EXAM OBJECTIVES COVERED
2.5 Summarize and explain server roles.
When using Linux there are a wide variety of network services that can be configured and run as part of the services you are providing. Below we cover a wide variety of the most commonly used services. This is by no means an exhaustive list, or a detailed coverage of these individual services.
Centralized authentication means that a single username and password, also referred to as credentials, can be used to access a number of different services because those services all look at the same database when performing authentication. This exchange with a centralized authentication source may or may not return a token that can be used in conjunction with a single sign-on (SSO) architecture.
Certificate of Authority
In cryptography, a certificate authority or certification authority (CA) is an entity that issues digital certificates. A digital certificate certifies the ownership of a public key by the named subject of the certificate. This allows others (relying parties) to rely upon signatures or on assertions made about the private key that corresponds to the certified public key. A CA acts as a trusted third party—trusted both by the subject (owner) of the certificate and by the party relying upon the certificate.
One particularly common use for certificate authorities is to sign certificates used in HTTPS, the secure browsing protocol for the World Wide Web. Another common use is in issuing identity cards by national governments for use in electronically signing documents.
A computer cluster is a set of loosely or tightly connected computers that work together so that, in many respects, they can be viewed as a single system. Unlike grid computers, computer clusters have each node set to perform the same task, controlled and scheduled by software.
The components of a cluster are usually connected to each other through fast local area networks, with each node (computer used as a server) running its own instance of an operating system. In most circumstances, all of the nodes use the same hardware and the same operating system, although in some setups (e.g., using Open Source Cluster Application Resources (OSCAR)), different operating systems can be used on each computer, or different hardware.
Clusters are usually deployed to improve performance and availability over that of a single computer, while typically being much more cost-effective than single computers of comparable speed or availability.
A database server is a server which uses a database application that provides database services to other computer programs or to computers, as defined by the client–server model. Database management systems (DBMSs) frequently provide database-server functionality, and some database management systems, such as MySQL, rely exclusively on the client–server model for database access.
Most database applications respond to a query language. Each database understands its query language and converts each submitted query to server-readable form and executes it to retrieve results.
Examples of proprietary database applications include Oracle, DB2, Informix, and Microsoft SQL Server. Examples of free software database applications include PostgreSQL; under the GNU General Public License examples include Ingres and MySQL. Every server uses its own query logic and structure. The SQL (Structured Query Language) query language is more or less the same on all relational database applications.
The Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on Internet Protocol (IP) networks, whereby a DHCP server dynamically assigns an IP address and other network configuration parameters to each device on the network, so they can communicate with other IP networks. A DHCP server enables computers to request IP addresses and networking parameters automatically from the Internet service provider (ISP), reducing the need for a network administrator or a user to manually assign IP addresses to all network devices. In the absence of a DHCP server, a computer or other device on the network needs to be manually assigned an IP address, or to assign itself an APIPA address, the latter of which will not enable it to communicate outside its local subnet.
DHCP can be implemented on networks ranging in size from home networks to large campus networks and regional ISP networks. A router or a residential gateway can be enabled to act as a DHCP server. Most residential network routers receive a globally unique IP address within the ISP network. Within a local network, a DHCP server assigns a local IP address to each device connected to the network.
A DNS hosting service is a service that runs Domain Name System servers. Most, but not all, domain name registrars include DNS hosting service with registration. Free DNS hosting services also exist. Many third-party DNS hosting services provide Dynamic DNS.
DNS hosting service is optimal when the provider has multiple servers in various geographic locations that provide resilience and minimize latency for clients around the world. By operating DNS nodes closer to end users, DNS queries travel a much shorter distance, resulting in faster Web address resolution speed.
DNS can also be self-hosted by running on generic Internet hosting services.
"Computer cluster" by Multiple Contributors, Wikipedia is licensed under CC BY-SA 3.0
"Database server" by Multiple Contributors, Wikipedia is licensed under CC BY-SA 3.0
"DNS hosting service" by Multiple Contributors, Wikipedia is licensed under CC BY-SA 3.0
"Certificate authority" by Multiple Contributors, Wikipedia is licensed under CC BY-SA 3.0