AIX V6.1 introduit le démon 'netcd' pour améliorer les performances des requêtes de résolution de noms(DNS ou NIS)
il se gére(démarrage et arrêt) de la même façon que les autres démons, par startsrc, stopsrc et lssrc.
Il est possible de mettre en cache plusieurs types d'objets, dont les entrées DNS, local ou distantes.
Le standard pour un cache DNS donne la syntaxe suivante :
cache dns hosts 128 60
Cette ligne dans le fichier /etc/netcd.conf permet de demander de stocker jusqu'à 128 entrées DNS avec un rafraichissement toutes les heures(60 minutes).
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
