Install multiple Operating Systems on the same GPT disk: cautions

I decided to include this post to highlight the importance of taking minimum precautions before making any changes in GPT Partition Table of a System Disk, it is an additional task of 5 minutes length, that can save countless hours of work and not a few dislikes.


In an environment where coexist different OSs on GPT Partition Table installing a new OS is not without risks:

• The mistakes we make during the partition configuration.
• The OSs Installers  may manipulate the Partition Tables  without notice -Solaris 11 is a "good" example of this-.

 So I recommend taking the following precautions before you begin to install:

1. Perform a Backup of all relevant information. If you have important work, such as programming projects with many hours spent, keep two copy in two different locations, in a usb disk and in a cloud storage, for example.
2. Backup  the GPT  Partition Table, usually I have two copies, one in the partition dedicated to GRUB2 and another in a pendrive.
3. Take screenshots of the listing of the GPT Partition Table before installing, to ensure that, after the installation process, have not changed the start and end sectors of the partitions.

 
If you have a copy of the GPT Partition Table, and during the installation process, was modified for whatever reason, we can leave the partitions as they were before starting and probably no major damage, but it all depends on the partition is overwritten.

Backup partition table with GDISK

When configuring the GPT partitions, I can not overemphasize my recommendation to leave about 128 MB of unallocated space between adjacent partitions.

With the current disk sizes this little "waste" of space is more than offset by its usefulness, many installers modify slightly the final boundaries of the partitions, which is disastrous if each partition begins at sector immediately following the previous one.

In contrast, if between partitions there are unallocated space, a slight change in the position of the end of the partition is completely harmless.