es:Kernel parameters hu:Kernel parameters ja:カーネルパラメータ pt:Kernel parameters ru:Kernel parameters zh-hans:内核参数

There are three ways to pass options to the kernel and thus control its behaviour:

1. When building the kernel—in the kernel's config file. See Kernel#Compilation for details.

2. When starting the kernel—using command line parameters (usually through a boot loader, or as well in unified kernel image).

3. At runtime—through the files in /proc/sys/ (see sysctl) and /sys/.

Between the three methods, the configurable options differ in availability, their name and the method in which they are specified. This page only explains the second method (kernel command line parameters) and shows a list of the most used kernel parameters in Arch Linux.

Most parameters are associated with subsystems and work only if the kernel is configured with those subsystems built in. They also depend on the presence of the hardware they are associated with.

Kernel command line parameters either have the format parameter, or parameter=value, or module.parameter=value.

Boot loader configuration

Kernel parameters can be set either temporarily by editing the boot entry in the boot loader boot selection menu, or permanently by modifying the boot loader configuration file.

The following examples add the quiet and splash parameters to the Clover, GRUB, GRUB Legacy, LILO, Limine, rEFInd, Syslinux and systemd-boot boot loaders.

Clover

• Add them to esp/EFI/CLOVER/config.plist:

• <string>initrd=\initramfs-linux.img root=UUID=0a3407de-014b-458b-b5c1-848e92a327a3 rw quiet splash</string>

GRUB

• Press e when the menu shows up and add them on the linux line:

• linux /boot/vmlinuz-linux root=UUID=0a3407de-014b-458b-b5c1-848e92a327a3 rw quiet splash

  Press Ctrl+x to boot with these parameters.

• To make the change persistent after reboot, you could manually edit /boot/grub/grub.cfg with the exact line from above, or if using grub-mkconfig:

• Edit /etc/default/grub and append your kernel options between the quotes in the GRUB_CMDLINE_LINUX_DEFAULT line:

  1. GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

  And then automatically re-generate the grub.cfg file with:

  1. # grub-mkconfig -o /boot/grub/grub.cfg

GRUB Legacy

• Press e when the menu shows up and add them on the kernel line:

• kernel /boot/vmlinuz-linux root=UUID=0a3407de-014b-458b-b5c1-848e92a327a3 rw quiet splash

  Press b to boot with these parameters.

• To make the change persistent after reboot, edit /boot/grub/menu.lst and add them to the kernel line, exactly like above.

LILO

• Add them to /etc/lilo.conf using append or addappend:

• 
  image=/boot/vmlinuz-linux
          ...
          append"quiet splash"

Limine

• To temporarily add kernel parameters, press e when the boot entry selection screen appears and modify the cmdline line:

• cmdline: root=UUID=0a3407de-014b-458b-b5c1-848e92a327a3 rw quiet splash

• To apply changes permanently, edit the kernel_cmdline line in the Limine configuration file:

• 
  /+Arch Linux
      ...
      kernel_cmdline: root=UUID=0a3407de-014b-458b-b5c1-848e92a327a3 rw quiet splash

• kernel_cmdline is alias of cmdline

rEFInd

• Press Insert, F2, Tab, or + on the desired menu entry and press it again on the submenu entry. Add kernel parameters at the end of the string:

• root=UUID=0a3407de-014b-458b-b5c1-848e92a327a3 rw initrd=\boot\initramfs-linux.img quiet splash

  Press Enter to boot with these parameters.

• To make the change persistent after reboot, edit /boot/refind_linux.conf and append them between the quotes in all required lines, for example

• "Boot using default options"   "root=UUID=0a3407de-014b-458b-b5c1-848e92a327a3 rw quiet splash"

• If you have disabled auto-detection of OSes in rEFInd and are defining OS stanzas instead in esp/EFI/refind/refind.conf to load your OSes, you can edit it like:

• 
  menuentry "Arch Linux" {
      ...
      options  "root=UUID=0a3407de-014b-458b-b5c1-848e92a327a3 rw quiet splash"
      ...
  }
  

Syslinux

• Press Tab when the menu shows up and add them at the end of the string:

• linux /boot/vmlinuz-linux root=UUID=0a3407de-014b-458b-b5c1-848e92a327a3 rw initrd=/boot/initramfs-linux.img quiet splash

  Press Enter to boot with these parameters.

• To make the change persistent after reboot, edit /boot/syslinux/syslinux.cfg and add them to the APPEND line:

• APPEND root=UUID=0a3407de-014b-458b-b5c1-848e92a327a3 rw quiet splash

systemd-boot

• Press e when the menu appears and add the parameters to the end of the string:

• initrd=\initramfs-linux.img root=UUID=0a3407de-014b-458b-b5c1-848e92a327a3 rw quiet splash

  Press Enter to boot with these parameters.

• To make the change persistent after reboot, edit /boot/loader/entries/arch.conf (assuming you set up your EFI system partition) and add them to the options line:

• options root=UUID=0a3407de-014b-458b-b5c1-848e92a327a3 rw quiet splash

• If you are using a unified kernel image to boot, edit /etc/kernel/cmdline.

dracut

dracut is capable of embedding the kernel parameters in the initramfs, thus allowing to omit them from the boot loader configuration. See dracut#Kernel command line options. Note that this only works for parameters understood by dracut, like root and rd.*. They do not become real kernel parameters.

EFI boot stub

See EFI boot stub#Using UEFI directly.

Hijacking cmdline

Even without access to your boot loader it is possible to change your kernel parameters to enable debugging (if you have root access). This can be accomplished by overwriting /proc/cmdline which stores the kernel parameters. However /proc/cmdline is not writable even as root, so this hack is accomplished by using a bind mount to mask the path.

First create a file containing the desired kernel parameters:

root=UUID=0a3407de-014b-458b-b5c1-848e92a327a3 ro console=tty1 logo.nologo debug

/root/cmdline

Then use a bind mount to overwrite the parameters:

# mount --bind -o ro /root/cmdline /proc/cmdline

You can cat /proc/cmdline to confirm that your change was successful.

Parameter list

This list is not comprehensive. In addition to the kernel itself, other programs can also read parameters from /proc/cmdline and change their behavior.

• For a mostly complete list of options understood by the kernel and boot loaders, see The kernel's command-line parameters. A basic list is in bootparam(7).

• For options understood by systemd, see kernel-command-line(7).

• For options understood by mkinitcpio with a busybox based initial ramdisk, see mkinitcpio(8) and Mkinitcpio#Runtime customization.

• For options understood by dracut, see dracut.cmdline(7).

• rw is required when using mkinitcpio's fsck hook (see https://bbs.archlinux.org/viewtopic.php?pid=1303683#p1303683) or when using F2FS as the root file system.

  The kernel uses rw if neither ro or rw are explicitly set on kernel command line (see bootparam(7)). However, mkinitcpio uses ro as the default value overriding the kernel's default (see mkinitcpio(8)). Boot loaders may also have their own configured default, for example, grub-mkconfig uses rw (see 36275 as a reference).

See also

• bootparam(7)

• kernel-command-line(7)

• Power saving#Kernel parameters

• Kernel Boot Command-Line Parameter Reference—the chapter 9 of the Linux Kernel in a Nutshell by Greg Kroah-Hartman