NetworkManager - network management daemon
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.
NetworkManager-dispatcher service can execute scripts for the user in response
to network events. See NetworkManager-dispatcher(8) manual.
The following options are understood:
--version | -V
Print the NetworkManager software version and exit.
--help | -h
Print NetworkManager's available options and exit.
--no-daemon | -n
Do not daemonize.
--debug | -d
Do not daemonize, and direct log output to the
controlling terminal in addition to syslog.
--pid-file | -p
Specify location of a PID file. The PID file is used for
storing PID of the running process and prevents running multiple
Specify file for storing state of the NetworkManager
persistently. If not specified, the default value of
/var/lib/NetworkManager/NetworkManager.state is used.
Specify configuration file to set up various settings for
NetworkManager. If not specified, the default value of
/etc/NetworkManager/NetworkManager.conf is used with a fallback to the older
'nm-system-settings.conf' if located in the same directory. See
NetworkManager.conf(5) for more information on configuration
Quit after all devices reach a stable state. The optional
initrd parameter enables mode, where no processes are left running after
NetworkManager stops, which is useful for running from an initial ramdisk on
List plugins used to manage system-wide connection
settings. This list has preference over plugins specified in the configuration
file. See main.plugins setting in NetworkManager.conf(5) for supported
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
logging in NetworkManager.conf(5) for more information.
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 logging in NetworkManager.conf(5)
for more information.
Print the NetworkManager configuration to stdout and
udev(7) device manager is used for the network device discovery. The
following property influences how NetworkManager manages the devices:
If set to "1" or "true", the device
is configured as unmanaged by NetworkManager. Note that the user still can
explicitly overrule this configuration via means like nmcli device set
"$DEVICE" managed yes or "device*.managed=1" in
NetworkManager process handles the following signals:
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
/etc/NetworkManager/dnsmasq.d. 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
The signal forces a rewrite of DNS configuration.
Contrary to SIGHUP, this does not restart the DNS plugin and will not
interrupt name resolution. When NetworkManager is not managing DNS, the signal
forces a restart of operations that depend on the DNS configuration (like the
resolution of the system hostname via reverse DNS, or the resolution of
WireGuard peers); therefore, it can be used to tell NetworkManager that the
content of resolv.conf was changed externally. 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.
The signal has no effect at the moment but is reserved
for future use.
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
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.
You can for example try to ping hosts (by IP address or DNS
name), look at ip link show, ip address show and ip route
show, and look at /etc/resolv.conf for name resolution issues. Also look
at the connection profiles that you have configured in NetworkManager
(nmcli connection and nmcli connection show
"$PROFILE") and the configured interfaces (nmcli
If that does not suffice, look at the logfiles of NetworkManager.
NetworkManager logs to syslog, so depending on your system configuration you
can call journalctl 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 nmcli general
logging level TRACE domains ALL. But usually a better way is to collect
full logs from the start, by configuring level=TRACE in NetworkManager.conf.
See NetworkManager.conf(5) manual. Note that trace logs of
NetworkManager are verbose and systemd-journald might rate limit some lines.
Possibly disable rate limiting first with the RateLimitIntervalSec and
RateLimitBurst options of journald (see journald.conf(5) manual).
The identity of a machine is important as various settings depend on it. For
example, ipv6.addr-gen-mode=stable and ethernet.cloned-mac-address=stable
generate identifiers by hashing the machine's identity. See also the
connection.stable-id connection property which is a per-profile seed that gets
hashed with the machine identity for generating such addresses and
If you backup and restore a machine, the identity of the machine
probably should be preserved. In that case, preserve the files
/var/lib/NetworkManager/secret_key and /etc/machine-id. 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
/etc/machine-id (see machine-id(5)).
The identity of the machine is determined by the
/var/lib/NetworkManager/secret_key. 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.
Since 1.16.0, NetworkManager supports a version 2 of secret-keys.
For such keys /var/lib/NetworkManager/secret_key starts with ASCII
"nm-v2:" 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,
/etc/machine-id is also hashed as part of the generation for addresses and
identifiers. The advantage is that you can keep
/var/lib/NetworkManager/secret_key stable, and only regenerate
/etc/machine-id when cloning a VM.
Please report any bugs you find in NetworkManager at the NetworkManager issue
NetworkManager home page, NetworkManager.conf(5),
nmcli-examples(7), nm-online(1), nm-settings(5),
nm-applet(1), nm-connection-editor(1), udev(7)
- NetworkManager issue tracker
- NetworkManager home page