System Administration
X-Ray: chmod 755
Permission structure in octal and binary
7
111
User (u)
r + w + x
5
101
Group (g)
r + - + x
5
101
Others (o)
r + - + x
Read (4)
Bit 2² = 100. Allows viewing content.
Write (2)
Bit 2¹ = 010. Allows modifying.
Execute (1)
Bit 2⁰ = 001. Allows running programs.
How is it calculated?
Each digit is the sum of its active bits. Example: 5 is Read (4) + Execute (1).
Symbolic Mode
Equivalent to rwxr-xr-x. Where the hyphen (-) indicates a bit set to 0 (off).
000 (0)
No permissions. Total lockdown.
444
Read-only for everyone.
644
Owner edits, rest only read.
777
Danger! Total control for anyone.
xeland314 4 (R) • 2 (W) • 1 (X)