Understanding and Creating Aliases

1. Understanding and Creating Aliases October 27, 2010

2. Agenda • Aliases • Redirects • Resources

3. Aliases vs. Redirects • Alias • False name to conceal one’s identity; Assumed name • Used to make a web page or directory on the same server available under many URLs • Redirect • To change the direction or course of • Used to make a web page or directory on the same or different server available under many URLs

4. Aliases • Common uses: • Create user-friendly URLs • Change URL for content • Types used at EPA: • Symbolic Links • DNS Aliases

5. Symbolic Links • A text string that is interpreted by the operating system as a path to another file or directory • Used on the static web Linux servers: www.epa.gov, intranet.epa.gov, staging.epa.gov • Also used on other Linux servers (e.g., OAS) • All TSSMS accounts are a symbolic link • Data resides at /public/data/TSSMS/web • Symlink resolves to /TSSMS/ so that the URL www.epa.gov/TSSMS/ will render the content

6. Symbolic Links • Since TSSMS accounts are 8-characters, need an alias to obtain a user-friendly URL • NCC Sys Admins place the symbolic link in the htdocs file • Example: • Content resides at www.epa.gov/opp00001/bedbugs/ • Request symbolic link (alias) to obtain URL: www.epa.gov/bedbugs/

7. Visit www.epa.gov/webguide • Select “Create or Remove Alias” under “Create a Web Area” • http://intranet.epa.gov/webmast3/webguide/aliasform.html Requesting an Alias

8. Fulfilling the Request • Request goes to technical contracting team, OEAEE (formerly known and OPA) and OEI • OEAEE and OEI have 24 hours to reject or ask questions about the request • If no objections are expressed within 24 hours, support contractor will create the alias

9. Alias Instructions Individual Filing the Request: Tracey Westfield EPA Federal Account Manager Name: Tracey Westfield EPA Federal Account Manager Phone Number: 202-564-5586 EPA Federal Account Manager Email:Westfield.Tracey@epa.gov EPA Server: public TSSMS Account Name: lawsregs/regstat/ Alias to be added or removed:http://www.epa.gov/regstat/ Action: create alias Additional Alias Names: Additional Notes: This is a request for an alias on a folder within the LAWSREGS TSSMS. The folder name is "regstat". That folder currently has one "placeholder" index page, but it'll be populated with a lot more files soon. The new Reg Stat website is under development and currently on a staging server, but I want to have the alias ready once we migrate the files to the "regstat" folder.

10. Managing Aliases • Linux is case-sensitive • Aliases will be granted for lowercase letters only • If you have more than one alias for your site, must identify a primary alias: http://www.epa.gov/cgi-bin/SPA/selectalias • Consider removing all aliases other than the primary alias (critical for consistent linking and WebCMS publication) • If the target site for your alias is moved or deleted, remember to update or remove your alias (use the Alias request form in the Web Guide) • OEI periodically reviews orphaned aliases and deletes them

11. Impact on Search / Stats • Some search engines do not recognize symlinks as the same file (e.g., Northern Light) – they will display each alias as a new site • Google search should reconcile aliases and display only one page (not 100% sure, though) • Analog statistics for each alias is collected separately www.epa.gov/water, www.epa.gov/ow, www.epa.gov/OW • Maxamine tries to aggregate statistics for multiple aliases, but does not always know when a new alias is created or one removed

12. DNS Aliases • Resource record in the Domain Name System (DNS) that specifies that the domain name is an alias for another domain • Used to create URLs for dedicated servers • Can have more than one DNS entry per server • Obtained during the ADC process

13. DNS Alias Example • IP address: 123.45.6.78 • Server name: kestrel.rtpnc.epa.gov • DNS alias entries: • intrawiki.epa.gov • intrablog.epa.gov • nationaldialogue.epa.gov

14. Redirects • Common Uses of Redirects • Redirect users away from a discontinued server • Load balancing • Display error pages for removed sites • Ensure old links still work when pages are moved or renamed • Allow users to use an abbreviated or more memorable URL • Types of Redirects Used at EPA: • Client-side redirects using redirect code • Server-side redirects using .htaccess file • NOTE: We don’t use the rewrite rule in the Apache config file

15. Client-Side Redirects • Used to redirect users from one server to an application or Website on another server • Use the web browser to redirect users to the new URL • Redirect code is read in the metadata tag field • Created and managed by the content owner • Directions and sample redirect code: http://yosemite.epa.gov/OEI/webguide.nsf/create/alias#dynamic • All bookmarks to the content will be displayed as the destination URL not the requested URL

16. Client-Side Redirects • Steps in creating a redirect for your site or application: • Create a new TSSMS account or a directory under an existing TSSMS account • Request an alias for that TSSMS account or directory • Place redirect code inside the new TSSMS account or directory • Example: • Create new TSSMS account “MYAPPLIC” (www.epa.gov/myapplic) • Request alias “www.epa.gov/myapplication” to go to (www.epa.gov/myapplic) • Write redirect code for www.epa.gov/myapplic to go to http://cfpub.epa.gov/myapplication • Effect: • User enters http://www.epa.gov/myapplication • Browser reads www.epa.gov/myapplication and sends user to www.epa.gov/myapplic • Host location redirects user to http://cfpub.epa.gov/myapplication

17. Client-Side Redirect Code • An example of a redirect page is epa.gov/npdes/, which uses an HTML redirect to send readers to cfpub.epa.gov/npdes/ as follows: <HTML> <HEAD> <meta http-equiv="refresh" content="0" URL=http://cfpub.epa.gov/npdes/"> </HEAD> </HTML> • This particular code does not incorporate a delay • To incorporate a delay, change the value of the content tag (For example, content="3" would provide a three second delay, which would allow you to display a transfer message)

18. .htaccess Redirect • Used to redirect users from a URL to a page or directory on either the same or different server • Place configuration directives in a text file called .htaccess • Place the .htaccess file in the directory to be configured • If the configuration is to be applied to the entire site, place the .htaccess file in the root directory of your site (/public/data/TSSMS/web) • The directives will be applied to the directory with the .htaccess file and all subdirectories thereof

19. Other Uses of .htaccess • Custom 404 Pages • Password-Protected Directories • IP-Protected Directories • For more information, see Leann Spradling’s “Using Apache .htaccess Files” presentation from the March 2007 Web Workgroup Meeting (Potomac Yard) (http://intranet.epa.gov/webgroup/meetings/03-07/agenda.html)

20. .htaccess Redirection • Place an .htaccess file in your root directory with this directive in the file: Redirect Code /path URL • The “code” is optional • Possible codes include: • 301: Moved Permanently • 302: Temporarily Moved (default) • 303: Other

21. Example Create a redirect to files on a different server: Redirect /sample01/old.html http://yosemite.epa.gov/sample01/new.html • Place .htaccess file under: /public/data/sample01/web/ • Redirects any user who requests www.epa.gov/sample01/old.html to yosemite.epa.gov/sample01/new.html

22. Example Create a redirect to files on the same server: Redirect /sample01/old.html http://www.epa.gov/sample01/new.html • Place .htaccess file under: /public/data/sample01/web • Redirects any user who requests www.epa.gov/sample01/old.html to www.epa.gov/sample01/new.html

23. Example Use a site alias (symlink) in the redirect • “sample” is an alias to “/public/data/sample01” Redirect /sample/old.html http://www.epa.gov/sample/new.html • Place the .htaccess file in the /public/data/sample01/web • Redirects any user who requests www.epa.gov/sample01/old.html to www.epa.gov/sample01/new.html

24. Redirect Match • Allows you to redirect multiple files with regular expressions redirectmatch /air(.*) /reg5oair$1 • Tells the server "if the request is /air, followed by anything else, remember the anything else. Then go to reg50air, and put the anything else after that. • This expression would redirect users who enter http://www.epa.gov/region5/air/glakes/ to content located at http://www.epa.gov/reg5oair/glakes/

25. Stacking Directives • There can only be one .htaccess file per directory • All directives for the directory must be in that one file, including: • Redirection • Password Protection • 404 Error • IP Protection

26. .htaccess Problems • Precedence • Applied in the order they are found by the web server • If there is a conflict, the .htaccess file in the subdirectory will take precedence when a file is requested from that subdirectory • Syntax Errors • Instructions depend on correct syntax • Might not render content if syntax error (HTTP 500 error) • Webserver Load • If there is an .htaccess file in a directory, Apache must check all the directories above it for other .htaccess files that may apply

27. Avoiding Problems • Test in staging and again when go to production • Ensure .htaccess files are world-readable • Use the webguide documentation • Consider if an .htaccess file is truly the best solution • Consider using an HTML redirect page instead • Minimize the number of .htaccess files in a site • Minimize the number of directives used • Maintain .htaccess files – remove outdated directives • Comment your .htaccess files for future reference • Keep track of existing .htaccess files to avoid conflicts

28. Resources • Web Guide: Customize A Web Areahttp://yosemite.epa.gov/oei/webguide.nsf/customize • Web Guide: Create or Remove an Aliashttp://yosemite.epa.gov/OEI/webguide.nsf/create/alias • 2007 Web Workgroup Presentation on .htaccess fileshttp://intranet.epa.gov/webgroup/meetings/03-07/agenda.html • Apache Tutorial on .htaccess files http://httpd.apache.org/docs/2.0/howto/htaccess.html