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, WiFi, 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 will execute scripts in the /etc/NetworkManager/dispatcher.d directory or subdirectories in alphabetical order in response to network events. Each script should be a regular executable file owned by root. Furthermore, it must not be writable by group or other, and not setuid. Each script receives two arguments, the first being the interface name of the device an operation just happened on, and second the action. For device actions, the interface is the name of the kernel interface suitable for IP configuration. Thus it is either VPN_IP_IFACE, DEVICE_IP_IFACE, or DEVICE_IFACE, as applicable. For the hostname and connectivity-change actions it is always "none". The actions are: pre-up The interface is connected to the network but is not yet fully activated. Scripts acting on this event must be placed or symlinked into the /etc/NetworkManager/dispatcher.d/pre-up.d directory, and NetworkManager will wait for script execution to complete before indicating to applications that the interface is fully activated. up The interface has been activated. pre-down The interface will be deactivated but has not yet been disconnected from the network. Scripts acting on this event must be placed or symlinked into the /etc/NetworkManager/dispatcher.d/pre-down.d directory, and NetworkManager will wait for script execution to complete before disconnecting the interface from its network. Note that this event is not emitted for forced disconnections, like when carrier is lost or a wireless signal fades. It is only emitted when there is an opportunity to cleanly handle a network disconnection event. down The interface has been deactivated. vpn-pre-up The VPN is connected to the network but is not yet fully activated. Scripts acting on this event must be placed or symlinked into the /etc/NetworkManager/dispatcher.d/pre-up.d directory, and NetworkManager will wait for script execution to complete before indicating to applications that the VPN is fully activated. vpn-up A VPN connection has been activated. vpn-pre-down The VPN will be deactivated but has not yet been disconnected from the network. Scripts acting on this event must be placed or symlinked into the /etc/NetworkManager/dispatcher.d/pre-down.d directory, and NetworkManager will wait for script execution to complete before disconnecting the VPN from its network. Note that this event is not emitted for forced disconnections, like when the VPN terminates unexpectedly or general connectivity is lost. It is only emitted when there is an opportunity to cleanly handle a VPN disconnection event. vpn-down A VPN connection has been deactivated. hostname The system hostname has been updated. Use gethostname(2) to retrieve it. The interface name (first argument) is empty and no environment variable is set for this action. dhcp4-change The DHCPv4 lease has changed (renewed, rebound, etc). dhcp6-change The DHCPv6 lease has changed (renewed, rebound, etc). connectivity-change The network connectivity state has changed (no connectivity, went online, etc). The environment contains more information about the interface and the connection. The following variables are available for the use in the dispatcher scripts: CONNECTION_UUID The UUID of the connection profile. CONNECTION_ID The name (ID) of the connection profile. CONNECTION_DBUS_PATH The NetworkManager D-Bus path of the connection. CONNECTION_FILENAME The backing file name of the connection profile (if any). CONNECTION_EXTERNAL If "1", this indicates that the connection describes a network configuration created outside of NetworkManager. DEVICE_IFACE The interface name of the control interface of the device. Depending on the device type, this differs from DEVICE_IP_IFACE. For example for ADSL devices, this could be 'atm0' or for WWAN devices it might be 'ttyUSB0'. DEVICE_IP_IFACE The IP interface name of the device. This is the network interface on which IP addresses and routes will be configured. IP4_ADDRESS_N The IPv4 address in the format "address/prefix gateway", where N is a number from 0 to (# IPv4 addresses - 1). gateway item in this variable is deprecated, use IP4_GATEWAY instead. IP4_NUM_ADDRESSES The variable contains the number of IPv4 addresses the script may expect. IP4_GATEWAY The gateway IPv4 address in traditional numbers-and-dots notation. IP4_ROUTE_N The IPv4 route in the format "address/prefix next-hop metric", where N is a number from 0 to (# IPv4 routes - 1). IP4_NUM_ROUTES The variable contains the number of IPv4 routes the script may expect. IP4_NAMESERVERS The variable contains a space-separated list of the DNS servers. IP4_DOMAINS The variable contains a space-separated list of the search domains. DHCP4_<dhcp-option-name> If the connection used DHCP for address configuration, the received DHCP configuration is passed in the environment using standard DHCP option names, prefixed with "DHCP4_", like "DHCP4_HOST_NAME=foobar". IP6_<name> and DHCP6_<name> The same variables as for IPv4 are available for IPv6, but the prefixes are IP6_ and DHCP6_ instead. CONNECTIVITY_STATE The network connectivity state, which can take the values defined by the NMConnectivityState type, from the org.freedesktop.NetworkManager D-Bus API: unknown, none, portal, limited or full. Note: this variable will only be set for connectivity-change actions. In case of VPN, VPN_IP_IFACE is set, and IP4_*, IP6_* variables with VPN prefix are exported too, like VPN_IP4_ADDRESS_0, VPN_IP4_NUM_ADDRESSES. Dispatcher scripts are run one at a time, but asynchronously from the main NetworkManager process, and will be killed if they run for too long. If your script might take arbitrarily long to complete, you should spawn a child process and have the parent return immediately. Scripts that are symbolic links pointing inside the /etc/NetworkManager/dispatcher.d/no-wait.d/ directory are run immediately, without waiting for the termination of previous scripts, and in parallel. Also beware that once a script is queued, it will always be run, even if a later event renders it obsolete. (Eg, if an interface goes up, and then back down again quickly, it is possible that one or more "up" scripts will be run after the interface has gone down.)
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. --plugins List plugins used to manage system-wide connection settings. This list has preference over plugins specified in the configuration file. Currently supported plugins are: keyfile, ifcfg-rh, ifcfg-suse, ifupdown. --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.
udev(7) device manager is used for the network device discovery. The following property influences how NetworkManager manages the devices: NM_UNMANAGED No default connection will be created and automatic activation will not be attempted when this property of a device is set to a true value ("1" or "true"). You will still be able to attach a connection to the device manually or observe externally added configuration such as addresses or routes. Create an udev rule that sets this property to prevent NetworkManager from interfering with virtual Ethernet device interfaces that are managed by virtualization tools.
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. 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.
The following environment variables are supported to help debugging. When used in conjunction with the --no-daemon option (thus echoing PPP and DHCP helper output to stdout) these can quickly help pinpoint the source of connection issues. Also see the --log-level and --log-domains to enable debug logging inside NetworkManager itself. NM_PPP_DEBUG: When set to anything, causes NetworkManager to turn on PPP debugging in pppd, which logs all PPP and PPTP frames and client/server exchanges.
NetworkManager.conf(5), nmcli(1), nmcli-examples(7), nm-online(1), nm- settings(5), nm-applet(1), nm-connection-editor(1), udev(7)
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