General troubleshooting
Failed to configure DNS (Linux)
This error commonly occurs on Ubuntu 22. Defguard client internally calls resolvconf to set DNS servers. The only tested backend is systemd-resolved, so make sure you use it before proceeding further (systemctl status systemd-resolved).
On newer Ubuntu distributions (23 and up) resolvconf is, by default, a symbolic link to resolvectl and this is the recommended way of interacting with the system's DNS configuration. On Ubuntu 22 the symbolic link doesn't exist and the most straightforward way to fix this issue is to manually create it:
If this fails, one may also try installing one of the packages providing the resolvconf command, like openresolv or resolvconf but this has not been tested and may possibly cause issues with systemd-resolved, so proceed at your own risk.
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