1© David Morgan 2003,2004Services: Apache –a patchy web serverDavid Morgan© David Morgan 2003,2004The Whole Business“…the whole business of a web server is to translate a URL either into a filename, and then send that file back over the Internet, or into a program name, and then run that program and send its output back. That is the meat of what it does: all the rest is trimming.”Apache, The Definitive Guide, page 12© David Morgan 2003,2004A Web Site = a Directory RedHat default: /var/www Holds “what to send” to connecting clients– content of files in: /var/www/html, or– output of programs in: /var/www/cgi-bin© David Morgan 2003,2004FILE CONTENTSubliminal messagePROGRAM OUTPUT3© David Morgan 2003,20044 important directories For HTML scripts /var/www/html For programs /var/www/cgi-bin For config files /etc/httpd/conf For logs /etc/httpd/logs -> /var/log/httpd© David Morgan 2003,2004Default directories and filesetchttpdvar/ html cgi-binerrorwwwmanualhttpd.conf noindex.html index.htmlconf logsyourwebpage files(index.html et.al.)yourexecutablesaccess_logerror_logDocumentRootServerRoot4© David Morgan 2003,2004FILE CONTENTSubliminal messagePROGRAM OUTPUT© David Morgan 2003,2004Placeholder default test page /var/www/error/noindex.html appears as long as administrator supplies no /var/www/html/index.html5© David Morgan 2003,2004Apache manual /var/www/manual/ installed by default© David Morgan 2003,2004Primary config file: httpd.conf Houses “directives” Categorized– global directives – apache process– default host directives– main “site”– virtual host directives – other (2nd, 3rd, …) sites directives number about 1506© David Morgan 2003,2004Turning services on and off Services re-read configuration files when restarted Starting– /etc/rc.d/init.d/<script for service> start or– service <script for service> start Stopping– /etc/rc.d/init.d/<script for service> stop or– service <script for service> stop© David Morgan 2003,2004Turning apache on and off Re-reads /etc/httpd/conf/httpd.conf when restarted Starting– /etc/rc.d/init.d/httpd start or– service httpd start Stopping– /etc/rc.d/init.d/httpd stop or– service httpd stop7© David Morgan 2003,2004Running programs - CGI A way to get a “page,” to send to a client Alternative to getting it out of a file (“.htm”) Instead call a program to generate it Write the program to output webpage-legal stuff CGI stands for “common gateway interface” (which could gain from improvement, as it’s creatively greatly inhibited)© David Morgan 2003,2004FILE CONTENTSubliminal messagePROGRAM OUTPUT8© David Morgan 2003,2004Running a CGI program Put the program file in /var/www/cgi-bin apache interprets files in cgi-bin as “runnables” Run by naming its URL in– “location/address” in client/browser– ACTION=<url> within an HTML FORM statement© David Morgan 2003,2004Virtual (multiple) servers IP-based– separate IP address for each virtual server Name-based– just one address for all virtual servers9© David Morgan 2003,2004IP-based: multiple IP addresses multiple physical interfaces, each with its own IP– replicate everything, or multiple “ip aliases” on a single physical interface– replicate the virtual, not the physical© David Morgan 2003,2004IP-based: number of daemons Multiple daemons– allows separate configurations– performance-expensive Single daemon– must share single configuration– performance-efficient10© David Morgan 2003,2004IP-based virtual servers<VirtualHost www.smallco.com>ServerAdmin [email protected] /groups/smallco/wwwServerName www.smallco.comErrorLog /groups/smallco/logs/error_logTransferLog /groups/smallco/logs/access_log</VirtualHost><VirtualHost www.baygroup.org>ServerAdmin [email protected] /groups/baygroup/wwwServerName www.baygroup.orgErrorLog /groups/baygroup/logs/error_logTransferLog /groups/baygroup/logs/access_log</VirtualHost>in /etc/httpd/conf/httpd.conf© David Morgan 2003,2004IP-based virtual servers Requires distinct name resolution– www.smallco.com  111.22.33.44– www.baygroup.org  111.22.33.45 Both addresses for the webserver machine Apache differentiates by address Destination address embedded in IP header11© David Morgan 2003,2004Name-based virtual serversNameVirtualHost 111.22.33.44<VirtualHost 111.22.33.44>ServerName www.domain.tldDocumentRoot /www/domain</VirtualHost><VirtualHost 111.22.33.44>ServerName www.otherdomain.tldDocumentRoot /www/otherdomain</VirtualHost>in /etc/httpd/conf/httpd.conf© David Morgan 2003,2004Name-based virtual servers Requires common name resolution– www.domain.tld  111.22.33.44– www.otherdomain.tld  111.22.33.44 Apache differentiates by name Destination name embedded in HTTP request12© David Morgan 2003,2004Differentiation by nameDestination domainname embeddedin HTTP request© David Morgan 2003,2004Differentiation by name13© David Morgan 2003,2004Some noteworthy directives Global– ServerRoot– Listen Host– User, Group– ServerAdmin– ServerName– DocumentRoot– UserDir– DirectoryIndex© David Morgan 2003,2004ServerRoot# ServerRoot: The top of the directory tree under which the server's# configuration, error, and log files are kept.#ServerRoot "/etc/httpd"from /etc/httpd/conf/httpd.conf14© David Morgan 2003,2004Listen# Listen: Allows you to bind Apache to specific IP addresses and/or# ports, in addition to the default. See also the <VirtualHost># directive.#Listen 12.34.56.78:80Listen 80from /etc/httpd/conf/httpd.conf© David Morgan 2003,2004User, Group# If you wish httpd to run as a different user or group, you must run# httpd as root initially and it will switch. ## User/Group: The name (or #number) of the user/group to run httpd as.#User apacheGroup apachefrom /etc/httpd/conf/httpd.conffrom /etc/passwddesktop:x:80:80:desktop:/var/lib/menu/kde:/sbin/nologinpostgres:x:26:26:PostgreSQL Server:/var/lib/pgsql:/bin/bashapache:x:48:48:Apache:/var/www:/sbin/nologinpostfix:x:89:89::/var/spool/postfix:/sbin/nologinsquid:x:23:23::/var/spool/squid:/dev/null15© David Morgan 2003,2004ServerAdmin# ServerAdmin: Your address, where problems with the server should be# e-mailed. This address appears on some server-generated pages, such# as error documents. e.g.