Err:1 http://deb.debian.org/debian buster InRelease
  Temporary failure resolving 'deb.debian.org'
Err:2 http://security.debian.org/debian-security buster/updates InRelease
  Temporary failure resolving 'security.debian.org'
Err:3 http://deb.debian.org/debian buster-updates InRelease
  Temporary failure resolving 'deb.debian.org'
Reading package lists... Done
Building dependency tree
Reading state information... Done
All packages are up to date.
W: Failed to fetch http://deb.debian.org/debian/dists/buster/InRelease  Temporary failure resolving 'deb.debian.org'
W: Failed to fetch http://security.debian.org/debian-security/dists/buster/updates/InRelease  Temporary failure resolving 'security.debian.org'
W: Failed to fetch http://deb.debian.org/debian/dists/buster-updates/InRelease  Temporary failure resolving 'deb.debian.org'
W: Some index files failed to download. They have been ignored, or old ones used instead.