dns

La commande 'netcd' permet d'utiliser une mise en cache pour les services de résolution de noms( DNS, NIS...)

Cela ne change en rien les méthodes de résolution mais peut éviter certaines communications réseaux inutiles.

Il est possible de lancer le service directement par la commande 'netcd' ou par le gestionnaire de ressource ( 'startsrc -s netcd')

Une méthode d'activation du Cache DNS consiste à effectuer les opérations suivantes :

- Créer un fichier /etc/netcd.conf avec comme contenu ' cache dns hosts 128 60'

- Activer le service maintenant et pour les prochains reboot : '/usr/sbin/chrctcp -S -a netcd'

Lorsque l'on souhaite vider le Cache( Flush), on peut utiliser la commande '/usr/sbin/netcdctrl -f'

netcd Daemon

Purpose

       Launches the network caching (netcd) daemon.

Syntax

       netcd [ -l file ] [ -c file ] [ -d level ] [ -h ]

Description

       The netcd daemon reduces the time taken by the local, DNS, NIS, NIS+ and user loadable module services to respond to a query
       by caching the response retrieved from resolvers.

       When the netcd daemon is running and configured for a resolver (for example, DNS) and a map (for example, hosts), the
       resolution is first made using the cached answers. If it fails, the resolver is called and the response is cached by the
       netcd daemon.

       The type of the maps that are supported for the local, NIS, NIS+ and user loadable modules resolutions are hosts, services,
       networks, protocols and netgroup. For DNS, hosts is the only type of map that you can use.

       In addition, for the specific case of Yellow Pages, the following maps have been added:
       *    passwd.byname
       *    passwd.byuid
       *    group.byname
       *    group.bygid
       *    netid.byname
       *    passwd.adjunct.byname

       You can use a configuration file to specify the resolvers and maps that you want to configure. You can also set other netcd
       parameters using this file. By default, the configuration file used is the /etc/netcd.conf file. You can change the path of
       this configuration file using the -c argument of the netcd daemon. If the /etc/netcd.conf file does not exist, the netcd
       daemon uses the default parameters. You can find a sample of this file under the /usr/samples/tcpip file. Do not use this
       file as a configuration file because it will be overwritten by a new installation of the package containing the file.

       You can specify the level of debugging using the -d argument. The debugging levels are similar to the one used by the syslogd
       daemon. Log messages are written to the /var/tmp/netcd.log file. You can override the default using the netcd configuration
       file. As with the syslogd daemon, you can specify rotation for the netcd log file.

       netcd Parameters

       When an entry is inserted in a netcd cache, a time-to-live (TTL) is associated to it. You can configure this TTL using the
       netcd configuration file (cache declarations). For DNS, this TTL is the one contains the response from the DNS.

       To clean the caches of outdated entries, you must run two tasks periodically, one to clean local caches and the other to
       clean the other caches. You can set the frequency of these tasks using the local_scan_frequency and net_scan_frequency
       parameters in the netcd configuration file.

       Caches are hashed tables. The size of the hash tables can be controlled using the netcd configuration file and the netcdctrl
       command.

       To communicate between the applications, the netcd daemon uses a socket (/dev/netcd). You can configure the size of the
       message queue using the netcd configuration file.

       netcd supports the System Resource Controller

       The netcd daemon is part of the netcd System Resource Controller (SRC) group. The following are the SRC commands you can use
       to manage the netcd daemon:

       *    You can start the netcd daemon using the startsrc command, or stop the netcd daemon using the stopsrc command.
       *    The lssrc command provides a short status output that includes the Process ID (PID) and the status of the netcd daemon.
       *    The lssrc -l command provides a long status output that includes the PID, the status of the netcd daemon, the
            configuration file used when starting the netcd daemon, and the configured caches.

            Note: You cannot use the refresh command with the netcd daemon.

Flags

       Item
            Description
       -c file
            Specifies a configuration file. The default file name is /etc/netcd.conf.
       -d level
            Specifies the logging level. The level value must be an integer between 0 and 7.
       -h
            Displays help information.
       -l file
            Loads caches from the specified binary file created by the netcdctrl command. The local files (for example, /etc/hosts,
            /etc/services) are loaded depending on the configuration file.

Examples
       1    To launch the netcd daemon using the SRC, enter:

            startsrc -s netcd
       2    To display the status of the netcd daemon using the SRC, enter:

            lssrc -s netcd
            This command produces the following output:

            Subsystem         Group            PID          Status
            netcd             netcd            299064       active
       3    To display the status of the netcd daemon in long form using the SRC, enter:

            lssrc -l -s netcd
            This command produces the following output:

            Subsystem         Group            PID          Status
            netcd             netcd            299064       active
            Configuration File       /etc/netcd.conf
            Configured Cache         local services
            Configured Cache         local protocols
            Configured Cache         local hosts
            Configured Cache         local networks
            Configured Cache         local netgroup
       4    To launch the netcd daemon without using the SRC, enter:

            netcd