Github Pages with a custom *sub*domain

[mtsnys]

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I have a Pages site at https://github.io/mtsnys that was working beautifully before I tried to add a custom subdomain. I've added the subdomain in Settings > Pages > Custom Domain.

It's created a CNAME file in my project repository, and at my domain host I've created a CNAME pointing to mtsnys.github.io. My understanding is that I do not need to create A records because this is a subdomain, and not an apex domain.

After doing all of this, Settings > Pages says "DNS check successful." But when I visit my (tnp.mtsnys.org), it redirects to mtsnys.github.io and gives me a 404 page with the message "There isn't a GitHub Pages site here."

I'm not sure what I'm doing wrong! Anyone have ideas to help me troubleshoot?

[khoinxd]

Issue Overview:
You've encountered a 404 error after setting up a custom subdomain (tnp.mtsnys.org) for your GitHub Pages site. Despite following the necessary steps, including updating DNS settings and verifying that the DNS check was successful, your site redirects to mtsnys.github.io and displays a "There isn't a GitHub Pages site here" message.

Steps You've Taken:

1. You've added the custom subdomain (tnp.mtsnys.org) in the GitHub Pages settings.
2. You've created a CNAME record pointing tnp to mtsnys.github.io at your domain host.
3. Since this is a subdomain, not an apex domain, you've rightly avoided creating A records.
4. GitHub Pages indicates that the DNS check is successful.

My Analysis:
The 404 error typically happens when GitHub Pages can't locate a site matching your subdomain. Given that your site is located at mtsnys.github.io/theory_and_practice, the issue seems to arise from a mismatch between the subdomain and the actual site path.

Suggested Solutions:

1. Verify CNAME Configuration:

   • I recommend checking that the CNAME file in your theory_and_practice repository correctly lists tnp.mtsnys.org as the domain. This file is crucial because it tells GitHub Pages which custom domain is associated with your site.

2. Ensure Proper DNS Settings:

   • Your DNS setup seems correct, with the CNAME pointing to mtsnys.github.io. However, DNS propagation delays or hidden configurations might be causing the redirect issue. It might be helpful to double-check your DNS settings or reach out to your domain registrar to confirm everything is configured as expected.

3. Review GitHub Repository Settings:

   • Double-check that your Pages source is set to the gh-pages branch and the root directory. This ensures it correctly points to where your site content is stored, which is essential for the custom domain to work properly.

4. Consider HTTPS Configuration:

   • Although HTTPS isn't currently enforced due to the lack of a certificate, enabling HTTPS is a good idea for better security. Sometimes, configuring HTTPS can also help resolve redirection issues.

Conclusion:
The likely cause of the 404 error is a disconnect between your subdomain and the actual content location. I suggest carefully reviewing your CNAME configuration and DNS settings. If these steps don't resolve the issue, try reconfiguring the custom domain in the GitHub Pages settings to refresh the DNS and address the problem.

This approach should provide a solid foundation for resolving your issue.

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