Explain briefly the procedure for re-installing Grub in Linux ?

Question

I wrote and compiled c code. I am using command "time a.out" . Every time output comes different.

$time ./a.out

real 0m0.002s
user 0m0.001s
sys 0m0.001s
-bash-3.2$ time ./a.out

real 0m0.001s
user 0m0.001s
sys 0m0.001s
-bash-3.2$ time ./a.out

real 0m0.001s
user 0m0.000s
sys 0m0.001s

Can someone please explain why these different different output come ?

Answer 1

1) Download Ubuntu Installation / Live cd

2) Boot from Ubuntu Installation / Live cd - usb, burned cd etc.

3) During boot select "Try Ubuntu" , Don't select install !

4) Mount your Linux root partitio
sudo mount /dev/sda6 /mnt ( Assuming /dev/sda6 is the Linux root partition)

5) Install / reinstall grub
$ sudo grub-install --root-directory=/mnt/ /dev/sda ( where /dev/sda is your primary disk)
Installation finished. No error reported.

6) Reboot your system, remove bootable CD and we should have the boot menu ready when the system starts.

Note : There would be slight difference when using with other distros.