The term Network Boot describes the process of booting a computer (desktop, laptop or server) from a network server. But with the computer network boot code must be equipped one, for As the TCP / IP BOOT-PROM or PXE PROM code. The network boot method is also automated operating system installations used for, and an "auxiliary operating system network loaded, the above and as a platform for the actual operating system installation serves. Moreover, in specific situations, this method can be used, with an emergency or maintenance, the operating system network loaded on to perform specific tasks, such as off-virus scanning, firmware updates, etc. For the network-boot TFTP are almost exclusively the standard protocols, PXE, DHCP, BOOTP and used. In current desktops, laptops and servers with LAN-on-motherboard chip sets, are usually the default settings already a PXE network boot code.
BOOTP (Bootstrap Protocol) is a standardized, vendor-independent protocol that allows a booting machine, address and additional configuration parameters over the network from a BOOTP server to obtain an IP. This can network boot file (also called the boot image) the name and the position of the include. DHCP (Dynamic Host Configuration Protocol) is the successor to BOOTP, provides the dynamic allocation of IP addresses, and performs other extensions, the concept of validity (IP lease) an IP address next. TFTP (Trivial File Transfer Protocol) is a standardized, vendor-independent protocol that allows booting of a machine, the assigned network boot file (boot image) over the network from a TFTP server to download it. PXE (Preboot Execution Environment) is an industry standard protocol, the DHCP and TFTP runs on top to network boot method to implement a common, and in addition a network boot API provide, by the downloaded network boot file can be used to network boot to perform other functions.
If your machines on a network-boot-code equipped with already, enable this code in the system setup of the computer. For machines that are not a network-boot-code feature, we provide add-on BOOT-PROM code physical PROM delivered into existing memory programmed or FLASH in the BIOS can be integrated system than that. On the server side operating system is not a special need. The only requirements are that the server TCP / IP "speaks" and related services for the network boot protocols (e.g. DHCP and TFTP) provides. There are DHCP (or BOOTP) and TFTP services on the network boot server needs. These services can be either the same server or different servers running on The hardware architecture of the server is not relevant as long as the server will boot services. On the side of the network-booting machine, all Intel-compatible x86 architectures supported, including 64-bit x64 architectures.
Basically, all the network adapter for network booting should be used provided they medium for the placement of the network boot code (i.e., the BOOT-PROM) provide a. This can be a blank PROM socket into which a PROM device is then inserted, or an onboard FLASH chip, in the BOOT-PROM code is then loaded into it. For LANOnBoard machines, the add-on boot code, the system BIOS are also integrated. Our list of supported network adapters and chipsets provides information about whether we specific network adapter or chipset your support.
During the DHCP or BOOTP phase, only very few packets between boot finished machine and boot server replaced, so that these protocols, the overall performance do not affect normal. TFTP is against the transfer of the entire boot image from the TFTP server booting machine responsible. Here the performance depends on several factors, mainly the size of the boot images, network speed, TFTP server performance, and of course the number of simultaneously-booting machines.
The Boot Files
When a PC starts, it must find its operating system, load and execute. This is called the boot. In the case of GNU / Linux, the most used is as follows:
- The BIOS has multiple boot options: hard disk, CD, etc. The most common value for this option is to boot from the hard disk.
- The BIOS then looks on the hard disk area called the MBR (Master Boot Record). This field contains the boot loader. This is GRUB or LILO. The BIOS gives his hand to this program.
- The boot loader is a Linux kernel on the hard disk, loads it into memory and then gives him her hand, passing parameters.
- Linux starts up and takes account of these parameters to determine what to do.
- But in the case of a diskless, the disc should not be used to host the operating system. We must therefore find other ways to boot.
- The method used is the method currently LAOG boot from network with PXE protocol.
Boot from the PXE NIC
The network boot is for a client to obtain from a server machine's network identity (its IP address, broadcast address, its subnet mask, its hostname, domain name, DNS server names, the address of the gateway) and information on the boot server (the server's IP address and name of the boot file). The client machine must be connected to the network and positioned to boot first on its network interface (UNDI / PXE): this is to position in the PC BIOS. The PXE protocol outlines the steps necessary for the effective start of the client machine.
Issuance by the client in a DHCPDISCOVER request application of its network identity, and this request contains the MAC address. Receipt by the DHCP server of the application which processes by seeking a match of the MAC address in dhcpd.conf, then sends the client a DHCPOFFER response containing its network identity if it has been found. Receipt by the customer and positioning of these parameters (ifconfig equivalent) then the server sends a request asking DHCPREQUEST boot information.
Received by the server in the DHCPREQUEST request that trafficking in seeking information requested in the dhcpd.conf file, then sends the client a response DHCPPACK containing the IP address of the TFTP server and boot file name (pxelinux.0 ). Receipt by the customer query DHCPPACK that connects to the TFTP server (port 69) request and loading the file specified.
After loading, execution of this file, always a connection TFTP load a configuration file in a directory pxelinux.cfg; it contains the name of the kernel and boot options then load the kernel and other files necessary to boot (initrd). The kernel is then started the initrd file is a compressed file system, the file system contains the kernel modules and anything else useful.
Bookmarks