Changing Ownership with chown and Permissions with chmod

Command chown will reassign the ownership of a directory:

• • sudo chown suzy:users /path_to/folder will reassign the directory "folder" to user "suzy" and group "users" but will leave the contents of "folder" unchanged
• • sudo chown -R suzy:users /path_to/folder will reassign the directory "folder" to user "suzy" and group "users" recursively (i.e. all the contained files and subdirectories are also reassigned).

Command chmod will reassign the permissions on a directory. You can express the options either numerically or in terms of patterns formed from r, w and x.

Chmod via patterns: Make patterns from u for user/owner, g for group and o for others (i.e. neither the owner of members of the group). Couple these with any or all of r for read, w for write and x for executable. For example you can set u=r, u=rw or u=rwx and so on. You can set an additional bit on a directory, the restricted deletion bit, denoted t, whereby only the owner (or root) can delete an included file or directory. There are many combinations of options. I will list some common ones to exemplify the usage:

• • sudo chmod u=r,g=,o= /path_to/folder will change a directory into readable only for the owner and otherwise forbidden (dr--------).
• • sudo chmod u=rwx,g=rx,o=rx /path_to/folder will create the normal Linux permissions on a directory: writeable by owner, readable by all and where files are executable by all (drwxr-xr-x).
• • sudo chmod u=rwx,g=rwx,o=rwx /path_to/folder gives a directory unlimited permissions: writeable by all, readable by all and executable by all (drwxrwxrwx).
• • sudo chmod +t /path_to/folder will add the "sticky" or "restricted deletion" bit to a directory whereby items inside the directory can be renamed or deleted only by the item's owner, the directory's owner, or the superuser.
• • sudo chmod -t /path_to/folder will remove the "sticky" or "restricted deletion" bit from a directory.

Chmod via numbers: This method is more elegant but perhaps harder to remember. Here's the template:

Calculate the number to use in chmod by adding the numbers from all the filled locations, using the table to the left or the graphic below.

Here are the examples I gave above, recast into the numerical format:

• • dr--------: sudo chmod 400 changes a directory into readable only for the owner and otherwise forbidden.
• • drwxr-xr-x: sudo chmod 755 sets the normal Linux permissions on a directory: writeable by owner, readable by all and where files are executable by all.
• • drwxrwxrwx: sudo chmod 777 gives a directory unlimited permissions: writeable by all, readable by all and executable by all.
• • Add 1000 to the numerical value you use in chmod if you wish to set the "sticky" or "restricted deletion" bit on a directory (items inside the directory can be renamed or deleted only by the item's owner, the directory's owner, or the superuser).

Footnote for the advanced: