I want to create two more primary partitions on unallocated space.
sda1 primary
sda2 primary
sda3 unallocated
sda4 extended
I want to create two more primary partitions on unallocated space.
sda1 primary
sda2 primary
sda3 unallocated
sda4 extended
Is it possible to create more than one extended partitions?
No. You can have per harddisk ...
The extended partition though can have a 'limitless' amount of logical partitions on Ubuntu. Nowadays the kernel can allocate device numbers dynamically (through udev) and the system will happily use 2 or more letters after reaching sdz. Though there will be a limit someone has tested this up to sdzzz and the idea is that it is safe up to 29 z's (though untested and there are people doubting it all their proof seems to have been deleted).
You can creat partitions from gParted but the partitions need to be unmounted (so you can not change the root partition from a running system). Boot from either an Ubuntu Live DVD or a Gparted Live DVD, start up gParted and shrink your partitions so you get unallocated space. Unallocated space needs to be adjacent to each other to create a big unallocated space. If you shrink sda1 and want that free space as part of sda3 you need to add it to sda2 and shrink sda2. That unallocated space can then be divided into partitions. You can have 1 more primary partition (I expect you'd use sda3 for that; but the 4th one will be impossible and needs to be added to the extended partition to create a logical partition).
Ubuntu (Unix/Linux in general) does not have any restrictions on where you can put the OS part of the installation. So any of these can be used to install Ubuntu (or any Linux based system).
Always create a backup when altering partitions. Making a fatal mistake is easily done but a power failure is always a possibility.
If we are talking modern systems there is also GUID Partition Table (or GPT). The default maximum number of partitions is 128, and if your operating system supports it you can have more No more hacks to force yourself to a primary/extended/logical partitioning scheme. When you are GParted and want to use GPT, just select the gpt option when formatting.
The differences between MBR and GPT are summed up nicely on the IBM site.
In a MBR? No. But inside the one extended partition you can create dozens (maybe hundreds?) of other partitions. And can expand/shrink partitions using gparted
, fyi.