Task 4: Update Flash Memory with New JavaOS

Tower model JavaStation computers include flash memory to store the JavaOS binary file. After JavaOS finishes its initialization, it determines whether it needs to update the flash memory with a new JavaOS based on the following criteria:

• The value of the JavaOS property javaos.alwaysUpdate

• Whether the JavaOS checksum value is different from the checksum of the JavaOS already in flash

Both the property and the checksum are delivered by DHCP as Vendor-Specific Options. See "Vendor-Specific Options".

The JavaOS checksum identifies the revision level of the JavaOS binary file. It is contained in the first four bytes of the last 12 bytes of the file. For more information, see "Managing the JavaOS Checksum".

The results of each possible set of conditions are shown in Table 8-2.

Table 8-2 Conditions for Updating JavaStation Flash Memory

Conditions		Results
javaos.alwaysUpdate	Checksum
not set	different	JavaOS opens a Flash Update dialog box on the JavaStation screen. You have the option of updating flash memory with the new copy of JavaOS.
not set	same	JavaOS does not update the flash memory.
true	different	JavaOS updates flash memory without querying the user.
true	same	JavaOS does not update the flash memory.
false	different	JavaOS does not update the flash memory.
false	same	JavaOS does not update the flash memory.

If the flash memory is updated, the JavaStation immediately reboots with the new copy of JavaOS.

Note that if any of the following conditions exist, flash memory is never updated:

• javaos.alwaysUpdate is set to false

• the checksum is set to zero

• the checksum is not delivered by the DHCP server