File Permissions

About Permissions

Here's a long listing of a file I've created with the touch command:

1-rw-rw-r-- 1 osboxes osboxes    0 Jan  7 07:30 myfile

This is the explanation to the first field you see:

Where:

• r means read
• w means write
• x means execute The numbers specify the values in binary converted to octal, so you can specify each 3 bits using single octal number.

Changing permission with chmod Using letters

• Create a file in the current directory
• change the permissions of this file, so that everybody can write/read/execute the file.
  Use only letters, for example:
  chmod u+x myfile
• remove everything for everybody else, and leave read/write/execute just for the user.

Changing permissions with chmod Using octal numbers

• example:
  6(octal) translates to 110(binary)
  so 6 actually means read+write but not execute.
  So: 664 menas read+write but not execute to owner and group, but only read for everybody else.

1$ chmod 664 myfile
2$ ls -l myfile
3-rw-rw-r-- 1 osboxes osboxes 0 Jan  7 07:30 myfile
4$ 

• Set the following:
  user:r-x group r-- others: r-x