkManager are verbose and systemd-journald might rate limit
some lines. Possibly disable rate limiting first with the <literal>RateLimitIntervalSec</literal> and
<literal>RateLimitBurst</literal> options of journald (see
<link linkend='journald.conf'><citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry></link> manual).
</para>
</refsect1>
<refsect1>
<title>/var/lib/NetworkManager/secret_key and /etc/machine-id</title>
<para>
The identity of a machine is important as various settings depend on it. For example,
<literal>ipv6.addr-gen-mode=stable</literal> and <literal>ethernet.cloned-mac-address=stable</literal>
generate identifiers by hashing the machine's identity. See also the
<literal>connection.stable-id</literal> connection property which is a per-profile seed
that gets hashed with the machine identity for generating such addresses and identifiers.
</para>
<para>
If you backup and restore a machine, the identity of the machine probably should be preserved.
In that case, preserve the files <filename>/var/lib/NetworkManager/secret_key</filename> and
<literal>/etc/machine-id</literal>. On the other hand, if you clone a virtual machine, you
probably want that the clone has a different identity. There is already existing tooling on Linux for
handling <literal>/etc/machine-id</literal> (see
<link linkend='machine-id'><citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry></link>).
</para>
<para>
The identity of the machine is determined by the <filename>/var/lib/NetworkManager/secret_key</filename>.
If such a file does not exist, NetworkManager will create a file with random content. To generate
a new identity just delete the file and after restart a new file will be created.
The file should be read-only to root and contain at least 16 bytes that will be used to seed the various places
where a stable identifier is used.
</para>
<para>
Since 1.16.0, NetworkManager supports a version 2 of secret-keys. For such keys
<filename>/var/lib/NetworkManager/secret_key</filename> starts with ASCII <literal>"nm-v2:"</literal>
followed by at least 32 bytes of random data.
Also, recent versions of NetworkManager always create such kinds of secret-keys, when
the file does not yet exist.
With version 2 of the secret-key, <literal>/etc/machine-id</literal> is also hashed as part
of the generation for addresses and identifiers. The advantage is that you can keep <filename>/var/lib/NetworkManager/secret_key</filename>
stable, and only regenerate <literal>/etc/machine-id</literal> when cloning a VM.
</para>
</refsect1>
<refsect1>
<title>Bugs</title>
<para>
Please report any bugs you find in NetworkManager at the
<ulink url="https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues">NetworkManager issue tracker</ulink>.
</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<ulink url="https://wiki.gnome.org/Projects/NetworkManager">NetworkManager home page</ulink>,
<link linkend='NetworkManager.conf'><citerefentry><refentrytitle>NetworkManager.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry></link>,
<link linkend='NetworkManager-dispatcher'><citerefentry><refentrytitle>NetworkManager-dispatcher</refentrytitle><manvolnum>8</manvolnum></citerefentry></link>,
<link linkend='nmcli'><citerefentry><refentrytitle>nmcli</refentrytitle><manvolnum>1</manvolnum></citerefentry></link>,
<link linkend='nmcli-examples'><citerefentry><refentrytitle>nmcli-examples</refentrytitle><manvolnum>7</manvolnum></citerefentry></link>,
<link linkend='nm-online'><citerefentry><refentrytitle>nm-online</refentrytitle><manvolnum>1</manvolnum></citerefentry></link>,
<link linkend='nm-settings'><citerefentry><refentrytitle>nm-settings</refentrytitle><manvolnum>5</manvolnum></citerefentry></link>,
<citerefentry><refentrytitle>nm-applet</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>nm-connection-editor</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>