The chmod command controls file permissions in Linux. The execute permission allows users to run scripts and programs. This guide shows how to use chmod executable to manage these permissions.
Apply the command with mode 755 to a file:
$ chmod 755 script.shThe breakdown shows owner with full access, group with read and execute, and others with read and execute.
Syntax of the chmod Command
chmod [options] [mode] [file_name]The mode represents permissions as a three-digit number or symbolic notation like u+x. The file_name identifies the target file or directory.
Common Permission Modes
| Mode | Owner | Group | Others | Use Case |
|---|---|---|---|---|
| 700 | rwx | — | — | Private scripts only you can run |
| 750 | rwx | r-x | — | Team-only executable |
| 755 | rwx | r-x | r-x | Everyone can run, owner edits |
| 775 | rwx | rwx | r-x | Group collaboration |
-R applies chmod executable permissions to all files in a directory structure.
Permission Types in Linux
Linux assigns three permission types to each file. Read allows viewing contents. Write enables modifications. Execute lets users run the file as a program.
Each permission applies to three categories: owner, group, and others. The owner created the file. The group includes members with shared access. Others represents all remaining users.
Using Octal Notation
Octal mode uses numbers to represent permissions. Each digit corresponds to a permission level.
| Value | Permission | Binary |
|---|---|---|
| 4 | Read | 100 |
| 2 | Write | 010 |
| 1 | Execute | 001 |
Add values together for combined permissions. The value 7 grants all permissions (4+2+1). The value 5 grants read and execute (4+1).
Grant the owner full access, group read and write, and others read only:
$ chmod 764 document.txtUsing Symbolic Notation
Symbolic mode uses letters instead of numbers. The format combines who, action, and permission.
Categories include u for user, g for group, o for others, and a for all. Actions include + to add, - to remove, and = to set exactly.
Add execute permission for the owner:
$ chmod u+x script.shRemove write permission from others:
$ chmod o-w file.txtReverting Permission Changes
Reset permissions by applying the correct mode again. Check current permissions first with ls -l.
Restore standard file permissions (owner read-write, others read-only):
$ chmod 644 file.txtMaking Scripts Executable in Linux
Scripts require execute permission to run. Without this permission, Linux blocks execution. Follow these steps to make a script executable.
Step 1: Navigate to the Script Directory
Move to the directory containing your script:
$ cd /path/to/scriptStep 2: Check Current Permissions
View existing permissions with the ls command:
$ ls -l script.shThe output displays permissions in the first column. Look for the x character in the permission string.
Step 3: Add Execute Permission
Apply the chmod executable command to the script:
$ chmod +x script.shThis adds execute permission for all users. For owner-only execution, use:
$ chmod u+x script.shStep 4: Verify the Changes
Confirm the permission change worked:
$ ls -l script.shThe permission string now shows x in the execute position.
Step 5: Run the Script
Execute the script using the current directory notation:
$ ./script.shThe dot-slash prefix tells Linux to look in the current directory for the file.
Practical Applications
Apply chmod executable to automation scripts that run scheduled tasks. Set mode 700 for scripts containing sensitive operations.
For shared team scripts, use mode 750. This allows team members to execute while preventing modifications from unauthorized users.
System-wide utilities need mode 755. This grants universal execute access while restricting modifications to the owner.
FAQs
The chmod +x command adds execute permission to a file for all users. This allows the file to run as a program or script directly from the terminal.
Use chmod u+x filename to add execute permission only for the owner. This restricts script execution to the file owner while blocking group members and others.
Run chmod -x filename to remove execute permission from all users. For specific categories, use chmod u-x, chmod g-x, or chmod o-x for owner, group, or others.
Mode 755 gives full access to owner, read-execute to others. Mode 777 grants full access to everyone. Avoid 777 as it creates security vulnerabilities on systems.
Yes, execute permission on directories allows users to access the directory contents. Use chmod +x directory_name or apply recursively with chmod -R +x to all subdirectories.
