映射表

passwd: /etc/passwd --> passwd.byname --> passwd.byuid .

group: /etc/group --> group.byname --> group.bygid.

hosts: /etc/hosts --> hosts.byname --> hosts.byaddr.

ethers: /etc/ethers --> ethers.byname --> ethers.byaddr (RARP).

networks: /etc/networks --> networks.byaddr --> ethers.byname .

protocols: /etc/protocols --> protocols.bynumber --> protocols.byname .

rpc: /etc/rpc --> rpc.byname --> rpc.bynumber.

services: /etc/services --> services.byname --> services.bynumber .

netgroup: --> netgroup, netgroup.byhost, netgroup.byuser.

aliases: /etc/aliases --> mail.aliases.