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Unix Help for Webpage Management

There are two basic ways to post webpages: manually by copying files to /stage/www-me/courses/... or through a webpage composer like Netscape Composer. Regardless of the method you choose, you are responsible for managing the file permissions.

Don't assume that files posted by a webpage composer automagically have the correct permissions; in most cases, they do not. Also, beware of copying files from Macintosh or Windoze platforms. Often, these transfers make text files executable and unwriteable by the group.

Group Management

Groups are UNIX's way of allowing users to share files in the most secure way possible. Each file has an owner and a group. By default, the group is the group of 1, the owner of the file. Each file has access permissions for the owner, the group, and other. By default, any file you create is writeable by the owner only. Thus, you have to change the group and group permissions to effectively share files.

A convenient script, chwebp, is available that will set the correct group and file permissions for files that you create or edit and plan to post as a webpages. Here is the usage

  unix% chwebp -g group-name file|directory

As an example, say you are a TA for ME3201 whose webpages live in /stage/www-me/courses/me3201. You have just created a new file called "hwk4.html". To update the permissions you would type

  unix% chwebp -g me3201 hwk4.html
where "me3201" is the name of the group. If you create a bunch of files or if you want to make sure the permissions are correct for an entire directory tree, you can type
  unix% chwebp -g me3201 *

The script will automatically descend sub-directories.

The Nitty-Gritty of Group Management

Here is an example listing (ls -l) of the ms5101 directory in /stage/www-me/courses/,

  unix% ls -l
  drwxrwxr-x   2 web      ms5101       2048 Jan 09  1998 ms5101/
   ^^^^^^^^^     ^^^      ^^^^^^                         ^^^^^^
   |||||||||    owner     group                      directory name
   |||||| the rwx bits for "other"
   ||| the rwx bits for "group"
   the rwx bits for "owner"

Note that "web" owns the file. The directory belongs to the "ms5101" group. The first three rwx bits refer to "owner," the next three to "group," and the last three to "other." These are the permissions given to the directory. The above listing shows that the ms5101 directory is readable (r), writeable (w), and executable (x) by the owner and the group (rwx). It is only readable and executable by other (r-x). Under no circumstances should any file or directory you manage be other writeable (ie. have rwx as the last three bits).

By default files and directories are part of group "user" and writeable only by the user. In order to make the files read/writable by the group you will need to 1) change the group and 2) change the group permissions.

To change the group name,
  unix% chgrp groupname file|directory
To make a directory read/writable by the group,
  unix% chmod 775 directory
To make a file read/writable by the group,
  unix% chmod 664 file
Please refer to the manpages for more info on options available for chmod and chgrp.

Questions? Contact web@me.umn.edu

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