Problem: "Could not resolve host" on AWS Lightsail – Domain Not Resolving Correctly

 

Problem: "Could not resolve host" on AWS Lightsail – Domain Not Resolving Correctly

Bash

$ curl -I http://mydomain.com
curl: (6) Could not resolve host: mydomain.com

Issue: 

Your Lightsail instance is accessible via its public IP but not when using your domain name. This typically happens due to:

• Missing or Incorrect DNS Records – The domain is not pointing to the Lightsail instance.
• Domain Not Configured in Lightsail DNS – The domain is registered elsewhere, but no DNS records exist in Lightsail.
• Propagation Delay – DNS changes take time to update globally.
• Incorrect Nameservers – The domain is using the wrong nameservers.

Fix: Check DNS Configuration, Update Records, and Verify Resolution

Bash

# Step 1: Check if the domain is configured in Lightsail
$ aws lightsail get-domains \
    --query "domains[].{Name:name}" \
    --output table

--------------------------------
|          GetDomains         |
--------------------------------
|  Name                       |
--------------------------------
# (No output means the domain is NOT configured)

# If missing, add the domain to Lightsail:
$ aws lightsail create-domain \
    --domain-name "mydomain.com"

# Step 1.1: Verify the domain is now listed
$ aws lightsail get-domains \
    --query "domains[].{Name:name}" \
    --output table

--------------------------------
|          GetDomains         |
--------------------------------
|  Name                       |
--------------------------------
|  mydomain.com               |
--------------------------------

# Step 2: List the DNS records for your domain
$ aws lightsail get-domain \
    --domain-name "mydomain.com" \
    --query "domain.resourceRecords" \
    --output table

--------------------------------------------------------
|                GetDomain (DNS Records)              |
--------------------------------------------------------
|  Name          |  Type   |  Value                   |
--------------------------------------------------------
# (If this is empty, no records exist)

# If no A record exists, create one pointing to the Lightsail instance
$ aws lightsail create-domain-entry \
    --domain-name "mydomain.com" \
    --domain-entry name="mydomain.com",type="A",target="54.123.45.67"

# Step 2.1: Verify DNS records after adding A record
$ aws lightsail get-domain \
    --domain-name "mydomain.com" \
    --query "domain.resourceRecords" \
    --output table

--------------------------------------------------------
|                GetDomain (DNS Records)              |
--------------------------------------------------------
|  Name          |  Type   |  Value                   |
--------------------------------------------------------
|  mydomain.com  |  A      |  54.123.45.67            |
|  www          |  CNAME  |  mydomain.com             |
--------------------------------------------------------

# Step 3: Check if your domain is using the correct Lightsail nameservers
$ dig +short NS mydomain.com

ns-123.awsdns-01.net.
ns-456.awsdns-02.org.
ns-789.awsdns-03.co.uk.

# If the output does NOT show AWS nameservers, update them 
# at your domain registrar (GoDaddy, Namecheap, etc.).

# Step 4: Verify if the domain resolves correctly
$ dig +short mydomain.com

54.123.45.67

# OR use nslookup:
$ nslookup mydomain.com

Non-authoritative answer:
Name: mydomain.com
Address: 54.123.45.67

# Step 4.1: What if the domain still doesn’t resolve?
# If the domain is still not resolving, force a DNS cache refresh:
$ sudo systemctl restart systemd-resolved  # For Linux
$ ipconfig /flushdns  # For Windows

# If DNS propagation is the issue, allow time (can take up to 24 hours).
# You can check DNS propagation using an online tool like:
# https://www.whatsmydns.net/

# If issues persist, double-check nameservers, DNS records, and SSL settings.

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