Ppt on file system in unix everything is a file

Stat, mmap, process syncing and file system interface Nezer J. Zaidenberg.

*/ u_long st_flags; /* user defined flags for file */ u_long st_flags; /* user defined flags for file */ u_long st_gen; /* file generation number */ u_long st_gen; /* file generation number */ }; }; Access permission Like everything in the IDF file system permissions in UNIX is divided to 3 parts Like everything in the IDF file system permissions in UNIX is divided to 3 parts ME – what I can do. ME – what I can do. MY GROUP – (every user have a group) – what my group can do. MY/


Tutorial of Unix/Linux Cédric Notredame (Adapted from NOMURA)

is a main program of Unix system. it controls hard wares, CPU, memory, hard disk, network card etc. Shell is an interface between user and kernel. Shell interprets your input as commands and pass them to kernel. Kernel Shell User input Unix Overview (cont.) Multi-user & Multi-process Many people can use one machine at the same time. File & Process Data, directory, process, hard disk etc (almost everything/


UNIX and Perl Lecture 2 Matt Hudson. Review Unix is text based: doesn’t waste computer resources on graphics allows you to write and use scripts easily.

to learn “where everything is” gives the user more power Review When negotiating file systems, it is important to remember the directory structure and the commands cd, ls and pwd. You must be very wary of creating multiple files with the same name, as it is easy to over-write an existing, important file There is no undelete or trash basket in UNIX – delete or overwrite a file and it is gone Review Edit/


1.1 The Linux System: Design Principles Linux is a multiuser, multitasking system with a full set of UNIX-compatible tools. Its file system adheres to.

data.  Directory files, which are stored on disk in a special format and form the backbone of the file system  Special file, which correspond to peripherals such as printers or disks. To the user, Linux file system appears as a hierarchical directory tree obeying UNIX semantics. 1.13 File System / is the root directory; reference point for all directories. Every file has a unambiguous pathname:  /home/user1/papers 1.14 Some directories found in UNIX systems /bin Binaries/


Copyright © 1995-2005 Clifford Neuman and Dongho Kim - UNIVERSITY OF SOUTHERN CALIFORNIA - INFORMATION SCIENCES INSTITUTE Advanced Operating Systems Lecture.

access.  @ client:  Processes file system system calls to determine whether access is local (passes it to UNIX FS) or remote (passes it to NFS client).  @ server:  NFS server receives request and passes it to local FS through VFS. Copyright © 1995-2005 Clifford Neuman and Dongho Kim - UNIVERSITY OF SOUTHERN CALIFORNIA - INFORMATION SCIENCES INSTITUTE VFS  If local, translates file handle to internal file id’s (in UNIX i-nodes).  V/


Introduction to Unix (CA263) File System

everything to be a file A file system is UNIX/Linux’s way of organizing files on mass storage devices A physical file system is a section of the hard disk that has been formatted to hold files The file system is organized in a hierarchical structure (inverted tree) Understanding UNIX/Linux File Systems (continued) UNIX File System Most versions of UNIX and Linux support the UNIX file system (ufs), which is the original native UNIX file system. ufs is a hierarchical (tree structure) file system that is/


Chapter 1: Introduction

hardware Provides the file system, CPU scheduling, memory management, and other operating-system functions; a large number of functions for one level UNIX System Structure Microkernel System Structure Moves as much from the kernel into “user” space Communication takes place between user modules using message passing Benefits: Easier to extend a microkernel Easier to port the operating system to new architectures More reliable (less code is running in kernel mode) More/


CS 140 Lecture: files and directories

inode array called an i-number. Internally, the OS refers to files by inumber When file is opened, the inode brought in memory, when closed, it is flushed back to disk. Inode array file blocks ... Example: (oversimplified) Unix file system Want to modify byte 4 in /a/b.c: readin root directory (inode 2) lookup a (inode 12); readin lookup inode for b.c (13); readin use inode to find blk for/


Herding Cats Managing a mobile Unix platform in the enterprise.

AES-128 encryption  Data is stored in a resizing disk image  Master certificate allows password recovery by admin Deemed mandatory in our organization  We had to hack things a bit  A script runs at login time/Networking setup Mounting network file systems Hotplugging disks, audio, video, … Why … choose OS X? Unix!  X-Windows capability Well designed, e.g. fixing long-time Unix issues (launchd, directory services, …) Everything is integrated  Applescript  User preference system  Server side preference/


1 Introduction to Unix: More Commands, Boot-up Actions and X Window We continue to give more information about the fundamental commands of the Unix operating.

introductory information about the the system’s bootup sequences. As before, everything told for Unix here is applicable to the Linux operating system also. 2 Working with Unix Unix is a powerfull system for those who know how to harness its power. In this chapter, we’ll try to describe various ways to use Unix’s shell, bash, more efficently. Wildcards You might want to copy all the files beginning with data into/


Redirection & Pipes Understanding UNIX Input and Output.

its output. –Monitor –Printer Any defined device capable of receiving output What is a file? UNIX is a file based operating systemEverything is a file Say What!? UNIX File Types Types of files –Directory File Contains references to other files –/dev –Regular File Text, configuration, etc. –/home/my.txt –Device Files –/dev/cdrom UNIX Commands Are commands Files too Typically single “specialized” functions Commands are files that accept input and perform some operation, either –On the input directly, or/


Guide To UNIX Using Linux Third Edition

, you can perform a range of editing tasks – this offers flexibility in terms of file manipulation Guide to UNIX Using Linux, Third Edition Reviewing UNIX/Linux File Types Regular files, also known as ordinary files Create information that you maintain and manipulate, and include ASCII and binary files Directories System files for maintaining file system structure Guide to UNIX Using Linux, Third Edition Reviewing UNIX/Linux File Types (continued) Special files Character special files relate to serial I/


CSCI 243: C & UNIX Kirk Anne South 124A

Everything AND the kitchen sink) –pico (the easy way out) Why “vi”? It’s on every UNIX system. If you do system adminstration, you will want to learn it. “Moded” editor After you learn it, it is a fast editor to work with. Why “emacs”? On many machines If you do a lot of programming, you will want to learn it. Multiple windows, multiple files/7 of UNIX in a Nutshell “emacs” - Control H t (tutorial) “vi” Chapter 8 of UNIX in a Nutshell “vi” “Introduction to ‘vi’” File permissions Major part of UNIX security /


File System Security 1. General Principles Files and folders are managed by the operating system Applications, including shells, access files through.

ancestors ignored when access is requested – Permissions set on a folder usually propagated to descendants (inheritance) – System keeps track of inherited ACE’s 7 Linux File Access Control File Access Control for: – Files – Directories – Therefore… dev : devices mnt : mounted file systems What else? Sockets, pipes, symbolic links… 8 Unix Permissions Standard for all UNIXes Every file is owned by a user and has an associated group Permissions often displayed in compact 10-character notation/


1 Introduction to UNIX UNIX & LINUX Fundamentals.

not. ● cp –R or cp - -recursive – Short options ‘-’, long options ‘- -’ 16 Who’s Path is it Anyway? ● UNIX treats the directory structure as a hierarchy of individual paths / usrhomedev bheckerbin 17 Directories ● What is a working directory? – The directory your shell is currently associated with. At anytime in the system your login is associated with a directory ● pwd – view the path of your working directory ● ls – view your working directory/


UNIX Utilities for Power Users Lecturer: Prof. Andrzej (AJ) Bieszczad Phone: 818-677-4954 “UNIX for Programmers and Users” Third.

--> look at the second test file. Lady of the night, I hold you close to me, And everything you say to me is right. $ cmp lady1 lady2--> files differ. lady1 lady2 differ: char 48, line 3 $ _ UNIX Utilities for Power-Users Prof. /in some Unix systems, to tar all.cc and.h files into a tar file named foo.tgz use: $ tar cvzf foo.tgz *.cc *.h This creates (c) a compressed (z) tar file named foo.tgz (f) and shows the files being stored into the tar file (v). The.tgz suffix is a convention for gzipped tar files/


A Mini UNIX Tutorial. What’s UNIX?  An operating system run on many servers/workstations  Invented by AT&T Bell Labs in late 60’s  Currently there.

makes a command recursive, that is, it will execute the same command on all subdirectories. Commonly used to perform file commands on directories Using “cp private/* public/ -r” copies everything from the private folder to the public folder, and also copies all subdirectories. Using “rm –r *” deletes everything in the current directory and all sub-directories. Never use this in the root directory! Programs  Some basic UNIX programs/


Unix/Linux basics 0010 Operating systems lab Gergely Windisch uni-obuda.hu room 4.12.

in the Unix Environment (Richard Stevens) könyvből vették unix file systems (4) Inode inode, cornerstone of all file storage – contains information about the file inode identifies the data itself (inode table) – link to the actual data – access times – owners, permissions etc. Name is not part of the inode – name is just a record in the directory file/tar (tape archiever) tar -cvzf nameoffile.tar.gz * – pack and compress everything in cwd tar -xvzf nameoffile.tar.gz – unpack the contents of nameoffile.tar.gz/


Lecture 1: UNIX HISTORY Prof. Guntis Bārzdiņš. Course homepage  Course requirements Lecture slides Assignments,

is a nice, modular microkernel system, with the memory manager and file system running as user-space processes. This makes the system cleaner and more reliable than a big monolithic kernel and easier to debug and maintain, at a small price in performance, although even on a 4.77 MHz 8088 it booted in maybe 5 seconds (vs. a minute for Windows on hardware 500 times faster). Instead of writing a new file system and a/


CIS 118: Unix Intro Slide 1 Today’s topics ’Unix history ’Unix philosophy ’Unix standards ’Unix future ’Future classes.

files. Ykmem file for internal memory used by the Unix kernel Yttyp1 file for pseudo-terminal 1 Ylp for the system default printer CIS 118: Unix Intro Slide 15 Traditional Unix directory tree Think of this tree as a “family tree”, with parents and children. Everything starts at root “/”, or the Null directory, which is the parent of itself. This is just a small portion of the whole directory tree on a real Unix system. In/


Introduction to Unix/Linux R Bigelow. Why Learn UNIX/Linux? Users are able to access the operating system at a lower level, thus gaining a higher level.

. (Which is a UNIX variant.) Can save developers/administrators months time and thousands of dollars. Interactive Discussion What is Open source? Is this different from Free software? How? What are some of the benefits of using open source software? Benefits of Unix/Linux UNIX is written in C/C++, a high level language, rather than assembly language, as most other OSs. UNIX is therefore easily ported from system to system. UNIX runs on everything from super/


Unix Startup Guntis Barzdins Girts Folkmanis Juris Krūmiņš Artūrs Lavrenovs.

in the Interrupt Descriptor Table (IDT). Another major initialization task is establishing support for various file system types and mounting a root file system. System initialization  OS Initialization The initial process must explicitly do for itself all the tasks accomplished by a call to fork(). This initial process, numbered 0 on UNIX systems/as they will run automatically Crontab Files  Minute 0-59  Hour 0-23  Day 1-31  Month 1-12  Weekday 0-6 (0=Sunday) * Matches everything 1-3 Matches range 1,5/


Introduction to UNIX AfNOG X May 2009 Cairo, Egypt.

Due to modular design has a reasonable security model − UNIX and its applications are not blameless though Initial topics: UNIX birds-eye overview Partitioning FreeBSD installation Kernel The "core" of the operating system Device drivers communicate with your /contain everything not in another partition − /boot for kernel, /bin, /sbin etc. A swap partition for virtual memory Small /tmp partition − so users creating temporary files cant fill up your root partition Small /var partition Rest of disk is /


Chapter Four UNIX/Linux File Processing Guide To UNIX Using Linux Fourth Edition Chapter 4 (27 Slides)1 CTEC 110.

you can directly access each character, you can perform a range of editing tasks – this offers flexibility in terms of file manipulation UNIX and Linux File Processing Chapter 4 (27 Slides)4 CTEC 110 Regular files, also known as ordinary files –Create information that you maintain and manipulate, and include ASCII and binary files Directories –System files for maintaining file system structure Reviewing UNIX/Linux File Types Chapter 4 (27 Slides)5 CTEC 110/


 2000 Prentice Hall, Inc. All rights reserved. Chapter 14 - Advanced C Topics Outline 14.1Introduction 14.2Redirecting Input/Output on UNIX and DOS Systems.

File "%s" could not be opened ", argv[ 1 ] ); 25 26 return 0; 27} Notice argc and argv[] in main argv[1] is the second argument, and is being read. argv[2] is the third argument, and is being written to. Loop until End Of File. fgetc a/Source- File Programs (III) Keyword static –Variables can only be used in the file they are defined Programs with multiple source files –Tedious to compile everything if small changes made to one file –Can recompile only the changed files –Procedure varies on system UNIX: make/


D u k e S y s t e m s CPS 310 Unix Broadly Defined Jeff Chase Duke University

or network storage applications etc. Unixfile descriptors” illustrated user space pipe file socket per-process descriptor table kernel space system-wide open file table tty Disclaimer: this drawing is oversimplified pointer Processes often reference OS kernel objects with integers that index into a table of pointers in the kernel. (Why?) Windows calls them handles. In Unix, processes may share I/O objects (i.e., “files”: in Unixeverything is a file”). But the descriptor name space/


CE01000-3 Operating Systems Lecture 6 Overview of Unix/Linux operating systems.

categories of system calls in Unix. File manipulation (same system calls also support device manipulation) Process control Information manipulation. File Manipulation A file is a sequence of bytes; the kernel does not impose a structure on files. In Unix almost everything is represented by a file Files are organized in tree-structured directories. Directories are files that contain information on how to find other files. File Manipulation (Cont.) Path name: identifies a file by specifying a path through/


TAMU CSCE 313 (the basics). Basic Unix/Linux programming Accessing CS systems  PuTTY (putty.exe) – a Telnet and SSH client  Common hosts: unix.cs.tamu.edu.

(ignores files that are ‘invisible’) cd bob – change directory to bob folder  cd.. (jumps one level up in directory) mkdir filename – makes a folder of given filename rm blah – removes file  rm *.ext – removes everything in current directory of a given extension/File Editors As the directory you log into with unix and linux is the same as your H drive in most cases, you can modify files in a normal windows environment  Visual Studio, Notepad++, GVIM, etc. If you want to modify files in the putty system/


Second edition Your UNIX: The Ultimate Guide Das © 2006 The McGraw-Hill Companies, Inc. All rights reserved. The Operating System Allocates memory for.

Companies, Inc. All rights reserved. Features of UNIX A multiuser system UNIX is a multiprogramming system it permits multiple programs to remain in memory and compete for CPU These programs can be run by different users – multiuser Windows - single user system CPU, memory and hard disk; all dedicated to a single user kernel uses the principle of time sharing A multitasking system UNIX is a multitasking system user can edit a file, print another one, send email to/


Operating Systems of The Future ( and Plan 9 ) Shilad Sen – April 26 th, 2007.

Pike, Ken Thompson, Brian Kernighan, Dennis Ritchie) Major Architectural Concepts: –Distributed Operating System –All resources are represented as files –Application resources are organized via customizable namespaces –Standardized communication protocol (9P) 7 Everything’s a File! In many early operating systems, different types of block devices had different API’s. One major innovation in UNIX was the single file I/O API for multiple devices. Plan 9 treats virtually all devices/


Unix Programming Environment Part 3-3 File Systems in Unix Prepared by Xu Zhenya(

be viewed using:  ls -l  stat: a system call to fetch a file’s attributes  Example : $ ls -ld / /dev  What type of files are / and /dev?  How come /dev is bigger than /? Unix Programming Environment Dept. of CSE, BUAA A typical file system in Unix Unix Programming Environment Dept. of CSE, BUAA A typical file system in Unix Unix Programming Environment Dept. of CSE, BUAA Unix Programming Environment Dept. of CSE, BUAA File Systems in Modern Unix Systems VFS XXX-FS BUFFER CACHE open read mount/


Unix Programming Environment Part 2 – An Introduction to Unix Systems Dept. of CSE BUAA.

and Sun, was first released in 1989:  Integrating features from SVR3, 4BSD, SunOS and XENIX  Virtual File System( VFS ) and Virtual Memory( VM ) from Sun  Real-time scheduling classes  Supporting Symmetric Multiple Processors( SMP )  Kernel-level threads  Fine-grained locks Unix Programming Environment Dept. of CSE, BUAA 2. A Brief History of Unix (7)  2.4 Baseline Release 3: Mach  The Unix kernel is small and simple, yet/


CSCI 330 T HE UNIX S YSTEM C Shell. C S HELL SPECIFICS Startup and initialization Shell variables Prompt Alias Redirections and pipe 2 CSCI 330 - The.

pathnames four parts to a path: head (h): everything from the beginning of the path up to the last slash in the path tail (t): the last directory or file in the path root (r): the filename without an extension extension (e): the filename name extension use a colon to separate the pathname modifier from the variable name 15 CSCI 330 - The UNIX System E XAMPLE : PATHNAME MODIFIER/


Chapter 1: Kernel Overview. 2 Objectives Review development and history of UNIX and Linux. Clarify the nature and extent of the kernel within the context.

would expect in a modern UNIX” –preemptive multitasking –virtual memory (protected memory, paging) –shared libraries –demand loading, dynamic kernel modules –shared copy-on-write executables –TCP/IP networking other features: –SMP support, large memory, large files –advanced networking, advanced filesystems –efficient, stable, highly portable, supports most device hardware –active development community, support, documentation, open source –GUIs, applications 5 What’s a Kernel? aka: executive, system monitor/


CE01000-3 Operating Systems Lecture 5 Overview of Unix/Linux operating systems.

categories of system calls in Unix. File manipulation (same system calls also support device manipulation) Process control Information manipulation. File Manipulation A file is a sequence of bytes; the kernel does not impose a structure on files. In Unix almost everything is represented by a file Files are organized in tree-structured directories. Directories are files that contain information on how to find other files. File Manipulation (Cont.) Path name: identifies a file by specifying a path through/


Operating Systems Structure what is the organizational principle?

functionality not well separated UNIX: Also “ Simple ” Structure Original UNIX OS consists of two separable parts: – Systems programs – The kernel Consists of everything below the system-call interface and above the physical hardware Provides the file system, CPU scheduling, memory management, and other operating-system functions Many interacting functions for one level UNIX System Structure User Mode Kernel Mode Hardware Applications Standard Libs Layered Structure OS is divided into many layers/


CE01000-6 Operating Systems Lecture 22 Operating Systems - Revision Lecture.

memory management Lecture 18 – Windows File System Lecture 19 – Linux/Unix file system Lecture 21 – Windows & Linux protection mechanisms Question from example test 1. Explain the mechanisms involved in mapping between logical (within file) location and disk (physical) locations in, a) Windows XP. In particular your discussion should include logical and virtual cluster numbers, the Master File Table, file and directory entries. (30 marks) b) Linux. In particular your discussion should include directory/


UNIX ™ /Linux Overview Unix/LINUX Intro. UNIX/Linux History.

following: “/” Small Root partition -this will contain everything not in another partition /bin, /sbin, /usr etc. A swap partition for virtual memory /var -For “variable” files, such as logs, mail spools, etc. /tmp -Where temporary files are located /usr -/usr/home contains user directories. This is the largest partition created. In Linux this is just /home. Partitioning Issues Note... Partitioning is just a logical division If your hard drive dies/


CSCI 330 The UNIX System Unit V Permissions. all access to directories and files is controlled UNIX uses discretionary access control (DAC) model each.

itself, SGID on directories doesnt solve everything. (All users need a default umask of 002 instead of 022 as well.) But it goes a long way to making systems governed by projects with multiple users on multiple projects run a lot smoother. 17CSCI 330 – UNIX and Network Programming Special Permissions: Sticky Bit not clearly defined for executable files: executable is kept in memory even after it ended (no longer/


Chapter 1: Introduction. 1.2 Silberschatz, Galvin and Gagne ©2005 Operating System Concepts – 7 th Edition, Jan 12, 2005 Chapter 1: Introduction What.

Silberschatz, Galvin and Gagne ©2005 Operating System Concepts – 7 th Edition, Jan 12, 2005 UNIX UNIX – limited by hardware functionality, the original UNIX operating system had limited structuring. The UNIX OS consists of two separable parts Systems programs The kernel  Consists of everything below the system-call interface and above the physical hardware  Provides the file system, CPU scheduling, memory management, and other operating-system functions; a large number of functions for one/


The UNIX Time-Sharing System Mosharaf Chowdhury EECS 582 – W1611/11/16.

.catb.org/esr/writings/taoup/html/graphics/kd14.j pg Simplicity Simple abstractions Everything is a file Simple file system design Hierarchical for programming simplicity Simple connectors Pipes that look like files Simple maintenance Self-maintained 1/11/16EECS 582 – W167 “It is hoped, however, the users of UNIX will find that the most important characteristics of the system are its simplicity, elegance, and ease of use.” - DR & KT, “The/


1 Plan 9 Dave Eckhardt 1 Synchronization ● Survey – How many have installed *nix on a box? ● Windows? – How many have done an upgrade?

legacy OSs right for this job? 1 The Plan 9 Approach ● “Build a UNIX out of little systems” –...not “a system out of little Unices” ● Compatibility of essence – Not real portability ● Take the good things – Tree-structured file system – “Everything is a file” ● Toss the rest (ttys, signals!!!) 1 Design principles ● Everything is a file – Standard naming system for all resources ● “Remote access” is the common case – Standard resource access protocol, 9P ● Personal namespaces – Naming conventions keep/


Introduction to Unix AfNOG 2006 Workshop May 7, 2006 Nairobi, Kenya Hervey Allen Phil Regnauld.

oversees memory access The Filesystem The file system is a tree. Objects include files, directories (folders), links, devices In UNIX, Everything Is A File! (well, almost) Files can be accessed via an explicit path, from the root, to the file: /usr/local/bin/bash -> this is an ABSOLUTE path... or in relation to where one is located:../../etc/passwd -> this is a RELATIVE path Access rights Files are owned by a user and a group (ownership) Files have permissions for the user/


Unix – Module I. Agenda – Basics of UNIX  Introduction to UNIX Variants of Unix Operating System UNIX Operating System Concepts Multiuser Multitasking.

pwd print working (current) directory rmdir [options] directoryremove a directory ls – one of the most used commands in any day. Syntax ls [options] [argument] -a lists all files, including those beginning with a dot (.). hidden files -d lists only names of directories, not the files in the directory -F indicates type of entry with a trailing symbol: File Maintenance & permissions 13 In Unix almost everything is file n text based. To create, copy, remove and/


Dr. Introduction to Computing Dr. Pierre Vignéras This work is licensed under a Creative Commons Attribution-Share Alike.

on Linux) II. History/OS Dr. 148 File System Files & Directories ● A directory (folder) is a mapping between a file name and the actual file (data) ● Directory structure can be: – Flat: all files into one folder – Hierarchical: folder can contain files and folders ● Attributes – Permissions (owner, groups, others in UNIX) – Creation, Modification date ● Extended Attributes – Icons, Author,... II. History/OS Dr. 149 File System Files & Directories ● In console mode, ● . means the current directory ● .. means/


UNIX Filesystem and Hierarchy AfNOG 2008 Workshop May 2008 - Rabat, Morocco.

Hierarchy AfNOG 2008 Workshop May 2008 - Rabat, Morocco The UNIX filesystem ● The file system is a tree. Objects include files, directories (folders), links, devices <- the root / tmp usr var dev bin etc local bin plain file executable file folder device file symbolic link bash ad0 sh rc.conf / usr / local / bin / bash The UNIX filesystem ● In UNIX, Everything Is A File! (well, almost): disks, terminals,... ● Files can be accessed via an explicit path, from the root, to/


Dr. Introduction to Computing Dr. Pierre Vignéras This work is licensed under a Creative Commons Attribution-Share Alike 2.0 France.

on Linux) II. History/OS Dr. 148 File System Files & Directories ● A directory (folder) is a mapping between a file name and the actual file (data) ● Directory structure can be: – Flat: all files into one folder – Hierarchical: folder can contain files and folders ● Attributes – Permissions (owner, groups, others in UNIX) – Creation, Modification date ● Extended Attributes – Icons, Author,... II. History/OS Dr. 149 File System Files & Directories ● In console mode, ● . means the current directory ● .. means/


Introduction to Unix AfNOG 2007 Workshop April 22, 2007 - Abuja, Nigeria Hervey Allen Phil Regnauld.

memory access The Filesystem ● The file system is a tree. Objects include files, directories (folders), links, devices ● In UNIX, Everything Is A File! (well, almost) ● Files can be accessed via an explicit path, from the root, to the file: ● /usr/local/bin/bash -> this is an ABSOLUTE path ●... or in relation to where one is located: ●../../etc/passwd -> this is a RELATIVE path Access rights ● Files are owned by a user and a group (ownership) ● Files have permissions for the user, the/


Safety measures in Linux Krzysztof Lichota

Unix security measures Standard Unix security model ● Root (uid==0) can do everythingFiles have owner, group, access permissions for user, group and others ● It is possible to pass privileges to executed application using SUID bit ● Hardcoded into Linux kernel POSIX capabilities ● Extension to standard Unix model ● Defined in POSIX draft 1003.1e ● In/Generating true random numbers (important problem on embedded, isolated systems) – Built-in generic encryption libraries used by kernel modules – Block /


The Future of Distributed Systems .

is authenticated ID In a distributed system, “who” and “what” and “whom” are distributed objects subject Object Permissions Security in Distributed Systems Security domain: nodes with a shared security server. Security domains can have trust relationships: A trusts B: A “believes” B when it says this is Jim@B Security domains form a hierarchy. Delegation: passing authority to a server when A asks B to do something (e.g. print a file, read a/-allocate everything on server preallocate memory pre-open files pre/


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