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# View current umask
umask
# 0022

# Set a more restrictive umask (new files: 640, dirs: 750)
umask 027

# Demonstrate umask effect
umask 022
touch testfile.txt && ls -l testfile.txt
# -rw-r--r-- (666 - 022 = 644)
mkdir testdir && ls -ld testdir
# drwxr-xr-x (777 - 022 = 755)

# Set umask permanently in ~/.bashrc or /etc/profile
echo "umask 027" >> ~/.bashrc

# ---- SUID bit ----
# Numeric: 4 prefix (e.g., 4755)
sudo chmod u+s /usr/bin/program    # Symbolic
sudo chmod 4755 /usr/bin/program   # Octal

# Find SUID files (security audit)
find / -perm -4000 -type f 2>/dev/null

# ---- SGID bit ----
# Numeric: 2 prefix (e.g., 2775)
sudo chmod g+s /shared/project/    # Symbolic
sudo chmod 2775 /shared/project/   # Octal

# New files in SGID dir inherit the directory group
# useful for collaborative directories

# ---- Sticky bit ----
# Numeric: 1 prefix (e.g., 1777)
sudo chmod +t /shared/uploads/     # Symbolic
sudo chmod 1777 /tmp/              # Octal

ls -ld /tmp/
# drwxrwxrwt 20 root root 4096 Apr 10 09:00 /tmp/
# Note the 't' at end — sticky bit set

# Find sticky directories
find / -type d -perm -1000 2>/dev/null