Name Service Switch (nss(5)) plugin for user-configurable hosts lookup (hosts(5)).

0. Build:
   cargo build --release

1. Copy libnss_userhosts.so to /lib/x86_64-linux-gnu/:
   sudo cp target/release/libnss_userhosts.so /lib/x86_64-linux-gnu/libnss_userhosts.so)

2. Notify ldconfig(8) of the change and add the .so.2 symlink:
   sudo ldconfig -n /lib/x86_64-linux-gnu

3. Add userhosts to the hosts line in nsswitch.conf(5):
   hosts: userhosts files mdns4_minimal [NOTFOUND=return] dns

Create and populate $HOME/hosts as you would /etc/hosts. Alternatively, set USERHOSTS_FILE to the path of a file you would like to use instead of $HOME/hosts.

The environment variable USERHOSTS can also be set to introduce hosts(5) entries. In this case, split multiple entries with a ; (semicolon):

$ USERHOSTS="127.1.1.1 one; 127.2.2.2 two" getent hosts one two
127.1.1.1       one
127.2.2.2       two