Based on your partition map, sda4 is your extended partition and sda6 and sda5 seem to be logical partitions within it.
Now, since you already have 4 primary partitions (including sda4, which is considered so too), you cannot define a new primary partition. Shrinking sda1 to split it is going to fail for this reason.
You have a couple of simple options to pick from.
(all of them are based on getting more space in your extended partition).
- Shrink your data partition
sda6 to create more logical partitions.
You can install unix based systems on these logical partitions, things like GRUB can handle this.
- Kill or move-out your unix partitions (
sda3 and sda6) and then restructure your disk.
- This implies you either backup your unix data to be restored in a fresh install or backup entire partition image to be restores (provided you have some experience doing that).
- If you do this, you will have an intermediate state where
sda1 and sda2 would be the only useful partitions on your system.
- At such time, you can also go ahead to shrink your
sda2 and release more free space into unallocated area (you would have already deleted the other partitions).
- Now, you can create a single extended partition of all available free space and start with new partitions within it where you will reinstall or recover your primary unix partition (which is
sda3 now) and then add in other unix systems as you choose.
Remember, you can share a single swap partition across all your unix systems. This is because you won't be running more than one at a time and that running system can use the common swap partition. The swap partition has no persistent data across reboots.
When you boot into Unix, try the command "sudo fdisk -l /dev/sda".
It will dump your partition table with the sda4 described as Extended and its Start and End range will encompass that of the remaining (sda6 and sda5) logical partitions. This Extended partition is also counted as a primary partition.
