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August 7th, 2024 3:04 PM Mr. Q Categories: Command

Understanding chmod Commands and Their Uses in Linux

In this article, we will explore the usage of the chmod command in Linux to set file and directory permissions. We will also discuss the importance of setting proper file and directory permissions to ensure security in Linux systems.

$ chmod 754 <filename>

The chmod command with arguments 754and a filename changes the permissions of that file. The specific way this works depends on the operating system you are using, but here is a general overview:

• The first argument to chmod, 754, specifies the new permission mode for the file. In this case, it sets the
  • owner’s permissions to read, write, and execute (rwx),
  • group’s permissions to read and execute (r-x),
  • world’s permissions to read (r--).
• The second argument to chmod is the filename you want to modify. This can be a relative or absolute path, depending on how you invoke the command.

This command will set the permissions for the file specified in the filename argument to the values specified in the first argument. The exact meaning of these permissions depends on your operating system and the specific context in which you are running this command. In general, the r stands for “read,” w stands for “write,” and x stands for “execute.” So, a permission like -rwxr-xr-- means that the owner has read, write, and execute permissions, the group has read and execute permissions, and others have only read permissions.

• 4 = r: read permission
• 2 = w: write permission
• 1 = x: execute permission

In this example 754 equates to rwxr-xr–

Avoid using 777, it gives everyone the power to mess with you.

It’s worth noting that you can also use the chmod command to set permissions for multiple files at once by specifying a pattern or a range of filenames. For example, you could use chmod 775 *.txt to change the permissions for all .txt files in the current directory and its subdirectories.

$ chmod 755 $(find /path/to/base/dir -type d)

• This command sets the permission for all directories under a specified path to 755 (read, write, and execute for owner, read and execute for group, and read and execute for others).
• The find command is used to recursively search for directories in the specified base directory.
• The $( ) syntax is used to execute the output of the find command as a shell command.

$ chmod 644 $(find /path/to/base/dir -type f)

• This command sets the permission for all files under a specified path to 644 (read and write for owner, read for group, and read for others).
• The find command is used to recursively search for files in the specified base directory.
• The $( ) syntax is used to execute the output of the find command as a shell command.

$ find /path/to/base/dir -type d -exec chmod 755 {} \;

• This command sets the permission for all directories under a specified path to 755 (read, write, and execute for owner, read and execute for group, and read and execute for others).
• The find command is used to recursively search for directories in the specified base directory.
• The -exec option is used to execute a shell command on each directory found by the find command.
• The {} syntax is used to replace the current file or directory being processed with the appropriate value.

$ find /path/to/base/dir -type f -exec chmod 644 {} \;

• This command sets the permission for all files under a specified path to 644 (read and write for owner, read for group, and read for others).
• The find command is used to recursively search for files in the specified base directory.
• The -exec option is used to execute a shell command on each file found by the find command.
• The {} syntax is used to replace the current file or directory being processed with the appropriate value.