NETWORKMANAGER - Online Linux Manual PageSection : 8
Updated :
Source : NetworkManager 1​.42​.0
Note : Network management daemons

NAMENetworkManager − network management daemon

SYNOPSISNetworkManager [OPTIONS...]

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

OPTIONSThe 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 PROPERTIESudev(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​.

SIGNALSNetworkManager 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​.

DEBUGGINGNetworkManager 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−IDThe 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​.

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

SEE ALSONetworkManager home page[2], NetworkManager.conf(5), NetworkManager-dispatcher(8), NetworkManager-wait-online.service(8), nmcli(1), nmcli-examples(7), nm-online(1), nm-settings(5), nm-applet(1), nm-connection-editor(1), udev(7)

NOTES 1. NetworkManager issue tracker ­https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues 2. NetworkManager home page ­https://networkmanager.dev
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