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On Mon, Feb 15, 2016 at 10:49:29AM +0000, Jonathan Dowland wrote:
[...]
> If the now-spare sda3 was large enough, and you were not already using LVM,
> I'd
> recommend formatting sda3 as an LVM PV and create a new LVM VG, then an LVM
> LV;
> then migrate your data from sda4 into that LV; then format sda4 as an LVM PV
> and
> add that into the VG, so you end up with all the space being available, again
> without changing the partition table at all.
Very insightful. In the interest of newbies (I was that in things
LVM a short while ago) I'll add a bit of explanation for those
mysterious acronyms:
The logical volume manager (LVM) concerns itself with collecting
slices of space from disk (PVs == "physical volumes") into bigger
units (VGs == "volume groups") to then dole out slices of it
("LVs" == "logical volumes") which then can be used as normal
partitions, although their backing store may be scattered across
several partitions (possibly on several "disks"[1])
This can be extremely useful: for example I have encrypted disks
on my laptop (in case it gets lost I can sleep well, because all
those nasty company secrets are not readable to anyone). But still
I have several partitions (/, home, /var, and most prominently,
swap, which I want encrypted as well. Now the LUKS disk encryption
is per "partition" -- at each boot I'd have to enter the LUKS
pass phrase for each of those partitions. Ugh.
No problem with the LVM -- I make one big (physical) partition,
encrypt that with LUKS, give that to the LVM as a physical
volume (PV), the only one in the volume group (VG) and section
that into the logical volumes (LVs) where my different file
systems will reside.
The other day my /var partition was too small. I had spare space
in /home. Using a bit of care (first shrink the file system on
/home) I could transfer as much space as needed to /var.
I think the Wikipedia article[2] is a nice writeup to get started.
[1] I'm using scare quotes there because a disk may denote an SSD, an USB
stick or whatever physical storage medium out there.
[2] https://en.wikipedia.org/wiki/Logical_Volume_Manager_(Linux)
regards
- -- t
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