Boot Mode Considerations: BIOS vs.
Revisions Date Description October 2017 Initial release June 2018 Added DHCP Server PXE configuration details. The information in this publication is provided “as is.” Dell Inc. makes no representations or warranties of any kind with respect to the information in this publication, and specifically disclaims implied warranties of merchantability or fitness for a particular purpose. Use, copying, and distribution of any software described in this publication requires an applicable software license.
Table of contents Revisions.............................................................................................................................................................................2 Executive Summary ............................................................................................................................................................4 1 Introduction ......................................................................................................................
Executive Summary Dell EMC servers provide the option of using the traditional BIOS boot mode or UEFI boot mode. The boot mode determines how the system BIOS interacts with adapter card firmware and operating system software. Specific security features and boot mechanisms are available only when the system is configured for UEFI boot mode. This Dell EMC Deployment and Configuration Guide has two goals.
1 Introduction Traditionally, the system BIOS performs initialization, boot, system management, and configuration tasks. The BIOS initializes the system’s processors, memory, bus controllers, and I/O devices. After initialization is complete, the BIOS passes control to operating system (OS) software. The OS loader uses basic services provided by the system BIOS to locate and load OS modules into system memory.
2 Comparing UEFI and Traditional BIOS This sections explains how UEFI corrects certain shortcomings in traditional BIOS implementations. The UEFI boot mode offers: • • • • 2.
separate interface for hard-disk or RAID configuration. Most boot devices require a system reboot after any firmware change, so system configuration requires multiple boots. UEFI defines a shared user interface known as the Human Interface Infrastructure (HII). A user can configure all the firmware settings - including BIOS, onboard management controller, and boot devices – using a single user interface, without needing a reboot between changes for each device.
3 Features Requiring UEFI Boot Mode As UEFI grows in popularity, modern capabilities are implemented natively for UEFI Boot Mode instead of BIOS Boot Mode. In Dell EMC servers, the following features are available only in UEFI Boot Mode: • • • 3.
4 Configuration Settings for UEFI Boot Mode This section provides an overview of the configuration changes needed to operate a Dell EMC PowerEdge server in UEFI Boot Mode. It is assumed that the reader is familiar with the traditional BIOS boot mode, and likely has existing infrastructure that uses BIOS boot mode. Unless otherwise noted, all configuration settings are accessible through integrated Dell Remote Access Controller (iDRAC) interfaces such as RACADM, or locally through the System Setup utility.
Figure 2 Setting Boot Mode in RACADM. When the system powers on with Boot Mode set to UEFI, the BIOS provides a list of available UEFI boot options. An administrator can view and edit the order of UEFI boot options. In System Setup, enter System BIOS > Boot Settings > UEFI Boot Settings (see Figure 3). Select UEFI Boot Sequence to edit the boot order. To disable specific boot options without changing the order, uncheck the desired options in the “Boot Option Enable/Disable” section on this page.
Figure 3 UEFI Boot Order Configuration. In RACADM, the “UefiBootSeq” attribute controls the UEFI Boot Order. Figure 4 shows an example of moving the PXE boot device to the beginning of the boot order. 11 : BIOS vs.
Figure 4 UEFI Boot Order Configuration in RACADM. 4.2 UEFI Boot from Local Media As a general rule, operating systems installed in a traditional BIOS environment will not be bootable in UEFI boot mode. There are no reliable means for converting or upgrading traditional bootable media to a UEFIbootable form, other than re-installing the operating system when the BIOS is in UEFI boot mode. The boot mode must be configured before installing operating systems or other bootable software.
iSCSI boot configuration (see the UEFI HTTP boot and UEFI iSCSI boot sections in this paper for details). Minimal changes are required for the PXE server and PXE client when transitioning from BIOS boot mode to UEFI boot mode. The following sections describe these changes. 4.3.1 PXE Server Configuration PXE server setup involves configuration of the DHCP server and boot server (a.k.a. TFTP server). In UEFI boot mode the Network Bootstrap Program (NBP) must be a UEFI bootable image (PE/COFF format).
filename "undionly.kkpxe"; } } For detailed information on how to configure your DHCP server please consult the user’s guide for the DHCP server. NOTE: Depending on the DHCP server configuration, the client may need to be configured for UEFI HTTP boot or UEFI iSCSI boot instead of PXE boot. If your current legacy boot DHCP server configuration contains an option 67 (filename) that is a URL instead of a simple filename, you need to configure the client UEFI HTTP boot settings instead of PXE boot.
Figure 5 UEFI PXE boot Configuration. The parameters to be configured in this page are: • • • 4.4 Interface: the network interface in the PXE client to configure for PXE boot; Protocol: the Internet Protocol that will be used for PXE boot (IPv4 or IPv6); VLAN: ID and Priority for Virtual LAN if enabled. UEFI HTTP Boot Configuration (Boot from URI) UEFI HTTP boot is supported beginning with Dell PowerEdge 14G systems.
The principle for HTTP boot is similar to PXE boot, except that HTTP boot uses HTTP (rather than TFTP) to transfer the NBP. 4.4.1 HTTP Boot Client Configuration As with other system settings, the HTTP boot client configuration settings are accessible through integrated Dell Remote Access Controller (iDRAC) interfaces such as RACADM, or locally through the System Setup utility.
4.4.2 HTTP Boot Server Configuration The HTTP boot server is composed of two major parts: DHCP server and HTTP server. A domain name system (DNS) server is necessary as well if the URI specifies the domain name instead of the IP address. The bootstrap program provided by the HTTP boot server must be a UEFI bootable image (PE/COFF format). For Linux environments, UEFI-capable bootstrap programs include ELILO, grub2, and syslinux. Windows environments (Windows Server 2012 and later) use bootmgfw.efi. 4.
Figure 7 UEFI iSCSI boot Initiator Name Configuration 18 : BIOS vs.
Figure 8 UEFI iSCSI boot Configuration. 19 : BIOS vs.
Figure 9 UEFI iSCSI boot Configuration (cont’d).
4.5.2 iSCSI Target Configuration The difference between iSCSI target configurations for UEFI and BIOS boot modes is the format of the bootable image on the target. In UEFI boot mode, the image must be a UEFI bootable image. iSCSI target configuration steps for Windows and Linux can be found on their respective official websites. 4.6 UEFI Secure Boot Configuration There are three primary settings involved in configuring UEFI Secure Boot.
Since the integrated device firmware supports both UEFI and BIOS boot modes, it is not necessary to update the firmware for one boot mode or the other. When the system is in UEFI boot mode, the BIOS automatically loads UEFI drivers for the devices instead of traditional option ROMs. RAID containers and virtual disk configurations do not require re-configuration when the system is changed to UEFI boot mode. The RAID metadata is independent of the system boot mode. 22 : BIOS vs.
5 Technical support and resources Dell.com/support is focused on meeting customer needs with proven services and support. Dell TechCenter is an online technical community where IT professionals have access to numerous resources for Dell EMC software, hardware and services. The Dell Systems Management portion of Dell TechCenter provides guidance for deployment, update, and configuration tasks. 5.
