[Technology] Resizing my encrypted /home partition

I just wrote a post about why I reinstalled Fedora 22: because I wanted root to be on the SSD, and I needed to purge a lot of old installed software anyway. :P  And how that led to trying out the open source b43 wireless driver.



This is more interesting than my wireless problem. 
Because I no longer needed a / partition on my HDD, I wanted to extend
my home partition.  It isn't as dead-simple as back a decade ago.  Back
then, I would use fdisk to delete and recreate partitions and resize2fs
to resize the file system.



Now I have layers upon
layers of useful abstraction.  I'm calling each something potentially
inaccurate, and the tool I needed in brackets. (Those with wildcards
match multiple tools with the same beginning.)



Top

• ext4 file system (resize2fs)


• Logical volume (lv*)


• Volume group (vg*)


• Physical volume (pv*)


• partitions (fdisk)

Bottom



At first I was almost a little annoyed
at the apparent complexity, but it's actually straight forward.  My
drive is still divided into multiple partitions in a partition table. 
(/dev/sda1, /dev/sda2, /dev/sda3, etc; I have 8 for various reasons).



Physical
volumes seem to correspond to those partitions, but mostly just the
useful storage ones (e.g. I don't have them for EFI or swap
partitions).  pvcreate lets me define them.



The
physical volumes are collected into volume groups.  For example,
/dev/sdb1 (my intended root) might be a part of "pantaloons-fedora-ssd"
(if I named my machine pantaloons), and /dev/sda2 and /dev/sda4 might
both be part of "pantaloons-fedora-hdd" (two large areas for my /home
that I'd like to combine later, but which are currently separated by some other, annoying partition).



The
volume group kind of looks like a single contiguous (!) entity (despite
being a collection of disparate physical partitions).  Then, I can
define logical volumes atop the volume groups.



I can
have both / and swap as separate logical volumes atop
"pantaloons-fedora-ssd" (talk about cramped - maybe I don't want to
hibernate after all), and have a single logical volume for /home atop
the "pantaloons-fedora-hdd" volume group.



This is where things get a little trippy though.  Where does the encryption happen?



For my root file system, it looks like it happens like:

partition /dev/sdb1 > LUKS > physical volume > EXT4 file system



For my home file system, it looks like this:

partitions
/dev/sda2,/dev/sda4 > two physical volumes > 1 volume group > 1
logical volume > LUKS > EXT4 file system

FS	Ext4		Ext4
(LUKS)			/dev/mapper/luks-BAR
LVs	root	swap	/home
VGs	pantaloons-fedora-ssd		pantaloons-fedora-hdd
PVs	/dev/mapper/luks-FOO		/dev/sda2	/dev/sda4
(LUKS)	/dev/mapper/luks-FOO		/dev/sda2	/dev/sda4
partitions	/dev/sdb3
disks	/dev/sdb (SSD)		/dev/sda (HDD)

The home partition and its LUKS (using
cryptsetup/dm-crypt) was originally configured through whichever tool
Fedora provided years ago (preupgrade? fedup? anaconda?), while the
configuration on my SSD was what was recommended in F22.



Basically, I had to (with steps that actually increase space emboldened):

• define a new partition in the partition table, 


• define a new Physical Volume (PV) over top it, 


• extend my Volume Group (VG) to include the new Physical Volume


• unmount the file system I was going to extend, 


• close its LUKS setup


• extend the file system's Logical Volume (LV) overtop the new space in the Volume Group


• reopen the LUKS setup


• resize the LUKS setup (are these two out of order? hope not!), and


• resize the Ext4 partition

A bit more detail, here are the steps I used on my system (from
my bash_history, probably missing some steps; I think I also used
lvremove
or pvremove to remove LVs and PVs related to the old home partition, oh
well!):

• # cfdisk, to delete the old root on the /dev/sda4 partition and recreate it


• # pvcreate /dev/sda4 (creates a physical volume)


• # vgextend pantaloons-fedora-hdd /dev/sda4 (add the PV into the VG increasing its overall size)


• make sure /home isn't mounted


• # fsck.ext4 -C 0 -f /dev/mapper/luks-BAR (let's make sure the inodes are fine on our file system before messing with it)


• # cryptsetup luksClose luks-BAR (close LUKS while we change the underlying LV)


• # lvextend -L +61G /dev/pantaloons-fedora-hdd/home (increase the size of our LV within the VG)


• # lvextend -L +242M /dev/pantaloons-fedora-hdd/home (catch a little more space)


• there is probably a way to just extend it to the full space available, maybe read the man page


• # cryptsetup luksOpen /dev/pantaloons-fedora-home luks-BAR


• # cryptsetup resize luks-BAR (resizing the LUKS setup)


• # fsck.ext4 -C 0 -f /dev/mapper/luks-BAR (for paranoia maybe)


• # resize2fs /dev/mapper/luks-BAR (finally, let's resize our Ext4 file system)

Sadly, I can't cite the sources I pieced some parts together from, because I did this form a live USB key which is supposed to keep history as persistent storage but the browser history was empty when I tried checking it later :S  However, man pages were also useful.