If you removed the data on /boot FS completely, here is the process how to recover the data on /boot FS.
NOTE: in my case I’m using LVM and LUKS encryption. /dev/sda1 is /boot partition /dev/sda2 is encrypted LVM partition with root VG.
1. Reinstall following packages
root@laptop ~# yum reinstall kernel -y
root@laptop ~# yum reinstall redhat-logos -y
root@laptop ~# yum reinstall grub -y
2. Refresh grub installation
root@laptop ~# grub-install /dev/sda1
3. Update MBR
root@laptop ~# grub
Probing devices to guess BIOS drives. This may take a long time.
GNU GRUB version 0.97 (640K lower / 3072K upper memory)
[ Minimal BASH-like line editing is supported. For the first word, TAB
lists possible command completions. Anywhere else TAB lists the possible
completions of a device/filename.]
grub> root (hd0,0)
root (hd0,0)
Filesystem type is ext2fs, partition type 0x83
grub> setup (hd0)
setup (hd0)
Checking if "/boot/grub/stage1" exists... no
Checking if "/grub/stage1" exists... yes
Checking if "/grub/stage2" exists... yes
Checking if "/grub/e2fs_stage1_5" exists... yes
Running "embed /grub/e2fs_stage1_5 (hd0)"... 27 sectors are embedded.
succeeded
Running "install /grub/stage1 (hd0) (hd0)1+27 p (hd0,0)/grub/stage2 /grub/grub.conf"... succeeded
Done.
grub> quit
quit
4. Create your grub.conf file
root@laptop ~# cat /boot/grub/grub.conf
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz.redhat
hiddenmenu
title RHEL6 (2.6.32-358.11.1.el6.x86_64)
root (hd0,0)
kernel /vmlinuz-2.6.32-358.11.1.el6.x86_64 ro root=/dev/vg_oc/lv_root_rhel LANG=en_US.UTF-8 KEYBOARDTYPE=pc KEYTABLE=us rhgb quiet
initrd /initramfs-2.6.32-358.11.1.el6.x86_64.img
5. Make a symlink
root@laptop ~# ln -s ./grub.conf /boot/grub/menu.lst
root@laptop ~# ls -la /boot/grub/menu.lst
lrwxrwxrwx 1 root root 11 Jul 4 19:53 /boot/grub/menu.lst -> ./grub.conf
6. Restore file(s) default SELinux security contexts on /boot
root@laptop ~# restorecon -Rv /boot/
7. FS check on /boot FS
root@laptop ~# umount /boot
root@laptop ~# fsck -fy /dev/sda1
8. Restart system
shutdown -r now
root@laptop ~# find /boot/ -ls
2 4 dr-xr-xr-x 4 root root 3072 Jul 4 19:41 /boot/
12 2352 -rw-r--r-- 1 root root 2407976 May 15 16:55 /boot/System.map-2.6.32-358.11.1.el6.x86_64
65025 1 drwxr-xr-x 2 root root 1024 Jul 4 19:53 /boot/grub
65033 12 -rw------- 1 root root 11956 Jul 4 19:36 /boot/grub/minix_stage1_5
65038 1 -rw------- 1 root root 30 Jul 4 19:36 /boot/grub/device.map
65039 2 -rw-r--r-- 1 root root 1341 May 6 2010 /boot/grub/splash.xpm.gz.redhat
65036 12 -rw------- 1 root root 11364 Jul 4 19:36 /boot/grub/vstafs_stage1_5
65041 1 -rw------- 1 root root 254 Jul 4 19:48 /boot/grub/grub.conf
65037 14 -rw------- 1 root root 13964 Jul 4 19:36 /boot/grub/xfs_stage1_5
65028 14 -rw------- 1 root root 13380 Jul 4 19:36 /boot/grub/e2fs_stage1_5
65034 15 -rw------- 1 root root 14412 Jul 4 19:36 /boot/grub/reiserfs_stage1_5
65027 124 -rw------- 1 root root 125992 Jul 4 19:36 /boot/grub/stage2
65031 12 -rw------- 1 root root 11756 Jul 4 19:36 /boot/grub/iso9660_stage1_5
65035 12 -rw------- 1 root root 12024 Jul 4 19:36 /boot/grub/ufs2_stage1_5
65026 1 -rw------- 1 root root 512 Jul 4 19:36 /boot/grub/stage1
65032 13 -rw------- 1 root root 13268 Jul 4 19:36 /boot/grub/jfs_stage1_5
65040 0 lrwxrwxrwx 1 root root 11 Jul 4 19:53 /boot/grub/menu.lst -> ./grub.conf
65029 13 -rw------- 1 root root 12620 Jul 4 19:36 /boot/grub/fat_stage1_5
65030 12 -rw------- 1 root root 11748 Jul 4 19:36 /boot/grub/ffs_stage1_5
11 1 -rw-r--r-- 1 root root 171 May 15 16:55 /boot/.vmlinuz-2.6.32-358.11.1.el6.x86_64.hmac
14 182 -rw-r--r-- 1 root root 185867 May 15 16:55 /boot/symvers-2.6.32-358.11.1.el6.x86_64.gz
15 3952 -rwxr-xr-x 1 root root 4046704 May 15 16:55 /boot/vmlinuz-2.6.32-358.11.1.el6.x86_64
32513 1 drwxr-xr-x 3 root root 1024 Jul 4 19:41 /boot/efi
32514 1 drwxr-xr-x 3 root root 1024 Jul 4 19:41 /boot/efi/EFI
32515 1 drwxr-xr-x 2 root root 1024 Jul 4 19:41 /boot/efi/EFI/redhat
32516 246 -rwxr-xr-x 1 root root 251274 Dec 6 2012 /boot/efi/EFI/redhat/grub.efi
13 102 -rw-r--r-- 1 root root 104086 May 15 16:55 /boot/config-2.6.32-358.11.1.el6.x86_64
16 19996 -rw-r--r-- 1 root root 20474925 Jul 4 19:43 /boot/initramfs-2.6.32-358.11.1.el6.x86_64.img
root@laptop ~# df -Ph /boot/
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 485M 37M 423M 8% /boot
If system will not boot, then you can use SysRescCD or any other Live Linux distro http://www.sysresccd.org/Download
boot sysresccd in 64 bit kernel mode (should be same arch as your OS you want to recover) once booted do following
cryptsetup luksOpen /dev/sda2 rheluncrypted
vgscan
vgchange -ay
mkdir /mnt/rhel
mount /dev/mapper/vg_oc-lv_root_rhel /mnt/rhel
mount --bind /dev /mnt/rhel/dev
mount --bind /dev/pts /mnt/rhel/dev/pts
mount --bind /proc /mnt/rhel/proc
mount --bind /sys /mnt/rhel/sys
mount /dev/sda1 /mnt/rhel/boot
chroot /mnt/rhel /bin/bash
grub-install /dev/sda1
grub
root (hd0,0)
setup (hd0)
quit
exit
umount /mnt/rhel/boot
umount /mnt/rhel/sys
umount /mnt/rhel/proc
umount /mnt/rhel/dev/pts
umount /mnt/rhel/dev
umount /mnt/rhel
vgchange -an
cryptsetup luksClose rheluncrypted
sync
umount /boot
fsck -fy /dev/sda1
shutdown -r now