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diff --git a/content/blog/2020-08-22-redirect-github-pages.md b/content/blog/2020-08-22-redirect-github-pages.md deleted file mode 100644 index b666c20..0000000 --- a/content/blog/2020-08-22-redirect-github-pages.md +++ /dev/null @@ -1,124 +0,0 @@ -+++ -date = 2020-08-22 -title = "Redirect GitHub Pages from Subdomain to the Top-Level Domain" -description = "" -draft = false -+++ - -# Short answer - -## Step 1 - -Add a new file CNAME to your GitHub Pages repository containing only one line: -your top-level domain name. E.g.: `example.com` - -## Step 2 - -[Optional] but highly recommended - -2.1: Remove all other top-level records (prefixed with @) of type A from your -DNS configuration. - -2.2: Remove a CNAME record for the second-level domain www if it is present. - -## Step 3 - -Add these 5 entries to the very top of your DNS configuration: - -```txt -@ A 185.199.108.153 -@ A 185.199.109.153 -@ A 185.199.110.153 -@ A 185.199.111.153 -www CNAME your_github_username.github.io. -``` - -Replace `your_github_username` with your actual GitHub username. - -## Step 4 - -Wait for your DNS changes to propagate. DNS changes aren't effective -immediately. They can take up to a full day to propagate. - -# Long answer - -This issue has two sides. One is the DNS configuration itself. Another one is -the way GitHub Pages will forward HTTP requests. - -We need to know a few things to understand what GitHub is trying to say in their -documentation. - -## DNS Entry Types - -There are two types of DNS records which interest us: CNAME and A. - -`A` is also known as `Apex` or sometimes as `root entry`. It forwards requests -to a specified fixed IP address. `CNAME` entry forwards requests to a specified -URL (actual valid plain text URL, not an IP address). - -## DNS Load balancing - -GitHub has one central URL address which accepts all DNS requests for GitHub -Pages: `http://username.github.io`. That URL is resolved to different IP -addresses based on your geographical location. Website hosted on GitHub Pages is -a simple collection of `HTML`, `CSS` and `JS` files. GitHub distributes these -files to different servers across the globe. So that when your browser sends a -request from Europe, it receives data from a server in Europe. The same is valid -for the requests from Asia and the USA. - -## What GitHub is trying to say - -Since `A` records in DNS must contain IP addresses, and they must be either -`185.199.108.153` or `185.199.109.153` or `185.199.110.153` or -`185.199.111.153`, there is no way to forward requests to a server located -somewhere in Europe or Asia. Your website hosted at GitHub Pages will be -downloaded from a central GitHub Pages server. There is a minor risk that if -GitHub Pages DNS servers (`x.x.x.153`) are down for some reason, all custom -domains which use fixed GitHub Pages IP addresses will not be accessible (their -DNS requests will not be resolvable). - -That is why GitHub strongly suggests to either use a second-level domain for -your GitHub Pages (e.g. `blog.example.com`) or use a DNS service provider that -supports a record type `ALIAS` that acts as `A` record but forwards request to a -URL address (e.g. `username.github.io`) instead of a fixed IP address. - -## How GitHub Pages treats HTTP requests - -After a DNS request for `your_github_username.github.io` is resolved into an IP -address, e.g. `185.199.108.153` your browser sends an HTTP request to that -server with an HTTP header `Host`. Below are `curl` examples that load the same -website (these examples might not work if you are behind a proxy server): - -```sh -curl --header "Host: your_github_username.github.io" http://185.199.108.153/ -curl --header "Host: www.example.com" http://185.199.108.153/ -curl --header "Host: example.com" http://185.199.108.153/ -``` - -This way GitHub Pages servers know which user website to serve. - -> GitHub Pages server will automatically redirect HTTP requests to the top-level -> domain if your `CNAME` file contains `example.com` but `www.example.com` is -> requested. -> -> The same is valid if your `CNAME` file contains `www.example.com` but the -> header `Host` in the `HTTP` request contains `example.com`. - -## Why can't I add a `CNAME` record entry that accepts a top-level request (`@`) to my DNS configuration? - -Quote from the GitHub Pages documentation: - -> Warning: Do not create a CNAME record for your custom apex domain! Doing so -> may cause issues with other services, such as email, on that domain. - -## References: - -1. [Setting up a custom domain with GitHub - Pages](https://docs.github.com/en/github/working-with-github-pages/configuring-a-custom-domain-for-your-github-pages-site) -2. [My custom domain isn't - working](https://docs.github.com/en/github/working-with-github-pages/troubleshooting-custom-domains-and-github-pages) -3. [Cannot access my GitHub Pages website by IP - Address](https://serverfault.com/questions/589370/cannot-access-my-github-pages-website-by-ip-address) -4. [How do I set up GitHub Pages to redirect DNS requests from a subdomain (e.g. - www) to the top-level domain (TLD, Apex - record)?](https://stackoverflow.com/questions/23375422/how-do-i-set-up-github-pages-to-redirect-dns-requests-from-a-subdomain-e-g-www) |