Deleting partitions

[Chris Jones]

This is not a grub question per se but I'm not sure where else I could
find _reliable_ information about this.¹

I am in the process of spring-cleaning my laptop's hard drives and would
like to delete a couple of partitions.

Here is the (partial) output of fdisk -l:

| Disk /dev/sdb: 320.1 GB, 320072933376 bytes
| 255 heads, 63 sectors/track, 38913 cylinders
|
| [..]
|
| Disk /dev/sda: 320.1 GB, 320072933376 bytes
| 255 heads, 63 sectors/track, 38913 cylinders
| Units = cylinders of 16065 * 512 = 8225280 bytes
| Sector size (logical/physical): 512 bytes / 512 bytes
| I/O size (minimum/optimal): 512 bytes / 512 bytes
| Disk identifier: 0x8f49dca2
| 
|    Device Boot      Start         End      Blocks   Id  System
| /dev/sda1   *           1         223     1782784    7  HPFS/NTFS
| Partition 1 does not end on cylinder boundary.
| /dev/sda2             223        7435    57936884    7  HPFS/NTFS
| /dev/sda3           35854       38914    24576344    7  HPFS/NTFS
| /dev/sda4            7435       33385   208437249    5  Extended
| /dev/sda5           21713       24145    19530752   83  Linux
| /dev/sda6           24145       26090    15624192   82  Linux swap / Solaris
| /dev/sda7           26090       28522    19529728   83  Linux
| /dev/sda8           28522       33385    39061504   83  Linux
| /dev/sda9            7435       11934    36132864   83  Linux
| 
| Partition table entries are not in disk order

The partitions that I want to delete are /dev/sda5 and /dev/sda8.

My /boot/grub directory is in the /dev/sda9 partition and if I boot off
of a live CD and delete the /dev/sda5 and /dev/sda8 partitions, the
current /dev/sda6, /dev/sda8 and /dev/sda9 will automatically be
renumbered and become /dev/sda5, /dev/sda6, and /dev/sda7 (msdos5,
msdos6, and msdos7).

As a result, if I proceed to reboot off of the hard drive, the grub boot
loader environement will fail to initialize because it will look for the
/boot/grub/ directory in the /dev/sda9 (msdos9) partition, which no
longer exists.²

Rather than go through the hassle of repairing a broken boot loader
manually from the grub rescue prompt (or worse do a grub-install
--root-directory= of a possibly incompatible version of grub from
a repair CD), is there a better strategy³..?

Would chroot'ing to the linux system on /dev/sda9 (now /dev/sda7)
immediately after deleting the two partitions and running update-grub
(and OS-prober) from the chroot be the best choice..?

Is there another, perhaps more elegant, solution..?

Thanks,

CJ

¹ Obviously, a detailed/reliable manual, wiki, howto.. that describes
  such scenarios would be fine, but I haven't been able to find one.

² /etc/fstab's should be OK since I use UUID='s everywhere.

³ Simple use case, the only complication being that there are two hard
  drives in this laptop - but no encryption, no lvm, no raid.. etc.