nscd

Table of Contents

1. Description
2. Setup - The basics of getting started with nscd
3. Usage - Configuration options and additional functionality
4. Reference - An under-the-hood peek at what the module is doing and how
5. Limitations - OS compatibility, etc.
6. Development - Guide for contributing to the module

Description

The nscd module installs, configures and manages the name service cache daemon on unix-like operating systems.

Setup

What nscd affects

• The nscd package will be installed unless package_manage is set to false
• The nscd.conf configuration file will be overwritten unless config_manage is set to false

Beginning with nscd

Declare the main ::nscd class and apply default cache configurations:

class { '::nscd' : service_defaults => true }

Usage

Daemon configuration is managed through the main ::nscd class while individual service caches (such as passwd or group) are managed using declarations of the ::nscd::cache resource type.

Install and start nscd with binary defaults

class { '::nscd' : }

This will install the nscd package, configure daemon defaults and start the nscd service. No caches will be configured or enabled.

Install and start nscd with distribution defaults

class { '::nscd' : service_defaults => true }

This will install the nscd package, configure daemon defaults, enable and configure service caches as per the defaults for your operating system and finally start the nscd service.

Install and start nscd with custom service cache configurations

class { '::nscd' : }

nscd::cache { 'passwd' : 
  positive_ttl   => 600,
  negative_ttl   => 20,
  persistent     => true,
  shared         => true,
  auto_propagate => true,
}

nscd::cache { 'group' : 
  positive_ttl   => 3600,
  negative_ttl   => 60,
  persistent     => true,
  shared         => true,
  auto_propagate => true,
}

This will install the nscd package, configure daemon defaults, enable and configure service caches for passwd and group and finally start the nscd service.

Reference

• Public classes
  • Class: nscd
• Private classes
  • Class: nscd::config
  • Class: nscd::install
  • Class: nscd::params
  • Class: nscd::service
  • Class: nscd::service_defaults
• Public defined types
  • Defined type: nscd::cache

Public classes

Class: nscd

Guides the basic setup and installation of the name service cache daemon on your system.

When this class is declared with the default options, Puppet:

• Installs the nscd software package for your operating system
• Replaces and manages the nscd.conf configuration file
  • Distribution defaults are used for the daemon itself
  • Binary defaults are used for all supported caches unless service_defaults is set to true in which case distribution defaults are configured
• Enables and starts the nscd service

You can validate the state of nscd and its caches by calling

$ nscd --statistics

Parameters within nscd:

config_file

Set the path fo the nscd configuration file to be managed. Default: /etc/nscd.conf

config_manage

Determines whether to manage the nscd daemon configuration file. If false, the configuration file must be managed manually and ::nscd::cache definitions will fail. Valid options: Boolean. Default: true.

debug_level

Sets the desired debug level for the log file. Default: 0.

log_file

Set the path of the daemon log file. Default: /var/log/nscd.log.

max_threads

Sets the maximum number of threads. Default: 32.

package_ensure

Controls the package resource's [ensure][] attribute. Valid options: 'absent', 'installed' (or the equivalent 'present'), or a version string. Default: 'installed'.

package_manage

Determines whether the nscd package will be installed and managed. Set to false if you wish to manually manage the installation. Valid options: Boolean. Default: true.

package_name

Sets the names of the package to be installed. Default: nscd.

paranoia

Determines whether to enable paranoia mode which causes nscd to restart itself periodically. Valid options: Boolean. Default: true.

reload_count

Sets the limit on the number of times a cached entry gets reloaded without being used before it gets removed. Default: 5.

restart_interval

Sets the restart interval to time seconds if periodic restart is enabled by enabling paranoia mode. Default: 3600 (1 hour).

service_defaults

Determines whether default cache service configurations should be applied by including the ::nscd::service_defaults class and its ::nscd::cache declarations. Valid options: Boolean. Default: true.

service_enable

Determines whether Puppet enables the nscd service when the system is booted. Valid options: Boolean. Default: true.

service_ensure

Determines whether Puppet should make sure the service is running. Valid options: 'true' (equivalent to 'running'), 'false' (equivalent to 'stopped'). Default: 'running'.

service_manage

Determines whether Puppet manages the nscd service's state. Valid options: Boolean. Default: true.

service_name

Sets the name of the nscd service. Default: nscd.

service_user

Sets the name of the service account under which the nscd service will run. Default: nscd.

service_user_gid

Sets the group ID of the nscd service account. Default: 28.

service_user_manage

Determines whether Puppet manages the nscd service account. Valid options: Boolean. Default: true.

service_user_uid

Sets the user ID of the nscd service account. Default: 28.

stat_user

Specifies the user who is allowed to request statistics.

threads

Set the number of threads that are started to wait for requests. At least five threads will always be created. Default: 4.

Private classes

Class: nscd::config

Manages the nscd configuration file.

Class: nscd::install

Installs the nscd package.

Class: nscd::params

Manages nscd parameters for different operating systems.

Class: nscd::service

Manages the nscd daemon and runtime user account.

Class: nscd::service_defaults

Defines default ::nscd::cache configurations for the targeted operating system.

Public defined types

Defined type: nscd::cache

Defines the configuration for a supported service cache.

Parameters within nscd::cache:

name

Sets the name of the service to be configured.

auto_propagate

When set to false for passwd or group service, then the .byname requests are not added to passwd.byuid or group.bygid cache. This can help with tables containing multiple records for the same ID. This parameter is valid only for services passwd and group. Default: undef.

check_files

Enables or disables checking the file belonging to the specified service for changes. Valid options: Boolean. Default: true.

enable

Enables or disables the specified service cache. Valid options: Boolean. Default: true.

max_db_size

The maximum allowable size, in bytes, of the database files for the service. Default: 33554432 (32MB).

negative_ttl

Sets the TTL (time-to-live) for negative entries (unsuccessful queries) in the specified cache for service. Value is in seconds. Can result in significant performance improvements if there are several files owned by UIDs (user IDs) not in system databases (for example untarring the Linux kernel sources as root); should be kept small to reduce cache coherency problems. Required. Default: undef.

persistent

Keep the content of the cache for service over server restarts; useful when paranoia mode is set. Valid options: Boolean. Default: false.

positive_ttl

Sets the TTL (time-to-live) for positive entries (successful queries) in the specified cache for service. Value is in seconds. Larger values increase cache hit rates and reduce mean response times, but increase problems with cache coherence. Required. Default: undef.

shared

The memory mapping of the nscd databases for service is shared with the clients so that they can directly search in them instead of having to ask the daemon over the socket each time a lookup is performed. Valid options: Boolean. Default: false.

suggested_size

Sets the the internal hash table size. Value should remain a prime number for optimum efficiency. Default: 211.

Limitations

Debian/Ubuntu

As per Ubuntu bug 1068889, the netgroup service cache is known not to work on Debian based systems and is therefore disable by default by this module.

Development

Contributions are welcome in the form of issues and pull requests on GitHub.