Linux Administration Part 2

1. Chapter 3 Linux Administration Part 2

2. Passwords and Permissions • 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.

3. 4 Passwords and Permissions

4. Passwords and Permissions • File and directory permissions in Linux are controlled through the use of the chown and chmod commands. • The chowncommand is performed by all users to specify the user and group ownership of a file or directory: • chownusername.group filename • For example: chownjdoe.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 • chmodmode filename • For example: chmod 700 report_01

5. File System Configuration Files • 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.

6. File System Configuration Files • 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.

7. File System Configuration Files • 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 lines are found in all scripts in any operating system. • These are the lines that are commented out using a pound sign (#). • Control lines are the lines that are read by the program.

8. VI Editor • 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.

9. Scripts • 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.

10. Benefits of Networking

11. Benefits of Networking • File, print, and application services. • Mail services • Directory and name services • The Internet • Network administration

12. File, Print, and Application Services • 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(e-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 .

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

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

15. Directory and Name Services • 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.

16. Directory and Name Services

17. Directory and Name Services • 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.

18. The Internet • 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.

19. Network Administration • 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.

20. Network Administration

21. Daemons

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

23. Introduction to Linux Daemons • 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.

24. Starting, Stopping, and Restarting Daemons • 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.

25. HTTP • The Linux NOS is not capable of providing the HTTP daemon to users. • 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.

26. FTP - File Transfer Protocol • 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.

27. Telnet • Telnetallows a remote user to log in to a system for the purposes of issuing commands and accessing files using a CLI. • Telnetmust 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. • A more secure alternative to Telnet is SSH.

28. Server Message Block (SMB) Protocol • The Server Message Blocks (SMB) protocol is designed to be a file sharing protocol. • It has since been renamed to Common Internet File systems (CIFS) but is still used for file and printer sharing. • 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.

29. NFS • NFSis 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.

30. Mail Client • To set up the e-mail 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. • The mailer uses the MTA to transfer the mail from the sender to the recipient and back. • The two major MTAs are SMTP and Sendmail.

31. Printing in a Linux Environment • The main component of Linux printing is the print queue. • 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/printcapfile is at the core of the LPRng printing software. • Linux uses it to knows which printers are online and available for printing.

32. Printing in a Linux Environment • 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.