[PLUG] Sharing on Ubuntu

Rich Shepard rshepard at appl-ecosys.com
Mon Jul 13 17:45:39 UTC 2009


On Mon, 13 Jul 2009, John Jason Jordan wrote:

> As a result I just use the command line. Unfortunately, I am not really
> smart enough to use Linux, so in order to figure out how to change
> permissions from command line I go here:

   Permissions have three categories: User, Group, Other (i.e., everyone).
Each category has three attributes: Read, Write, eXecute. These attributes
are represented by a binary word (8 bits); from left to right the bit values
(in base-10) are 4, 2, 1.

   Files generally have rw-r--r-- permissions. That is, everyone (file owner,
everyone in that owner's group, and everyone else can read the file, but
only the owner can write to it.

   Directories ("folders" in Microsoft) are different:

     * Execute permission is required for a user to cd into a directory.
     * Read permission is required for a user to use a command such as "ls" to
 	view the files contained in a directory.
     * Execute-only permission allows a user to access the files in a
 	directory as long as the user knows the names of the files in the
 	directory, and the user is allowed to read the files.
     * Write permission allows the user to create, delete, or modify any
 	files or subdirectories, even if the file or subdirectory is owned
 	by another user.

   You can change file/directory permissions in either of two ways:
category/attribute or number. With category/attribute you can, for example,
make a file globally executable by the chmod command (as root): "chmod a+x
<filename>". Doing the same thing by numbers (again, as root) you'd type,
"chmod 755" and that gives the owner full permissions, group and other
read/executte permissions. This is also a good default for directories.

Rich

-- 
Richard B. Shepard, Ph.D.               |  Integrity            Credibility
Applied Ecosystem Services, Inc.        |            Innovation
<http://www.appl-ecosys.com>     Voice: 503-667-4517      Fax: 503-667-8863



More information about the PLUG mailing list