Changes for page UEFI Secure Boot
Last modified by Sabrina V. on 2026/02/02 10:18
From version 1.1
edited by Sabrina V.
on 2026/02/02 10:06
on 2026/02/02 10:06
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To version 2.1
edited by Sabrina V.
on 2026/02/02 10:18
on 2026/02/02 10:18
Change comment:
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... ... @@ -1,3 +1,5 @@ 1 +and verifies its signature using the distribution certificates embedded in the Shim package. 2 + 1 1 {{aagon.floatingbox/}} 2 2 3 3 For systems with UEFI firmware and Secure Boot activated, the PXE boot process differs fundamentally from classic legacy boot via BIOS. UEFI uses a modern architecture model based on 64-bit operation, modular expandability and cryptographic verification. While legacy boot loads arbitrary code without integrity checks, Secure Boot enforces a continuous chain of trust that extends from the firmware starter to the kernel. Each component must be digitally signed in order to be executed. ... ... @@ -5,37 +5,37 @@ 5 5 Since the Shim bootloader is signed by Microsoft, it is classified as trustworthy by the firmware. The Shim package also contains certificates for the respective distribution, which are used to verify the subsequent components (such as GRUB, the kernel and the initramfs). It is crucial that the certificate chain remains unchanged throughout the entire boot process so that each component is only loaded from an authorized source. 6 6 7 7 8 -= Ablauf desPXE-Boots imUEFI-Modus=10 += PXE boot process in UEFI mode = 9 9 10 - DerAblauf gestaltetsichtypischerweisewiefolgt:12 +The process typically proceeds as follows: 11 11 12 -1. **UEFI -Firmware-Initialisierung**13 - DieFirmware initialisiertHardwarekomponentenundprüft,obSecure Boot aktivist.AnschließendstartetsiedenNetzwerkstack fürdenPXE-Boot.14 -1. **DHCP -AnfrageundBootdatei-Zuweisung**15 - DerPXE-Client sendeteineDHCP-Anfrageunderhält IP-Adresse,Bootserver (TFTP/HTTP)unddenNamenderzuladendenBootdatei, typischerweise##bootx64.efi##.16 -1. **Shim -Start (Microsoft-signiert)**17 - DieFirmware lädt##bootx64.efi## (denShim-Bootloader).Da dieservon Microsoftsigniert ist,wirderalsvertrauenswürdig akzeptiert.18 -1. **GRUB -Start(Distribution-signiert)**19 - DerShim-Bootloader lädt##grubx64.efi##undüberprüft dessenSignaturanhand derimShim-PaketeingebettetenZertifikate derDistribution.20 -1. **Kernel -undInitramfs-Start**21 -GRUB l ädtdenKernel (##vmlinuz##)unddieInitramfs (##initrd.img##). Beidemüssensigniert sein,sonstverweigertSecure Boot denStartvorgang.22 -1. **Systemstart undSchlüsselprüfung**23 - ErstwennalleSignaturengültig sind,wirdderKernelausgeführtunddasBetriebssystemgebootet.14 +1. **UEFI firmware initialisation** 15 +The firmware initialises hardware components and checks whether Secure Boot is active. It then starts the network stack for PXE boot. 16 +1. **DHCP request and boot file assignment** 17 +The PXE client sends a DHCP request and receives the IP address, boot server (TFTP/HTTP) and the name of the boot file to be loaded, typically ##bootx64.efi##. 18 +1. **Shim start (Microsoft signed)** 19 +The firmware loads ##bootx64.efi## (the Shim bootloader). Since this is signed by Microsoft, it is accepted as trustworthy. 20 +1. **GRUB boot (Distribution signed)** 21 +The Shim bootloader loads ##grubx64.efi## and verifies its signature using the distribution certificates embedded in the Shim package. 22 +1. **Kernel and initramfs start** 23 +GRUB loads the kernel (##vmlinuz##) and the initramfsd (##initrd.img##). Both must be signed, otherwise Secure Boot will deny access to the boot process. 24 +1. **System start and key verification** 25 +Only when all signatures are valid will the kernel be executed and the operating system booted. 24 24 25 - DieseArchitekturstelltsicher, dass während desgesamtenBootvorgangsnurverifizierteund signierteKomponentenausgeführtwerden.27 +This architecture ensures that only verified and signed components are executed during the entire boot process. 26 26 27 -= VorbereitungderBootdateien=29 += Preparation of the boot files = 28 28 29 -F ürdenPXE-Boot unter Secure BootbenötigenSie folgendeDateien,dievonderjeweiligenDistributionbereitgestellt werden:31 +For PXE booting under Secure Boot, you need the following files, which are provided by the respective distribution: 30 30 31 -* ##bootx64.efi## – Shim -Bootloader (Microsoft-signiert,aus demPaket shim-signed)32 -* ##grubx64.efi## – GRUB EFI -Bootloader (Distribution-signiert)33 -* ##vmlinuz## – Linux -Kernel (signiert)34 -* ##initrd.img## – Initial -RAM-Disk (signiert)33 +* ##bootx64.efi## – Shim bootloader (Microsoft signed, from the shim-signed package) 34 +* ##grubx64.efi## – GRUB EFI bootloader (distribution signed) 35 +* ##vmlinuz## – Linux kernel (signed) 36 +* ##initrd.img## – Initial RAM disk (signed) 35 35 36 - DieseDateienwerdeninderRegelimVerzeichnis##/tftpboot/##odereinem Unterordnerwie##/tftpboot/uefi/## abgelegt undüberDHCP/TFTPverteilt.38 +These files are usually stored in the ##/tftpboot/## directory or a subfolder such as ##/tftpboot/uefi/## and deployed via DHCP/TFTP. 37 37 38 - BeispielhafteStruktur40 +Example structure 39 39 40 40 {{code language="bash"}} 41 41 /tftpboot/ ... ... @@ -48,15 +48,15 @@ 48 48 {{/code}} 49 49 50 50 {{aagon.warnungsbox}} 51 - BeachtenSiebeimehrerenDistributionen,dassShimund GRUBimmeralspassendesPaarverwendetwerdenmüssen.JedeDistributionbringtihreigenesZertifikatsset mit.EineMischungunterschiedlicherVersionenführtdaherzuSignaturfehlernundBootabbrüchen.53 +If you have multiple distributions, please note that Shim and GRUB must always be used as a matching pair. Each distribution comes with its own set of certificates. Mixing different versions will therefore lead to signature errors and boot failures. 52 52 {{/aagon.warnungsbox}} 53 53 54 -= Anlage derGRUB-Konfiguration =56 += GRUB configuration file = 55 55 56 - Im Gegensatzzum Legacy-BootverwendetSecure BootüberUEFIeineGRUB-KonfigurationanstellederPXELINUX-Dateien.57 - DieseKonfigurationliegtüblicherweiseineinerDatei namens##grub.cfg##,dievon##grubx64.efi##geladen wird.58 +Unlike legacy boot, UEFI Secure Boot uses a GRUB configuration instead of PXELINUX files. 59 +This configuration is usually stored in a file called ##grub.cfg##, which is loaded by ##grubx64.efi##. 58 58 59 - BeispielhafteStrukturdesGRUB-Konfigurationsverzeichnisses61 +Example structure of the GRUB configuration directory 60 60 61 61 {{code language="bash"}} 62 62 /tftpboot/ ... ... @@ -64,21 +64,25 @@ 64 64 {{/code}} 65 65 66 66 {{aagon.infobox}} 67 - Anmerkung:Die ##grub.cfg## Datei wird vonmanchenGRUB-Implementierungenim folgendenOrterwartet##tftpboot/grub/grub.cfg##69 +Note: Some GRUB implementations expect the ##grub.cfg## file to be located in the following location: ##tftpboot/grub/grub.cfg## 68 68 {{/aagon.infobox}} 69 69 70 -**Wichtige GRUB-Parameter:** 71 71 72 -* **set timeout: **Legt den Timeout in Sekunden fest, bevor der Standard-Eintrag gestartet wird 73 -* **menuentry: **Definiert einen Boot-Eintrag im Menü 74 -* **linuxefi: **Lädt den Kernel (EFI-spezifischer Befehl) 75 -* **initrdefi**: Lädt die Initramfs (EFI-spezifischer Befehl) 76 -* **set root:** Definiert das Root-Dateisystem oder den TFTP-Pfad 77 77 78 - = Beispielkonfiguration(Standard-Variante) =74 +**Important GRUB parameters:** 79 79 80 -Eine einfache GRUB-Konfigurationsdatei für PXE-Start mit Secure Boot kann wie folgt aussehen: 76 +* **set timeout: **Sets the timeout in seconds before the default entry is started 77 +* **menuentry: **Defines a boot entry in the menu 78 +* **linuxefi: **Loads the kernel (EFI-specific command) 79 +* **initrdefi**: Loads the initramfs (EFI-specific command) 80 +* **set root:** Defines the root file system or TFTP path 81 81 82 + 83 + 84 += Example configuration (standard variant) = 85 + 86 +A simple GRUB configuration file for PXE boot with Secure Boot may look as follows: 87 + 82 82 {{code language="ba"}} 83 83 set default=0 84 84 set timeout=5 ... ... @@ -95,16 +95,21 @@ 95 95 } 96 96 {{/code}} 97 97 98 - DieseKonfigurationbietetzweiMenüoptionen:104 +This configuration offers two menu options: 99 99 100 -1. Start desRescue-oderInstallationssystemsüberKernelundInitramfs101 -1. Lo kalerBootvorgangüber „exit“(übergibtKontrolleanFirmware)106 +1. Start the rescue or installation system via kernel and initramfs 107 +1. Local boot process via ‘exit’ (transfers control to firmware) 102 102 103 - WennSienunausgehendvondieserKonfigurationstarten,erhaltenSiedie folgendeBildschirmansichtundderBoot würdenach5 SekundenautomatischvonderlokalenFestplatte starten.109 +If you now start from this configuration, you will see the following screen and the boot will start automatically from the local disk after 5 seconds. 104 104 105 -[[UEFI Boot Screen>>image:UEFI Boot_Bootscreen.png||alt="UEFI Boot Screen"]]111 +[[UEFI Boot screen>>image:UEFI Boot_Bootscreen.png||alt="UEFI Boot Screen"]] 106 106 107 -= Hinweis zum Secure Boot in ACMP = 108 108 109 -Das PXE-Boot-System in ACMP unterstützt sowohl Legacy-BIOS, UEFI Boot als auch UEFI mit Secure Boot. 110 -Bei aktiviertem Secure Boot kann die Funktionalität jedoch eingeschränkt sein. Für maximale Kompatibilität wird empfohlen, eine Distribution mit offiziell signierten Bootloadern (Shim + GRUB) zu verwenden oder Secure Boot zu deaktivieren. 114 + 115 += Note on Secure Boot in ACMP = 116 + 117 +The PXE boot system in ACMP supports Legacy BIOS, UEFI Boot and UEFI with Secure Boot. 118 + 119 +However, functionality may be limited when Secure Boot is activated. For maximum compatibility, it is recommended to use a distribution with officially signed boot loaders (Shim + GRUB) or to disable Secure Boot. 120 + 121 +

