On 16 Jun 2015 12:12, "Always Learning" <centos at u64.u22.net> wrote: > > > On Tue, 2015-06-16 at 11:30 +0100, John Hodrien wrote: > > On Tue, 16 Jun 2015, Always Learning wrote: > > > > > ON Centos 5, using GPARTED I created partitions for filing systems ext3 > > > and ext4. 4 primary and unlimited (except by space) extended partitions. > > > That suggests those partitions are not GPT but old fashioned M$DOS > > > > If it is old fashioned MSDOS, you can have four total primary and extended, > > not four primary plus extended. An extended partition then provides a > > container for further logical partitions. > > Yes you are correct. Maximum 4 primary or maximum 3 primary and 1 > extended which is then sub-divided into more partitions. > > > LUKS provides a UUID, so being encrypted isn't a barrier to having a UUID. > > But my point was M$ DOS partitions, not being GPT partitions, can have > UUIDs. The original poster appeared to suggest that was not possible. He > wrote > Those were filesystem UUIDs not partition UUIDs ... LUKS has its own header similar to ext4, lvm, etc headers which has a UUID in it. This UUID being associated with the LUKS header indicates it is not a partition UUID. A dd of this (or lvm snapshot) to another partition will keep the same UUID. A partition UUID within a GPT table would not be persisted in this manner, and msdos labeled disks have no concept of this to begin with. > > > Non-GPT partitions do not have a UUID. The _content_ (filesystem, > > > LVM physical volume, non-encrypted swap space, etc.) of such a > > > partition could have a UUID, but the partition itself does not. > > When I think I am mounting a M$ DOS partition, am I mounting a real > partition or merely 'the file system' within that partition ? Some may > think one can't have one without the other. > > Of course you can have a partition or filesystem without the other. This is how raw devices work and you can mkfs a block device with no partitions. When you mount something you mount the filesystem.