LVM complaining about device smaller than logical volume

Question

I just installed Slackware on my laptop, with full disk encryption (LVM on LUKS). It works fine but there is a warning from LVM:

WARNING: Device /dev/mapper/lukssda2 has size of 115996431 sectors which is
smaller than corresponding PV size of 115996464 sectors. Was device resized?

Here is how I partitioned the disk:

mkfs.fat -F32 /dev/sda1 # /boot

cryptsetup luksFormat /dev/sda2
cryptsetup luksOpen /dev/sda2 slackluks

pvcreate /dev/mapper/slackluks
vgcreate cryptvg /dev/mapper/slackluks
lvcreate -L 8G -n swap cryptvg
lvcreate -l 100%FREE -n root cryptvg # /

mkswap /dev/cryptvg/swap

Should I try to fix it? What did I do wrong?

Solution

You need to fix this or you will run into problems later on. The problem is, that the PV is larger than the room you have in /dev/mapper/slackluks. The step lvcreate -l 100%FREE -n root cryptvg # / is not the problem.

What you need to do is:

1) boot form a CD/DVD/USBstick or live-image and do the luksopen

2) make the filesystem / smaller

e2fsck -fy /dev/root-on-the-lv
resize2fs /dev/root-on-the-lv <smaller size>

3) make the LV for root smaller

lvreduce -L -100M /dev/vg/disk-name

4) make the PV smaller with pvresize

I've never done this on LUKS, but it works on 'normal' PV/LV's. However:

• first backup
• read the man-pages of all the commands; don't cut-and-past them from this answer
• be prepared to re-install (and give sizes to the PV and LV's by hand)

Comments

[davidgo]

Yes, you should try and fix it. My guess is a software error when calculating using "100%FREE" which I've not seen before. I've. came across something similar when going from HDD to an SSD with slightly smaller geometry - can't remember the exact command - it was pvresize or something like that. You might need to get rid of your swap, then resize then recreate a slightly smaller swap.