Solve Let\\’s Encrypt\\”DNS problem: NXDOMAIN looking up A..\\” configuration problem

In the early years, if our website needed to configure an SSL certificate, including the free Let\\’s Encrypt certificate, it still required a little technical content. After all, the installation and configuration according to the official steps was cumbersome and difficult for some users. But now many one-click scripts and WEB panels provide quick installation of certificates, especially those that support Let\\’s Encrypt certificates, which can achieve one-click installation.

Generally, as long as we first resolve the domain name where Let\\’s Encrypt certificate is installed to the current server and it takes effect, we can install it when adding a site. But today, a netizen saw an error message “DNS problem: NXDOMAIN looking up A for…..\\” during the wizard process of installing the Let’s Encrypt certificate.

So Snail also got the server information of this netizen, and then tried to add the site according to this one-click package command and install the SSL certificate at the same time. There was also the prompt in the picture above. The solution process is recorded below:

First, based on online methods

Some articles on the Internet mentioned that it is a server DNS cache problem. It is necessary to install nscd and then update the server cache, but it does not have this effect after use.

Second, check for parsing issues

Before adding a domain name, we need to resolve the domain name A record to the server IP address, and we need to wait for it to take effect before automatically verifying it. If the parsing is unsuccessful, the above error will occur. However, I detected through the PING tool that both WWW without the current domain name and WWW without the current domain name are resolved to the server.

Third, server internal PING test

From most external nodes, including the local PING test, we can see that the current domain name WWW and without WWW are resolved. Here, directly use PING to test the current server. It is found that the domain name resolution without WWW is 127.0.0.1, which is not the same as WWW. PING shows the corresponding server IP address. It seems that the problem lies here.

Fourth, only add WWW sites

It seems that the problem is that there is no WWW, so the solution is not to find the cause. When adding a site directly, only add the WWW domain name, and you can install the Let\\'s Encrypt certificate. Then after the installation is completed, modify the conf configuration file to manually add the WWW domain name without it, and set 301 to force jump. Problem solve.

In summary, this problem generally occurs in domain name resolution, because when automatically installing the Let\\’s Encrypt certificate, it is necessary to verify domain name ownership through resolution.

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