[xubuntu-users] Help me understand please

cesar mena cesar.mena at gmail.com
Wed May 17 13:08:21 UTC 2017

Joao Monteiro <jmonteiro257 at gmail.com> writes:

> Hi folks,
> My move from windows to xubuntu is final (lol)... preparing this
> samsung r20 to be my working laptop and all's going like a breeze :)
> I do of course have more than a million questions now, which I am quite
> happily answering through studying the best I can at my own pace. But I
> feel that what works best for me is to start from scratch, from the
> fundamentals, so I'm studying the Linux filesystem structure, etc. And
> there is one thing that is bugging me and I can't understand, so any
> help - when time permits it - will be more than welcome.
> OK, Windows 7 is forever gone and I made of the whole laptop a strictly
> Xubuntu Xfce machine. During the install, I used the option to encrypt
> the disk for extra security. When I boot up, it asks me for the
> password, I type it in, it says that crypt key was successful, voila,
> all works like a charm haha...
> But... when I then fired Gparted to se the structure graphically and
> start to try to understand it all, I noticed two things that are
> confusing me:
> 1) The structure of my hard disk now shows as: (sorry, don't know yet
> how to take a screen shot and then paste it here... will get there soon
> I hope)
> /dev/sda1      ext2        /boot    487.00MiB
> /dev/sda2      extended             111.31GiB
>   /dev/sda5    crypt.luks           111.31GiB
> Ok, I understand that sda1 ext2 is the type of fylesystem and this is a
> 487MiB boot partition
> But the sda5 partition which is the whole rest of the hard disk, shows
> graphically in Gparted as inside the sda2 extended partition, which is
> also the same size of sda5, coz it is the whole rest of the hard disk.
> So... why do I have sda2 and sda5? The way I see it, the crypt.luks is
> the encrypted partition, which is what I want for the whole disk, and
> for the little I understand so far, I have the boot and the extended
> partition. Why does it create an extended partition and then it creates
> an encrypted partition inside the extended one, of the exact same size?
> I would have expected to just have /dev/sda2 extended crypt.luks and
> not sda2 and sda5...

it's a long story, and a bit of a mess:

that said, the extended partition can now be chopped up into logical
partitions which are managed by a "partition manager". in this case that
is LVM. the encryption on LVM is then managed by LUKS (see
cryptsetup). once this is done you can create as many "LVM partitions"
(they're called volume groups) inside the crypt partition, and they are
all encrypted automatically; including swap. you can also resize them,
add new ones etc ... very flexible.

do an lsblk, it will show you a tree of the partitioning scheme. you
should see entries labeled xubuntu--vg-root, and xubuntu--vg-swap (vg =
volume group)

> Can anyone please find the patience to explain this to me when you have
> a chance? Thanks upfront
> 2) On the /dev/sda5, I have a yellow warning triangle in front of it
> (in Gparted) and when I right click and select Information, it says:

that's probably a Gparted limitation. to make sure you're ok type
"lsblk" in the terminal.

> Warning: Linux Unified Key Setup encryption is not yet supported
> So I'm a bit confused here... does this mean that I'm only beneffiting
> from having an extra password safety at boot up time and the disk is
> actually not encrypted (which confuses me because when I give the
> correct password it says that crypt key has been successful), or is
> this referring to some sort of Key management system that is not yet
> supported, but the disk is indeed encrypted?

you're fine. 


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