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 The Linux system of permissions is much more difficult than that of Windows  System administrators are given more control with the use of three distinct permission categories of read, write, and execute. 2

Access typeFileFolder ReadIf the file contents can be read If the directory listing can be obtained Write If user or process can write to the file (change its contents) If user or process can change directory contents somehow: create new or delete existing files in the directory or rename files. ExecuteIf the file can be executed If user or process can access the directory, that is, go to it (make it to be the current working directory) 4 3

 File and directory permissions in Linux are controlled through the use of the chown and chmod commands.  The chown command is performed by all users to specify the user and group ownership of a file or directory: ◦ chown username.group filename ◦ For example: chown jdoe.executives report_01  File and directory ownership is an important concept in Linux because permissions are declared for both users and groups based on this ownership ◦ chmod mode filename ◦ For example: chmod 700 report_01 4

 There are two types of configuration files for the Linux file system, User and System configuration files.  The user configuration files are stored as dot (.) files  The user settings for the KDE interface are stored in the.kde and.kderc files.  These dot files are hidden and are ignored by most Linux tools, They can be listed by the ls –a command. 5

 System configuration files control system functions after the system has been booted up.  These files control programs that run in the background, most often unnoticeable to the user.  Each program has a configuration file found in its corresponding subdirectory located in the /etc directory.  The /etc/fstab file provides access to disk partitions and removable media devices. 6

 The /etc/inittab file is responsible for controlling initial processes, which runs the startup scripts on a Linux system.  There are two types of lines that will be found in the /etc/inittab files: comment lines and control lines.  Comment  Comment lines are found in all scripts in any operating system.  These are the lines that are commented out using a pound sign (#).  Control  Control lines are the lines that are read by the program. 7

 Linux includes text editing tools that allows the creation of the configuration and script files as well as editing them.  They are vi Editor and Pico.  The vi editor is the most common one.  The three modes of operation in vi Editor are command, edit/entry, and last-line.  Enter "edit" mode by choosing the command i. 8

 The Linux operating system can accommodate many different scripting languages. The most common and basic of these is its built-in ’shell scripting’ abilities.  A shell script is a text file that contains any number of Linux commands listed successively.  Each command is executed in turn exactly as if it had been typed at the command prompt.  Shell scripts can also contain programming logic such as looping and conditional statements. 9

Benefits of Networking 10

 File, print, and application services.  Mail services  Directory and name services  The Internet  Network administration 11

 The desire to share important information was one of the main reasons for the development of computer networks.  Networks enable multiple computers to connect together to share files and communicate via electronic mail( ).  Network devices such as printers connect to the network so that multiple users can share one printer which allows for more efficient use of printers. 12

 works as a “storage-and-retrieval” application.  Mail messages are stored on an server until the recipient retrieves the .  There will also be a post office box created for the users.  When messages are received, the server will redirect the messages to the users post office box where the messages remain until the user retrieves them. 13

 The storage-and-retrieval nature of systems does not require that the recipient be connected when the is sent.  It can be picked up or retrieved at a later time. 14

 To enable users and systems on the network to find the services they require, computer networks make use of directories and name services.  The network assigns a name to users, services, and devices so that they can be identified and accessed.  Knowing the name of a service on the network enables users to contact that service without having to know its physical location. 15

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 People work easily with names for services than numeric addresses.  They can rely on network directory and name services to translate those names into the addresses used to communicate with the desired service. 17

 The Internet is a worldwide public network, interconnecting thousands of other networks to form one large "web" for communication.  This facilitates exchange between geographically separated users, organizations, and branches of companies.  These connections enable long distance access to network services for information and device sharing. 18

 Computer networks need to be monitored and maintained to remain efficient.  They must also change and grow in response to new technologies and user requirements. 19

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Daemons 21

‘  The functions that are called ‘services’ in Windows are referred to as Daemons in Linux.  Examples of Linux Daemons are FTPD and HTTPD.  Daemons run as a background process and run continuously without producing any visible output. 22

 There are several common Linux Daemons: ◦ HTTPD: This daemon is responsible for web browser requests. ◦ Inetd: This daemon will wait for an incoming request to be made and then forwards that request to the appropriate Daemon. ◦ Crond: This daemon will run scripts at a specified time. ◦ Syslogd: This daemon will record information about currently running programs to the system log file.  Daemons can be loaded or unloaded into memory at any time.  They can also be restarted without having to restart the entire system. 23

 Sys V scripts  Sys V scripts can be used to start, stop, or restart Linux Daemons.  To execute these scripts they need to be followed by options such as start, stop, or restart.  To know the current state of a daemon use status. 24

 The Linux NOS is not capable of providing the HTTP daemon to users. Apache  Instead, a separate web-hosting program named Apache is the common solution.  Apache provides the same HTTP Daemons for Linux that the Internet Information Services (IIS) tool does for Windows.  Users do not have to be running a Linux system to access the apache web server daemon because the apache web-server is accessed by the HTTP protocol, which is operating system independent. 25

Linux FTP service (FTPD)  The Linux FTP service (FTPD) needs no configuring.  This setting is found in the /etc/rc.d/init.d/xinetd.  If a system administrator wishes to disable the service, a pound sign (#) can be placed at the start of the line.  Otherwise, Linux automatically starts the FTP Daemon (FTPD) during the boot process, and users are able to remotely FTP to the machine at any time. 26

 Telnet  Telnet allows a remote user to log in to a system for the purposes of issuing commands and accessing files using a CLI.  Telnet  Telnet must be configured so that only authorized users are able to access the server.  When a server is listening for Telnet requests, a hacker can try to use brute force to break into a system.  The hacker may use a program that guesses the password, then he can log in to the system. SSH.  A more secure alternative to Telnet is SSH. 27

 The Server Message Blocks (SMB)  The Server Message Blocks (SMB) protocol is designed to be a file sharing protocol. Common Internet File systems (CIFS  It has since been renamed to Common Internet File systems (CIFS) but is still used for file and printer sharing. non-Linux mount Linux file systems printers  This protocol is used to allow non-Linux or UNIX systems to mount Linux file systems and printers over the network.  The SMB protocol allows a Windows client to do this the same way as if they were connecting to another Windows system. 28

 NFS  NFS is used as a means to share files between multiple computer systems connected on a network.  NFS stands for Network File System.  The xxx is the location of the share in the file server. 29

Daemon mail transfer agent (MTA), transport protocol  To set up the Daemon on Linux, the administrator will need to set up a mail user agent, the mail transfer agent (MTA), and the transport protocol.  The mailer provides the user with an interface for reading and composing messages. MTA  The mailer uses the MTA to transfer the mail from the sender to the recipient and back. SMTP Sendmail  The two major MTAs are SMTP and Sendmail. 30

the print queue  The main component of Linux printing is the print queue. Linux print server  It resides on a Linux print server to handles all of the incoming print jobs directed to network printers.  The LPRng software provides the server with the ability to handle multiple printers and queues as well as provides the security that will be needed in a large network.  The /etc/printcap file is at the core of the LPRng printing software.  Linux uses it to knows which printers are online and available for printing. 31

GUI tool printtool  Red Hat comes with a GUI tool that can be used to setup printers called printtool.  To use the tool, type printtool at a shell prompt, this will launch the GUI printer configuration tool.  This tool aids in configuring a client workstation to connect to a printer either locally or to a print server over the network. 32