I have only recently installed ubuntu 18.04 on one of my machines as a means of becoming competent in using a Linux system, when I attempt to use the command

sudo apt-get update 

I receive an error message saying

Could not resolve 'security.ubuntu.com'

and likewise for all four of the main repositories. If it is necessary for me to print the exact output just let me know..


I was able to update upon reboot of my system, however only partially, receiving the following error message in my output:

E: The repository 'http://security.ubuntu.com bionic-security Release' does not have a Release file.

N: Updating from such a repository can't be done securely, and is therefore disabled by default.

N: See apt-secure(8) manpage for repository creation and user configuration details.

  • 2
    In general, one should show the error messages (properly formatted, in a Edit ( askubuntu.com/posts/1105366/edit ) to your post, so that more knowledgable users can try to diagnose the problem. So far, your complaint looks like a networking or routing problem, but without the actual messages, no one can tell. – waltinator Dec 29 '18 at 14:00
  • ok thanks very much I will reformat things appropriately and edit the post accordingly – Adam Dec 29 '18 at 14:02

Could not resolve 'security.ubuntu.com means the system cannot find to which IP address security.ubuntu.com is pointing to. This means your DNS is broken.

To fix it, make sure of a few things:

  1. Your linux has an ip address.
  2. If you have an ip address, you are connected to the internet (ping to
  3. If you can ping to, try ping to google.com
  4. If step 2 worked but step 3 didn`t, you need to fix your dns. Make sure that in the file /etc/resolv.conf there's a valid dns server.

I'm using umbrella DNS servers:

cat /etc/resolv.conf
  • 1
    Some folks with this problem are on school or corporate networks that require the use of network login or apt proxies. – user535733 Dec 29 '18 at 14:12
  • ok thanks I do believe I must be connected to the internet seeing that I was able to complete a partial update as I have described in what I appended to this post, I will check my dns as you have mentioned to see if this maybe to the new problem I am encountering – Adam Dec 29 '18 at 14:51
  • @user535733 sorry are there other alternatives to google for step 3? – Adam Jan 15 '19 at 8:44
  • @Jean Novak sorry are there other alternatives to google for step 3? – Adam Jan 15 '19 at 8:45
  • Of course there are alternatives. Millions of them. The suggestion for is simply because it's easy to remember and certain to be up. Look up and ping as many alternatives you wish. There are two alternatives right there in the answer already. – user535733 Jan 15 '19 at 10:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.