1.  grub/* missing
linux rescue
chroot /mnt/sysp_w_picpath
cd /boot
grub-install /dev/sda


2 . boot/*  missing
linux rescue
chroot /mnt/sysp_w_picpath
service network restart
rpm -ivh --force http://192.168.1.1/inst/kernel-2.6.18-53.el5.i686.rpm
cd /boot
grub-install /dev/sda
cd /boot/grub
vi grub.conf
title redhat
   root (hd0,0)
   kernel /vmlinuz-2.6.18-53.el5 ro root=/dev/sda6
   initrd /initrd-2.6.18-53.el5.img

3. corrup /etc/fstab
file system problem  will boot  to emergency mode or maintainance mode request root passwd.
fdisk -l
mount
e2label /dev/sd* 
mount -o remount,defaults /dev/sda6 /
vi /etc/fstab    fix the file manually

4 mising /bin/sh or /bin/bash
linux rescue
rpm -qf /bin/sh --root /mnt/sysp_w_picpath
rpm -ivh --force http://192.168.1.1/inst/CentOS/bash-3* --root /mnt/sysp_w_picpath
 
sympton: can not excute /etc/rc.d/rc
no more processes left in this run level
chroot in rescue mode is fail due to /bin/sh missing.
 
 
5.missing mount command
stop at enable swap. into single mode mount not found
linux rescue
rpm -ivh --force http://192.168.1.1/inst/CentOS/util-linux-2* --root /mnt/sysp_w_picpath
 
6.missing /etc/inittab
linux rescue
chroot /mnt/sysp_w_picpath
has to put full name of the rpm , won't reconized glob .

#if only first CD available in rescue mode
then mount /dev/cdrom /mnt
or mount -t iso9660 /dev/cdrom /mnt
rpm -ivh --force /mnt/Centos/kernel-2.6* --root /mnt/sysp_w_picpath/
#



tsboot 1
tslocal 1
tsservice 1
tsnetwork 1