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Mastering File Systems in Linux/Unix

Learn about filenames, paths, directory operations, and access permissions in Linux/Unix systems. Explore absolute and relative paths, standard directories, file manipulation, and changing access permissions with practical examples. Understand how to create, copy, move, and delete directories and files, and manage user access with read, write, and execute permissions. Instructor: Bo Sheng.

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Mastering File Systems in Linux/Unix

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  1. Lecture 5: File Systems (ch 4) IT244 - Introduction to Linux / Unix Instructor: Bo Sheng

  2. Outline • Filename and paths • Directory operations • Access permissions

  3. Filenames and Paths • Absolute path name • ls /home/it244/it244 • ls /home/it244/it244/ /home/it244/it244/hello Path Filename

  4. Filenames and Paths • Absolute path name

  5. Filenames and Paths • Absolute path name • ~ represents “home directory” • ls ~ =ls /home/your username • cd ~ • pwd • ls ~it244 =ls /home/it244

  6. Filenames and Paths • Relative path name • cd /home/it244 • ls it244 /home/it244/it244/hello Path Filename

  7. Filenames and Paths • Relative path name • . : Current directory • .. :Parent directory • ls –la • ls . • ls .. • cd .. • cd ../..

  8. Filenames and Paths • Relative path name

  9. Filenames and Paths • Standard directories (Pg95~98)

  10. Directory Operations • Create a directory • mkdir book • ls -l • ls book • ls ./book • cd book • ls ../book

  11. Directory Operations • Delete a directory (when it’s empty) • cd .. • rmdir book • Example • mkdir book • cd book • echo “this is a book” > book1 • cd .. • rmdir book (not empty)

  12. Directory Operations • Example • rm book/book1 • rmdir book • Delete directories by rm • mkdir book • rm book • rm –r book (cautious)

  13. Directory Operations • Example • mkdir book • cd book • mkdir novel • cd .. • rmdir book • cd book/novel • rmdir .

  14. Directory Operations • Copy and move files to directories • cd ../.. • cp hello book • ls book • mv welcome linux book • ls • ls book

  15. Directory Operations • Copy and move files to directories • mv book newbook • mv newbook book • ls • mkdirnewbook • mv book newbook

  16. Directory Operations • Copy and move files to directories • mv newbook/book book • cp book newbook ??? • cp –r book newbook • lsnewbook

  17. Access Permissions • Three types of users • Owner • Group member • Others • Three access permissions • Read • Write • Execute

  18. Access Permissions

  19. Access Permissions • Change access permissions (chmod) • Symbolic arguments • a (all), u (owner), g (group), o (others) • r (read), w (write), x (execute) • + / - • chmoda+w book1 • chmod go-rw book1

  20. Access Permissions • Change access permissions (chmod) • Numeric arguments -rw-r--r-- 644 -rwxr-xr-x 755

  21. Access Permissions • Change access permissions (chmod) • Numeric arguments • chmod 644 book1 • chmod 755 book1

  22. Access Permissions • Example • Read permission • chmod a-r hello • cat hello • chmoda+r hello • cat hello

  23. Access Permissions • Example • Read permission • chmod a-r book • ls book • ls book/book1 • chmoda+r book

  24. Access Permissions • Example • Write permission • chmod a-w hello • echo hi>hello • rm hello • chmoda+w hello • rm hello

  25. Access Permissions • Example • Write permission • cd book • chmod a-w . • chmoda+rw book1 • echo hi>book2 (create a file) • mv book1 book2 (rename a file) • rm book1 (delete a file) • chmoda+w .

  26. Access Permissions • Example • Execute permission (directory) • Determine if the files are searchable • chmod a-x book • ls book • ls book/book1 • cd book • chmoda+x book Why?

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