Configuration files and common settings of NetworkManager - Alibaba Cloud Linux

NetworkManager is a tool that is used to manage network interface controller (NIC) configurations and the connection status. NetworkManager can automatically detect available networks and switch between networks based on your business requirements. NetworkManager also allows you to configure network settings such as IP addresses, gateways, and Domain Name System (DNS) settings. This topic describes the configuration files and common settings of NetworkManager in Alibaba Cloud Linux 3. You can modify the configurations based on your business requirements.

NetworkManager configuration files

NetworkManager manages the following configuration files that are loaded in sequence and prioritized in ascending order: configuration files in the /usr/lib/NetworkManager/conf.d directory, configuration files in the /run/NetworkManager/conf.d/ directory, /etc/NetworkManager/NetworkManager.conf, and configuration files in the /etc/NetworkManager/conf.d directory.

/usr/lib/NetworkManager/conf.d: mainly stores the default settings of software. Custom settings must be saved in configuration files that have a higher priority, such as files in the /etc/NetworkManager/conf.d directory, to prevent the custom settings from being overwritten when the software package is updated.
/run/NetworkManager/conf.d/: stores temporary running configurations. Files in this directory are created by system services or by using startup scripts on system startup. We recommend that you do not store custom settings in this directory because the configurations are lost when the system is restarted.
/etc/NetworkManager/NetworkManager.conf: is the primary configuration file of NetworkManager and is updated when the software package is removed or updated. To prevent custom settings from being overwritten, we recommend that you do not modify the NetworkManager.conf file.
/etc/NetworkManager/conf.d: stores .conf files that you create to modify the default settings of NetworkManager. This ensures that custom settings are retained when the software package is updated. Take note that files in this directory are read based on the lexicographic order of the file name.

Common settings of NetworkManager

NetworkManager log settings

In the following example, level is set to TRACE and domains is set to ALL to record all operation logs.

Run the following command to create and open the set-log.conf file:
```
sudo vim /etc/NetworkManager/conf.d/set-log.conf
```

Press the I key to enter Insert mode and copy the following content to the set-log.conf file:

[logging]
level=TRACE
domains=ALL

Description of the level parameter

Value	Description
OFF	Disables logs. No logs are output.
ERR	Outputs logs at the error level.
WARN	Outputs logs at the warning level and higher levels.
INFO	Outputs logs at the information level.
DEBUG	Outputs logs at the debug level.
TRACE	Outputs detailed logs at the trace level.

Description of the domains parameter

Value	Description
NONE	Does not record logs in domains.
ALL	Records logs of all available domains.
DEFAULT	Records logs of default domains.
DHCP	Records logs related to Dynamic Host Configuration Protocol (DHCP) clients.
IP	Records logs related to IP management.

Press the Esc key, enter :wq, and then press the Enter key to save and close the configuration file.
Run the following command for the changes to take effect:
```
sudo systemctl restart NetworkManager
```
Run the following command to view NetworkManager logs:
```
journalctl -u NetworkManager
```

NetworkManager does not take over NIC configurations

To configure NetworkManager not to take over NIC configurations, specify the unmanaged-devices key in the keyfile section. In the following example, NetworkManager is configured not to take over secondary NICs such as eth1.

Run the following command to check the status of NICs:
```
nmcli device status
```
The command output shown in the following figure indicates that NetworkManager takes over eth0 and eth1, but not lo.
Run the following command to create and open the unmanaged.conf file:
```
sudo vim /etc/NetworkManager/conf.d/unmanaged.conf
```
Press the I key to enter Insert mode and copy the following content to the unmanaged.conf file:
```
[keyfile]
unmanaged-devices=interface-name:eth1
```
Press the Esc key, enter :wq, and then press the Enter key to save and close the configuration file.
Run the following command for the changes to take effect:
```
sudo systemctl restart NetworkManager
```
Run the following command to check whether the changes in the configuration file take effect:
```
nmcli device status
```

NetworkManager plug-in configurations

NetworkManager uses the ifcfg-rh/keyfile plug-ins to read and write network settings. By default, the ifcfg-rh plug-in is used to manage the primary NIC, for example, eth0, and the keyfile plug-in is used to manage secondary NICs, for example, eth1.

The ifcfg-rh plug-in is used to read configurations from and write configurations to /etc/sysconfig/network-scripts/ifcfg-* files.
The keyfile plug-in is a generic plug-in for NetworkManager. Each connection has a corresponding .nmconnection configuration file.

Run the following command to open the NetworkManager.conf file:
```
sudo vim /etc/NetworkManager/NetworkManager.conf
```
Press the I key to enter Insert mode and add or change the values of the plugins parameter.
Note
The plugins are sorted based on the declaration order. The leftmost plug-in has the highest priority.
```
[main]
plugins = ifcfg-rh, keyfile
```
Press the Esc key, enter :wq, and then press the Enter key to save and close the configuration file.
Run the following command for the changes to take effect:
```
sudo systemctl restart NetworkManager
```
Run the following command to check whether the changes in the configuration file take effect:
```
sudo journalctl -u NetworkManager | grep -i "settings plugin"
```