Provided by: systemd_239-7ubuntu10_amd64
systemd-boot, sd-boot - A simple UEFI boot manager
systemd-boot (short: sd-boot) is a simple UEFI boot manager. It provides a graphical menu to select the entry to boot and an editor for the kernel command line. systemd-boot supports systems with UEFI firmware only. systemd-boot loads boot entry information from the EFI system partition (ESP), usually mounted at /boot, /efi, or /boot/efi during OS runtime. Configuration file fragments, kernels, initrds and other EFI images to boot generally need to reside on the ESP. Linux kernels must be built with CONFIG_EFI_STUB to be able to be directly executed as an EFI image. During boot systemd-boot automatically assembles a list of boot entries from the following sources: · Boot entries defined with Boot Loader Specification description files located in /loader/entries/ on the ESP. These usually describe Linux kernel images with associated initrd images, but alternatively may also describe arbitrary other EFI executables. · Unified kernel images following the Boot Loader Specification, as executable EFI binaries in /EFI/Linux/ on the ESP. · The Microsoft Windows EFI boot manager, if installed · The Apple MacOS X boot manager, if installed · The EFI Shell binary, if installed · A reboot into the UEFI firmware setup option, if supported by the firmware kernel-install(8) may be used to copy kernel images onto the ESP and to generate description files compliant with the Boot Loader Specification. bootctl(1) may be used from a running system to locate the ESP, list available entries, and install systemd-boot itself. systemd-boot will provide information about the time spent in UEFI firmware using the Boot Loader Interface. This information can be displayed using systemd-analyze(1).
The following keys may be used in the boot menu: ↑ (Up), ↓ (Down), j, k, PageUp, PageDown, Home, End Navigate up/down in the entry list ↵ (Enter) Boot selected entry d Make selected entry the default e Edit the kernel command line for selected entry +, t Increase the timeout before default entry is booted -, T Decrease the timeout v Show systemd-boot, UEFI, and firmware versions P Print status Q Quit h, ? Show a help screen Ctrl + l Reprint the screen The following keys may be used during bootup or in the boot menu to directly boot a specific entry: l Linux w Windows a OS X s EFI shell 1, 2, 3, 4, 5, 6, 7, 8, 9 Boot entry number 1 ... 9 In the editor, most keys simply insert themselves, but the following keys may be used to perform additional actions: ← (Left), → (Right), Home, End Navigate left/right Esc Abort the edit and quit the editor Ctrl + k Clear the command line Ctrl + w, Alt + Backspace Delete word backwards Alt + d Delete word forwards ↵ (Enter) Boot entry with the edited command line Note that unless configured otherwise in the UEFI firmware, systemd-boot will use the US keyboard layout, so key labels might not match for keys like +/-.
The files systemd-boot reads generally reside on the UEFI ESP which is usually mounted to /boot/, /efi/ or /boot/efi during OS runtime. systemd-boot reads runtime configuration such as the boot timeout and default entry from /loader/loader.conf on the ESP (in combination with data read from EFI variables). See loader.conf(5). Boot entry description files following the Boot Loader Specification are read from /loader/entries/ on the ESP. Unified kernel boot entries following the Boot Loader Specification are read from /EFI/Linux/ on the ESP.
bootctl(1), loader.conf(5), Boot Loader Specification, Boot Loader Interface
1. Boot Loader Specification https://github.com/systemd/systemd/blob/master/doc/BOOT_LOADER_SPECIFICATION.md 2. Boot Loader Interface https://www.freedesktop.org/wiki/Software/systemd/BootLoaderInterface