Re: [gentoo-user] LVM and moving things around

[Dale]

Wol wrote:
> On 27/03/2022 20:17, Dale wrote:
>> Howdy,
>>
>> I sort of started this on another thread but wanted to nail a few things
>> down first.  I'm wanting to encrypt some parts of my data on /home.
>> This is what I got hard drive wise.
>>
>>
>> root@fireball / # pvs
>>    PV         VG     Fmt  Attr PSize    PFree
>>    /dev/sda7  OS     lvm2 a--  <124.46g 21.39g
>>    /dev/sdb1  Home2  lvm2 a--    <5.46t     0
>>    /dev/sdc1  Home2  lvm2 a--    <7.28t     0
>>    /dev/sdd1  Home2  lvm2 a--    <7.28t     0
>>    /dev/sde1  backup lvm2 a--   698.63g     0
>> root@fireball / #
>>
> One big piece of missing information. What does fdisk say about
> sd[b,c,d]1? And can you add sdf1?

I have the entire drive as one large partition for each drive.  I could
have done it as a whole device but I wanted partitions to give a hint
that the drive is in use, if booted from other medium for example. 

I have enough extra space that I can remove either a 6TB or a 8TB
drive.  Once that is done, I can start to encrypt and move data around. 
This is some additional info from df for /home:


/dev/mapper/Home2-Home2     20T  8.7T   12T  45% /home


If I remove a 8TB drive, I'd still have enough room for my data.  I
could then rebuild /home starting with the 8TB drive just freed up. 
Then as I move data, I could expand them one at a time encrypting as I
go.  I'd rather not have to buy a hard drive right now.  Tight budget
given other things I got going on.  I do have backups, more than one in
a couple important data spots. 


>
> I'm guessing you've got three 8TB drives? Or is it two 8s and a 6? Can
> you get a third 8TB? And if you're encrypting *parts* of /home ...
> what parts?
>>
>> I've done some checking on sizes of things I want to encrypt and am
>> weighing options.  I use LVM which should help make things easier.  I've
>> downloaded and printed some howtos regarding shrinking the file system
>> and LVM thingys.  It seems I need to shrink the file system while my
>> /home partition is unmounted.  Then move the data off whichever drive I
>> want to remove and then remove the drive itself.  After that I can
>> encrypt the just removed drive and start moving files over, using rsync
>> is my plan.  I think that is the basic steps.
>
> Not necessarily.
>>
>> My question now comes to this.  When I encrypt one of the drives, can I
>> then expand that drive with it being encrypted or is that not a option?
>> I plan to encrypt two of the drives as one volume group and leave one
>> other volume group as normal.  I just want to be sure whether or not I
>> can expand a encrypted LVM drive the same as a normal LVM since both
>> uses LVM.  I use cryptsetup commands to accomplish the encryption if
>> that matters.  So as a example, I start with one 7TB drive encrypted,
>> move some data to it, then want to add either the 5TB or 7TB drive.  Can
>> I just expand it like a normal LVM or does it being encrypted change
>> things?
>>
>> Thoughts?  My remove steps look sensible?  Expanding encrypted LVM
>> possible?
>
> If you are using LVM to do the encryption, then I can't see any
> problems adding a new PV to an encrypted VG.
>>
>> Dale
>>
> Personally, I'd use dm-crypt to encrypt the drive, and then the whole
> lot is encrypted, and put plain LVM over that. I've got dedicated
> layers for everything.
>
> It looks like your home2 is 6TB+8TB+8TB. I'd get a new 8TB, put
> dm-crypt on it, and add it. Now I can remove the first 8TB, dm-crypt
> it and re-add it. Same with the second 8TB. Now remove the 6TB and
> there you are ...
>
> My layout's rather different from yours, so I don't think I ought to
> say too much :-)
>
> Cheers,
> Wol
>
>


What is the advantage of dm-crypt over cryptsetup?  I've learned how to
use cryptsetup with my external drive so was hoping to stick with what I
already know.  Unless there is a advantage to dm-crypt. 

Thanks.

Dale

:-)  :-)