Archive for the ‘Senior Level Linux Professional (LPIC-3)’ category

LDAP is a protocol that helps us to access the database on different types of platforms. To implement LDAP on a Linux server, you need to download OpenLDAP Software. It is open source software. OpenLDAP Software comprises mainly two basic daemons:

• slapd (Stand-alone LDAP daemon)

Linux operating systems are predominantly known for their use in different types of servers. These are installed on a wide variety of computer hardware, ranging from embedded devices and mobile phones to supercomputers. A Senior Level Linux Professional should be able to measure hardware resources and network bandwidth usage of a Linux system. There are so many tools (command-line as well as graphical tools) supported by different Linux distributions described in this article:

ypbind is a UNIX/Linux daemon that finds the server for an NIS domain and stores the information in a file. The binding files reside in the directory /var/yp/binding and are conventionally named [domainname].[version]. After establishing the binding, the ypbind daemon sends YPPROC_DOMAIN requests to the NIS server at 20-second intervals. It searches a new server if no response is found. If more than one response is found, ypbind sends a ping request to all of the servers and binds with the one that responds first.

tdbdump is a tool for printing the contents of a TDB file. This tool is a part of the samba suite and is used to store the contents of a TDB (Trivial DataBase) file to the standard output when debugging problems with TDB files. The samba database (such as secrets.tdb) can be checked by the tdbdump tool.

ypldapd is a tool that is used to start the NIS/LDAP Gateway daemon. NIS/LDAP Gateway is a Network Information Service (NIS) server that uses LDAP as its information source. It allows existing NIS clients to transparently use LDAP to access user, group, and host information. It also supports the Microsoft services for UNIX Active Directory schema. ypldapd caches NIS maps for maximum performance.

Shared libraries are libraries that are used by programs when the corresponding program runs on the system. A shared library is automatically recognized by the programs after they are installed, and the programs automatically start using the new shared library. Shared libraries must be placed somewhere in the filesystem. The ldd command is used to see the list of shared libraries used by a program.

The accesslog overlay is used to record accesses to the databases, mainly the backend databases. This overlay enables users to review all the activities of the given database using LDAP queries. Users can use various logging types and automatically reduce log records from the logging database. These log records are saved in the audit schema. The accesslog overlay is also used with delta-syncrepl replication.

slapo-auditlog is an auditlog overlay that is used to record all the changes on a particular backend database to a specific log file. This overlay can be used to record changes as standard LDIF with an additional comment header giving the timestamp of the change and the identity of the user that has changed the database. The configuration file of the auditlog overlay is /etc/openldap/slapd.conf (the default slapd configuration file).

The TLSVerifyClient directive belongs to the global directives section of slapd.conf. This specifies the checks that are to be operated on client certificates in an incoming TLS session. Below is the list of options used with this directive:

• never: Never ask the client for a certificate.

The structural object-class usually defines the identity of an object, whereas the auxiliary object-class is used to add attributes. Some common examples of the structural object-classes are organizationalUnit, inetOrgPerson, etc. The auxiliary object-classes are usually used in extensions such as authentication. An entry must contain one and only one structural object-class, whereas it may contain any number of auxiliary object-classes.