Week Twelve Agenda

1. Week Twelve Agenda • Announcements • If you need to change your proctor, do it soon. Final will have the same format as midterm – just more questions and more time given. • Link of the week • Review week eleven lab assignment • Week eleven expected outcomes • Next lab assignment • Upcoming deadlines • Lab assistance

2. Link of the week • Domain name registration Web site http://www.godaddy.com • Determine if a domain is currently in use. http://www.pair.com/ or http://www.godaddy.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?

3. 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

4. Link of the week http://www.iana.org/cctld/cctld.htm Iana - Internet Assigned Numbers Authority Observe the Root Zone Database at the above Web site. It represents the list of top-level domains. Each country has an ISO (International Organization for Standardization) country code designated as its domain name. The URL (Uniform Resource Locator) is also a hierarchy. Its top-level domain name appears at the end, but is read from left to right). alpha.einstein.edu beta.ca.mail2web.com

5. Link of the week

6. 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.

7. 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

8. Review week eleven lab assignment UNIX commands: ps –s (view zombie processes) ps –x (view only active 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 job in the foreground, and make it the current job) bg (Resume the suspended job in the background, as if it had been started with &) cat /etc/shells (Display available shells on system). echo $SHELL (Display current shell being utilized). Chsh –s /bin/ksh (Change to a different shell) . printenv or env (commands to display environment variables).

9. Review Process States PROCESS STATE CODES D uninterruptible sleep (usually IO) R runable (on run queue) S sleeping T traced or stopped Z a defunct ("zombie") process For BSD formats and when the "stat" keyword is used, additional letters may be displayed: W has no resident pages < high-priority process N low-priority task L has pages locked into memory (for real-time and custom IO) Use the ps –aux | less command to display the above mentioned codes listed under the STAT column heading.

10. Review Week Twelve Lab Assignment PROCESS STATE Code USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 1 0.0 0.0 1424 488 ? S Oct19 0:24 init root 2 0.0 0.0 0 0 ? SW Oct19 0:00 [migration/0] root 3 0.0 0.0 0 0 ? SW Oct19 0:00 [migration/1] root 4 0.0 0.0 0 0 ? SW Oct19 0:00 [migration/2] root 5 0.0 0.0 0 0 ? SW Oct19 0:00 [migration/3] root 6 0.0 0.0 0 0 ? SW Oct19 0:00 [keventd] root 7 0.0 0.0 0 0 ? SWN Oct19 0:00 [ksoftirqd/0] root 8 0.0 0.0 0 0 ? SWN Oct19 0:00 [ksoftirqd/1] root 9 0.0 0.0 0 0 ? SWN Oct19 0:00 [ksoftirqd/2] root 10 0.0 0.0 0 0 ? SWN Oct19 0:00 [ksoftirqd/3] VSZ – virtual memory usage of the entire process. RSS – non-swapped physical memory that a task has used.

11. Review week eleven lab assignment Unix/Linux Processes Linux defines a unit of work as a task or process. Unix defines 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.

12. Week Fifteen Agenda The fork () function is used to create a new process from an existing process. The new process is called the child process, and the existing process is called the parent. Their differences can be verified by checking the return value from fork (). The parent gets the child’s pid returned to him, but the child get 0 (zero) to him. The attributes the child inherits from the parent varies depending on the UNIX implementation. Inherits: Process credentials (uids and gids) Scheduling Class Environment Root Directory Stack Current Working Directory Memory Controlling Terminal Open file descriptors Resource Limits Close on exec flags Nice Value Signal handling settings

13. Week Fifteen Agenda Unique to child process: Process ID Different parent process ID Own copy of file descriptors and directory streams Process, text, data and other memory locks are NOT inherited Process times, in the tms struct Resource utilization are set to zero. Pending signals initialized to the empty set Timers created by timer_create operations not inherited Asynchronous input or output operations not inherited

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.

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 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. * * * * * /export/home/varneyg/checkfiles.sh 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 * echo “Welcome to Franklin University” 30 * * * * echo “Unix Administration” >/tmp/class.title

18. Review week eleven lab assignment crontab restrictions If your name appears in the cron.allow file or 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 crontab commands crontab -e Edit crontab file crontab –l Display your crontab file crontab –r Remove your crontab file crontab –v Display last time crontab was edited.

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. Background/foreground, b. 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 gives the same pointer for a resource. The primary advantage is that if a caller never makes any modifications, no private copy is needed. This strategy is used in virtual memory operating systems pages in memory that might be modified by either the process or its copy are marked copy-on-write. http://en.wikipedia.org/wiki/Copy-on-write

22. 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. Metadata can be the name of a US corporation, or a registered trademark. Metadata is structured information that describes and allows us to find, manage, control and understand other information. There are many different types of metadata. Business Intelligence metadata General IT metadata IT metadata management products File system metadata Image metadata

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).

24. 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.

25. Next Lab Assignment File System It is an organization of data and metadata on a storage device. It 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. Think of a file system as a protocol. File systems give meaning to the data on a particular storage device. What is a block device? It is a device in which the data that moves to and from occurs in blocks (like a disk sector) and supports attributes such as buffering and random access behavior. Block devices include hard drives, CD-ROMs, and RAM disks. What is a character device? It is a device that does not have a physical addressable media. Character devices include serial ports and tape devices, where data is streamed character by character.

26. Next Lab Assignment File System

27. 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.

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29. Next Lab Assignment

30. Next lab assignment Linux Virtual File System (VFS) The purpose of a VFS is to allow client applications to access different types of file systems in a uniform way. Manages kernel file “abstractions” in one formatfor all file systems. File Manager Is a program that provides a user interface to work with the file system. They are very useful for speeding up interaction with files. The most common operations on files are create, open, edit, print, rename, move, and copy.

31. 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)

32. 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.

33. Review fsck (filesystem check) fsck fsck is a utility that analyses and repairs file system inconsistencies. The file system is checked by providing the name of the block or character special device or by giving the name of its mount point if a matching entry exists in /etc/fstab. fsck File System Inconsistency checks include: Blocks claimed by more than one inode or the free list. Blocks claimed by an inode or the free list outside the range of the file system. Incorrect link counts. Incorrect directory sizes. Bad inode format. Blocks not accounted for anywhere. Directory checks, file pointing to unallocated inode, inode number out of range, and absence of `.' and `. .' as the first two entries in each directory. Super Block checks: more blocks for inodes than there are in the file system. Bad free block list format. Total free block and/or free inode count incorrect.

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

35. Next lab assignment Linux Security SELinux developed by the U.S. National Security Agency (NSA), implements Mandatory Access Control (MAC) in the Linux kernel. MAC enforces security policies that limit what a user or program can do. It defines a security policy that controls some or all objects, such as files, devices, sockets, and ports, and some subjects like processes. Utilizing SELinux, you can grant a process only those permissions it needs to be functional.

36. Review week eleven lab assignment Linux Security TCP Wrapper is part of the client/server model, and can be used with any daemon that is linked against libwrap.a, and relies on the /etc/hosts.allow and /etc/hosts.deny files as the basis of a simple access control language. This access control language defines rules that selectively allow clients to access server daemons on a local system based on the client’s address and the daemon the client tries to access.

37. Upcoming deadlines Knoppix File System Exercise, 11-1 is due March 25. Programming Assignment 2, 12-1 is due April 1. Archives Exercise, 12-2 is due April 1. Presentations for Public Domain/Open Source Lab Assignment 13-1 will be April 2. Programming Assignment 3, 14-1 is due April 14. Final Exam, 15-1 will be administered April 9-14. Module 6, contains study information for weeks 10, 11, and 12. Final Exam Outline will be posted between March 30, 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.

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