nsscache.conf5

Usage

Overview

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.

Options

source

Specifies the source to use to retrieve NSS data from.

Valid Options: ldap, s3, http, gcs

cache

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 https://github.com/google/libnss-cache.)

maps

Specifies the names of the maps that will be queried and cached by nsscache

Valid options: passwd group shadow netgroup automount sshkey

timestamp_dir

Specifies the directory where update and modify timestamps are stored.

Options

These options configure the behaviour of the ldap source.

ldap_ad

Set to 1 if connecting to Active Directory. If enabled, default Active Directory attributes will be used for mapping. Leave disabled if connecting to openldap.

ldap_uri

The LDAP URI to connect to.

ldap_base

The base to perform LDAP searches under.

ldap_filter

The search filter to use when querying.

ldap_scope

The search scope to use. Defaults to one

Valid options: sub[tree] one[level] base

ldap_bind_dn

The bind DN to use when connecting to LDAP. Empty string is an anonymous bind. Defaults to the empty string.

ldap_bind_password

The bind password to use when connecting to LDAP. Empty string is used for anonymous binds. Defaults to the empty string.

ldap_timelimit

Timelimit in seconds for search results to return. -1 means no limit. Defaults to -1.

ldap_retry_max

Number of retries on soft failures before giving up. Defaults to 3.

ldap_retry_delay

Delay in seconds between retries. Defaults to 5.

ldap_tls_require_cert

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.

ldap_tls_cacertdir

Directory for trusted CA certificates. By default, the system's default CA certificate directory will be used.

ldap_tls_cacertfile

Filename containing trusted CA certificates.

ldap_tls_certfile

Filename of an optional LDAP client certificate. If specified, ldap_tls_keyfile must also be specified.

ldap_tls_keyfile

Filename of an optional LDAP client key. Only plaintext (unencrypted) keys are currently supported. If specified, ldap_tls_certfile must also be specified.

ldap_tls_starttls

Set to 1 to enable STARTTLS. Leave absent to disable.

ldap_uidattr

The uid-like attribute in your directory. Defaults to uid.

ldap_use_rid

If enabled (set to 1) the relative identifier (RID) wll be used for mapping. By default uidNumber and gidNumber will be mapped when connecting to OpenLDAP with a POSIX-like schema. When using Samba4 AD, these attributes won't exist. Leave disabled for default. It has no effect if the option ldap_ad is enabled.

ldap_offset

Default Offset option to map uidNumber and gidNumber to higher number. This can be useful to avoid conflict with already existing uidNumber and gidNumber.

ldap_uidregex

A Python regex to extract uid components from the uid-like attribute. All matching groups are concatenated without spaces. For example: '(.*)@example.com' would return a uid to the left of the @example.com domain. Default is no regex.

ldap_groupregex

A Python regex to extract group member components from the member or memberOf attributes. All matching groups are concatenated without spaces. For example: '(.*)@example.com' would return a member without the the @example.com domain. Default is no regex.

ldap_nested_groups

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.

ldap_override_shell

If specified, set every user's login shell to the given one. May be useful on bastion hosts or to ensure uniformity. Enable for Active Directory since the attribute (loginShell) is not default.

ldap_home_dir

Set a home directory for all users in passwd. If enabled (set to 1), all users will have their home directory in /home.

ldap_rfc2307bis

Default uses rfc2307 schema. If rfc2307bis (groups stored as a list of DNs in 'member' attr), set this to 1.

ldap_debug

Sets the debug level for the underlying C library. Defaults to no logging.

Options

These options configure the behaviour of the s3 source.

s3_bucket

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.

s3_passwd_object

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

s3_group_object

Object containing group array of records in json format. E.g. [{"Value": {"gid": 20000, members : user1\nuser2\nuser3 }, Key : group1 }]. Valid attributes: gid , members Members should be sequence of usernames split by \n (see example above)

s3_shadow_object

Object containing shadow array of records in json format. E.g. [{"Value": {"passwd": * }, Key : user1 }]. Valid attributes: passwd , lstchg , min , max , warn , inact , expire

s3_sshkey_object

Object containing sshkey array of records in json format. E.g. [{"Value": {"sshPublicKey": ssh-rsa ... }, Key : user1 }]. Valid attributes: sshPublicKey

Options

These options configure the behaviour of the http source.

http_passwd_url

URL for an HTTP endpoint that returns a file containing passwd records in the standard format. E.g. root:*:0:0:System Administrator:/var/root:/bin/sh

http_group_url

URL for an HTTP endpoint that returns a file containing group records in the standard format. E.g. users:x:100:memberships....

http_shadow_url

URL for an HTTP endpoint that returns a file containing shadow records in the standard format. E.g. root:*:18866:0:99999:7:::

http_sshkey_url

URL for an HTTP endpoint that returns a file containing sshkey records in the standard format. E.g. root:ssh-rsa ...

Options

These options configure the behaviour of the files cache.

files_dir

Directory location to store the plain text files in. Defaults to the current directory.

files_cache_filename_suffix

A suffix appended to the cache filename to differentiate it from, say, system NSS databases. Defaults to '.cache'.

files_local_automount_master

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'.

prefix

A regular expression to capture a prefix, or mount point.

suffix

A regular expression to modify the prefix.

Examples

A typical example might look like this:

[DEFAULT]
source = ldap
cache = files
maps = passwd, group, shadow
ldap_uri = ldap://ldap.example.com
ldap_base = ou=People,dc=example,dc=com
ldap_filter = (objectclass=posixAccount)

files_dir = /etc
files_cache_filename_suffix = cache

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

[shadow]
ldap_filter = (objectclass=posixAccount)

And a complementary /etc/nsswitch.conf might look like this:

passwd: files cache
group: files cache
shadow: files cache

Options

These options configure the behaviour of the gcs source.

gcs_bucket

Google Cloud Storage bucket containing passwd, group, shadow blobs.

gcs_passwd_object Name for a object containing passwd records in the standard format. E.g. root:*:0:0:System Administrator:/var/root:/bin/sh

gcs_group_object Name for a object containing group records in the standard format E.g. users:x:100:memberships....

gcs_shadow_object Name of the object containing shadow records in the standard format. E.g. root:*:18866:0:99999:7:::

Files

/etc/nsscache.conf

The system-wide nsscache configuration file