Docker apt-get update fails

Question

Can somebody help me get apt-get working in my docker container? Whenever I try running any apt-get command in my docker container, the command fails. I\'m running Docker ve

Answer 1

$ sudo docker run -i -t --net=host ubuntu /bin/bash
# apt-get update

No errors! - Note the added --net=host.

---

Below I show how to reproduce the error.
I did the following on a clean machine having nothing but Ubuntu 18.04 installed on it.

First install docker. Copy-paste one line at a time and hit Enter after each line:

sudo apt update                         # took 11 seconds for me
sudo apt install -y apt-transport-https ca-certificates \
curl software-properties-common

The second of the two commands above (one command broken up on two lines) is optional and took ~20 seconds for me.

echo "cacert=/etc/ssl/certs/ca-certificates.crt" >> ~/.curlrc
curl -fsSL https://download.docker.com/linux/ubuntu/gpg \
| sudo apt-key add -

sudo add-apt-repository "deb [arch=amd64] https://\
download.docker.com/linux/ubuntu $(lsb_release -cs) stable"

The command above took ~7 seconds for me.

sudo apt update                         # ~3 seconds this time
sudo apt install -y docker-ce           # ~1 minute for me

Optional -- if you don't like to prefix docker with sudo every time:

sudo usermod -aG docker ${USER}

Log out and back in.
Confirm that docker is now added to your groups:

id -nG

---

Now to the core part of interest:

$ sudo docker run -it ubuntu /bin/bash  # ~10 seconds for me
# apt update                            # first Err after ~1 minute
Err:1 http://archive.ubuntu.com/ubuntu focal InRelease
  Connection failed [IP: 91.189.88.152 80]
Err:2 http://security.ubuntu.com/ubuntu focal-security InRelease
  Connection failed [IP: 91.189.88.152 80]
Err:3 http://archive.ubuntu.com/ubuntu focal-updates InRelease
  Connection failed [IP: 91.189.88.152 80]
Err:4 http://archive.ubuntu.com/ubuntu focal-backports InRelease
  Connection failed [IP: 91.189.88.152 80]
...
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/focal/InRelease [...]
...
W: Some index files failed to download. They have been ignored, [...]

Note how I just recreated the error described by the OP!
The OP got Could not resolve 'archive.ubuntu.com',
while I got Failed to fetch http://archive.ubuntu.com.
But the root cause is the same: the docker container has no access to the internet.

I don't want to stay in this bad docker container so I hit Ctrl + D.
No wish to keep it either, so I do:

sudo docker container ps -a

which tells me that the CONTAINER ID in my case is c05ec98236f0.

I remove this container:

sudo docker container rm c05ec98236f0

Heads up for something that doesn't give me an error.

$ sudo docker run -it --net=host ubuntu bash
# apt update                            # ~7 seconds
Get:1 http://archive.ubuntu.com/ubuntu focal InRelease [265 kB]
...
Fetched 16.4 MB in 4s (4332 kB/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
3 packages can be upgraded. Run 'apt list --upgradable' to see them.

Voilà! No error!

References:
https://askubuntu.com/questions/1162163#1162198
https://www.digitalocean.com/community/tutorials/how-to-install-and-use-docker-on-ubuntu-18-04
https://stackoverflow.com/questions/3160909#31424970
https://stackoverflow.com/questions/43316376#43317607