Pro chmod Visual Calculator
Visual calculation of permissions, reverse parsing, and generation of practical commands for professional engineers.
📖View chmod Command Cheat Sheet & Permission Specs
Permission Basics
In Linux/Unix filesystems, permissions are set for three classes: User, Group, and Other.
- 4 (Read): View files, list directory contents
- 2 (Write): Edit files, create/delete files in directories
- 1 (Execute): Execute files, change directories (cd)
Common Permissions (Octal)
- 755 (rwxr-xr-x): Standard for directories. Full control for owner, read/execute for others. Used often for web servers.
- 644 (rw-r--r--): Standard for files. Editable by owner, read-only for others. E.g., HTML, configs.
- 600 (rw-------): Read/write for owner only. Essential for sensitive files like SSH private keys (id_rsa).
- 777 (rwxrwxrwx): Full control for everyone. High security risk; not recommended except for temporary testing.
Special Permissions (4th Digit)
- SUID (4): Set on executables. Runs with the privileges of the file owner (e.g., /usr/bin/passwd).
- SGID (2): Set on directories. Files created within inherit the group of the parent directory.
- Sticky Bit (1): Set on directories. Restricts file deletion to the file owner even if the directory is writable by all (e.g., /tmp).
Permission Settings
4-digit (Special)
Paste an octal value or ls -l output to automatically parse.
Owner (User)
Group (Group)
Other (Other)
Octal
755
Symbolic
-rwxr-xr-x
Practical Command Snippets
Standard Change
chmod 755 <file/dir>Batch Change Directories Only
find . -type d -exec chmod 755 {} +Batch Change Files Only (Exclude Execute)
find . -type f -exec chmod 644 {} +About Security
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