Inside Linux Not (Linux web host) much to it -all operations
Inside Linux Not much to it -all operations should be this easy! The ps x command is executed to verify the existence of the ypserv daemon. Notice that it is running as a background process because there is no controlling terminal. Normally, the ypserv daemon is executed at system startup. The process continues to run on an NIS server machine that maintains a complete NIS database. At startup, or when the process receives the SIGHUP signal, ypserv will parse the /etc/ypserv.conf file for configuration information. The ypserv.conf Configuration File The ypserv.conf file is a typical Linux configuration file that contains options for ypserv. The file is normally found in the /var/yp directory but may also be found in the /etc directory. It also contains a list of rules for host and map access for the ypserv and rpc.ypxfrd daemons. The ypserv and rpc.ypxfrd daemons will read this file at startup or if they receive a SIGHUP signal. There should be only one entry per line. If the entry is an option line, the format is as follows: option: [yes | no] If the entry is an access rule, the format is as follows: host:map:security:mangle[:field] If any rules exist, they are tried one at a time. If a match is not found, access to a map is allowed. Table 11.3 lists the options available to the ypserv.conf file. Table 11.3. Options for the ypserv.conf File Option Description dns If this option is specified, the NIS server will query nameserver for hostnames that are not found in the hosts.* maps. The default is no. xfr_check_port This option tells the NIS master server that it must run on a port less than 1024. The default is yes. Table 11.4 describes the fields used for the access rules. Table 11.4. Field Descriptions for Access Rules in ypserv.conf Option Description host IP address. Wildcards are allowed. Examples are 131.234. = 131.234.0.0/255.255.0.0, and 131.234.214.0/255.255.254.0. map Identifies the name of the map, or you can use an asterisk for all maps. security The choices are: none, port, deny, and des. The option none always allows access. Mangle the passwd field if so configured; default is not to mangle. The option port allows access if the port is less than 1024. If mangle is not set, do not allow access. If mangle is yes, allow access and mangle the passwd field. The option deny is used to deny access to this map. The option des requires DES authentication. mangle The possible values are yes or no. If yes, the field entry is mangled. field Determines the field that should be mangled. The default is the second field. NOTE Some of the options mentioned in Table 11.4 use the term mangle. This means the field is replaced by x if the port check reveals that the request originated from an unprivileged user. Do not rely on the access rules to provide robust security. The access rules might slow down a cracker, but they will not stop him. page 204
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