Beginner LevelLinux Commands & SysAdmin
What is umask and how does it determine default file permissions?
❓ Interview Prompt: Explain umask (user file-creation mask), default base permissions (666 files / 777 directories), subtraction math, and setting umask.
'umask' (User Mask) specifies permission bits automatically turned OFF (subtracted) when creating new files and directories:
Base Permissions:
•
Default Directory Base: 777 ('rwxrwxrwx')
•
Default File Base: 666 ('rw-rw-rw-')
Math Calculation:
With a umask of '022':
•
New Directory: 777 - 022 = 755 ('rwxr-xr-x')
•
New File: 666 - 022 = 644 ('rw-r--r--')
Code Implementation Example
bash
# Display current umask setting
umask
# Output: 0022
# Set restrictive umask for secure shell session
umask 077
# New files will be created with 600 (rw-------) permissions!💡Inspecting and setting default file creation permission umask.
🎯 Interview Key Takeaway
umask subtracts permission bits from default 666 (files) and 777 (directories) base creation modes.
#umask#Permissions#Security#Beginner
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