Chmod Calculator

Permission Settings

Owner Group Others
Read
Write
Execute

Permission Result

Numeric 755
Symbolic rwxr-xr-x

Common Permissions

Permission Description

755 (rwxr-xr-x): Owner has read, write and execute permissions, group and others have read and execute permissions.

This is the most common permission setting for directories and executable files, suitable for most web server website files and script files.

Features

Visual Selection

Intuitively set read/write/execute permissions through checkboxes

Two-way Conversion

Real-time conversion between numeric and symbolic representation

Common Presets

One-click setting of common permissions like 755, 644 etc.

Permission Explanation

Detailed explanation of each permission's meaning and use cases

Real-time Update

Modify permission settings to instantly update results

Free to Use

Completely free, no registration login required

How to Use

1

Set Permissions

In the permission settings table, check read, write, execute permissions for owner, group and others respectively. Results will update in real-time after checking.

2

View Results

View corresponding numeric representation (like 755) and symbolic representation (like rwxr-xr-x) in the permission result area, as well as detailed permission explanation.

3

Use Presets

Can also directly click common permission preset buttons to quickly set common permission configurations, like 755 (directories/executable files), 644 (regular files) etc.

Use Cases

Server Management

Linux server file permission configuration

Web Development

Website file directory permission settings

Shell Scripts

Script file execute permission configuration

Database Files

Data file security permission settings

Security Hardening

Minimum privilege principle configuration

Team Collaboration

Multi-user file sharing permissions

CHMOD Permission Knowledge

What is CHMOD?

CHMOD is a command in Unix/Linux systems used to change file or directory access permissions. It stands for change mode. File permissions are divided into three user categories: Owner/User, Group, Others, each category has Read, Write, Execute three permissions.

Numeric representation:r=4, w=2, x=1, e.g. rwx=4+2+1=7, r-x=4+0+1=5
Symbolic representation:rwxr-xr-x corresponds to Owner rwx, Group r-x, Others r-x

Common permission configurations and uses

777 (rwxrwxrwx): All users have read write execute permissions, lowest security, not recommended.
755 (rwxr-xr-x): Owner full control, others can read and execute, commonly used for executable files and directories.
644 (rw-r--r--): Owner can read write, others read only, standard permission for regular files.
600 (rw-------): Only owner can read write, others no permission, suitable for sensitive files like private keys.

What's the difference between directory and file permissions?

For files: Read permission can view file content, write permission can modify file content, execute permission can run file (scripts/programs).
For directories: Read permission can list directory contents (ls), write permission can create/delete files in directory, execute permission can enter directory (cd) and access files inside.

Frequently Asked Questions

Q: Is CHMOD permission calculator free?
A: Completely free, no registration login required, no usage limit, open webpage to use.
Q: How are numeric permissions calculated?
A: Read(r)=4, Write(w)=2, Execute(x)=1. Each user category's permission value is sum of these three. For example, owner has read write execute is 4+2+1=7, group has read and execute is 4+0+1=5, others only read is 4+0+0=4, combined is 754.
Q: What scenarios are 755 and 644 suitable for?
A: 755 (rwxr-xr-x) usually used for directories and executable files, because execute permission needed to enter directory or run program. 644 (rw-r--r--) usually used for regular files, like text files, images, HTML files etc., only need read not execute.
Q: Why not recommend using 777 permission?
A: 777 permission means any user can read write execute the file or directory, has serious security risks. Anyone can modify or delete your files, may be maliciously exploited. Recommend following minimum privilege principle, only give necessary permissions.
Q: What are special permissions SUID/SGID/Sticky Bit?
A: SUID(4): File runs with owner identity when executed; SGID(2): File runs with group identity when executed, new files in directory inherit group; Sticky Bit(1): Files in directory only owner can delete. Numeric representation is 4 digits, like 4755 means 755 with SUID set.
Q: How to modify file permissions in Linux?
A: Use chmod command, e.g.: chmod 755 file.txt (numeric mode) or chmod u+rwx,g+rx,o+rx file.txt (symbolic mode). Modify directory and all subfiles can use chmod -R 755 directory/.