4.11.25. HOWTO Enable Redundant LDAP

This section describes how to set up redundant OpenLDAP servers in SIMP. These servers are also referred to as “slave” servers.

4.11.25.1. Set up the Master

The easiest way to set up an LDAP master is to set it up on the Puppet master using simp config during the initial configuration of the Puppet master. This is done by answering “yes” when asked if you want to use LDAP during your initial simp config run and answering the basic questions it asks you. If it is not desirable to have the LDAP server on the Puppet master, a LDAP server can be set up on an alternate server by including the simp::server::ldap on the node of your choice.

Note

If you use another node, you may want to re-run simp config and answer the questions with this new LDAP master server in mind.

If you do not want to run simp config again, you will need to configure the following settings in Hiera:

# === ldap ===
# Whether or not to use LDAP on this system.
# If you disable this, modules will not attempt to use LDAP where possible.
simp_options::ldap: true

# The Base DN of the LDAP server
simp_options::ldap::base_dn: "dc=your,dc=domain"

# LDAP Bind Distinguished Name
simp_options::ldap::bind_dn: "cn=hostAuth,ou=Hosts,%{hiera('ldap::base_dn')}"

# The LDAP bind password
simp_options::ldap::bind_pw: "MyRandomlyGeneratedLargePassword"

# The salted LDAP bind password hash
simp_options::ldap::bind_hash: "{SSHA}9nByVJSZFBe8FfMkar1ovpRxJLdB0Crr"

# The DN of the LDAP sync user
simp_options::ldap::sync_dn: "cn=LDAPSync,ou=Hosts,%{hiera('ldap::base_dn')}"

# The LDAP sync password
simp_options::ldap::sync_pw: "MyOtherRandomVeryLargePassword"

# The SSHA hash for ldap::sync_pw
simp_options::ldap::sync_hash: "{SSHA}VlgYUmRzyuuKZXM3L8RT28En/eqtuTUO"

# The LDAP root DN.
simp_options::ldap::root_dn: "cn=LDAPAdmin,ou=People,%{hiera('ldap::base_dn')}"

# The LDAP root password hash.
# If you set this with simp config, type the password and the hash will be
# generated for you.'
simp_openldap::server::conf::rootpw: "{SSHA}GSCDnNF6KMXBf1F8eIe5xvQxVJou3zGu"

# This is the LDAP master in URI form (ldap://server)
simp_options::ldap::master: ldap://ldap_server1.your.domain

# === ldap::uri ===
# List of OpenLDAP servers in URI form (ldap://server)
simp_options::ldap::uri:
  - ldap://ldap_server1.your.domain

# === sssd::domains ===
# A list of domains for SSSD to use.
# `simp config` will automatically populate this field with `FQDN` if
# `use_fqdn` is true, otherwise it will comment out the field.
#
sssd::domains:
  - LDAP

Add the simp::server::ldap class into the yaml file for the LDAP server in Hiera, for example: data/hosts/ldap_server1.your.domain.yaml:

classes :
  - 'simp::server::ldap'

Leave any other classes that are there if they are needed. Run the Puppet agent on the LDAP server until it runs cleanly. Run the agent on the Puppet server. Once all the other clients update against the Puppet master, they will be able to authenticate against the LDAP server. Adding users and groups is described in the User Management.

Note

Information on how the create salted ({SSHA}) passwords can be found at the OpenLDAP site.

4.11.25.2. Set up the Redundant (Slave) Servers

4.11.25.2.1. Default Settings

Once the LDAP master is ready, LDAP slave nodes can be configured to replicate data from the master. These servers are read-only, and modifications cannot be made to LDAP entries while the master is down.

Slave nodes can be configured via Hiera by setting simp::server::ldap::is_slave to true, setting the replication id (RID) , and adding the simp::server::ldap class. This will set up your redundant server using the defaults. To do these three things, add the following lines to the data/hosts/ldap_server2.your.domain.yaml file:

simp_openldap::server::conf::rootpw: "{SSHA}GSCDnNF6KMXBf1F8eIe5xvQxVJou3zGu"
simp::server::ldap::is_slave: true
simp::server::ldap::rid: 888

classes :
  - 'simp::server::ldap'

To make other clients aware of this server, add the redundant server’s URI to lists of URIs in the data/default.yaml file:

# === ldap::uri ===
# List of OpenLDAP servers in URI form (ldap://server)
simp_options::ldap::uri:
  - ldap://ldap_server1.your.domain
  - ldap://ldap_server2.your.domain

Note

To see the defaults for LDAP replication in SIMP, review the parameters passed to the module simp_openldap/manifests/server/syncrepl.pp. These parameters are used to add the replication settings to the syncrepl.conf file. Definitions can be found in the syncrepl.conf (5) man page.

4.11.25.2.2. Custom Replication Settings

If settings other than the defaults are needed, create a manifest under site and use the simp_openldap::server::syncrepl class with the necessary parameters.

In this example, the site profile is called site::ldap_slave and the RID of the server is 999 (these can be changed). One setting, sizelimit, is being overwritten but you can overwrite any number of them.

class site::ldap_slave {

  include 'simp::server::ldap'

  # custom settings:
  simp_openldap::server::syncrepl { '999':
    sizelimit  => '5000',
  }
}

The name of the simp_openldap::server::syncrepl instance must be a unique replication id.

Place this file in the site module’s manifests/ directory using the name ldap_slave.pp. Include this class from the slave server’s Hiera YAML file:

classes :
  - 'site::ldap_slave'

Lastly, add the server to the URI listing in default.yaml so all the clients know about it once they have updated from the Puppet master.

4.11.25.3. Promote a Slave Node

Slave nodes can be promoted to act as the LDAP master node. To do this, change the node classifications of the relevant hosts. For a node with the default settings, just remove the simp::server::ldap::is_slave : true from the server’s Hiera YAML file and change the setting for the master LDAP in Hiera. This setting is needed by all LDAP servers. (It defaults to the Puppet master if it is not set.)

# This is the LDAP master in URI form (ldap://server)
simp_options::ldap::master: ldap://ldap_server2.your.domain

For a redundant server setup using custom settings, remove the call to the custom class and replace it with the call to the site::ldap_server class in the servers yaml file and set the master setting in the Hiera as shown above.

In both cases, if the current master is not down, make sure it has completed replication before changing the settings. Once the settings are changed, run puppet agent -t on the LDAP server. After the next Puppet run on all the hosts the server will be promoted to master and all the slaves will point to it.

4.11.25.4. Remove a Node or Demote a Master

To demote a master, simply configure it as slave in either of the configurations above after the new master has been configured and put in place. Then run the Puppet agent. Lastly, manually remove the active database from the server. (Check the setting simp_openldap::server::conf::directory setting for the location of the files.)

To remove an LDAP server, first remove the server from the simp_options::ldap::uri settings in Hiera. Give the clients time to update from the Puppet master so they do not attempt to call it. Then remove relevant settings from its hiera.yaml file and run the Puppet agent.

4.11.25.5. Troubleshooting

If the system is not replicating, it is possible that another user has updated the simp_options::ldap::sync_pw and simp_options::ldap::sync_hash entries in Hiera file without also updating the value in LDAP itself; this is the most common issue reported by users. If simp config was used to set up the server these values are in the simp_config_settings.yaml file.

Currently, SIMP cannot self-modify the LDAP database directly; therefore, the LDAP Administrator needs to perform this action. Refer to the User Management chapter for more information on manipulating entries in LDAP.

The example below shows an example ldif used to update the sync user information in LDAP.

dn: cn=LDAPSync,ou=Hosts,dc=your,dc=domain
changetype: modify
replace: userPassword
userPassword: <Hash from simp_options::ldap::sync_hash>

Likewise if the bind password has changed in heira, the simp_options::ldap::bind_pw and simp_options::ldap::bind_hash in the simp_config_settings.yaml file, the password must be updated in LDAP. If it is not, the clients will not be able to connect to the LDAP server. Use the following ldif to update the bind entry in LDAP:

dn: cn=hostAuth,ou=Hosts,dc=simp,dc=test
changetype: modify
replace: userPassword
userPassword: <Hash from simp_options::ldap::bind_hash>

4.11.25.6. Further Information

The OpenLDAP site contains more information on configuring and maintaining OpenLDAP servers.