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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:
+   <code bash>sudo gedit /etc/default/grub</code>
+  * 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 option ''isolcpus=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.
+<code bash>
+GRUB_CMDLINE_LINUX_DEFAULT="quiet splash isolcpus=2,3"
+</code>
+  * Run the command:
+<code bash>
+sudo update-grub
+</code>
+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:
+<code bash>
+GRUB_DEFAULT=1>2
+</code>
+and to make effective modification you have to run the command:
+<code bash>
+sudo update-grub
+</code>
+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:
+<code bash>
+GRUB_DEFAULT=2
+</code>
+There is also the option to specify directly the name of the kernel (this is the solution I prefer):
+<code bash>
+GRUB_DEFAULT="Advanced options for Ubuntu>Ubuntu, with Linux 3.2.0-18-generic-pae"
+</code>
+To know the names of the kernels you can type the command:
+<code bash>
+grep menuentry /boot/grub/grub.cfg
+</code>
+===== 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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