AIX File & Folder Ownership

Every file or folder in AIX has three key players:

• Owner (user) – The user who created the file.
• Group – Users who share access to the file.
• Others – Everyone else.

Permissions define what each category can read, write, or execute. Master these, and you’ll tame any AIX filesystem.

Permission Basics: Read, Write, Execute
Permissions come in three flavors for each category (owner, group, others):

Permission Meaning

Permission	Meaning
Read (r)	View file or list folder contents
Write (w)	Modify file or add/delete in folder
Execute (x)	Run file (if program) or enter folder

Check file permissions using:
# ls -l filename
Example output:
-rwxr-xr--

• - = File type (d for directory)
• rwx = Owner: full access
• r-x = Group: read/execute, no write
• r-- = Others: read-only

Changing Permissions with chmod
You can tweak file access in two modes:
Symbolic Mode (Easy Adds/Removes)
Letters represent categories:

• u = owner
• g = group
• o = others
• a = all

Examples:
# chmod u+r filename # Owner gains read permission
# chmod g-w filename # Group loses write permission
# chmod o+x filename # Others gain execute permission

Numeric (Octal) Mode

Assign numbers:

• Read = 4
• Write = 2
• Execute = 1

Add them up for each category:

Number	Permissions	Meaning
7	rwx	Full access
6	rw-	Read + write
5	r-x	Read + execute
4	r--	Read only

Example:
# chmod 755 filename

• Owner = 7 (rwx)
• Group = 5 (r-x)
• Others = 5 (r-x)

Perfect for scripts and executable files.

Ownership: chown and chgrp
Files can change ownership if you’re root:
# chown newuser filename # Change file owner
# chgrp newgroup filename # Change file group

Special Permissions:
AIX has advanced flags to control behavior:

• Setuid (s): Runs the file as the file owner instead of the caller. Example: rwsr-xr-x
• Setgid (s): New files inherit the folder’s group.
• Sticky bit (t): Only the owner can delete a file in the directory. Common in /tmp:

drwxrwxrwt 14 root system 4096 Sep 26 12:00 /tmp
That t keeps your temp files safe from accidental deletion by others.

Hidden Files: 
Files starting with a dot (.) are hidden—ideal for configuration files like .bashrc or .ssh/.
# ls -l → skips hidden files
# ls -la → shows all files, including hidden ones

Example:
-rw-r--r-- 1 user group 123 Sep 26 12:00 file.txt
-rw-r--r-- 1 user group 50 Sep 26 12:05 .hiddenfile

Why hide?

• Prevent accidental modifications
• Keep configuration files safe
• Permissions still apply (e.g., chmod 600 .hiddenfile = owner-only read/write)

Quick Hidden File Actions
# touch .myhiddenfile # Create a hidden file
# echo "Hello" > .myhiddenfile
# cd .ssh # Enter a hidden directory
# rm .hiddenfile # Delete hidden file