1. POS/420 Introduction to Unix Philip Robbins – March 19, 2013 (Week 2) University of Phoenix Mililani Campus

2. Agenda: Week 2 • Quiz #1 Due (Review & Grade) • Week 2 • File Structure • Basic Terminal Commands • Permissions • In Class Lab (Assignment) #1 Due Today • Take Quiz #2

3. Review Week 1 List of Commands • man – manual pages • ls– list directory contents • pwd– print working directory • passwd– change password • sudo– execute command as superuser • su– login as superuser • shutdown – shutdown

4. Linux File System Structure

5. Linux File System Structure

6. root (/)

7. File Structure: Binaries • What’s the difference between: • /bin • /sbin • /usr/bin • /usr/sbin

8. File Structure: Binaries • What’s the difference between: /bin & /usr/bin • When UNIX was first written, /bin and /usr/bin physically resided on two different disks: /bin being on a smaller faster (more expensive) disk, and /usr/bin on a bigger slower disk.

9. /bin • Essential User Command Binaries • Contain commands used by both system administrators and users. • There must be no subdirectories in /bin.

10. /boot • Static files of the boot loader • Contains everything for the boot process (at boot time). • Does not include boot configuration files not needed at boot time. • Stores data that is used before the kernel begins executing. • OS Kernel is stored in either / or /boot.

11. /dev • Device Files • Location of special or devices files.

12. /etc • Host-specific system configuration • Contains configuration files. • Must be Static and cannot be an executable binary. • Required in /etc: opt, X11, sgml, xml

13. /etc

14. /srv • Data for services provided by this system. • - Contains site-specific data which is served by this system. • - Naming methodology not specified. • e.g. /srv/ftp, /srv/pos420/www • Data that is of interest to a specific user should go into that users home directory.

15. /tmp • Temporary Files • Must be made available for programs that require the use of temporary files. • Recommend that /tmp files be deleted upon system reboot.

16. /usr • User Hierarchy • Second major section of the file system. • Used for shareable, read-only data. • Required directories: • bin - essential command binaries • sbin - essential system binaries • include - header files used by C programs • lib - object files, binaries, libraries • local - put apps you build yourself here • share - shared (Static)

17. /usr • What’s the difference between: /usr & /usr/local

18. /usr/share/man • Directory for System Manual Pages • man1: • User programs Manual pages that describe publicly accessible commands are contained in this chapter. Most program documentation that a user will need to use is located here. • man2: • System calls. This section describes all of the system calls (requests for the kernel to perform operations). • man3: • Library functions and subroutines. Section 3 describes program library routines that are not direct calls to kernel services. This and section 2 are only really of interest to programmers. • man4: • Special files. Section 4 describes the special files, related driver functions, and networking support available in the system. Typically, this includes the device files found in /dev and the kernel interface to networking protocol support.

19. /usr/share/man • Directory for System Manual Pages • man5: • File formats. The formats for many data files are documented in the section 5. • This includes various include files, program output files, and system files. • man6: • Games. This chapter documents games, demos, and generally trivial programs. Different people have various notions about how essential this is. • man7: • Miscellaneous. Manual pages that are difficult to classify are designated as being section 7. The troff and other text processing macro packages are found here. • man8: • System administration. Programs used by system administrators for system operation and maintenance are documented here. Some of these programs are also occasionally useful for normal users.

20. /usr/share/man • Manual Section Summary

21. man apropos

22. apropos

23. apropos man6: Games. This chapter documents games, demos, and generally trivial programs. Different people have various notions about how essential this is.

24. /var • Variable Hierarchy • Contains variable data files. • Spool files & directories, logging data, temporary files (for system reboots). • Not Shareable. • e.g. /var/log, /var/mail, /var/cache, /var/crash (dump files) • Can be placed in /usr/var. (If separate partition for /var is not possible).

25. /var • Use the “more” command to view files. • man more for more information • view syslog • view kern.log • Also use the “head” and “tail” command to view files. • man head & tail for more information • know how to head & tail –n lines of a file

26. /proc • Kernel and process information virtual file system • Used for handling process and system information • Kernel and memory information

27. man ps

28. top

29. FHS Compliant System • Rationale: • Not all files can be shared • Static and Variable files should be segregated • Static files can be stored on read-only media • Different backup schedules

30. man fdisk

31. sudo fdisk -l • Use fdisk to list all partitions (as root)

32. fdisk

33. Typical Partitions

34. Virtual Terminals (TTY) • Six tty (1 – 6) • Hold Ctrl + Alt, press F1 (for tty1) • F2 (for tty2) … F6 (for tty6) • Hold Ctrl + Alt, press F7 (to return to GUI) • Press and hold Ctrl + Alt to switch between VM and GUI

35. who

36. who

37. User ($) vs. Root (#)

38. Shells • What is an OS shell? • Types • ksh, tcsh, csh, sh, bash • What shell are you running? • echo $SHELL

39. Shells • csh

40. man usermod

41. man ssh

42. ssh

43. Directory Notation • / • Represents a directory • /. • Represents current directory • /.. • Represents the parent directory • /~ • Represents a user’s home directory

44. File Permissions

45. File Permissions • Octal (numerical) Representation

46. man chmod

47. man chown

48. man chgrp

49. File Permissions Command Summary

50. Run Levels • runlevel • Previous runlevel, current runlevel • init • Change between run levels (process id 1) • telinit • Change system run level (user process)