Step by Step to BootManage Remoteboot

The bootstrap process on all PCs is a matter of one program starting another, each more intelligent than the one before. The very first program is stored in Read Only Memory in the system BIOS. TCP/IP remoteboot is no different, except that instead of passing control over to very simple boot routines in a known place on a hard disk the PROM on the network card is initialised instead. The PROM contains enough code to contact a server and install a boot image in memory, which is in turn enough to start a full operating system.

bootix's engineers have achieved a remarkable feat in packing a fully featured TCP/IP stack into a tiny chip of 16 or 32 Kilobytes. The PROM uses the standard Internet TFTP protocol to talk to a server. A choice of servers is available for all platforms from many different suppliers, ensuring that whatever the requirements are a suitable solution will be found. This translates into savings on network management costs because the PROM fits into any standards-based environment.

1. Plug the PROM into the corresponding socket on the network adapter. This has the effect of enhancing the PC BIOS. When the computer is switched on this code is detected and takes over control of the boot procedure immediately after the Power On Self Test (POST) routines have been run. It is not possible to interrupt this process, so complete security is maintained.
2. The PROM checks its configuration. Depending on the site-specific configuration, it may attempt to boot off the network, check the hard disk before it tries the network, or merely check for a keypress before booting from one of these sources. For most sites, the default is to attempt to boot from the network first.
3. A network boot starts with a standard Dynamic Host Configuration Protocol (DHCP) discovery broadcast. This is a request to any DHCP server on the network to give the PROM basic configuration information such as its IP address, subnet mask and so on. Dynamic TCP/IP makes network management much easier, which is why modern operating systems such as Windows 95, Warp Connect and Unix workstations often use it. A DHCP server can be a Windows NT, Warp, Unix or Novell server, or any other operating system that supports Internet-standard protocols. Should DHCP not be available, the older (and compatible) protocol BOOTP can be used. BOOTP is more widely supported than DHCP at present.
4. Using this information, the PROM can now start up its own TCP/IP stack. One of the parameters returned by the DHCP/BOOTP reply was the address of a server to boot from, and the PROM starts up the Trivial File Transfer Protocol (TFTP) to fetch the specified file from the server. The file is normally a boot image, which is an exact byte-for-byte image of a floppy disk. of any size that is valid for a bootable floppy disk - eg 1.44 Megabytes. A ramdisk is created and this image is placed into it.
5. The PC is then instructed to boot from this ramdisk as if it were the A: floppy drive. After this there is an operating system present, whatever operating system is on the disk image from DOS to Unix to Windows 95. Typically this operating system will make connections to a server and set itself up to be independant of the A: ramdrive, and then at a suitable point will release the ramdrive and restore the real A:.

For large and complex sites (many of which bootix counts as valued customers) each of these steps has several alternatives. The boot file need not be just a container file, it can be a menu, upgraded PROM software, or any user-specified program. It can even be a menu-selectable PROM image from another manufacturer, such as a Pathworks MOP, Novell RPL or Linux NFS boot. For those extra-special jobs, there is a documented API set for building completely custom solutions.

bootix provides the ultimate in flexibility.