2 W: Some index files failed to download. They have been ignored, or old ones used instead

Question

find /etc/apt -name '*.list' -exec bash -c 'echo -e "\n$1\n"; cat -n "$1"' _ '{}' \;

etc/apt/sources.list

 1  #deb cdrom:[Ubuntu 19.04 _Disco Dingo_ - Release amd64 (20190416)]/ disco main restricted
 2  
 3  # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
 4  # newer versions of the distribution.
 5  deb http://us.archive.ubuntu.com/ubuntu/ disco main restricted
 6  # deb-src http://us.archive.ubuntu.com/ubuntu/ disco main restricted
 7  
 8  ## Major bug fix updates produced after the final release of the
 9  ## distribution.
10  deb http://us.archive.ubuntu.com/ubuntu/ disco-updates main restricted
11  # deb-src http://us.archive.ubuntu.com/ubuntu/ disco-updates main restricted
12  
13  ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
14  ## team. Also, please note that software in universe WILL NOT receive any
15  ## review or updates from the Ubuntu security team.
16  deb http://us.archive.ubuntu.com/ubuntu/ disco universe
17  # deb-src http://us.archive.ubuntu.com/ubuntu/ disco universe
18  deb http://us.archive.ubuntu.com/ubuntu/ disco-updates universe
19  # deb-src http://us.archive.ubuntu.com/ubuntu/ disco-updates universe
20  
21  ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu 
22  ## team, and may not be under a free licence. Please satisfy yourself as to 
23  ## your rights to use the software. Also, please note that software in 
24  ## multiverse WILL NOT receive any review or updates from the Ubuntu
25  ## security team.
26  deb http://us.archive.ubuntu.com/ubuntu/ disco multiverse
27  # deb-src http://us.archive.ubuntu.com/ubuntu/ disco multiverse
28  deb http://us.archive.ubuntu.com/ubuntu/ disco-updates multiverse
29  # deb-src http://us.archive.ubuntu.com/ubuntu/ disco-updates multiverse
30  
31  ## N.B. software from this repository may not have been tested as
32  ## extensively as that contained in the main release, although it includes
33  ## newer versions of some applications which may provide useful features.
34  ## Also, please note that software in backports WILL NOT receive any review
35  ## or updates from the Ubuntu security team.
36  deb http://us.archive.ubuntu.com/ubuntu/ disco-backports main restricted universe multiverse
37  # deb-src http://us.archive.ubuntu.com/ubuntu/ disco-backports main restricted universe multiverse
38  
39  ## Uncomment the following two lines to add software from Canonical's
40  ## 'partner' repository.
41  ## This software is not part of Ubuntu, but is offered by Canonical and the
42  ## respective vendors as a service to Ubuntu users.
43  # deb http://archive.canonical.com/ubuntu disco partner
44  # deb-src http://archive.canonical.com/ubuntu disco partner
45  
46  deb http://security.ubuntu.com/ubuntu disco-security main restricted
47  # deb-src http://security.ubuntu.com/ubuntu disco-security main restricted
48  deb http://security.ubuntu.com/ubuntu disco-security universe
49  # deb-src http://security.ubuntu.com/ubuntu disco-security universe
50  deb http://security.ubuntu.com/ubuntu disco-security multiverse
51  # deb-src http://security.ubuntu.com/ubuntu disco-security multiverse
52  
53  # This system was installed using small removable media
54  # (e.g. netinst, live or single CD). The matching "deb cdrom"
55  # entries were disabled at the end of the installation process.
56  # For information about how to configure apt package sources,
57  # see the sources.list(5) manual.

While I do t@ubuntu:/etc/apt$ sudo apt-get update

[sudo] password for t: 
Err:1 http://security.ubuntu.com/ubuntu disco-security InRelease            
  Temporary failure resolving 'security.ubuntu.com'
Err:2 http://us.archive.ubuntu.com/ubuntu disco InRelease                   
  Temporary failure resolving 'us.archive.ubuntu.com'
Err:3 http://us.archive.ubuntu.com/ubuntu disco-updates InRelease
  Temporary failure resolving 'us.archive.ubuntu.com'
Err:4 http://us.archive.ubuntu.com/ubuntu disco-backports InRelease
  Temporary failure resolving 'us.archive.ubuntu.com'
Reading package lists... Done           
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/disco/InRelease  Temporary failure resolving 'us.archive.ubuntu.com'
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/disco-updates/InRelease  Temporary failure resolving 'us.archive.ubuntu.com'
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/disco-backports/InRelease  Temporary failure resolving 'us.archive.ubuntu.com'
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/disco-security/InRelease  Temporary failure resolving 'security.ubuntu.com'
W: Some index files failed to download. They have been ignored, or old ones used instead.

All these are coming on Ubuntu 19.04 64 bit running in Vmware environment. What should I do to resolve them?