Ubuntu – /etc/hosts file not being used before DNS server query

The file /etc/nsswitch.conf will let you reconfigure the order of the name resolution. By default, the host file is the first, then the configured DNS. There could be more options.

The file /etc/hosts only lists IP addresses and hostnames (multiple names for one IP if you want)

The file /etc/resolv.conf will list the default search domains, and will also list in sequence the name servers to use.

You are doing everything right like putting the entries in /etc/hosts, server address in /etc/resolv.conf, the /etc/nsswitch.conf looks good too.

The problem you are having is due to the understanding of a very specific term "nameserver". All the commands used to resolve IP address to hostname and vice versa used the nameserver addresses from /etc/resolv.conf unless mentioned explicitly. You have put nameserver 127.0.0.1 which is not a valid name server because it is not configured as a nameserver. It is there because of dnsmasq which acts as a DNS cacher (and DHCP server) but host, dig, nslookup take data from a valid, configured nameserver only.

As the host, nslookup, dig commands will use the "nameserver" mentioned in /etc/resolv.conf (unless specified), hostname resolution will not work using these in your case. Although the programs that use /etc/nsswitch.conf or read /etc/hosts will resolve the hostname to IP addresses and vice versa.

If you want to resolve hostnames from /etc/hosts the you need to use getent. For example to resolve "node1-VirtualBox", you need the following command :

getent hosts node1-VirtualBox