The User Interface (UI)

The User Interface is a grid-users initial point of access to the LCG grid. The prerequisite for access is that the user has a local account and has a valid grid certificate installed in $HOME/.globus/. From here the user's identity can be authenticated and their authority to use specific resources can be determined.

A general procedure for submitting a job to the Grid involves:

creating a proxy:

grid-proxy-init

or

voms-proxy-init

Using voms-proxy-init creates a proxy with VOMS extensions. Of particular importance here is that the proxy will identify which VO the user will be acting as a member of. If a user is a member of multiple VO's, and, those VO's are managed from different servers, then the user will need to create a proxy with a command like:

voms-proxy-init -voms voms.server

where voms.server is the fully.qualified.domain.name of the voms server host for that VO.

The user can check the proxy created using:

voms-proxy-info

Output will be something like:

subject   : /C=AU/O=APAC-GRID/OU=The University of Melbourne/CN=John public/CN=proxy
issuer    : /C=AU/O=APAC-GRID/OU=The University of Melbourne/CN=John public
identity  : /C=AU/O=APAC-GRID/OU=The University of Melbourne/CN=John public
type      : proxy
strength  : 512 bits
path      : /tmp/x509up_u5511
timeleft  : 11:56:33

Job description files are created using the Job Description Language (JDL). This is in fact the Classified Advertisement Language of Condor.

The JDL is basically a mapping of attribute names to expressions. An extremely simple, yet functional example follows:

Executable = "myprogram.sh";
StdOutput = "std.out";
StdError = "std.err";

InputSandbox = {"test.sh"};
OutputSandbox = {"std.out, std.err"};

In this example, we are defining the executable we wish to run, the file in which we want the standard output to go, the file in which we want the standard error to go, what the system should bundle as the input sandbox and what will be returned in the output sandbox.