Partitioning Error Elemenentary OS

When determining the partition layout of a hard drive, there are a few things you need to keep in mind. For a traditional MBR-style disk, there are 512 bytes reserved at the start of the disk for the partition table. Many older disks had 512-byte sectors, so starting your first partition directly after the partition table was not an issue.

Something else to keep in mind is that, on large hard drives like this one, some BIOS will not boot the OS if the required files are not close enough to the beginning of the disk. To work around this, one uses a separate /boot partition.

It seems that your new drive has a (rather common) 4 KiB sector size. This is 4096 bytes. In this case, placing a partition directly after the table will cause this partition to occur in the middle of a sector — in other words, to be misaligned. If you are allowing the installer to automatically create and arrange partitions, it may not account for this fact.

To clear up the warning and have all your partitions start on sector boundaries, ensure that the first partition starts 4 KiB into the disk, at byte 4096. You'll want a few hundred MB for your /boot partition, but as long as every partition is a multiple of 4 KiB, they will be aligned in your case. Note that any whole number of MiB or GiB is a multiple of 4 KiB.

In order to actually achieve this proper layout, it may be best to place partitions from the end to the beginning, as from first glance the installer does not seem to allow you to specify a start location for a partition. I will assume this will be the only OS on your disk and that you want /boot, /, and a swap partition, in that order. Then you would first select "Something different" when the installer asks how you would like to format your drive, and follow these steps:

• Start by creating a new partition table, or simply deleting any existing partions
• Click the free space
  • Add a new partition,
  • Select "end" for the location,
  • Select "swap" in the "Use as" box
  • Set its size to something reasonable (some multiple of 64 MB¹)
• Click the free space again
  • Add a new partition,
  • Select "end" for its location
  • Select a filesystem type, such as Ext4 from the "Use as" box
  • Set the mount point to /
  • Set its size to the size of the free space minus 512 MB or so, making sure that the resulting size is a multiple of 64 MB
• Click the free space a final time
  • Add a new partition
  • Select "end" for its location
  • Select a simple filesystem type from the "Use as" box, such as Ext2
  • Set the mount point to /boot
  • Set its size to the 512 MB (or whatever you chose) that you saved above

¹ The installer explicitly sizes in "megabytes (1000000 bytes)", which is not automatically a multiple of your sector size. However, 64 MB is equal to 15625 sectors, so as long as you size partitions in multiples of 64 MB it will be fine under either interpretation.