What can a job expect to be installed on a WN?
In general terms a job will find a “standard” environment for whatever OS runs on the WN, currently this is generally Scientific Linux or compatible. However, there is no particular guarantee as to what exactly will be installed; some sites install essentially the full Linux distribution by default, others only a minimal set. For mainstream use VOs should validate sites before use, publishing a tag which can be selected in the JDL so that jobs only go to suitable sites. If sites are found to be missing some components which are required there are basically three possible approaches. The simplest is to ignore the site and send jobs elsewhere. Secondly, GGUS tickets can be opened to request that the site installs the missing package(s). Thirdly, the VO can incorporate the missing component(s) into its own VO-specific software.
