Why can't apt resolve names?

Question

Like a bunch of other questions, I can't run apt-get update sometimes. Restarting or waiting for a while makes the problem go away. I never have issues pinging or visiting the respective URLs in a browser.

I've tried every up-voted answer to no avail. What is apt doing that is so different to ping or my browser? For example, when I run apt-get update I see this:

Err:1 https://download.docker.com/linux/ubuntu xenial InRelease
  Could not resolve host: download.docker.com
Err:2 https://deb.opera.com/opera-stable stable InRelease
  Could not resolve host: deb.opera.com
Err:3 http://ppa.launchpad.net/danielrichter2007/grub-customizer/ubuntu xenial InRelease
  Could not resolve 'ppa.launchpad.net'
Err:4 http://ppa.launchpad.net/saiarcot895/myppa/ubuntu xenial InRelease
  Could not resolve 'ppa.launchpad.net'
Err:5 http://ppa.launchpad.net/yannubuntu/boot-repair/ubuntu xenial InRelease
  Could not resolve 'ppa.launchpad.net'
Err:6 http://repository.spotify.com stable InRelease
  Could not resolve 'repository.spotify.com'
Err:7 http://dl.google.com/linux/chrome/deb stable InRelease
  Could not resolve 'dl.google.com'
Err:8 http://archive.ubuntu.com/ubuntu xenial InRelease
  Could not resolve 'archive.ubuntu.com'
Err:9 http://archive.ubuntu.com/ubuntu xenial-updates InRelease
  Could not resolve 'archive.ubuntu.com'
Err:10 http://archive.ubuntu.com/ubuntu xenial-backports InRelease
  Could not resolve 'archive.ubuntu.com'
Err:11 http://archive.ubuntu.com/ubuntu xenial-security InRelease
  Could not resolve 'archive.ubuntu.com'
Reading package lists... Done
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial/InRelease  Could not resolve 'archive.ubuntu.com'
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-updates/InRelease  Could not resolve 'archive.ubuntu.com'
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-backports/InRelease  Could not resolve 'archive.ubuntu.com'
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-security/InRelease  Could not resolve 'archive.ubuntu.com'
W: Failed to fetch https://download.docker.com/linux/ubuntu/dists/xenial/InRelease  Could not resolve host: download.docker.com
W: Failed to fetch http://ppa.launchpad.net/danielrichter2007/grub-customizer/ubuntu/dists/xenial/InRelease  Could not resolve 'ppa.launchpad.net'
W: Failed to fetch http://dl.google.com/linux/chrome/deb/dists/stable/InRelease  Could not resolve 'dl.google.com'
W: Failed to fetch https://deb.opera.com/opera-stable/dists/stable/InRelease  Could not resolve host: deb.opera.com
W: Failed to fetch http://ppa.launchpad.net/saiarcot895/myppa/ubuntu/dists/xenial/InRelease  Could not resolve 'ppa.launchpad.net'
W: Failed to fetch http://repository.spotify.com/dists/stable/InRelease  Could not resolve 'repository.spotify.com'
W: Failed to fetch http://ppa.launchpad.net/yannubuntu/boot-repair/ubuntu/dists/xenial/InRelease  Could not resolve 'ppa.launchpad.net'
W: Some index files failed to download. They have been ignored, or old ones used instead.

Running ping download.docker.com:

PING d2h67oheeuigaw.cloudfront.net (52.85.41.233) 56(84) bytes of data.
64 bytes from server-52-85-41-233.mel50.r.cloudfront.net (52.85.41.233): icmp_seq=1 ttl=251 time=18.8 ms
64 bytes from server-52-85-41-233.mel50.r.cloudfront.net (52.85.41.233): icmp_seq=2 ttl=251 time=18.4 ms
64 bytes from server-52-85-41-233.mel50.r.cloudfront.net (52.85.41.233): icmp_seq=3 ttl=251 time=19.5 ms

And visiting the page in my browser works fine. How can I make apt-get "just work"?

Here is the contents of my /etc/apt/resolv.conf:

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 127.0.1.1
search home.gateway

Solution 1

Run this command from terminal and you could use apt and apt-get normally in the future :)

echo 'Acquire::ForceIPv4 "true";' | sudo tee /etc/apt/apt.conf.d/99force-ipv4

Solution 2

If /etc/atp/apt.conf exists, make a copy of the file and then edit the original to comment out the following line (if not behind a proxy server):

Acquire::http::Proxy "http://proxyaddress:proxyport";

Comments

[Admin]

try apt-get -o Acquire::ForceIPv4=true update

[Admin]

Does /etc/apt/apt.conf exist and if so, is it using a proxy? A quick fix would be to add the lookup info for those servers in /etc/hosts. The down side of that approach would be if the IPs of those servers ever changes.

[Admin]

@jones0610 it exists. Why can't apt just resolve hostnames like any other applicaton?

[Admin]

@Arun that first one seems to work. Why is that?

[Admin]

@arman I "think" it gets created if, at some point, you connect the machine to a proxy server. I've seen this problem before and the addition of apt.conf becomes permanent. I "think" you can safely rename it which should solve your problem. Or make a copy of it and edit the original, commenting out the proxy line.

[mikezter]

do you know the underlyig problem? why does ipv6 not work?