Access Information Through World Wide Web
Access to networked multimedia data has become commonplace on the Internet. Chances are good that you've gone surfing in search of data for a project or technical paper or out of simple curiosity. You have probably passed through a large number of sites scattered across the globe and have seen what can be done. Now you want to set up your own collection of information, images, and sound so that the networked world can come and visit. One of the first steps is to set up a world wide web (WWW) server. The remainder of this article will endeavor to provide the necessary information to successfully install the WWW server provided by CERN.
The three basic parts of the CERN WWW source package are the line-mode client, the daemon, and the common library. Of these, the daemon and common library source are necessary to compile the server. You may also want to retrieve and compile the client code for future use. These packages may be retrieved by clicking on the appropriate links in the document found at URL www.w3.org/hypertext/WWW/Daemon/Status.html, or by anonymous ftp from gatekeeper.dec.com in directory /put/net/infosys/www/src. The file names are shown in the tar commands below. Once you have retrieved the tar archives, move them to the directory where you wish to compile the server, then extract the source. Using GNU's tar this can be done by executing the following commands:
tar xzvf WWWDaemon.tar.Z tar xzvf WWWLibrary.tar.Z tar xzvf WWWLineMode.tar.Z
The final file and tar command is optional since it extracts the line-mode client. Once extracted, the source will be in subdirectory WWW. To build the server under Linux, change to subdirectory WWW and execute BUILD. This is done as follows:
cd WWW ./BUILD
The build process should recognize that it is running on a Linux system, and proceed to compile the common library followed by the server. If you have not extracted the source for the line-mode client, the build process will exit with an error once the server has been built. This is normal and can be ignored. You can verify that you have successfully built the server by examining the files in subdirectory Daemon/linux. In addition to a number of .o files there should be the following six files:
cgiparse: A tool for parsing CGI environment variables.
cgiutils: A tool for generating replies from CGI scripts.
htimage: Used to parse the input from a clickable image.
httpd_3.0: The server or daemon.
httpd: A symbolic link to httpd_3.0
htadm: An administration tool for managing server access files.
CGI stands for Common Gateway Interface. CGI is a set of specifications for how scripts and other programs can interact with a WWW server.
Sidebar: The NCSA http Daemon
You may install the server and associated tools in any directory you see fit. This article assumes that the installation directory is /usr/local/WWW. If you are installing in some other directory, be sure to make the necessary changes in the following references.
To install the server list, create a user id and a group for the server. This user id and group will help control what access rights the server possesses and allow selective access to the server files for administrative users. This article uses user www and group wwwgroup. They can be created using your favorite method for adding users and groups to the system.
Next, create the directory tree where the server and associated tools and files will reside. A typical server directory will have the following directories (and possibly others):
config: Configuration files.
cgi-bin: CGI scripts and programs.
htdocs: HTML documents.
To create these directories, execute the following:
mkdir /usr/local/WWW cd /usr/local/WWW mkdir config cgi-bin icons htdocs
Now these directories can be populated. Return to the directory where you compiled the WWW server, and execute the following:
cd Daemon/linux tar cf - htadm httpd httpd_3.0 | \ (cd /usr/local/WWW; tar xvf -) tar cf - htimage cgiparse cgiutils | \ (cd /usr/local/WWW/cgi-bin; tar xvf -) cd ../../server_root/icons tar cf - * | (cd /usr/local/WWW/icons; tar xvf -) cd ../config tar cf - * | (cd /usr/local/WWW/config; tar xvf -)
This sequence of commands copies the server binaries, CGI utility programs, supplied icons, and several example server configuration files to the proper subdirectories in /usr/local/WWW. Note how tar is used. This is an often-used method to successfully copy files, links, and subdirectories without accidentally modifying links and other characteristics during the copy operation due to improper flags passed to cp.
You should also set the ownership and permissions on this directory tree. Here is a possible set of permissions:
cd /usr/local chown -R www.wwwgroup WWW chmod a+rx WWW WWW/htdocs WWW/icons \ WWW/cgi-bin WWW/config chmod g+rx WWW/httpd_3.0 cd WWW/icons chmod a+r * cd ../cgi-bin chmod a+rx *
These are typical permissions that allow access to the server when documents or icons are requested or the execution of a CGI program or script is required. However, it is possible to remove world permissions from most of these files as long as the server runs as user www and group wwwgroup (see UserId and GroupId below).
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
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