I had a similar problem with this one: Why can't I create a logical partition with gparted?, where a logical partition cannot be created/formatted. Only in my case I was in a live session and it still didn't work.

The error happened during the installation of Solus Linux where the installer should have formatted a Linux system partition and install the Solus. (I had two Linux systems and a swap space inside an extended partition and wanted to replace one of the two with Solus.) After it failed, that partition was first deleted in gparted (live session) but then the same tool could not re-format the space to create a new partition.

That is until I did what the answer under the linked question said: leave 1MB before and after the new logical partition and set align to 'none'.

Then everything worked fine: the new logical partition was created in gparted and during the installation of Solus Linux even the installer was able to format again the same partition.

What the two 1MB gaps may signify? What does "align" mean?

  • 1
    Read up on 4k sector alignment for example here linuxquestions.org/questions/slackware-14/… – ajeh Apr 19 '18 at 16:53
  • 4k does not explain why a 1MB gap is needed. – Johan Myréen Apr 19 '18 at 17:32
  • Are you using an MS-DOS partition table? That might...or might not...help us out... – 0xSheepdog Apr 19 '18 at 18:13
  • @oxsheepdog - yes. that's why i need the extended partition. I already have a windows partition, a large ntfs for depositing stuff: and I wanted two linux ones and a swap; that's 5 partitions, more than ms-dos partitioning can handle; true? – user32012 Apr 19 '18 at 20:15

The Master Boot Record partition table, aka the MS-DOS partition table, allows you to create 4 primary partitions. One of these partitions can be designated as an extended partition, which can then be subdivided further.

This extended partition contains within it a linked list of partition tables, allowing an arbitrary number of partitions. Each of these partition tables defines one extended partition and contains the address of the next extended partition table. This data requires a single sector (512b) to store on disk.

Modern partitioning tools like gparted will enforce 1MB (2048 sector) data alignment - this is the 'align' parameter that you ask about. This is done to improve performance. Paritioning tools will leave a gap of 2047 sectors between the partition table and the start of the data to create this alignment; this explains the 1MB gap.

Many partition tools allow you to disable, or change, this alignment requirement, which you did in your case by setting 'align' to 'none'.

More details and pretty pictures available on the Wikipedia page for Extended Boot Records: https://en.wikipedia.org/wiki/Extended_boot_record.

  • but how is this in accord with what happened? 1. no 1MB gap was created automatically: that was done manually in order to avoid error and create a logical partition; 2. the 'none' align setting seems also a condition to avoid that error – user32012 Apr 23 '18 at 20:48

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