Get contents from hosts, passwd, groups even if they're in DB/LDAP/other
getent [group|hosts|networks|passwd|protocols|services] [keyword]
getent allows to get the contents of several databases in their native file format even if they are not actually in /etc. For example, if you are using a LDAP or a DB to authenticate your users, you won't find their info by catting /etc/passwd, but "getent passwd" will concatenate /etc/passwd to the LDAP/DB.
Sample Output
$ getent passwd root
root:x:0:0:root:/root:/bin/bash
$ getent services smtp
smtp 25/tcp mail
$ getent protocols l2tp
l2tp 115 L2TP