Linux – primary partition limit on Linux

I would mount the NTFS read-only partition and, assuming there's enough space inside the partition being used for Ubuntu, copy all of the data that you're interested in keeping out of the NTFS partition into the Ubuntu partition.

Once that's done, I'd any one of the various LiveCD distributions such as the GParted LiveCD to resize the Ubuntu partition (which I'm assuming is probably formatted with the ext3 filesystem).

In the beginning there was the original IBM PC BIOS partition scheme, which allowed up to four partitions. The FAT16 file system as used by MSDOS 2.x and 3.x would only support a formatted volume of 32MB. When a PC hard disk was 20MB this wasn't an issue but the advent of much larger ESDI(1) disks in the mid 1980s drove an urgent need for a scheme that could support more partitions.

The key issue here is backward compatibility. Older BIOS and DOS versions only supported the four partition scheme, so a partitioning scheme that would not break older versions but could support more partitions was needed. The solution was to allow partitions to be further sliced up by setting up another partition table within that partition.

Thus, the 'extended' partition was born. Extended partitions are just a format for slicing up a partition into sub-partitions. It exists solely as a kludge to preserve backward compatibility with the old partition format.

1. ESDI stands for 'Enhanced Small Device Interface'. It was a refinement on the ST-506 interface that allowed more sectors on the disk, faster data transfer and also removed the artificial 1024 cylinder limit of the ST-506 interface. In 1982-3 a typical PC hard disk might have been about 20-30MB where you had one at all (they were quite expensive at the time). By 1986 you could purchase an ESDI hard disk with capacities up to about 330MB.