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diff --git a/blog/2020-08-22-redirect-github-pages.org b/blog/2020-08-22-redirect-github-pages.org deleted file mode 100644 index bd86a26..0000000 --- a/blog/2020-08-22-redirect-github-pages.org +++ /dev/null @@ -1,120 +0,0 @@ -#+date: 2020-08-22 -#+title: Redirect GitHub Pages from Subdomain to the Top-Level Domain - -* 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: - -#+BEGIN_SRC 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. -#+END_SRC - -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): - -#+BEGIN_SRC 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/ -#+END_SRC - -This way GitHub Pages servers know which user website to serve. - -#+BEGIN_QUOTE -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=. -#+END_QUOTE - -** 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: - -#+BEGIN_QUOTE -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. -#+END_QUOTE - -* References: - -1. [[https://docs.github.com/en/github/working-with-github-pages/configuring-a-custom-domain-for-your-github-pages-site][Setting up a custom domain with GitHub Pages]] -2. [[https://docs.github.com/en/github/working-with-github-pages/troubleshooting-custom-domains-and-github-pages][My custom domain isn't working]] -3. [[https://serverfault.com/questions/589370/cannot-access-my-github-pages-website-by-ip-address][Cannot access my GitHub Pages website by IP Address]] -4. [[https://stackoverflow.com/questions/23375422/how-do-i-set-up-github-pages-to-redirect-dns-requests-from-a-subdomain-e-g-www][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)?]] |