How to rescue your partition tables with gpart - and reinstall grub in Red Hat

Extending disk in vmware.
All the partition tables are missing. Whole disc are unallocated.

start with gpart livecd
Start with gpart /dev/sda (searching for missing partition tables in sda) Write down your cylinder.
Start parted
-unit s
-rescue
--start (cylinder number 'start' in partition1)
--end (cylinder number 'end' in partition1)

Repeat that if you have more than one partition.

You will now find sda1 and sda2 in /dev/*.

Sda1 = boot (ok)
sda2 = / (ok)
sda3 = SWAP-sda3 (I recreate a new swap disk with gpart, it is not necessary but it is far easier because sda3 has many links around the configuration files in my system.)

mount sda2 to /mnt/sda2/
mount sda1 to /mnt/sda2/boot/

go too /mnt/sda2/sbin/
start: grub-installation /dev/sda2
installing grub.

It perfectly works.

In some cases you also need to reconfigure the network card.
nano /etc/sysconfig/network-scripts/ifcg-eth0 .

Scan HBA for new devices - PowerPath

The host bus adapter driver in the 2.6 kernel exports the scan
function to the /sys directory which can be used to rescan the SCSI
devices on that interface. The scan function is available as follows:
# cd /sys/class/scsi_host/hostX/
# ls -al scan
# echo ‘- - -’ > scan
"X" will be the HBA number which is zoned to see the disk.
The three dash marks refer to channel, target, and LUN numbers.

Commit your change
#powermt config

Find your new logical device and write down the Pseudo name.
#powermt display dev=all


Find your new disk and pseudo name in
#fdisk -l

Run fdisk command which used to create and manipulate partition tables.
#fdisk
n - 1 - t (83 for linux system)
You should find pseudname and pseudname1 in /dev/
(in my system emcpowerb - emcpowerb1)

Format the new partition with
#mkfs.ext3 /dev/pseudoname1/

Mount the new disk in a directory and use it.