➜  ~ docker start xen_build 
xen_build
➜  ~ docker attach xen_build
root@107eadc215e9:/# apt update
Err:1 http://archive.ubuntu.com/ubuntu bionic InRelease                  
  Temporary failure resolving 'archive.ubuntu.com'
Err:2 http://security.ubuntu.com/ubuntu bionic-security InRelease        
  Temporary failure resolving 'security.ubuntu.com'
Err:3 http://archive.ubuntu.com/ubuntu bionic-updates InRelease          
  Temporary failure resolving 'archive.ubuntu.com'
Err:4 http://archive.ubuntu.com/ubuntu bionic-backports InRelease
  Temporary failure resolving 'archive.ubuntu.com'
Reading package lists... Done        
Building dependency tree       
Reading state information... Done
6 packages can be upgraded. Run 'apt list --upgradable' to see them.
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic/InRelease  Temporary failure resolving 'archive.ubuntu.com'
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic-updates/InRelease  Temporary failure resolving 'archive.ubuntu.com'
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic-backports/InRelease  Temporary failure resolving 'archive.ubuntu.com'
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/bionic-security/InRelease  Temporary failure resolving 'security.ubuntu.com'
W: Some index files failed to download. They have been ignored, or old ones used instead.
root@107eadc215e9:/# exit
exit
➜  ~ sudo systemctl stop firewalld && sudo systemctl restart docker
➜  ~ docker start xen_build 
xen_build
➜  ~ docker attach xen_build
root@107eadc215e9:/# apt update
Hit:1 http://security.ubuntu.com/ubuntu bionic-security InRelease
Hit:2 http://archive.ubuntu.com/ubuntu bionic InRelease
Get:3 http://archive.ubuntu.com/ubuntu bionic-updates InRelease [88.7 kB]
Get:4 http://archive.ubuntu.com/ubuntu bionic-backports InRelease [74.6 kB]
Fetched 163 kB in 0s (421 kB/s)                            
Reading package lists... Done
Building dependency tree       
Reading state information... Done
6 packages can be upgraded. Run 'apt list --upgradable' to see them.
root@107eadc215e9:/#