This Guide is intended for people administrating areas of GridSite websites or fileservers, or managing GridSite's DN List groups - that is, how to use GridSite to manage other people's access to parts of the site - for example, people's write access to areas devoted to specific subprojects.
There is a separate User Guide which explains how to authenticate to the server with X.509 certificates, and how to manage files via a standard web browser or with command-line HTTPS clients. You should be familiar with the User Guide to fully understand this Admin Guide.
You may also find the Config Guide useful to understand how the Apache webserver is configured with GridSite extensions. If you are also the Apache webmaster for your site, you will definitely need to read the Config Guide to create the httpd.conf file. However, if you only need to manage webpages and files, then this Admin Guide and the User Guide should be sufficient.
GridSite defines groups of people using plain text DN Lists - that is, lists of people's certificate DNs. Each DN List has a URL which uniquely identifies the list (and may also allow other sites to obtain the list and use it themselves.) For example, the list of all GridPP members is https://www.gridpp.ac.uk/dn-lists/gridpp (note that it's https:// not http:// - this means that other sites that download the list can check the certificate of www.gridpp.ac.uk and know they're talking to the authoritative source of the lists.)
The system can also have a number of other DN Lists which are associated with specific groups of people and perhaps with specific areas of responsibility of the website. If the DN List directory URI is /dn-lists/ then there is a full list of the DN Lists exported by the server at that URI (for example, https://www.gridpp.ac.uk/dn-lists/ )
If you have permission to modify a DN List, you can start changing it by going to /dn-lists/ (via HTTPS), using the "Manage directory" button and finding the URL of your DN List in the listings. You may need to go down into a subdirectory to find your list. For example, https://www.gridpp.ac.uk/dn-lists/atlas is in the atlas subdirectory of /dn-lists/ (You may wish to bookmark the listing of such a directory if you frequently work with one.)
DN List directories are managed by the ACLs described in the next section, and if you have write permission, you can edit the lists already there, and add new lists with the same prefix (this means you can readily create your own subgroups.)
DN Lists appear in the Grid Access Control Lists (GACL) used by GridSite. These are stored as .gacl files in directories: if the .gacl file is present, it governs access to the directory; if it is absent, then the parent directories are searched upwards until a .gacl is found.
The GridSite GACL Reference explains the XML format of these files, but they can be edited using the ACL editor built into the GridSite system by people who have the Admin permission within the ACL.
If you have this permission in a given directory, when you view directory listings or files in that directory you will see the option "Manage Directory" in the page footer. This allows you to get a listing of the directory and the .gacl file will appear at the top if it's present. If not, then there will be a button to create a new .gacl file with the same permissions as have been inherited by that directory from its parent.
GACL allows quite complex conditions to be imposed on access, but normally you can think of an ACL as being composed of a number of entries, each of which contains one condition (the required credential) and a set of allowed and denied permissions.
Credentials can be individual user's certificate names or whole groups of certificate names if a DN List is given. (You can also specifiy hostname patterns using Unix shell wildcards (eg *.ac.uk) or EDG VOMS attribute certificates - see the GACL Reference for details.)
Permissions can be Admin (edit the ACL), Write (create, modify or delete files), List (browse the directory) or Read (read files.) Permissions can be allowed or denied. If denied by any entry, the permission is not available to that user or DN List (depending on what credential type was associated with the Deny.)