kexec

allows the system to boot directly into a new kernel without going

TLDR

Load a new kernel

$ kexec -l [path/to/kernel] --initrd=[path/to/initrd] --command-line=[arguments]

Load kernel with current boot parameters

$ kexec -l [path/to/kernel] --initrd=[path/to/initrd] --reuse-cmdline

Execute the loaded kernel

$ kexec -e

Unload current kexec target kernel

$ kexec -u

kexec allows the system to boot directly into a new kernel without going through the BIOS/UEFI and bootloader. This enables faster reboots and is essential for kdump (kernel crash dumping).The process involves loading a kernel into memory with -l, then executing it with -e. This bypasses hardware initialization, significantly reducing reboot time.

PARAMETERS

-l, --load KERNEL

Load a new kernel into memory

-e, --exec

Execute the currently loaded kernel

-u, --unload

Unload the loaded kernel

--initrd FILE

Specify initramfs/initrd image

--command-line ARGS

Kernel command line arguments

--reuse-cmdline

Use current kernel's command line

-p, --load-panic

Load kernel for crash dump (kdump)

INSTALL

sudo apt install kexec-tools

sudo dnf install kexec-tools

sudo pacman -S kexec-tools

sudo apk add kexec-tools

sudo zypper install kexec-tools

nix profile install nixpkgs#kexec-tools

CAVEATS

Requires CONFIG_KEXEC in the kernel. Some hardware may not work correctly after kexec due to missing initialization. Not all drivers handle kexec transitions properly.

HISTORY

kexec was developed to enable fast reboots and kernel crash dumping. It was merged into the Linux kernel in version 2.6.13 (2005) and has become essential for kdump functionality.