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nsscache.conf - NSS local cache synchroniser configuration file


nsscache synchronises a local NSS cache, and other databases, against a remote data source. This approach allows the administrator to separate the network from the NSS lookup codepath, improving speed and reliability of name services.
The nsscache configuration file comprises of one DEFAULT section, followed by zero or more map-specific configuration sections. The file format is similar to that of ".ini" files.
The DEFAULT section must provide at least one source keyword, specifying the data source to use, one cache keyword, specifying the means in which the cache data will be stored locally, one maps keyword, specifying which NSS maps should be cached, and one timestamp_dir keyword, specifying the location of the timestamps used for incremental updates.
Additional global defaults, such as LDAP search parameters, or the filesystem location of the cache, may also be included in the DEFAULT section.
Additional sections may be included that allow per-map overrides to configuration options. For example, one might specify their global LDAP search base as ou=People but want to override that for the group mapping as ou=Groups
Apart from the source, cache, and maps configuration options, all options are prefixed by the name of the module that they configure.
A complete list of configuration options follows.

Specifies the source to use to retrieve NSS data from.
Valid Options: ldap, s3
Specifies the cache method to use to store the data, which will be queried by the NSS itself.
Valid options: files Store in a plain text file, similar in format to /etc/passwd. If the files-module option files_cache_filename_suffix is also set to cache then not only will the files be created with a .cache suffix, but also an index file will be written alongside, for use with the nss-cache NSS module. (See
nssdb Store in a Berkeley DB file, for use with the nss_db NSS module. Please note that this option is deprecated in favour of cache
Specifies the names of the maps that will be queried and cached by nsscache
Valid options: passwd group shadow netgroup automount sshkey
Specifies the directory where update and modify timestamps are stored.

These options configure the behaviour of the ldap source.
The LDAP URI to connect to.
The base to perform LDAP searches under.
The search filter to use when querying.
The search scope to use. Defaults to one
Valid options: sub[tree] one[level] base
The bind DN to use when connecting to LDAP. Empty string is an anonymous bind. Defaults to the empty string.
The bind password to use when connecting to LDAP. Empty string is used for anonymous binds. Defaults to the empty string.
Timelimit in seconds for search results to return. -1 means no limit. Defaults to -1.
Number of retries on soft failures before giving up. Defaults to 3.
Delay in seconds between retries. Defaults to 5.
Sets expectations for SSL certificates, using TLS. One of 'never', 'hard', 'demand', 'allow', or 'try' ('demand' is the default). See ldap.conf(5) for more information.
Directory for trusted CA certificates. By default, the system's default CA certificate directory will be used.
Filename containing trusted CA certificates.
Filename of an optional LDAP client certificate. If specified, ldap_tls_keyfile must also be specified.
Filename of an optional LDAP client key. Only plaintext (unencrypted) keys are currently supported. If specified, ldap_tls_certfile must also be specified.
Set to 1 to enable STARTTLS. Leave absent to disable.
The uid-like attribute in your directory. Defaults to uid.
A Python regex to extract uid components from the uid-like attribute. All matching groups are concatenated without spaces. For example: '(.*)' would return a uid to the left of the domain. Default is no regex.
A Python regex to extract group member components from the member or memberOf attributes. All matching groups are concatenated without spaces. For example: '(.*)' would return a member without the the domain. Default is no regex.
To enable expansion of nested groups, set this to 1. Note that this only applies during a full sync, and incremental synchronization should not be used if this is set.
If specified, set every user's login shell to the given one. May be useful on bastion hosts or to ensure uniformity.
Default uses rfc2307 schema. If rfc2307bis (groups stored as a list of DNs in 'member' attr), set this to 1.
Sets the debug level for the underlying C library. Defaults to no logging.

These options configure the behaviour of the s3 source.
AWS S3 bucket containing passwd, group, shadow objects. boto3 python package should be installed to use this type of source. It is highly recommended to use s3 source only with AWS IAM role attached to the ec2 instance configured for read-only access to the bucket. So no extra configuration options like access_key and secret provided in config. Though they may be used via ~/.aws/config and ~/.aws/credentials because python boto3 library used in implementation is capable to read them by itself.
Object containing passwd array of records in json format. E.g. [{"Value": {"gid": 10000, uid : 10000}, Key : user1 }]. Valid attributes: comment , home , shell , passwd , gid , uid
Object containing group array of records in json format. E.g. [{"Value": {"gid": 20000, members : user1ser2ser3 }, Key : group1 }]. Valid attributes: gid , members Members should be sequence of usernames split by \n (see example above)
Object containing shadow array of records in json format. E.g. [{"Value": {"passwd": * }, Key : user1 }]. Valid attributes: passwd , lstchg , min , max , warn , inact , expire

These options configure the behaviour of the nssdb cache.
Directory to store the Berkeley DB databases. Defaults to the current directory. Note that nss_db hardcodes the path to /var/db/nsscache on Debian systems, and /var/db on Red Hat systems.
Path to the makedb(1) command, which is used by the nssdb cache code to ensure that the Berkeley DB version created by the module matches that expected by the nss_db NSS module.

These optiosn configure the behaviour of the files cache.
Directory location to store the plain text files in. Defaults to the current directory.
A suffix appended to the cache filename to differentiate it from, say, system NSS databases. Defaults to '.cache'.
A yes/no field only used for automount maps. A 'yes' value will cause nsscache to update the auto.master file with the master map from the source. A 'no' value will cause nsscache to leave auto.master alone, allowing the system to manage this file in other ways. When set to 'no', nsscache will only update other automount maps defined both locally and in the source. Defaults to 'yes'.
A regular expression to capture a prefix, or mount point.
A regular expression to modify the prefix.

A typical example might look like this:

source = ldap
cache = nssdb
maps = passwd, group, shadow
ldap_uri = ldap://
ldap_base = ou=People,dc=example,dc=com
ldap_filter = (objectclass=posixAccount)
nssdb_dir = /var/db/nsscache

ldap_base = ou=Group,dc=example,dc=com
ldap_filter = (objectclass=posixGroup)
ldap_nested_groups = 1

ldap_filter = (objectclass=posixAccount)
And a complementary /etc/nsswitch.conf might look like this:

passwd: files db
group: files db
shadow: files db

The system-wide nsscache configuration file

The system name service switch configuration file
Details on LDAP configuration options exposed by the LDAP client libraries.

Written by Jamie Wilkinson ( and Vasilios Hoffman (
The source code lives at

Copyright © 2007 Google, Inc.
This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
2018-11-01 nsscache 0.37

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