Manually configuring the /etc/resolv.conf file(RHEL7/8 )

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/configuring_and_managing_networking/manually-configuring-the-etc-resolv-conf-file_configuring-and-managing-networking

By default, NetworkManager on Red Hat Enterprise Linux (RHEL) 8 dynamically updates the /etc/resolv.conf file with the DNS settings from active NetworkManager connection profiles. This section describes different options on how to disable this feature to manually configure DNS settings in /etc/resolv.conf.

31.1. Disabling DNS processing in the NetworkManager configuration

This section describes how to disable DNS processing in the NetworkManager configuration to manually configure the /etc/resolv.conf file.

Procedure

  1. As the root user, create the /etc/NetworkManager/conf.d/90-dns-none.conf file with the following content by using a text editor: [main] dns=none
  2. Reload the NetworkManager service: # systemctl reload NetworkManagerNote After you reload the service, NetworkManager no longer updates the /etc/resolv.conf file. However, the last contents of the file are preserved.
  3. Optionally, remove the Generated by NetworkManager comment from /etc/resolv.conf to avoid confusion.

Verification steps

  1. Edit the /etc/resolv.conf file and manually update the configuration.
  2. Reload the NetworkManager service: # systemctl reload NetworkManager
  3. Display the /etc/resolv.conf file: # cat /etc/resolv.conf If you successfully disabled DNS processing, NetworkManager did not override the manually configured settings.

Additional resources

  • For further details, see the description of the dns parameter in the NetworkManager.conf(5) man page.

31.2. Replacing /etc/resolv.conf with a symbolic link to manually configure DNS settings

NetworkManager does not automatically update the DNS configuration if /etc/resolv.conf is a symbolic link. This section describes how to replace /etc/resolv.conf with a symbolic link to an alternative file with the DNS configuration.

Prerequisites

  • The rc-manager option is not set to file. To verify, use the NetworkManager --print-config command.

Procedure

  1. Create a file, such as /etc/resolv.conf.manually-configured, and add the DNS configuration for your environment to it. Use the same parameters and syntax as in the original /etc/resolv.conf.
  2. Remove the /etc/resolv.conf file: # rm /etc/resolv.conf
  3. Create a symbolic link named /etc/resolv.conf that refers to /etc/resolv.conf.manually-configured: # ln -s /etc/resolv.conf.manually-configured /etc/resolv.conf

Additional resources

  • For details about parameters you can set in /etc/resolv.conf, see the resolv.conf(5) man page.
  • For further details about why NetworkManager does not process DNS settings if /etc/resolv.conf is a symbolic link, see the description of the rc-manager parameter in the NetworkManager.conf(5) man page.

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