User:Csfore/Blocks
For arches that support EFI
Assume all block links are prefixed with Handbook:ABC/Blocks/EFI unless it has Blocks before it, i.e. /Blocks/ABC.
Handbook:Parts/Installation/Disks
Blocks link: /Mkfs
EFI system partition filesystem
The EFI system partition () must be formatted as FAT32:
root #mkfs.vfat Blocks link: /Mount
The ESP should also be mounted under the root partition location:
root #mkdir --parents Handbook:Parts/Installation/Base
Blocks link: /Preparing
UEFI systems
For UEFI systems, was formatted with the FAT32 filesystem and will be used as the EFI System Partition (ESP). Create a new directory (if not yet created), and then mount ESP there:
root #mkdir
root #mount
Handbook:Parts/Installation/Kernel
Blocks link: /Blocks/Secure_Boot/Manual
Optional: Signing the kernel image (Secure Boot)
When signing the kernel image (for use on systems with Secure Boot enabled) it is recommended to set the following kernel config options:
General setup --->
Kexec and crash features --->
[*] Enable kexec system call
[*] Enable kexec file based system call
[*] Verify kernel signature during kexec_file_load() syscall
[*] Require a valid signature in kexec_file_load() syscall
[*] Enable ""image"" signature verification support
[*] Enable loadable module support
-*- Module signature verification
[*] Require modules to be validly signed
[*] Automatically sign all modules
Which hash algorithm should modules be signed with? (Sign modules with SHA-512) --->
Security options --->
[*] Integrity subsystem
[*] Basic module for enforcing kernel lockdown
[*] Enable lockdown LSM early in init
Kernel default lockdown mode (Integrity) --->
[*] Digital signature verification using multiple keyrings
[*] Enable asymmetric keys support
-*- Require all keys on the integrity keyrings be signed
[*] Provide keyring for platform/firmware trusted keys
[*] Provide a keyring to which Machine Owner Keys may be added
[ ] Enforce Machine Keyring CA Restrictions
Where ""image"" is a placeholder for the architecture specific image name. These options, from the top to the bottom: enforces that the kernel image in a kexec call must be signed (kexec allows replacing the kernel in-place), enforces that kernel modules are signed, enables lockdown integrity mode (prevents modifying the kernel at runtime), and enables various keychains.
On arches that do not natively support decompressing the kernel (e.g. arm64 and riscv), the kernel must be built with its own decompressor (zboot):
Device Drivers --->
Firmware Drivers --->
EFI (Extensible Firmware Interface) Support --->
[*] Enable the generic EFI decompressor
After compilation of the kernel, as explained in the next section, the kernel image must be signed. First install app-crypt/sbsigntools and then sign the kernel image:
root #emerge --ask app-crypt/sbsigntoolsroot #sbsign /usr/src/linux-x.y.z/path/to/kernel-image --cert /path/to/kernel_key.pem --key /path/to/kernel_key.pem --out /usr/src/linux-x.y.z/path/to/kernel-imageFor this example the same key that was generated to sign the modules is used to sign the kernel image. It is also possible to generate and use a second sperate key for signing the kernel image. The same OpenSSL command as in the previous section may be used again.
Then proceed with the installation.
To automatically sign EFI executables installed by other packages, enable the secureboot USE flag globally:
/etc/portage/make.confEnable Secure BootUSE="modules-sign secureboot"
# Optionally, to use custom signing keys.
MODULES_SIGN_KEY="/path/to/kernel_key.pem"
MODULES_SIGN_CERT="/path/to/kernel_key.pem" # Only required if the MODULES_SIGN_KEY does not also contain the certificate.
MODULES_SIGN_HASH="sha512" # Defaults to sha512
# Optionally, to boot with secureboot enabled, may be the same or different signing key.
SECUREBOOT_SIGN_KEY="/path/to/kernel_key.pem"
SECUREBOOT_SIGN_CERT="/path/to/kernel_key.pem"
The SECUREBOOT_SIGN_KEY and SECUREBOOT_SIGN_CERT may be different files. For this example the pem file generated by OpenSSL includes both the key and the accompanying certificate, and thus both variables are set to the same value.
When generating an Unified Kernel Image with systemd's
ukify the kernel image will be signed automatically before inclusion in the unified kernel image and it is not necessary to sign it manually.
Blocks link: /Blocks/Secure_Boot/Dist_Kernel
Optional: Signing the kernel image (Secure Boot)
The kernel image in the prebuilt distribution kernel (sys-kernel/gentoo-kernel-bin) is already signed for use with Secure Boot. To sign the kernel image of kernels built from source enable the secureboot USE flag, and optionally specify which key to use for signing in /etc/portage/make.conf. Note that signing the kernel image for use with secureboot requires that the kernel modules are also signed, the same key may be used to sign both the kernel image and the kernel modules:
/etc/portage/make.confEnable custom signing keysUSE="modules-sign secureboot"
# Optionally, to use custom signing keys.
MODULES_SIGN_KEY="/path/to/kernel_key.pem"
MODULES_SIGN_CERT="/path/to/kernel_key.pem" # Only required if the MODULES_SIGN_KEY does not also contain the certificate.
MODULES_SIGN_HASH="sha512" # Defaults to sha512.
# Optionally, to boot with secureboot enabled, may be the same or different signing key.
SECUREBOOT_SIGN_KEY="/path/to/kernel_key.pem"
SECUREBOOT_SIGN_CERT="/path/to/kernel_key.pem"
The SECUREBOOT_SIGN_KEY and SECUREBOOT_SIGN_CERT may be different files. For this example the pem file generated by OpenSSL includes both the key and the accompanying certificate, and thus both variables are set to the same value.
For this example the same key that was generated to sign the modules is used to sign the kernel image. It is also possible to generate and use a second separate key for signing the kernel image. The same OpenSSL command as in the previous section may be used again.
See the above section for instructions on generating a new key, the steps may be repeated if a separate key should be used to sign the kernel image.
To successfully boot with Secure Boot enabled, the used bootloader must also be signed and the certificate must be accepted by the UEFI firmware or Shim. This will be explained later in the handbook.
Blocks link: /Blocks/UKI
Optional: Building an Unified Kernel Image
An Unified Kernel Image (UKI) combines, among other things, the kernel, the initramfs and the kernel command line into a single executable. Since the kernel command line is embedded into the unified kernel image it should be specified before generating the unified kernel image (see below). Note that any kernel command line arguments supplied by the bootloader or firmware at boot are ignored when booting with secure boot enabled.
An unified kernel image requires a stub loader, currently the only one available is systemd-stub. To enable it:
For systemd systems:
/etc/portage/package.use/systemdsys-apps/systemd boot
For OpenRC systems:
/etc/portage/package.use/systemd-utilssys-apps/systemd-utils boot kernel-install
Installkernel can automatically generate an unified kernel image using either dracut or ukify, by enabling the respective flag. The uki USE flag should be enabled as well to install the generated unified kernel image to the $ESP/EFI/Linux directory on the EFI system partition (ESP).
For dracut:
/etc/portage/package.use/installkernelsys-kernel/installkernel dracut uki
/etc/dracut.confuefi="yes"
kernel_cmdline="some-kernel-command-line-arguments"
For ukify:
/etc/portage/package.use/installkernelsys-apps/systemd ukify # For systemd systems
sys-apps/systemd-utils ukify # For OpenRC systems
sys-kernel/installkernel dracut ukify uki
/etc/kernel/cmdlinesome-kernel-command-line-arguments
Note that while dracut can generate both an initramfs and an unified kernel image, ukify can only generate the latter and therefore the initramfs must be generated separately with dracut.
Generic Unified Kernel Image
The prebuilt sys-kernel/gentoo-kernel-bin can optionally install a prebuilt generic unified kernel image containing a generic initramfs that is able to boot most systemd based systems. It can be installed by enabling the generic-uki USE flag, and configuring installkernel to not generate a custom initramfs or unified kernel image:
/etc/portage/package.use/generic-ukisys-kernel/gentoo-kernel-bin generic-uki
sys-kernel/installkernel -dracut -ukify uki
Secure Boot
The generic Unified Kernel Image optionally distributed by sys-kernel/gentoo-kernel-bin is already pre-signed. How to sign a locally generated unified kernel image depends on whether dracut or ukify is used. Note that the location of the key and certificate should be the same as the SECUREBOOT_SIGN_KEY and SECUREBOOT_SIGN_CERT as specified in /etc/portage/make.conf.
For dracut:
/etc/dracut.confuefi="yes"
kernel_cmdline="some-kernel-command-line-arguments"
uefi_secureboot_key="/path/to/kernel_key.pem"
uefi_secureboot_cert="/path/to/kernel_key.pem"
For ukify:
/etc/kernel/uki.conf[UKI]
SecureBootPrivateKey=/path/to/kernel_key.pem
SecureBootCertificate=/path/to/kernel_key.pem
Blocks link: /Installkernel
systemd-boot
When using systemd-boot (formerly gummiboot) as the bootloader, systemd's kernel-install must be used. Therefore ensure the systemd and the systemd-boot USE flags are enabled on sys-kernel/installkernel, and then install the relevant package for systemd-boot.
On OpenRC systems:
/etc/portage/package.use/systemd-bootsys-apps/systemd-utils boot kernel-install
sys-kernel/installkernel systemd systemd-boot
root #emerge --ask sys-apps/systemd-utilsOn systemd systems:
/etc/portage/package.use/systemdsys-apps/systemd boot
sys-kernel/installkernel systemd-boot
root #emerge --ask sys-apps/systemdHandbook:Parts/Installation/System
Blocks link: /Fstab
(Just move to Handbook:AMD64/Blocks/Fstab?)
UEFI systems
Below is an example of an /etc/fstab file for a system that will boot via UEFI firmware:
/etc/fstabA full /etc/fstab example for an UEFI system# Adjust for any formatting differences and/or additional partitions created from the "Preparing the disks" step
0 2
none sw 0 0
/ defaults,noatime 0 1
/dev/cdrom /mnt/cdrom auto noauto,user 0 0
When auto is used in the third field, it makes the mount command guess what the filesystem would be. This is recommended for removable media as they can be created with one of many filesystems. The user option in the fourth field makes it possible for non-root users to mount the CD.
To improve performance, most users would want to add the noatime mount option, which results in a faster system since access times are not registered (those are not needed generally anyway). This is also recommended for systems with solid state drives (SSDs). Users may wish to consider lazytime instead.
Due to degradation in performance, defining the
discard mount option in /etc/fstab is not recommended. It is generally better to schedule block discards on a periodic basis using a job scheduler such as cron or a timer (systemd). See Periodic fstrim jobs for more information.Double-check the /etc/fstab file, then save and quit to continue.