[Docker] Error: Can’t not access internet from container in Ubuntu 14.04

When I use Docker, I create container from image (Ex: Ubuntu:14.04) and ssh to this container by command:

docker run -it <image_id> bash

When I ssh to container, I used command ping google.com 

but I get error:  ping: unknown host google.com

To fix it, I have 2 solutions, but first, you must get DNS of your machine by command

nm-tool 

Result in my machine:

DNS: 192.168.30.29
DNS: 192.168.30.66

=> I’ll use DNS: 192.168.30.29

1. Solution 1

– Go to file sudo nano /etc/docker/daemon.json and add your DNS to this file

{
    "dns": ["192.168.30.29", "8.8.8.8", "8.8.4.4"]
}

Save it and restart docker by command: sudo service docker restart

2. Solution 2

solution 1- Go to file sudo nano /etc/default/docker, uncomment and add your DNS to this row:

DOCKER_OPTS="--dns 192.168.30.29 --dns 8.8.8.8 --dns 8.8.4.4 --ip-masq=true"

Save it and restart docker by command: sudo service docker restart

If when restart, you get error:

docker stop/waiting
start: Job failed to start

or error:

stop: Unknown instance: 
start: Job failed to start

– You shoud go to file sudo nano /etc/default/docker, and comment row

DOCKER_OPTS="--dns 192.168.30.29 --dns 8.8.8.8 --dns 8.8.4.4 --ip-masq=true"

and try again with solution 1.

==> After you try adding DNS successfully, you can ssh to container and run

ping google.com once again. And this is my result after try fixing with solution 1

root@2beb109bc7b3:~# ping google.com
PING google.com (113.171.239.123) 56(84) bytes of data.
64 bytes from static.vnpt.vn (113.171.239.123): icmp_seq=1 ttl=56 time=1.06 ms
64 bytes from static.vnpt.vn (113.171.239.123): icmp_seq=2 ttl=56 time=1.51 ms
64 bytes from static.vnpt.vn (113.171.239.123): icmp_seq=3 ttl=56 time=2.32 ms
64 bytes from static.vnpt.vn (113.171.239.123): icmp_seq=4 ttl=56 time=1.19 ms
64 bytes from static.vnpt.vn (113.171.239.123): icmp_seq=5 ttl=56 time=1.55 ms
.....

That’s all. Thank you for reading. 🙂

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[Docker] Error Cannot connect to the Docker daemon. Is the docker daemon running on this host?

In Ubuntu, when I install Docker successfully, I try running with command:

docker images #show all images in local

but it has error

Cannot connect to the Docker daemon. Is the docker daemon running on 
this host?

because it doesn’t have permission of root. I can run it by command

sudo docker images

Another way, we can config it to needn’t use sudo

  • Step 1: go to /var/run

    cd /var/run
  • Step 2: Add permission for file docker.sock
    sudo chmod -R 776 docker.sock
    

And now, we can use command docker images for shorter code