Linux Permissions:
Chmod Calculator is a free utility to calculate the numeric (octal) or symbolic value for a set of file or folder permissions in unix or unix-like systems such as linux or ubuntu.
How it Works?
Check the desired boxes or directly enter a valid numeric value (e.g. 777) or symbolic notation (e.g. rwxrwxrwx) to see its value in other formats.
How to use chmod?
You can change file permissions in this format:chmod [options] [mode] [file_name]
What are permissions?
Each file on a system has a set of permissions associated with it, meaning which users have access and what type of access they have.
There are three types of users:
- User, meaning the user who owns the file
- Group, meaning the files defined ownership group
- Other, meaning everyone else
File permissions in Linux file system are managed in three distinct user classes: user/owner, group and others/public. Each class can have read, write and execute permissions. File permission can be represented in a symbolic or numeric (octal) format.
Examples
Chmod examples in octal mode:
Readable by owner only
$ chmod 400 chmodExample.txt
Readable by group only
$ chmod 040 chmodExample.txt
Readable by anyone
$ chmod 004 chmodExample.txt
Writeable by owner only
$ chmod 200 chmodExample.txt
Writeable by group only
$ chmod 020 chmodExample.txt
Writeable by anyone
$ chmod 002 chmodExample.txt
Executeable by owner only
$ chmod 100 chmodExample.txt
Executeable by group only
$ chmod 010 chmodExample.txt
Executeable by anyone
$ chmod 001 chmodExample.txt
Allow read permission to owner and group and anyone.
$ chmod 444 chmodExample.txt
Allow everyone to read, write, and execute file.
$ chmod 777 chmodExample.txt
Chmod examples in symbolic mode:
Deny execute permission to everyone.
$ chmod a-x chmodExampleFile.txt
Allow read permission to everyone.
$ chmod a+r chmodExampleFile.txt
Make a file readable and writable by the group and others.
$ chmod go+rw chmodExampleFile.txt
Make a shell script executable by the user/owner.
$ chmod u+x chmodExampleScript.sh
Allow everyone to read, write, and execute the file and turn on the set group-ID.
$ chmod =rwx,g+s chmodExampleScript.sh