Ubuntu Manpage: NetworkManager - network management daemon

Provided by: network-manager_1.50.0-1ubuntu2_amd64

NAME

       NetworkManager - network management daemon

SYNOPSIS

       NetworkManager [OPTIONS...]

DESCRIPTION

       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.

DISPATCHER SCRIPTS

       NetworkManager-dispatcher service can execute scripts for the user in response to network
       events. See NetworkManager-dispatcher(8) manual.

OPTIONS

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 instances.

--state-file
Specify file for storing state of the NetworkManager persistently. If not specified,
the default value of /var/lib/NetworkManager/NetworkManager.state is used.

--config
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 file.

--configure-and-quit [initrd]
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 rearly boot.

--plugins
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 options.

--log-level
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.

--log-domains
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-config
Print the NetworkManager configuration to stdout and exit. See NetworkManager.conf(5).
This does not include connection profiles. View them with nmcli connection.

This reads configuration files from disk. If NetworkManager is currently running, make
sure that it has the same configuration loaded.

UDEV PROPERTIES

       udev(7) device manager is used for the network device discovery. The following property
       influences how NetworkManager manages the devices:

       NM_UNMANAGED
           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.conf.

       ID_NET_MANAGED_BY
           If NM_UNMANAGED is set, this has no effect. Otherwise, if the attribute is set to
           anything but "org.freedesktop.NetworkManager", the device is unmanaged.

       NM_AUTO_DEFAULT_LINK_LOCAL_ONLY
           If set to "1" or "true", the automatically generated connections "Wired connection N"
           will only enable link local addressing for IPv4 and IPv6. This can be useful on
           thunderbolt devices or host-to-host USB devices.

       ID_NET_AUTO_LINK_LOCAL_ONLY
           Honored and treated the same as if NM_AUTO_DEFAULT_LINK_LOCAL_ONLY were set.

       ID_NET_DHCP_BROADCAST
           If set to "1" or "true", use broadcast requests for DHCPv4 offers. This can make sense
           of devices that can't handle unicast messages until being configured.

SIGNALS

NetworkManager process handles the following signals:

SIGHUP
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

SIGUSR1
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.

SIGUSR2
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 PolicyKit.

DEBUGGING

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 device).

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).

NetworkManager does not log any secrets. However, you are advised to check whether
anything private sensitive gets logged before posting. When reporting an issue, provide
complete logs and avoid modifications (for privacy) that distort the meaning.

/VAR/LIB/NETWORKMANAGER/SECRET_KEY AND /ETC/MACHINE-ID

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 identifiers.

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.

BUGS

       Please report any bugs you find in NetworkManager at the NetworkManager issue tracker[1].

NOTES

        1. NetworkManager issue tracker
           https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues

        2. NetworkManager home page
           https://networkmanager.dev