CSC 352 Exam 2 Concepts

fscks tasks

fixes damaged or inconsistent inodes unreferenced inodes large link counts unused data blocks not recorded in block maps data blocks listed as free but also used in a file incorrect summary info in superblock

Disk Superblock

length of a disk block size and location of inode tables disk block map and usage information size of the cylinder groups other important parameters of the filesystem

getty

A Unix program running on a host computer that manages physical or virtual terminals (TTYs). When it detects a connection, it prompts for a username and runs the 'login' program to authenticate the user.

Daemon

A background process that performs a specific function or system-related task

modified bit

A bit that is associated with a block of computer memory and indicates whether or not the corresponding block of memory has been modified

context switch

A context switch (also sometimes referred to as a process switch or a task switch) is the switching of the CPU (central processing unit) from one process or thread to another.

Policy

A course or principle of action adopted or proposed by a government, party, business, or individual.

inetd

A daemon that manages other daemons

page table

A page table is the data structure used by a virtual memory system in a computer operating system to store the mapping between virtual addresses and physical addresses.

data area

A portion of an object file or the corresponding virtual address space of a program that contains initialized static variables, that is, global variables and static local variables.

What is PID?

A process id, used to identify an active process.

sleeping/blocked

A process is described as blocking or waiting when it is set inactive until a specific event occurs.

What is a memory manager?

A software utility that operates in conjunction with the operating system. It helps manage memory more efficiently and provides additional features such as flushing out unused segments of memory

page fault

A type of exception raised by computer hardware when a running program accesses a memory page that is not currently mapped by the memory management unit (MMU) into the virtual address space of a process.

System Administrator Tasks

Account maintainence Backups Restoring files Answering user questions Monitor and tune systems Maintain printers and print queues System Security Installing Software Installing patches Monitoring disk space Correct network problems Troubleshooting system and user problems Installing new equipment Add new systems to the network Writing scripts to automate tasks Maintain documentation

useradd

Add user account

wait()

Allows a process to wait until one of its child processes change its state

zombie process

Also known as a defunct process is when it has completed execution ( it ended ) but still has an entry in the process table

What is a Process?

An instance of a running program

What is fork()?

An operation whereby a process creates a copy of itself. It is usually a system call, implemented in the kernel. Fork is the primary (and historically, only) method of process creation on Unix-like operating systems

cooperation

Being able to work together

Responsibility

Being accountable if something were to happen to the system due to your actions

A user is consuming too much CPU Resources, what is your response?

Call them or email them and let them know what's going on and find out why they may be using that many resources. A call is better because it is possible someone hacked their account. So if you email them, only the hacker will receive it.

apt-get/yum

Command line tool that installs and updates software, and check for updates

Process Table

Data structure maintained by the operating system to facilitate context switching and scheduling, and other activities. Includes: process id process owner process priority environment variables for each process the parent process pointers to the executable machine code of a process. Real and effective UID and GID Process state Location of its code, data, stack and user area List of all pending signals

userdel

Deleting user accounts

Effective UID vs Real UID

Effective - Id of user that owns the file Real - Id of User that started the process

Backup strategy

Grandfather father son. Grandfather, do a backup every year, father do it every month, and son do it every day. Back up from another machine

User vs kernal mode

Kernel mode is generally reserved for the lowest-level, most trusted functions of the operating system. Crashes in kernel mode are catastrophic; they will halt the entire PC. In User mode, the executing code has no ability to directly access hardware or reference memory.

usermod

Modifying user accounts

Termination status normal vs abnormal

Normal - A process terminates normally when its program signals it is done by calling exit Abnormal - Killing or interrupting the process

Basic Strategy

Plan Make it reversible Make changes incrementally Test Know how things really work Document

Planned Procedures

Regularly changing root passwords Regular backups Log out and clear terminal screen Test changes several times then implement Stick to policies

rpc protocal

Rpc - remote procedure call - call functions that exists from another machine

Constraints

Security, other users needs, capabilities of systems

System Administration

System administration is the field of work in which someone manages one or more systems, software, hardware, servers or workstations. Its goal is ensuring the systems are running efficiently and effectively.

service

The act of helping or doing work for someone or performing repair work on a system

crontab

The crontab is a list of commands that you want to run on a regular schedule, and also the name of the command used to manage that list. crontab stands for "cron table," because it uses the job scheduler cron to execute tasks

init

The first process started during booting of the computer system. Init is a daemon process that continues running until the system is shut down.

What is a Magic Number?

The magic number is a way to recognize what format a file is in.

Authority

The power to give orders, make decisions etc. As a system administrator you have the authority to monitor everyone's System

exit

The process finished

running

The process is running

cron

The software utility Cron is a time-based job scheduler in Unix-like computer operating systems. People who set up and maintain software environments use cron to schedule jobs (commands or shell scripts) to run periodically at fixed times, dates, or intervals.

stack area

The stack segment is used by the process for the storage of automatic identifier, register variables, and function call informatio

user area

The u area contains information specific to the process

at

Used to schedule commands to be executed once, at a particular time in the future.

swap space

Used when the amount of physical memory (RAM) is full. If the system needs more memory resources and the RAM is full, inactive pages in memory are moved to the swap space. While swap space can help machines with a small amount of RAM, it should not be considered a replacement for more RAM.

orphan process

a child process without a parent process

What does the backup schedule depend on?

activity on filesystem capacity of dump device length of "dump window" amount of redundancy number of tapes available how far back you must be able to recover

process states

idle, suspended, running, ready, zombie, exit, sleeping/blocked

reference bit

keep a counter for each page at regular intervals, do: for every page: if ref bit = 0, increment its counter if ref bit = 1, zero its counter zero the reference bit the counter will thus contain the number of intervals since the last reference to the page. the page with the largest counter will be least recently used one. the counter is the age in this case and the pages would be the page daemon

nfs

network file system

idle

process is idle

suspended

process is not running

ready

process is ready to run

user needs

users must get jobs done easily and effectively