Running the first node

The jnode script (Appendix ) starts a new node. Jnode is just a runnable node which also has group communication features. It is thus little more than a runnable version of Nodality. See Appendix .

The first jnode parameter is a node ID. We can use any number, as long as this is unique for each node in the LAN. The second parameter just tells the node to output the standard I/O of all its netlets. Useful for debugging and general interest.

The rest of the parameters are just a series of netlet descriptors, each of which is followed by a number of netlet-specific arguments of the form X=Y.

Each of these netlets is a bootstrap netlet, which is just a netlet which will have special access to local I/O streams. This stream access is a special privilege because netlets are not normally granted direct access to system resources. However jnode gives this privilege only to those netlets we've specified on the command line, and initialises those netlets in sequence. Each X=Y argument is one of these I/O streams (Y) with a name (X) which the netlet is expecting.

For example, we can see from the output above that the hos01-boot netlet (from the netlet descriptor hos01-boot.xml) outputs to its stream called hosting-out. It writes an admin warrant to file hos01-admin.xml, which we specified on the command line. We can also see, on the line before, that it tried to read a SAS warrant from the stream called sas-in, but since we've not specified this it does without.

Also notice how the telnet netlet starts, next. It reads the file hos01-admin.xml from its stream called hosting-in, which is a file just output from the previous netlet. Similarly for the SAS netlet, which reads from one stream and writes to three others.

Stringing netlets together in this way is only possible when booting Jnode.

Finally, the files produced by the boot process:

• hos01-admin.xml is a warrant to use the hosting service just started. It is an admin-level warrant and is used by both the telnet and SAS netlets. It is actually only usable on the current node because a warrant should point to a SAS and we don't have a SAS at this stage. So this warrant is, and can only be, used by the other bootstrap netlets on this node.
• sas01-real-desc.xml is a descriptor for our SAS. Although we already have a SAS descriptor that contained the JARs embedded in it, and hence was very large. But by this stage the SAS has loaded its own JARs into itself. Hence this ``real'' descriptor references the now-downloadable JARs as URLs.
• sas01-warrant.xml is a warrant for admin-level access to the SAS.
• hos01-real-admin.xml is another admin-level warrant for the hosting service. Unlike the other warrant this is usable from any node because the hosting service's JARs are now uploaded into the SAS.