I am using Linux. What is the meaning of
chmod command change attributes from a file/folder:
chmod 666 file/foldermeans that all users can read and write but cannot execute the file/folder;
chmod 777 file/folderallows all actions for all users;
chmod 744 file/folderallows only user (owner) to do all actions; group and other users are allowed only to read.
permission to: user(u) group(g) other(o) /¯¯¯\ /¯¯¯\ /¯¯¯\ octal: 6 6 6 binary: 1 1 0 1 1 0 1 1 0 what to permit: r w x r w x r w x binary - 1: enabled, 0: disabled what to permit - r: read, w: write, x: execute permission to - user: the owner that create the file/folder group: the users from group that owner is member other: all other users
Alternatively, you can execute the command with a more intuitive syntax, without needing to think in binary or octal (but the knowledge of numeric syntax is so important):
chmod u=rw, g=rw, o=rw file/folder
Remember that the permission changes with
chmod command requires at least 3 arguments, so
chmod 666 does nothing without explicit file/folder to change permissions.
Also be sure to criticize if it does not produce insecure issues or simply if it is an useless permission change, because
chmod 666 will allow file/folder write to all and the execution to none.
As mentioned in other answers, chmod means change mode. It affects the read, write and executable permissions for the owner, group and other categories of users. The numbers that follow the command (in this case 666), indicate how those permissions are modified for the file the command is run on (for 666, it means that owner, group and other have read and write permissions, but no executable permissions).
By changing the numbers to different values you effectively change the permissions for the file. The link I've referenced above has a little tool for figuring out what values you need to put in to get the permissions scheme you're after. It also goes over the switch options available for the command and some examples to help you understand better how it works.
In really plain speak: it makes a file read- and write-able by the file owner, the file owner's group and every one else using the machine (all). Applied against a directory it lets everyone read (get file contents lists) of a directory and write (create, edit files in the directory) but not execute files from the directory.
For more detailed information how
chmod works check out this handy tutorial.
If your questions is more about the 666 part than the chmod part, I would refer you to The Linux Documentation Project where is a decent explanation of how file permissions work in Linux.