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Linux

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

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Linux

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  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

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