Configure grub.cfg for two CPU cores

• if two cpu cores ...
  

  GRUBCFG=/boot/efi/EFI/BOOT/grub.cfg
  # backup original grub.cfg if not backup before
  [[ ! -f $GRUBCFG.bak ]] && cp -a $GRUBCFG{,.bak} 
  
  # display current setting
  grep --color -E '(isolcpus|rcu_nocbs)=\S*' $GRUBCFG
  
  # change isolcpus=* rcu_nocbs=* to change isolcpus=1-2 rcu_nocbs=1-2
  sed -i "s/isolcpus=\S*/isolcpus=1-2/; s/rcu_nocbs=\S*/rcu_nocbs=1-2/" $GRUBCFG
  
  # verification
  grep --color -E '(isolcpus|rcu_nocbs)=\S*' $GRUBCFG
  
  # if the grub.cfg is correct, reboot machine
  reboot
  

• recover to the original grub.cfg ...
  

  GRUBCFG=/boot/efi/EFI/BOOT/grub.cfg
  
  # display current setting
  grep --color -E '(isolcpus|rcu_nocbs)=\S*' $GRUBCFG
  
  # recover
  [[ -f $GRUBCFG.bak ]] && cp -a $GRUBCFG.bak $GRUBCFG
  
  # verification
  grep --color -E '(isolcpus|rcu_nocbs)=\S*' $GRUBCFG
  
  # if the grub.cfg is recovered, reboot machine
  reboot