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Hello everyone! I am aware of the fact that hard disk supports only 4 partitions and thus I have basically two partitions (I don't know if I should be counting system reserve as a partition or not). To install Ubuntu Mate 15.10, I shrinked the c: drive (where windows is installed) to create some unallocated space where Ubuntu can be installed. But when I tried to install ubuntu, the installer shows 4 partitions and some "unusable space" instead of showing free space. I have:

  1. checked the sha1 checksum of the iso,
  2. disabled secure boot, fast boot, hibernate.
  3. shutdown the computer completely before starting the installation process
  4. shrinked c: to create some free space for ubuntu
  5. made sure I have less than 4 partitions

I am suspecting there are some issues with the partition but am not being able to figure it out. Could anyone shed some lights please?

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  • If those are the 1Mb partitions: those are markers to align the partitions. what does 1, 2, 3, 4 and 5 have to do with the question about the "unusable space"? and it would probably be better to add in the image from gParted at the point you want to create the partitions instead of one with just windows on it. – Rinzwind Nov 24 '15 at 17:54
  • @Rinzwind, could be that the OP has created just 4 primary partitions and no extended ones? If the partition table is traditional, they are almost stuck... – Rmano Nov 24 '15 at 17:57
  • Sorry I don't understand the difference between primary and extended partition. Just started using Ubuntu. – freerunner Nov 24 '15 at 18:01
  • ...primary and extended partition is a thing of... MS-DOS or before ;-). Ubuntu, like Windows, just suffers the legacy... (btw --- you can have much more than 4 partition in a disk. I do not remember the limit, but it's quite higher. The trick is having one extended partition and more partitions into it). en.wikipedia.org/wiki/Disk_partitioning – Rmano Nov 24 '15 at 18:03
  • Is the problem I am facing related to it somehow? – freerunner Nov 24 '15 at 18:06
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I am aware of the fact that hard disk supports only 4 partitions

That's not strictly true. Partitions are defined by data structures known as partition tables. One very common partition table type, the Master Boot Record (MBR), supports a maximum of four primary partitions; however, one of these can be an extended partition, which can hold an arbitrary number of logical partitions. The trick when using MBR is to avoid creating four primary partitions unless one of them is an extended partition. With an extended partition in place, you can have as many partitions as you like, although all but a maximum of three of them will be logical partitions. That's fine for Linux, but Windows can't boot from a logical partition. (Windows can still use logical partitions as data disks, though.)

Other partition table types, such as the GUID Partition Table (GPT), have other limits. GPT supports up to 128 partitions by default. (Since GPT doesn't support extended or logical partitions, the modifier "primary" is meaningless with reference to GPT partitions.) GPT is important because it's more-or-less required when booting in EFI mode, which is the most common boot mode for new computers.

In any event, given your symptoms, you seem to have an MBR partition table.

I have basically two partitions (I don't know if I should be counting system reserve as a partition or not).

Your screen shot shows you have four partitions. You do count the System Reserved partition, but you do not count the areas shown as "unallocated" in your screen shot. One puzzling thing is that two of your partitions are marked as E:. I don't know if this is some Windows feature that enables you to tie two partitions together or if there's something weird going on.

You have a number of choices for how to proceed, given your current configuration. I recommend you read this question and my answer to it:

Where can I install ubuntu if I have 4 primary partitions?

In your case, if you want to stick with BIOS-mode booting from an MBR disk, you may need to move your C: drive up to the end of the disk. You should then be able to convert your 181 GB disk to logical form using FixParts. You'll then be able to install Linux in the free space. Be aware, though, that partition-moving operations are risky, so before you move C:, you should back it up. It's safest to move it using a Windows tool, but do not use the standard Windows tools to create new partitions; the Windows tools are dangerously buggy when dealing with logical partitions and may convert the disk from a conventional setup to a Logical Disk Manager (LDM) configuration if given half an excuse. The trouble with LDM is that it's pretty much impossible to install Ubuntu on an LDM configuration, and converting back from LDM is another challenge you don't want to face.

Alternatively, if you're accessing your two E: partitions as if they were one partition, you might consider backing up the 181 GB partition (it looks like it's barely used), delete it, expand the 99 GB partition to fill its space (plus the 6 GB between them), and then restore your backed-up data. This will free up one primary partition, enabling you to create an extended partition after your C: partition. You can then put Ubuntu in logical partitions inside the extended partition. If E: is sufficiently weird or damaged, you might delete both of them and create a single new partition in their place, for much the same effect.

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