Chapter 7: Permissions and ACLs

Read and change file permissions and ownership, build shared team directories with setgid and sticky bits, and grant exceptions with access control lists.

What you will learn

• Read the permission string of ls -l and predict which user class applies and what it allows on files and directories.
• Change modes with chmod in symbols and octal, change owner and group, and apply changes safely to a tree.
• Explain the umask and the setuid, setgid and sticky bits, and build shared and drop-box directories.
• Read getfacl, grant and remove ACL entries with setfacl, and set default ACLs for new files.

Sections

1. Reading file permissions
2. Exercise: Who can read this?
3. Changing permissions and ownership
4. Exercise: Secure a web folder
5. Default permissions and shared directories
6. Exercise: Build a team directory and a drop box
7. Access control lists
8. Exercise: Give the auditors read access
9. Exercise: Permissions and ACLs review
10. Linux permissions and ACLs quiz
11. Linux permissions and ACLs cheat sheet