cs:kernel_boot_parameters
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Kernel boot parameters
How to configure kernel boot parameters with grub2
Example of the "isolcpus" option
- Open the file
/etc/default/grub
. Example:
sudo gedit /etc/default/grub
- Edit the option
GRUB_CMDLINE_LINUX_DEFAULT
in the file/etc/default/grub
to boot all the kernels with the new option. In this case, the kernel boot optionisolcpus=2,3
has been used, on a 4 cores CPU, to boot the kernel (and the other OS processes) using CPU cores 0 and 1, while CPU cores 2 and 3 are isolated, i.e., not used.
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash isolcpus=2,3"
- Run the command:
sudo update-grub
to make active the GRUB configuration at the next reboot.
Choose which kernel use for boot
If you want to boot the third kernel of the second sub-menu, you have to modify in file /etc/default/grub
the variable GRUB_DEFAULT
in the following way:
GRUB_DEFAULT=1>2
and to make effective modification you have to run the command:
sudo update-grub
If you want to choose directly an entry of the main menu, for instance the third entry, the variable GRUB_DEFAULT
has to be modified in the following way:
GRUB_DEFAULT=2
There is also the option to specify directly the name of the kernel (this is the solution I prefer):
GRUB_DEFAULT="Advanced options for Ubuntu>Ubuntu, with Linux 3.2.0-18-generic-pae"
To know the names of the kernels you can type the command:
grep menuentry /boot/grub/grub.cfg
Boot in recovery mode
- Select Recovery mode among kernel options
- Select a root section
- Type
mount -o remount,rw /
, if you want to enable write access to the filesystem
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You can reuse, distribute or modify the content of this page, but you must cite in any document (or webpage) this url: https://www.skenz.it/cs/kernel_boot_parameters
/web/htdocs/www.skenz.it/home/data/pages/cs/kernel_boot_parameters.txt · Last modified: 2024/04/08 22:34 by 127.0.0.1