Linux

1. Linux Files

2. Files and directories • As in Windows directories are structures which contain • Other directories • Files

3. Root directory • Base directory • All others are contained within this directory • Not to be confuse with /root • This is the home directory of the root user

4. Typical directories • /etc configuration • /var files that change (vary) such as logs • /home structure containing user home directories • /bin executables • /sbin root user executables • /usr regular user files • /tmp • /root • /boot • /dev used to access hardware resources • /lib system libraries

5. Shell • Command line environment • Like the Windows “DOS command line” • Prompt displayed • Enter a command and bit [enter] • Result (if any) returned, and next prompt displayed • Or.. Error message

6. Commands • pwd • print working directory • cd • change directory • mkdir • rmdir • ls • touch

7. cd • cd name • changes to the name directory • uses relative and absolute names • one dot refers to current directory • two dots refers to parent directory • forward slash ( / ) indicates a directory name • no slash indicates a subdirectory in the current directory

8. ls • lists the names of files in a directory • ls –l • long listing

9. touch • updates the time stamp of a file to that time • creates a new file (0 bytes) if the file does not exist

10. cp • copy cp file1 file2

11. rm • remove rm file1 • no “undelete” • file is not placed into a ‘recycle’ bin as in Windows

12. mv • move mv file1 file2 • can be used to rename a file • move it to a file with a different name

13. file • displays the type of file file myfilename • can be used to determine if the file is an executable or a “text” file which can be displayed using cat, more or less

14. cat • views the contents of a file • will scroll off the screen • use the “ | “ (pipe) to the more command cat | more • displays a screen, then stops • spacebar will bring up next screen • enter key brings up next line • ctrl-x will exit the cat command

15. zcat • “cats” a compressed file to the screen

16. less • displays a screen at a time • use “Q” to exit • pageUp and pageDown as well as arrow keys can navigate the file

17. more • displays a screen at a time

18. Filenames • Length can be 256 characters • upper or lower case • peridos, numbers, punctuation marks • NO SLASHES!

19. File Properties ls test -rwxr-xr-x 1 cmalinow users 1839423 Apr 1 15:12 test • permissions • user, group, other • user • group • timestamp • size

20. File Properties ls test -rwxr-xr-x 1 cmalinow users 1839423 Apr 1 15:12 test first character indicates type - regular file d directory user permission rwx group permission “other” permission

21. Changing owner • chown username.groupname filename • chown cmalinow.faculty testfileA • command is invoked by root

22. chmod • Changes permissions assigned to the file or directory • used by root • uses “g”, “u”, or “o” for group, user and other • chmod o+w test • allows “other” to write to file • chmod g=rw test • allows the group to read and write

23. chmod • read, write and execute assigned • 4, 2, 1 respectively • chmod 640 test • user has “6” 4 and 2 (read and write) • group has “4” (read) • others have “0” no access

24. File permissions • When creating a file, permission are assigned • umask determines the permissions to assign • umask 022 • same pattern as permission in chmod • umask executed as part of logging in

25. What’s a “sticky bit”? • Dilemma • depending on permissions set, any user in the group might be able to delete a file of another group member • setting the sticky bit on a directory only allows the owner, the directory owner, or root to rename or delete the file • set the sticky bit by chmod 1nnn • 1 indicates to put a sticky bit on the directory chmod 1777 mydir ls –ld mydir drwxrwxrwxt 2 cmalinow faculty … etc… • “t” indicates the ‘sticky bit’ is on