Week Twelve Agenda

2. Week Twelve Agenda • Announcements • Proctor fax final answer sheets before mailing final exam to the Student Learning Center. • Grade submission is August 13 before 12:00 PM EST • Link of the week • Review week eleven lab assignment • Week eleven expected outcomes • Next lab assignment • Break-out problems • Upcoming deadlines • Lab assistance

3. Link of the week • Domain name registration Web site https://www.pairnic.com/services.html?gclid=COXiuLv6mI0CFSCTWAod81M57A • Determine if a domain is currently in use. http://www.pair.com/ • What is a domain name? • What is the function of the Domain Name System? • BIND (Berkley Internet Name Domain) • What is meant by top level domain?

4. Link of the week Top Level Domain (TLD) • gov – Government • edu – Educational • org – Organizations (nonprofit) • mil – Military • com – Commercial business • net – Network organizations • ca – Canada • th - Thailand

5. Link of the week The URL is hierarchy.

6. Review week eleven lab assignment User Initialization The /etc/inittab runlevel field format: id:runlevels:action:process /etc/inittab file 1:2345:respawn:/sbin/mingetty tty 1 /etc/profile file Basic setup for all users $HOME/.profile User preferred environment Use the ls –a command to display the .profile file under your $HOME directory. Use the printenv or env commands to display environment variables.

7. Review week eleven lab assignment Metadata Metadata is data about data. It may describe a single piece of data or multiple content items and hierarchical levels. There are many different types of metadata. Business Intelligence metadata General IT metadata IT metadata management products File system metadata Image metadata

8. Review week eleven lab assignment $HOME/.profile or .bash_profile The $HOME/.profile file in your home directory is a collection of shell commands that are executed whenever you login. The $HOME/.profile file is used to set environmentvariables and shell options. PATH – executable search path - adding a directory either pre or post within PATH variable - set PATH for single user or all users umask – defaults: umask 077 Alias - alias search=grep TERM=vt100 export SHELL TERM EDITOR VISUAL MAIL PRINTER USER PS1 • Display available shells on system. cat /etc/shells • Display current shell being utilized. echo $SHELL • Change to a different shell . chsh –s /bin/ksh

9. Review week eleven lab assignment Linux runlevels: 0 - halt (Do NOT set initdefault to this) 1 - Single user mode 2 - Multiuser, without NFS (The same as 3, if you do not have networking) 3 - Full multiuser mode 4 - unused 5 - X11 6 - reboot (Do NOT set initdefault to this) The runlevel may contain multiple characters for different runlevels. 1:23:respawn:/sbin/mingetty tty1 2:23:respawn:/sbin/mingetty tty2 3:23:respawn:/sbin/mingetty tty3 4:23:respawn:/sbin/mingetty tty4

10. Review week eleven lab assignment /etc/inittab actions respawn – The process will be restarted whenever it terminates. wait – The process will be started once when the specific runlevel is entered. once – The process will be executed once when the specific runlevel is entered. boot – The process will be executed during system initialization. initdefault – This entry specifies the runlevel which should be entered after system boot. sysinit – The process will be executed during system boot. It will be executed before any boot or bootwait entries.

11. Review week eleven lab assignment /etc/inittab actions powerwait – The process will be executed when the power goes down. powerokwait – This process will be executed as soon as init process is informed that the power has been restored. powerfailnow – This process will be executed when the init process is informed that the battery of the external UPS power is failing. ctraltdel – The process is executed when the init process receives the SIGINT signal. This means that someone on the system console has pressed the Ctrl-Alt-Del key combination.

12. Review week eleven lab assignment UNIX-like commands: ps –s (view zombie processes) ps –x (view only active processes) ls –a (view “.” processes) ps -aux | grep crond (view crond executing) nice (execute with modified scheduling priority) umask (displays umask numeric values) umask –S (displays umask symbolic values) fg (Resume jobspec in the foreground, and make it the current job) bg (Resume the suspended job jobspec in the background, as if it had been started with &)

13. Review week eleven lab assignment Unix/Linux Processes Linux defines a unit of work as a task or process. UNIXdefines a unit of work as a process. Each process is identified by a unique PID. Each process is started from a previous process using the fork and exec command. The init process is created by the kernel using a non-traditional procedure called hand-crafted or spontaneous. Background processes run with a relatively low priority, require little or no input, and generate a minimum of output. Background process is unlike with a foreground process, the shell does not have to wait for a background process to end before it can run more processes. Background jobs are run at a lower priority to the foreground jobs. Foreground process is one that canshow the user an interface, throughwhich the user can interact with the program.The user must wait for one foreground process to complete before runninganother one.

14. Review week eleven lab assignment Daemon processes offer services like web pages serving, email transferring, time synchronization, and similar. They usually consume little CPU and memory, and run quietly without user interaction. They mainly communicate with other computer programs, or with other computers via network. Non-Inherited Process Attributes File locks Resource utilization of a child process are set to zero Pending signals

15. Review week eleven lab assignment cron is the periodic event scheduler of your system. The following examples give you an idea of its usefulness and necessity. • regular daily backups • periodic mail checking • polling a device for input • sending regular reports • sends user email every time a cron function is performed cron file locations /etc/crontab /etc/cron.deny /etc/cron.allow Typical directory configuration /etc/cron.d/hourly /etc/cron.d/daily /etc/cron.d/weekly /etc/cron.d/monthly How frequent does cron execute on a Unix-like system? Disable email 0 * * * * echo “Email Sent” 2>&1 /dev/console

16. Review week eleven lab assignment • Demonstrate: Display crontab entries and /var/mail/dandrear file • Who can use the crontab commands (create, list, edit or remove)? • Each line of CRONTAB has the following structure: <Minute> <Hour> <Day> <Month> <Day of Week> <Command line> There are a total of 6 fields in the crontab file # This is a comment. * * * * * c:\tools\CheckForNewFiles.exe • What does the “*” character represent in the first five fields of a crontab record? • A single integer that matches that exact value. • A comma separated list of integers, like 1,2,3 to match one of the listed values.

17. Review week eleven lab assignment crontab format: * * * * * command to be executed crontab values: Field Value minute 00-59 hour 00-23 (military time) day 1-31 month 1-12 weekday 0-6 (0=Sunday) Example records: 30 5 11 12 * “Welcome to Franklin University” 30 * * * * “Unix Administration”

18. Review week eleven lab assignment crontab restrictions If your name appears in the cron.allow file. If that files doesn’t exist, you can use crontab. if your name does not appear in the cron.deny file. If cron.deny exists and is empty, all users can use crontab. If neither file exists, only the root user can use crontab. crontab command without options Read standard input Exit using “Control C” so that the existing crontab is unmodified. Exit using “Control D” will cause the current users’ crontab to be replaced with no information.

19. Review week eleven lab assignment Lab exercise: Create a crontab entry The command part of the entry should perform a simple shell function Monitor your mail file using the tail command

20. Week ten, eleven, and twelve expected outcomes • Upon successful completion of this module, the student will be able to: Manipulate user accounts. Describe how cron is used to invoke repetitive processes. Manipulate process structure including: a. fork and exec, b. Initialization process, c. Background/foreground, d. PS tool. Explain basic UNIX security issues. Describe disk and file system structure. Use backup and restore archival operations on a system. Establish network services. Investigate the structure of the LDAP directory using LDAP commands.

21. Next lab assignment • Copy-on-Write It is an optimization strategy for multiple users can give the same pointer for a resource. The primary advantage is that if a caller never makes any modifications, no private copy is needed. Use: Virtual memory operating systems pages in memory that might be modified by either the process or its copy are marked copy-on-write.

22. Next lab assignment • Network Services A variety of services available across a network NFS Remote login Utilize a Web browser • All network services rely on the ability to convert a host or domain name to an IP address. DNS are complex. The number of host names and IP addresses in the Internet is very large. DNS Local contains actual translations for the machines in its local network DNS Global contains more information about translations. A single translation could involve several DNS before resolving the IP address.

23. Next Lab Assignment • UNIX/Linux file system is contained under the root directory denoted by a slash “/”. • Users don’t have to worry about the physical locations of files. • The system administrator must be familiar with mounting and un-mounting storage space (/mnt). • NIS+ (Network Information Service) is a directory service.

24. Next Lab Assignment What is the functionality of Network File System (NFS) • It is a remote filesystem designed by Sun Microsystems, available on computers from most UNIX system vendors. • It allows the server to share selected local directory hierarchies with client systems on a heterogeneous network. Files on the remote computer (fileserver) appear as if they are present on the local system. The physical location of a file is irrelevant to an NFS user.

25. Next Lab Assignment File System Is the methods and data structure that an operating system uses to keep track of files on a disk or partition; that is the way the files are organized on the disk. Inode (Index node (metadata)) An inode contains all information about a file, except its name and the actual data. The name is stored in the directory, together with the number of inode. A directory consists of a file name and the inode which represents the file. The inode contains the number of several data blocks. On many file system types the number of inodes available is fixed when the filesystem is created, giving a maximum number of files the file system can hold. Typically when a file system is created about 1% of it is devoted to inodes.

26. Next Lab Assignment Super Block Contains information about each mounted file system. The actual data structure in Linux is called struct vfsmount. Information held is mount flags, mount time, device name, pointer to super block and device block size. The Linux 2.0 kernel keeps a static array of such structures to store up to 64 mounted file systems. Data Block Data blocks are used to store the data in the file. There is space only for a few data block numbers in the inode, however if more are needed, more space for pointers to the data blocks is allocated dynamically. These dynamically allocated blocks are indirect blocks. The name indicates that in order to find the data block, one has to find its number in the indirect block first.

27. Next lab assignment

28. Next Lab Assignment

29. Next lab assignment UNIX base root file system tree structure /bin (commands) /dev (devices) /etc (system configuration/executables) /sbin (boot commands) /usr/sbin (administrative commands) /home (users home directories) /lib (shared libraries) /mnt (temporary mount directory) /opt (optional software) /proc (processes) /stand (boot-related files) /var (spooling)

30. Next lab assignment lost+found directory fsck is generally able to repair most system damage and the frequency with which you will find anything at all in your lost+found directories has slowed significantly If you have a system crash and the Linux file system checker (fsck) recovers corrupt files they are placed here.

31. Next lab assignment Unix-like System Security • Security on UNIX-like systems has focused on the following areas: Files and directories PATH variable password authenication uucp commands One-way function

32. Break-out problems 1. How often do the following 2 commands execute? # This is a comment. 1.1 * * * * * c:\tools\CheckForNewFiles.exe # This is a comment. 1.2 0 * * * * c:\tests\backup.bat 2. Define: File System Super block 3. Define: Domain Name Server 4. Define: Domain name 4. Define: RFC 6. What application is BIND associated 7. What is the “lost+found” area considered on a Unix-like system? 8. Linux Virtual File System 9. One-Way Encryption or One-Way Function

33. Upcoming deadlines Knoppix File System Exercise, 11-1 is due July 19, 2009. Programming Assignment 2, 12-1 is due July 26, 2009. Archives Exercise, 12-2 is due July 26, 2009. Presentations for Public Domain/Open Source Lab Assignment 13-1 will be July 27 and August 3, 2009. Programming Assignment 3, 14-1 is due August 8, 2009. Final Exam, 15-1 will be administered August 3 – 8, 2009. Final Exam Outline will be posted on the Bulletin Board July 19, two weeks prior to the final exam date. This outline will be considered a “living” document. I will add additional information to it up to one week prior to the exam. All additional information posted after the initial posting will be highlighted/indicated.

34. Lab assistance • Questions • Comments • Concerns • I will be available after this Franklin Live session to discuss any problems and/or concerns regarding lab assignments.