LQ1 - Operating Systems - Operating-System Services

operating systems

provides an environment for execution of programs and services to programs and users

• user interface

• program execution

• i/o operations

• file-system manipulation

• communications

• error detection

Enumerate a set of operating services that may help the user

• resource allocation

• logging

• protection and security

Enumerate a set of operating services that ensures efficient operation of the system itself

logging

used to keep track of which users use how much and what kinds of computer resources

protection

involves ensuring that all access to system resources is controlled

security

requires user authentication from outsiders.

command line interpreter

allows direct command entry (it fetches user commands and executes them)

user operating system interface - GUI

User-friendy desktop metaphor interface

touchscreen interfaces

• actions and selection based on gesture

• virtual keyboard for text entry

• voice commands

system calls

programming interface to the services provided by the OS

system-call interface

maintains a table indexed according to the numbers associated with each system call

system call interface

invokes the intended system call in OS kernel and returns status of the system call and any return values

• pass the parameters in registers

• pass block addresses as a parameter in a register (the blocks contain the parameters)

• parameters placed onto the stack by the program and popped off the stack by the operating system

three general methods used to pass parameters to the OS

1. process control

2. file management

3. device management

4. information maintenance

5. communications

6. protection

types of system calls

debugger

used for determining bugs, single step execution

locks

used for managing access to shared data between processes

system programs

provide a convenient environment for program development and execution.

• file manipulation

• status information

• programming language support

• program loading and execution

• communications

• background services

• application programs

system programs can be divided into:

file management

create, delete, copy, rename, print, dump, list, and generally manipulate files and directories

registry

used to store and retrieve configuration information

communications

provide the mechanism for creating virtual connections among processes, users, and computer systems

background services

known as services, subsystems, daemons; they provide facilities like disk checking, process scheduling, error logging, printing

relocatable object file

source code compiled into object files designed to be loaded into any physical memory location

linker

combines these (relocatable object files) into single binary executable file and brings in libraries

loader

programs residing on a secondary storage as a binary executable must be brought into memory by ___ to be executed

dynamically linked libraries

____ ____ ____ are loaded by modern general purpose systems

Application Binary Interface (ABI)

is architecture equivalent of API, defines how different components of binary code can interface for a given operating system on a given architecture, CPU, etc.

policy

refers to what needs to be done (in the context of designing and implementing an OS)?

mechanism

how to do something (in the context of designing and implementing an OS)?

false

it makes it easier to port but slower in performance

true or false: OS implementation utilizing a more higher-level language makes it hard to port but faster in performance

UNIX

• utilizes a monolithic structure

• limited by hardware functionality

• its original version had limited structuring

• system programs

• the kernel

Two inseparable parts of the UNIX OS

monolithic plus modular design

the linux system structure

layered approach

is an OS implementation/approach that divides the OS into a number of layers (levels), each built on top of lower layers. The bottom layer (layer 0), is the hardware; the highest (layer N) is the user interface.

microkernels

an OS implementation that moves as much from the kernel into the user space.

message passing

communication in microkernels takes place between user modules using ___ ____

loadable kernel modules (LKMs)

• uses object-oriented approach

• each core component is separate

• each talks to the others over known interfaces

• each is loadable as needed within the kernel

bootstrap loader, BIOS

the ___ ____, ____, stored in ROM or EEPROM locates the kernel, loads it into memory, and starts it to boot the system

debugging

is finding and fixing errors or bugs

log files

OS generate ___ ___ containing error information

core dump

Application failure can generate ___ ___ file capturing memory of the process

crash dump

Operating system failure can generate ___ ___ file containing kernel memory

performance tuning

can optimize system performance (besides from crashing)

is per

Kernighan’s Law

debugging is twice as hard as writing the code in the first place

performance tuning

improves performance by removing bottlenecks

tracing

collects data for a specific event, such as steps involved in a system call invocation

strace

trace system calls invoked by a process

gdb

source-level debugger

perf

collection of Linux performance tools

tcpdump

collects network packets

BCC (BPF Compiler Collection)

is a rich toolkit providing tracing features for Linux