This version of libnss-pool plugin is not production quality. It was developed only for joy, just to proove the possibility of the username and uid/gid assignment on getpwnam call. For the potential use case description please check my blog post.
#What is the functionality of pool service?
The general idea behind the pool service is to use uid's from a predefined pool as a precofigured set of accounts with yet unknown names, so up to the number of preconfigured accounts getpwnam() calls, happening as a result of getent passwd username orsu will not fail but will return struct passwd results matching the name provided as getpwnam argument with the uid,gid,gecos,dir,shell details preconfigured for the used pool.
#How to use it?
Simply compile like specified for nsswitch libraries:
gcc -fPIC -Wall -shared -o libnss_pool.so -Wl,-soname,libnss_pool.so libnss_pool.c
and copy the .so file to the location used on your system, for Centos 7 it can be for instance /usr/lib64:
cp ./libnss_pool.so /usr/lib64/
and add it to passwd database configuration of nsswitch.conf:
[root@localhost ~]# grep passwd /etc/nsswitch.conf
passwd: files pool sss