To make Unbound (a validating, recursive, and caching DNS resolver) alias a hostname on Debian, you typically want to create a DNS alias (also known as a CNAME record) or a host override (for local resolution). Here’s how you can do it:

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1. Edit the Unbound Configuration File

Open the Unbound configuration file for editing:

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sudo nano /etc/unbound/unbound.conf.d/aliases.conf

If the file doesn’t exist, create it.

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2. Add a Local Zone for the Alias

To alias a hostname (e.g., alias.example.com to real.example.com), add a local-zone and local-data entry:

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server:
    # Alias 'alias.example.com' to 'real.example.com'
    local-zone: "alias.example.com" redirect
    local-data: "alias.example.com. IN CNAME real.example.com."

• local-zone: "alias.example.com" redirect
  This tells Unbound to treat alias.example.com as a local zone and redirect queries for it.
• local-data: "alias.example.com. IN CNAME real.example.com."
  This creates a CNAME record, aliasing alias.example.com to real.example.com.

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3. Restart Unbound

After saving the file, restart Unbound to apply the changes:

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sudo systemctl restart unbound

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4. Verify the Alias

Test the alias using dig or nslookup:

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dig alias.example.com @127.0.0.1

or

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nslookup alias.example.com 127.0.0.1

You should see the alias resolving to the target hostname.

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Alternative: Using /etc/hosts for Local Resolution

If you only need the alias to work locally (not for other machines querying your Unbound server), you can also add an entry to /etc/hosts:

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sudo nano /etc/hosts

Add a line like this:

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192.0.2.1 alias.example.com

(Replace 192.0.2.1 with the actual IP of real.example.com.)

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Notes

• If you want the alias to work for all clients querying your Unbound server, use the Unbound configuration method.
• If you only need it for the local machine, /etc/hosts is simpler.
• Ensure Unbound is configured to listen on the correct interfaces and that your system or network is set to use Unbound as its DNS resolver.