Are you curious to know why does the error ‘curl (6) could not resolve host ubuntu’ appear?

Usually, such curl errors happen when there are problems with DNS resolvers on the server.

At Bobcares, we often get requests from our customers to fix curl (6) could not resolve host Ubuntu as part of our Server Management Services.

Today, let’s discuss why this error occurs and see how our Support Engineers fix it.

What is curl (6) could not resolve host?

Many of our customers have experienced this error ‘curl (6) could not resolve host’ while trying to connect to a webpage from the terminal.

This error mainly occurs due to a wrong DNS set up or bad settings on the server.

Also, we’ve seen this error appearing in different ways which include.

1. curl: (6) Could not resolve host: application
2. curl: (6) Could not resolve host: domain.com
3. curl: (6) Could not resolve host: google.com; Name or service not known

This essentially means the server was not able to connect to the remote host.

How we fixed the error curl (6) could not resolve host in ubuntu

At Bobcares, where we have more than a decade of expertise in managing servers, we see many customers face problems while managing a server.

Now, let’s see the major reasons for curl errors and how our Support Engineers fix this error.

1. Missing working DNS nameserver

Sometimes, users may receive a problem when trying to install packages like wget, apt-get not being able to resolve hosts.

For example, when executing a command apt-get install wget.

Users may get an error as curl#6 - "Could not resolve host: repo.xxx.com; Unknown error"

This mainly occurs when we don’t have nameservers in the /etc/resolv.conf

So, we added the following line in the file.

nameserver 8.8.8.8

Then, this fixed the error and the host started resolving.

2. Syntax error

Recently, one of our customers had a problem while executing the command curl on his terminal. He used the command as below,

curl -X 'GET https://www.mywebsite.com/Web2/PDF.aspx?page=1' \

Also, the error said Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.119 Safari/537.36 OPR/51.0.2830.26' \
curl: (6) Could not resolve host:

On checking, our Support Engineers found that the error was due to the incorrect syntax used to access the website.

So, we corrected the syntax as below. This happened as he had included space after one of the / escape sequences.

curl -X GET https://www.mywebsite.com/Web2/PDF.aspx?page=1/

Similarly, an error happened when running the following command

curl -i -H 'Content-Type: application/json' -d '{"Code":"FR","Name":"France"}' http://127.0.0.1:8080/countries

The error said Curl: (6) Could not resolve host: application.

This error was also due to the syntax error in the command. Thus, we resolved this problem editing like this in windows:

"{/"Code/":/"FR/"}"

In another case, we corrected it by deleting an extra space from the command.

curl -H Content-Type:application/json ~

Finally, this fixed the error.

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Conclusion

In short, an error curl (6) could not resolve host on ubuntu happens due to syntax error or due to the wrong DNS set up. Today, we saw how our Support Engineers assisted our customers to solve this error.