final

asymmetric encryption algorithm

In an ___ ____ ___ , there are different encryption and decryption keys.

DLL data link layer

layer 2 of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between adjacent network nodes in a wide area network (WAN) or between nodes on the same local area network (LAN) segment.[1] The data link layer provides the functional and procedural means to transfer data between network entities and might provide the means to detect and possibly correct errors that may occur in the physical layer.

shell

user interface for access to an operating system's services; term for command interpreters on a systems with mulitiple command interpreters to choose from;

symmetric encryption algorithm

this encryption algorithm uses the same key is used to encrypt and to decrypt

ELF

executable and linkable format - is a common standard file format for executables, object code, shared libraries, and core dumps; contains ELF header

virtual memory

feature of an operating system that allows a computer to compensate for shortages of physical memory by temporarily transferring pages of data from random access memory to disk storage; involves the separation of logical memory as perceived by users from physical memory (when only a smaller physical memory is available)

direct communication

Processes that want to communicate must have a way to refer to each other. Under ____ _____, each process that wants to communicate must explicitly name the recipient or sender of the communication. In this scheme, the send () and receive () primitives are used

monolithic

an OS architecture where the entire operating system (which includes the device drivers, file system, and the application IPC) is working in kernel space. Able to dynamically load and unload executable modules at runtime (doesn't partition modules, however); in which functionally distinguishable aspects (for example data input and output, data processing, error handling, and the user interface), are not architecturally separate components but are all interwoven--ex. mainframes

clustered system

another type of multiprocessor system, which gathers together multiple CPUs. Differ from multiprocessor systems in that they are composed of two or more individual systems--or nodes--joined together. These are considered to be loosely- clustered. General accepted definition is that clustered computers share storage and are closely linked via a local-area network or a faster interconnect, such as InfiniBand

API

application program interface - set of routines, protocols, and tools for building software and applications

absolute path name

begins at the root and follows a path down to the specified file, giving the directory names in the path

process control block ( PCB)

in brief, simply serves as a repository for any information that may vary from process to process also known as a task control block-data structure in the operating system kernel containing the information needed to manage a particular process (process state, program counter, cpu registers, cpu-scheduling information, memory-management information, I/O status information); the manifestation of the operating system;

symmetric multiprocessing SMP

in which each processor performs all tasks within the operating system. All processors are peers; no boss-worker relationship exists between processors. ____ _____ _____ architecture where two or more identical processors connect to a single, shared main memory, have full access to all I/O devices, and are controlled by a single operating system instance that treats all processors equally, reserving none for special purposes; each processor performs all tasks within the operating system

Peterson's Solution

is a concurrent programming algorithm for mutual exclusion that allows two or more processes to share a single-use resource without conflict, using only shared memory for communication. It was formulated by Gary L. Peterson in 1981. Provides a good algorithmic description of solving the critical-section problem and illustrates some of the complexities involved in designing software that addresses the requirements of mutual exclusion, progress, and bounded waiting

multicore

is a single computing component with two or more independent actual processing units (called cores) which are the units that read and execute program instructions; multiple computing cores on a single chip;

paravirtualization

paravirtualization is a virtualization technique that presents a software interface to virtual machines that is similar, but not identical to that of the underlying hardware

critical section, Peterson's solution

part of a multi-process program that may or may not be concurrently executed by more than one of the program's processes; certain segment of code in a process in which the process may be changing common variables, updating table, writing a file, and so on;

Storage Area Network (SAN)

private network (using storage protocols rather than networking protocols) connecting servers and storage units (host-attached storage) ; beneficial because network attached storage systems consume data bandwidth; the power lies in its flexibility; uses SCSI

asymetric multiprocessing

processor-schema in which each processor is assigned a specific task. A boss processor controls the system; the other processors either look to the boss for instruction or have predefined tasks. This scheme defines a boss-worker relationship. The boss processor schedules and allocates work to the worker processors.

microkernel

the near-minimum amount of software that can provide the mechanisims needed to implement an operating system (OS); includes low-level address space management, thread management, and inter-process communication

thread

the smallest sequence of programmed instructions that can be managed independently by a scheduler, which is typically a part of the operating systems, but in most cases a _____ is a component of process; multiple _____s can exist within one process, executing concurrently and share resources such as memory, while different processes do not share these resources, while different processes do not share these resources , aka _____ of execution

symmetric clustering

two or more hosts are running applications and are monitoring each other. This structure is more efficient as it uses all of the available hardware. However, it does require that more than one application be available to run.

interprocess communication / IPC

type of communication which allows processes to exchange data and information: two fundamental models of _______ _______ : shared memory and message passing

Graphical User Interface ( GUI)

type of interface that allows users to interact with electronic devices through graphical icons and visual indicators such as secondary notation, as oposed to text-based interfaced, typed command labels or text navigation

von Neumann architecture

typical instruction-execution cycle, as executed on a system with a __ ___ ___ , first fetches an instruction from memory and stores that instruction in the instruction register. What we use today; computer architecture with parts consisting of a processing unit containing an arithmetic logic unit and processor registers, a control unit containing an instruction register and program counter, a memory to store both data and instructions, external mass storage, and input and output mechanisms f

byte

unit of digital information that most commonly consists of eight bits; 1024 = 1 kilobyte, 1024^2 = 1 megabyte, etc.

deadlock

usually when implementation of a semaphore with a waiting queue results in a situation where two or more processes are waiting indefinitely for an even that can be caused only by one of the waiting processes; think of the dining philosophers (hungry Ron); situation where waiting processes are waiting to change state but are unable to because resources are taken up by the other waiting processes

semaphore

variable or abstract data type that is used for controlling access, by multiple processes, to a common resource in a concurrent system such as a multi-programming operating system; an integer variable that, apart form initialization, is accessed only through two atomic operations: wait() and signal()

bankers algorithm

called as such because this algorithm can be used in a banking system to ensure that the bank never allocated its available cash in such a way that it could no longer satisfy the needs of all its customers; resource allocation and deadlock avoidance algorithm that tests for safety by simulating the allocation of predetermined maximum possible amounts of all resources, then makes an "s-state" check to test for possible deadlock conditions for all other pending activities, before deciding whether allocation should be allowed to continue; DOESN'T guarantee safe state

COM

component object model - mechanism for interprocess communication that was developed for WIndows. COM objects provide a well-defined interface to manipulate the data in the object. For instance, COM is the infrastructure used by Microsoft's object linking and embedding (OLE) technology for inserting spreadsheets into Microsoft Word documents. Many windows services provide COM interfaces.

NUMA / non-uniform memory access

computer architecture in which CPU has faster access to some parts of main memory than to other parts, creating a performance penalty; prior, computers were designed equidistant from cpu to RAM memory, nowadays, memory placed all over

beowulf cluster

computer cluster of what are normally identical, commodity-grade (COTS--consumer off the shelf) computers networked into a small local area network with libraries and open-source programs installed which allow processing to be shared among them. No single specific software package is required to construct a cluster. The result is a high-performance parallel computing cluster from inexpensive personal computer hardware. You should be able to build this yourself. In fact, some _______ clusters are built from discarded PCs.

thunking

conversion layer that translates 16-bit API calls into equivalent 32-bit calls in Windows

process

(or job) fundamental unit of work in an operating system; program loaded into memry and executing; different states are: running, waiting, terminated, and new.

computer cluster

A computer cluster consists of 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.[1][better source needed] The components of a cluster are usually connected to each other through fast local area networks ("LAN"), 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[2] and the same operating system, although in some setups (i.e. using Open Source Cluster Application Resources (OSCAR)), different operating systems can be used on each computer, and/or different hardware

hypervisor types

A hypervisor or virtual machine monitor (VMM) is a piece of computer software, firmware or hardware that creates and runs virtual machines; type 1 (run directly on host hardware aka bare metal) or type 2 (run on OS like other computer programs do and abstract guest OS)

high-availability

Clustering is usually used to provide ___ ____ service that will continue even if one or more systems in a cluster fail.

Kernel

Computer program that constitutes the central core of a computer's operating system --connects application software to the hardware; the one program running at all times on the computer

DLM

Distributed Lock manager - provides exclusive access within a shared system; system supplies access control and locking to ensure that no conflicting operations occur. Included in some cluster technology. Used for example, in storage-area networks. This is an example of an asymmetrical cluster. Earlier version was the Global Lock Manager. Red Hat had used GFS in the past, Rink didn't like it.

exception dispatcher

Exception handling is the process of responding to the occurrence, during computation, of exceptions - anomalous or exceptional conditions requiring special processing - often changing the normal flow of program execution. It is provided by specialized programming language constructs or computer hardware mechanisms. In general, an exception is handled (resolved) by saving the current state of execution in a predefined place and switching the execution to a specific subroutine known as an exception handler. If exceptions are continuable, the handler may later resume the execution at the original location using the saved information. For example, a floating point divide by zero exception will typically, by default, allow the program to be resumed, while an out of memory condition might not be resolvable transparently.

IKE / internet key exchange

IPSec uses symmetric encryption for key exchange. Based on public key exchange. Widely popular as basis for securing Virtual Private Networks, in which all traffic is between two IPSec endpoints is encrypted to make a private network out of one that may be otherwise be public. In computing, _______ _______ _______ (___ or ___v2) is the protocol used to set up a security association (SA) in the IPsec protocol suite. ___ builds upon the Oakley protocol and ISAKMP. _______ uses X.509 certificates for authentication - either pre-shared or distributed using DNS (preferably with DNSSEC) and a Diffie-Hellman key exchange - to set up a shared session secret from which cryptographic keys are derived. In addition, a security policy for every peer which will connect must be manually maintained

public-key

In an asymmetric key encryption scheme, this key can be available to anyone that wants it and can use that key to encrypt a communication.

data cluster

In computer file systems, a cluster or allocation unit is a unit of disk space allocation for files and directories. To reduce the overhead of managing on-disk data structures, the filesystem does not allocate individual disk sectors by default, but contiguous groups of sectors, called clusters. On a disk that uses 512-byte sectors, a 512-byte cluster contains one sector, whereas a 4-kibibyte (KiB) cluster contains eight sectors. A cluster is the smallest logical amount of disk space that can be allocated to hold a file. Storing small files on a filesystem with large clusters will therefore waste disk space; such wasted disk space is called slack space. For cluster sizes which are small versus the average file size, the wasted space per file will be statistically about half of the cluster size; for large cluster sizes, the wasted space will become greater. However, a larger cluster size reduces bookkeeping overhead and fragmentation, which may improve reading and writing speed overall. Typical cluster sizes range from 1 sector (512 B) to 128 sectors (64 KiB). A cluster need not be physically contiguous on the disk; it may span more than one track or, if sector interleaving is used, may even be discontiguous within a track. This should not be confused with fragmentation, as the sectors are still logically contiguous. The term cluster was changed to allocation unit in DOS 4.0. However the term cluster is still widely used.[1]

virtualization

In computing, ___________ refers to the act of creating a virtual (rather than actual) version of something, including virtual computer hardware platforms, operating systems, storage devices, and computer network resources.

kernel module

In computing, a ____ _____ _____ is an object file that contains code to extend the running kernel, or so-called base kernel, of an operating system. ___s are typically used to add support for new hardware (as device drivers) and/or filesystems, or for adding system calls. Here, the kernel has a set of core components and links in additional services via modules, either at boot time or during run time. This type of design is common in modern implementations of UNIX, such as Solaris, Linux, and Mac OS X, as well as Windows.

multiprocessing

Multiprocessing is the use of two or more central processing units (CPUs) within a single computer system.[1][2] The term also refers to the ability of a system to support more than one processor and/or the ability to allocate tasks between them.[3] There are many variations on this basic theme, and the definition of multiprocessing can vary with context, mostly as a function of how CPUs are defined (multiple cores on one die, multiple dies in one package, multiple packages in one system unit, etc.). NOTE: not all multiprocessor systems are multicore

high-performance computing

Since a cluster consists of several computer systems connected via network, clusters can also be used to provide _______ _______ environments. Such systems can supply significantly greater computational power than single-processor or even SMP systems because they can run an application concurrently on all computers in the cluster. The application must have been written specifically to take advantage of the cluster, however. This involves a technique known as parallelization, which divides a program into separate components that run in parallel on individual computers in the cluster. Typically, these applications are designed so that once each computing node in the cluster has solved its portion of the problem, the results from all the nodes are combined into a final solution.

OS operating system

System software that manages computer hardware and software resources and provides common services for computer programs; acts as intermediate between the user of a computer and computer hardware

well-known ports

The port numbers in the range from 0 to 1023 [below 1024]f are the well-known ports or system ports.[2] They are used by system processes that provide widely used types of network services. On Unix-like operating systems, a process must execute with superuser privileges to be able to bind a network socket to an IP address using one of the well-known ports; 22 for SSH, 53 for DNS, 80 for HTTP,

public-key encryption

This is an asymmetric encryption method in which there are two keys: a private key and a public key; breakthrough in cryptography, that allowed anyone to encrypt a message to the receiving entity no matter who is listening and allows only that entity can decrypt the message

>

To redirect standard output to a file, the ">" character is used. Repeating this will overwrite the file. If you want the new results to be appended to the file instead, use ">>"

Orange Book

Trusted Computer System Evaluation Criteria (TCSEC) is a United States Government Department of Defense (DoD) standard that sets basic requirements for assessing the effectiveness of computer security controls built into a computer system. The TCSEC was used to evaluate, classify and select computer systems being considered for the processing, storage and retrieval of sensitive or classified information. Classifications range from A, B, C, and D [being the lowest]. C provides discretionary protection and accountability of users and their actions through the use of audit capabilities. Has 2 levels: C1 [environment in which cooperating users access data at the same levels of sensitivity] and C2 [adds an individual-level access control to the requirements of a C1 system. For example, access rights of a file can be specified to the level of a single individual. In addition, the system administrator can selectively audit the actions of any one or more users based on individual identity. The TCSEC, frequently referred to as the Orange Book, is the centerpiece of the DoD Rainbow Series publications.

AD Active Directory

Window's version of LDAP ; stores the topology information about the domain, keeps the domain-based user and group accounts and passwords, and provides a domain-based store for windows features that need it.

C2 Security classification

Windows NT 4.0 to receive a __ security classification; __, a computer security class, defined in the Trusted Computer System Evaluation Criteria __ — Controlled Access Protection More finely grained Discretionary Access Control (capable of enforcing access limitations on an individual basis) Individual accountability through login procedures Audit trails Object reuse Resource isolation

cmdline command line interface

a command line interface that allows users to directly enter commands to be performed by the operating system

Direct memory access (DMA)

a feature of computer systems that allows certain hardware subsystems to access main system memory (RAM) independently of the central processing unit

chown changeowner

changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed

<

character used to redirect standard input from a file instead of the keyboard

command interpreter

command-line interface that allows user to directly enter commands to be performed by the operating system. The other allows users to interface with the operating system via a graphical interface, or GUI.

direct attached storage / das

common on small file systems; accessed through local I/O ports; uses i/o bus architecture called IDE or ATA, and newer SATA; higher end stuff uses fibre channel (FC) or high-speed serieal architecture over optical fibre or four-conductor copper cable; can also be used for RAID arrays, disk drives; aka Host-Attached storage

open-source

development model that promotes universal access via an open-source or free license to a product's design or blueprint, and universal redistribution of that design or blueprint, including subsequent improvements to it by anyone; source-code freely availablef

relative path name

defines a path from the current directory

Saas software as a service

one or more applications (such as word processors or spreadsheets) available via the Internet

HTTPS

http over tls/ssl or http secure - is a protocol for secure communication over a computer network which is widely used on the Internet. HTTPS consists of communication over Hypertext Transfer Protocol (HTTP) within a connection encrypted by Transport Layer Security or its predecessor, Secure Sockets Layer. The main motivation for HTTPS is authentication of the visited website and protection of the privacy and integrity of the exchanged data. Protects against man-in-the-middle attacks. Additionally, it provides bidrectional encryption of communications between a client and a server, which protects against eavesdropping and tampering with or forging the contents of the communication. Feasibly guarantees that one is communicating with precisely the website one intends to communicate.

high-availability clusters

include two or more computers and a set of shared disks. Any given application can be stored on the computers or on the shared disk, but the data must be stored on the shared disk. The running application's node has exclusive access to the application's data on disk. The application is monitored by the the cluster software, and if it fails it is automatically restarted. If it cannot be restarted, or if the entire computer fails, the node's exclusive access to the application's data is terminated and is granted to another node in the cluster. The application is restarted on that new node. The application loses whatever state information was in the failed system's memory but can continue based on whatever state it last wrote to the shared disk. From a user' point of view, a service was interrupted and then restarted, possibly with some data missing.

OLE / object linking and embedding

inserting spreadsheets into microsoft word documents

swapping

intermediate level of scheduling that will remove a process from memory and then can be reintroduced into memory at a later time, and its execution can be continued where it left off; makes it possible for the total physical address space of all processes to exceed the real physical memory of the system, thus increasing the degree of multi-programming in a system

iscsi

internet small computer storage interface - latest network-attached storage protocol. In essence, it uses IP network protocol to carry the SCSI protocol. Thus, networks--rather than SCSI cables--can be used as the interconnects between hosts and their storage. As a result, hosts can treat their storage as if were directly attached, even if the storage is distant from the host.

PID process ID

is a number used by most operating system kernels--such as that of UNIX, Mac OS X etc.--to uniquely identify an active process; this number may be used as a parameter in various function calls, allowing processes to be manipulated, such as adjusting the process's priority or killing it altogether; (aka pid)

hypertext transfer protocol http

is an application protocol for distributed, collaborative, hypermedia information systems. ____ is the foundation of data communication for the World Wide Web. Hypertext is structured text that uses logical links (hyperlinks) between nodes containing text. ____ is the protocol to exchange or transfer hypertext.

cloud computing

kind of internet-based computing that provides shared processing resources and data to computers and other devices on demand

lightweight process

means of achieving multitasking; runs in user space on top of a single kernel thread and shares its address space and system resources with other tasks within the same process

hot-standby mode

non-active host machine does nothing except monitor the active server (teeter-totter); CYSCO uses HSRP and open-source is VRRP

SSD solid state disks

nonvolatile memory that is used like a hard drive with tons of variation. Same characteristics as traditional hard disks but can be more reliable because they have no moving parts and faster because they have no seek time or latency. In addition, they consume less power. However, they are more expensive per megabyte than traditional hard disks, have less capacity than the larger hard disks, and may have shorter life spans than hard disk, so their uses are somewhat limited. One use for ___s is in storage array, where they hold file-system metadata that require high performance. ___s are also used in some laptop computers to make them faster. Faster than magnetic disk drives so standard bus interfaces can cause a major limit on throughput. Since no disk heads, no disk-scheduling algorithms largely do not apply. Uses Noop scheduler

LDAP / lightweight directory access protocol

open, secure, vendor-neutral, industry standard application protocol for accessing and maintaining distributed directory information services over an Internet Protocol (IP) network. One distributed ________ directory could be used by an organization to store all user and resource information for all the organization's computers. The result would be secure single sign-on for users, who would enter their authentication information once for access to all computers within the organization. It would also ease system-administration efforts by combining, in one location, information that is currently scattered in various files on each system or in different distributed information services.

stderr / standard error

output stream used by programs to output error messages or diagnostics. It is a stream independent of standard output and can be redirected separately.

asymmetric clustering

one machine is in hot-standby mode while the other is running the applications. The hot-standby machine does nothing but monitor the active server. If that server fials, the hot-standby host becomes the active server. Think of it like a teeter-totter system

DNS domain name systems

provides host-name-to-network-address translations for the entire Internet. ___ specifies the naming structure of the hosts, as well as the name-to-address resolution. Hosts on the internet are logically addressed with multipart names known as IP addresses. The parts of an IP address progress form the most specific to the most general, with periods separating the fields. For instance, "bob.cs.brown.edu" refers to host "bob" in the Department of Computer Science at Brown University within the top-level domain "edu". Generally, the system resolves addresses by examining the host-name components in reverse order. Each component has a name server--simply a process on a system--that accepts a name and returns the address of the name server responsible for that name. As the final step, the name server for the host in question is contacted, and a host-id is returned.

RAID

redundant array of independent disks - data storage virtualization technology that combines mulitiple physical disk drive components into a single logical unit for the purposes of data redundancy and performance; first considered for economic reasons now for its reliability

process synchronization

refers to the idea that multiple processes are to join up or handshake at a certain point, in order to reach an agreement or commit to a certain sequence of action.

mutex

refers to the requirement of ensuring that two concurrent processes are in their critical section at the same time; it is a basic requirement in concurrency control, to prevent race conditions

IPC send () receive ()

send (P, message) - send a message to process P receive (Q, message) - Receive message from process Q. Communication link in this scheme has the following properties: - link is established automatically between every pair of processes that want to communicate. The processes need to know only each other's identity to communicate - a link is associated with exactly two processes. - between each pair of processes, there exists exactly one link This scheme exhibits symmetry in addressing; that is, both the sender process and the receiver process must name the other to communicate. A variant of this scheme employs asymmetry in addressing. Here, only the sender names the recipient; the recipient is not required to name the sender. In this scheme, the send () and receive () primitives are defined as: - send (P, message) send a message to process P - receive (id,message) - receive a message from any process. The variable id is set to the name of the process with which communications has taken place.

2>/dev/null

send stderr to /dev/null

IaaS Infrastructure as a service

servers or storage available over the Internet (for example, storage available for making backup copies of production data)

sticky bit

set of a file or directory that lets only the owner/superuser of the file/directory or the root user to delete or rename the file. No other user is given privileges to delete the file created by some other user, even if they have write permissions to the directory,

dining-philosophers problem

simple representation of the need to need to allocate allocate several resources among several processes in a deadlock-free and starvation-free manner

command redirection

simply means capturing output from a file, command, program, script, or even code block within a script and sending it as input to another file, command, program, or script

race condition

situation in where multiple processes are accessing the same data concurrently and the outcome of the execution depends on the particular order in which the access takes place

scsi

small computer-systems interface - a set of standards for physically connecting and transferring data between computers and peripheral devices; SAS scsi; has a controller card that enabled scsi to become faster; today's hard drive have controller boards with cache chipsets already in the hd ; hook these drives with some kind of connector;

Paas platform as a service

software stack ready for application use via the Internet (for example, a database server)

UI User Interface

space where interactions between humans and machines occur; goal is to allow effective operation and control of the machine from the human end, whilst the machine simultaneously feeds back information that aids the operators' decision-making process

NAS (network attached storage)

special purpose storage system that is accessed remotely over a data network. Clients access via Remote Procedure Call interface (RPC) such as NFS (Network FIle System) for UNIX and CIFS (Common Internet File Systems) for Windows; ___s are carried out via TCP/IP or UDP over an IP network, usually over an LAN. Thus, it may be easiest to think of ___ as another storage-access protocoll; usually implemented as a RAID array w/ software that implements the ___interface

volatile

storage type that loses its contents when the power to the device is removed.

stdin / standard in

stream of data going into a program; requests data transfers by use of the READ operation; usually by the keyboard

stdout / standard out

stream where a program writes its output data; requests data transfer wtih the WRITE operation

daemon

system processes that run the entire time the kernel is running; computer program that runs as a background process (the entire time the kernels running) rather than being under the direct control of an interactive user; ends with letter 'd'; kernel intermediate between OS and ______ (system calls)

thrashing

when a process is spending more time paging than executing

closed-source

where the code isn't visible to anyone and they charge for the product/license or use of their product

windows SID

windows uses what's called a Security Identifier, which is a unique, immutable identifier of a user, user group, or other security principal. A security principal has a single SID for life, and all properties of the principal, including its name, are associated with the SID. This design allows a principal to be renamed (for example, from "John" to "Jane") without affecting the security attributes of objects that refer to the principal.