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This section describes how to configure a network interface manually by editing the ifcfg files.
NetworkManager supports profiles stored in the keyfile format. However, by default, NetworkManager uses the ifcfg format when you use the NetworkManager API to create or update profiles.
In a future major RHEL release, the keyfile format will be default. Consider using the keyfile format if you want to manually create and manage configuration files. For details, see Manually creating NetworkManager profiles in keyfile format.
Interface configuration (ifcfg) files control the software interfaces for individual network devices. As the system boots, it uses these files to determine what interfaces to bring up and how to configure them. These files are usually named ifcfg-name, where the suffix name refers to the name of the device that the configuration file controls. By convention, the ifcfg file’s suffix is the same as the string given by the DEVICE directive in the configuration file itself.
31.1. Configuring an interface with static network settings using ifcfg files
This procedure describes how to configure a network interface using ifcfg files.
Procedure
To configure an interface with static network settings using ifcfg files, for an interface with the name enp1s0, create a file with the name ifcfg-enp1s0 in the /etc/sysconfig/network-scripts/ directory that contains:
For IPv4 configuration:
DEVICE=enp1s0 BOOTPROTO=none ONBOOT=yes PREFIX=24 IPADDR=10.0.1.27 GATEWAY=10.0.1.1For IPv6 configuration:
DEVICE=enp1s0 BOOTPROTO=none ONBOOT=yes IPV6INIT=yes IPV6ADDR=2001:db8:1::2/64
Additional resources
- nm-settings-ifcfg-rh(5) man page
31.2. Configuring an interface with dynamic network settings using ifcfg files
This procedure describes how to configure a network interface with dynamic network settings using ifcfg files.
Procedure
To configure an interface named em1 with dynamic network settings using ifcfg files, create a file with the name ifcfg-em1 in the /etc/sysconfig/network-scripts/ directory that contains:
DEVICE=em1 BOOTPROTO=dhcp ONBOOT=yesTo configure an interface to send:
A different host name to the DHCP server, add the following line to the ifcfg file:
DHCP_HOSTNAME=hostnameA different fully qualified domain name (FQDN) to the DHCP server, add the following line to the ifcfg file:
DHCP_FQDN=fully.qualified.domain.name
You can use only one of these settings. If you specify both DHCP_HOSTNAME and DHCP_FQDN, only DHCP_FQDN is used.
To configure an interface to use particular DNS servers, add the following lines to the ifcfg file:
PEERDNS=no DNS1=ip-address DNS2=ip-addresswhere ip-address is the address of a DNS server. This will cause the network service to update /etc/resolv.conf with the specified DNS servers specified. Only one DNS server address is necessary, the other is optional.
31.3. Managing system-wide and private connection profiles with ifcfg files
This procedure describes how to configure ifcfg files to manage the system-wide and private connection profiles.
Procedure
The permissions correspond to the USERS directive in the ifcfg files. If the USERS directive is not present, the network profile will be available to all users.
As an example, modify the ifcfg file with the following row, which will make the connection available only to the users listed:
USERS="joe bob alice"
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Under Red Hat Enterprise Linux, all network communications occur between configured software interfaces and physical networking devices connected to the system. The configuration files for network interfaces are located in the /etc/sysconfig/network-scripts/ directory. The scripts used to activate and deactivate these network interfaces
are also located here. Although the number and type of interface files can differ from system to system, there are three categories of files that exist in this directory: Interface configuration files Interface control scripts Network function files
The files in each of these categories work together to enable various network devices.
This chapter explores the relationship between these files and how they are used.
11.1. Network Configuration Files
Before delving into the interface configuration files, let us first itemize the primary configuration files used in network configuration. Understanding the role these files play in setting up the network stack can be helpful when customizing a Red Hat Enterprise Linux system.
The primary network configuration files are as follows:
/etc/hosts
The main purpose of this file is to resolve host names that cannot be resolved any other way. It can also be used to resolve host names on small networks with no DNS server. Regardless of the type of network the computer is on, this file should contain a line specifying the IP address of the loopback device (127.0.0.1) as localhost.localdomain. For more information, see the hosts(5) manual page.
/etc/resolv.confThis file specifies the IP addresses of DNS servers and the search domain. Unless configured to do otherwise, the network initialization scripts populate this file. For more information about this file, see the resolv.conf(5) manual page.
/etc/sysconfig/networkThis file specifies routing and host information for all network interfaces. It is used to contain directives which are to have global effect and not to be interface specific. For more information about this file and the directives it accepts, see Section D.1.14, “/etc/sysconfig/network”.
/etc/sysconfig/network-scripts/ifcfg-interface-nameFor each network interface, there is a corresponding interface configuration script. Each of these files provide information specific to a particular network interface. See Section 11.2, “Interface Configuration Files” for more information on this type of file and the directives it accepts.
The /etc/sysconfig/networking/ directory is used by the now deprecated Network Administration Tool (system-config-network). Its contents should not be edited manually. Using only one method for network configuration is strongly encouraged, due to the risk of configuration deletion. For more information about configuring network interfaces using graphical configuration tools, see Chapter 10, NetworkManager.
11.1.1. Setting the Host Name
To permanently change the static host name, change the HOSTNAME directive in the /etc/sysconfig/network file. For example:
HOSTNAME=penguin.example.comRed Hat recommends the static host name matches the fully qualified domain name (FQDN) used for the machine in DNS, such as host.example.com. It is also recommended that the static host name consists only of 7 bit ASCII lower-case characters, no spaces or dots, and limits itself to the format allowed for DNS domain name labels, even though this is not a strict requirement. Older specifications do not permit the underscore, and so their use is not recommended. Changes will only take effect when the networking service, or the system, is restarted.
Note that the FQDN of the host can be supplied by a DNS resolver, by settings in /etc/sysconfig/network, or by the /etc/hosts file. The default setting of hosts: files dns in /etc/nsswitch.conf causes the configuration files to be checked before a resolver. The default setting of multi on in the /etc/host.conf file means that all valid values in the /etc/hosts file are returned, not just the first.
Sometimes you may need to use the host table in the /etc/hosts file instead of the HOSTNAME directive in /etc/sysconfig/network, for example, when DNS is not running during system bootup.
To change the host name using the /etc/hosts file, add lines to it in the following format:
192.168.1.2 penguin.example.com penguin- Previous
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