Grub with RH or Fedora

Grub with RH or Fedora
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hi,

can someone tell me how to restore boot menu without updating linux OS,
before i was using lilo, so if i miss boot data on mbr i just run linux
rescue --> chroot /mnt/sysimage -->an lunch lilo with the old
configuration file, but with grub i see that it is more complicated.

thanx 4all.

.