Putting Information on the Web
In order for information to be accessible through the World Wide Web, it has to be placed on a computer system that is running http (hypertext transfer protocol) server software. One place to read more about how a Web server works is How Web Servers Work by Marshall Brain, http://www.howstuffworks.com/web-server.htm.
One such computer system available for you to use with this course has the Internet domain name rosemary.umw.edu henceforth referred to as rosemary. The server software is Apache, an open-source, free, and the Web server most commonly in use.
Where to put your files
The configuration file is set so that the server may access files (and thus make them available on the Web) from a specific immediate subdirectory of any user's home directory. The name of that directory is public_html. The common Unix notation for this is ~/public_html with the ~ in this case indicating the user's home directory. Note that this isn't the URL for a file on the server.
The URL includes the login name for a user as described here. If a user with login name mwashing has a file named greatone.html, for example, that is located in the subdirectory public_html then the URL for that file is http://rosemary.umw.edu/~mwashing/greatone.html. Furthermore, only the files contained in public_html are accessible by the Web server.
http://rosemary.umw.edu/~mwashing/greatone.html
You can see from this that in order for you to make information available through the Web server on paprika that you must be a registered user of that computer system, i.e. have a login name and password, and you need to create a directory named public_html (use mkdir public_html) in your home directory after connecting to paprika through ssh and secure FTP
You can work on paprika as you would on any text based system through ssh. If you'd rather prepare files on another computer and upload them to paprika then use a secure version of ftp. rosemary is set so the access permissions are set correctly when you transfer files through sftp or create them using an editor.
Access file permissions
You may have to adjust access file permissions on a file you create on or transfer to paprika. All files available on through the Web server on paprika have to have have read access set so any user on paprika may read them. Here's why:
When a client requests a file from the server using a URL such as http://rosemary.umw.edu/~mwashing/greatone.html, the server software will attempt to transfer the file to the client. In order to transfer the file, access privileges have to be set so the file can be copied by the server. Each executing processes is associated with a user, and common sense security dictates that the executing server software (or any software that's open to the public without restriction) should be associated with a user with no special privileges. So since the server software has to be able to read the file requested, and since the software has no special access privileges, we have to give read access to all users on every file that we want to be available on the Web.
- To set access permissions for a file named, for example, greatone.html so that it will be accessible to the Web server enter the following:
chmod a+r greatone.html (if you're accessing the host system using ssh)
chmod 644 greatone.html (If you're using ftp)
You're using the program named chmod. Writing chmod a+r filename grants read access to all users of the computer system. You may also use a numeric scheme for setting access permission, and you have to use it if you're using ftp. Take a look at chmod tutorial for more information and practice.
- To set access permissions so that all files in a directory are accessible by the Web server enter:
chmod a+r *
- To set access permissions so that all files in a directory and all the files in subdirectories are accessible by the Web server enter :
find . -exec chmod a+r {} \;
There is one more point.
The directory that holds the files have to be browsable by anyone. In Unix/Linux that means the access permissions for a directory have to set so any user has execute permission for that directory. You can set the the permissions for $HOME/public_html (your Web space) and all its files and subdirectories by entering:
chmod -R a+rx $HOME/public_html
Checklist for putting information on the Web
- Know your username or login name and password on the system that hosts the Web server software.
- Connect to the host using ssh or sftp and create a directory named public_html. You do this by entering mkdir public_html
- Set access permissions on the directory by entering chmod a+x public_html
- cd to public_html.
- If you're using ssh you're probably thinking of entering the source using the keyboard. Open any text editor - for example vi, vim, or pico -and save your work in a file whose name ends with .html or .htm if the source file is for a Web page or a file whose name ends with .php if the file contains php to be processed through the Web server.
- If you're using sftp use the same naming conventions as noted in the previous statement.
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