network does not works on a bash shell inside the new pod

kakhavk

Hello
I am learning kubernetes on LFS258 course and there is example when need to run apt-get update from shell inside te new pod
student@lfs458-node-1a0a:~$ kubectl exec -it thirdpage-5cf8d67664-zcmfh -- /bin/bash
root@thirdpage-5cf8d67664-zcmfh:/# apt-get update

but when runnig command apt-get update it cannot conect to server

Err:1 http://security.debian.org/debian-security stretch/updates InRelease
Temporary failure resolving 'security.debian.org'
Err:2 http://deb.debian.org/debian stretch InRelease
Temporary failure resolving 'deb.debian.org'
Err:3 http://deb.debian.org/debian stretch-updates InRelease
Temporary failure resolving 'deb.debian.org'
Reading package lists... Done

serewicz

Ah, I had hoped the ping command was also in the container. You could deploy a different container using a full OS like Ubuntu to further troubleshoot, but that will take a lot of resources. What does the containers /etc/resolv.conf file show as a nameserver? (cat /etc/resolv.conf)

serewicz

Great! Glad to hear that worked. DNS is an area of much change and growth with Kubernetes and there are several settings which change the name resolution order.

Cheers,

serewicz

Hello,

This looks to be a DNS issue. Each of the attempts to update APT show "failure resolving" as the issue. From the same container can you ping an exterior IP address or name? Please try to ping 4.2.2.2 and some site like linux.com. If these also fail it indicates that the issue is with DNS instead of the container.
To troubleshoot the DNS issue, are you using an online provider or using VirtualBox? From where you are running kubectl, do you find any issues with access to the outside world? Do you have any firewalls in place which could prevent access from the container to the outside world?

Regards,

kakhavk

Thank for answer!
Yes I have nstalled ubuntu 16 on virtualbox
firewall is disabled
network is in bridge mode so ip addres is in same type as physicalcomputer
when I am runnig ping it seems that there is not ping installed in pod's environment

hi@lfs258-node-1a0a:~$ kubectl exec -it thirdpage-7c9b56bfdd-4pmhr -- /bin/bash

root@thirdpage-7c9b56bfdd-4pmhr:/# ping
bash: ping: command not found

kakhavk

cat command works and gets:

root@thirdpage-7c9b56bfdd-4pmhr:/# cat /etc/resolv.conf
nameserver 10.96.0.10
search default.svc.cluster.local svc.cluster.local cluster.local
options ndots:5

kakhavk

Oh yes I fixed it
Thanks for helping, I added with command "echo nameserver 8.8.8.8 > /etc/resolv.conf"

serewicz

On your system which node has 10.96.0.10 as an IP? If it is one of your instances, what does that instance show for /etc/resolv.conf?

anjireddy1991

root@master:~# kubectl exec nginx -it -- /bin/bash
root@nginx:/# cat /etc/resolv.conf
search default.svc.cluster.local svc.cluster.local cluster.local
nameserver 10.96.0.10
options ndots:5
root@nginx:/# ping 4.2.2.2
bash: ping: command not found
root@nginx:/# "echo nameserver 8.8.8.8 > /etc/resolv.conf"
bash: echo nameserver 8.8.8.8 > /etc/resolv.conf: No such file or directory
root@nginx:/# echo nameserver 8.8.8.8 > /etc/resolv.conf
root@nginx:/# apt update -y
Err:1 http://deb.debian.org/debian bullseye InRelease
Temporary failure resolving 'deb.debian.org'
0% [Connecting to deb.debian.org]

anjireddy1991

root@master:~# kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx 1/1 Running 1 (87m ago) 96m 10.44.0.1 worker
root@master:~# kubectl get node -o wide
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
master Ready control-plane 26h v1.26.1 192.168.122.31 Ubuntu 20.04.5 LTS 5.15.0-58-generic containerd://1.6.15
worker Ready 25h v1.26.1 192.168.122.226 Ubuntu 20.04.5 LTS 5.15.0-58-generic containerd://1.6.15
root@master:~#

root@master:~# kubectl exec nginx -it -- /bin/bash
root@nginx:/# cat /etc/resolv.conf
search default.svc.cluster.local svc.cluster.local cluster.local
nameserver 10.96.0.10
options ndots:5
root@nginx:/# ping 4.2.2.2
bash: ping: command not found
root@nginx:/# "echo nameserver 8.8.8.8 > /etc/resolv.conf"
bash: echo nameserver 8.8.8.8 > /etc/resolv.conf: No such file or directory
root@nginx:/# echo nameserver 8.8.8.8 > /etc/resolv.conf
root@nginx:/# apt update -y
Err:1 http://deb.debian.org/debian bullseye InRelease
Temporary failure resolving 'deb.debian.org'
Err:2 http://deb.debian.org/debian-security bullseye-security InRelease
Temporary failure resolving 'deb.debian.org'
Err:3 http://deb.debian.org/debian bullseye-updates InRelease
Temporary failure resolving 'deb.debian.org'
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
All packages are up to date.
W: Failed to fetch http://deb.debian.org/debian/dists/bullseye/InRelease Temporary failure resolving 'deb.debian.org'
W: Failed to fetch http://deb.debian.org/debian-security/dists/bullseye-security/InRelease Temporary failure resolving 'deb.debian.org'
W: Failed to fetch http://deb.debian.org/debian/dists/bullseye-updates/InRelease Temporary failure resolving 'deb.debian.org'
W: Some index files failed to download. They have been ignored, or old ones used instead.
root@nginx:/#

fazlur.khan

If you have VPN running, stop it and try again. It worked for me ...