creating a "new" home directory

[Howard White]

My google-foo is in another dimension. I am creating a new bare-metal
server with Ubuntu 22.04 and LVM. The initial build uses the installer
defaults which results in a base system with 100GB / directory. This is
"fine" and it runs.

Used lvcreate for two new LVM logical items: home and var. Doing this
one step at a time. Renamed (mv) /home to /orighome. Want to modify
/etc/fstab to point to /dev/mapper/ubuntu-vg/home.

If I run lvdisplay, there is an LV-UUID reported but attempting to use
that value in a mount command or in /etc/fstab results in "nocando"
error. How to obtain a blkid for an LVM member??

This is what happens when one uses such commands ever other three years.

Howard

[Tilghman Lesher]

I think this is the answer you're looking for:

https://askubuntu.com/questions/900309/blkid-cant-find-lvms-uuid

For the sake of the archive, in case the link goes stale, the problem
is that there are separate block IDs for the logical volume versus the
filesystem on the logical volume, and you want to use the block ID for
the filesystem to mount it, not the block ID for the logical volume.

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Tilghman

[Howard White]

Tilghman (and everyone else):

I'm going to step through some of this and maybe someone may point out
the gaps in my logic.

(to prove that the lv exists)
root@sass60:/# lvdisplay
--- Logical volume ---
LV Path /dev/ubuntu-vg/ubuntu-lv
LV Name ubuntu-lv
VG Name ubuntu-vg
LV UUID sXSZ05-lDLW-5reh-ujb1-Jz92-Rmzk-9xxMrK
LV Write Access read/write
LV Creation host, time ubuntu-server, 2023-12-12 14:02:53 +0000
LV Status available
# open 1
LV Size 100.00 GiB
Current LE 25600
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:0

--- Logical volume ---
LV Path /dev/ubuntu-vg/home
LV Name home
VG Name ubuntu-vg
LV UUID CvL3Hy-fSo8-ME2W-ajlZ-3ucf-2Qyw-b6Zvc4
LV Write Access read/write
LV Creation host, time sass60, 2023-12-12 17:51:02 +0000
LV Status available
# open 0
LV Size 40.00 GiB
Current LE 10240
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:1

--- Logical volume ---
LV Path /dev/ubuntu-vg/var
LV Name var
VG Name ubuntu-vg
LV UUID 0i3a0G-ulkw-Ve22-04yj-ITeP-kHY3-f1eY2i
LV Write Access read/write
LV Creation host, time sass60, 2023-12-12 17:55:53 +0000
LV Status available
# open 0
LV Size 40.00 GiB
Current LE 10240
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:2

Get the blkid of the original / partition:
root@sass60:/# blkid /dev/ubuntu-vg/ubuntu-lv
/dev/ubuntu-vg/ubuntu-lv: UUID="c2b8265f-b025-41ff-a216-0e48c344a121"
BLOCK_SIZE="4096" TYPE="ext4"

Use the same syntax against the home lv:
root@sass60:/# blkid /dev/ubuntu-vg/home
{nothing}

Attempt to mount /dev/ubuntu-vg/home thinking that if it gets mounted,
maybe it'll get a UUID...

root@sass60:/# pwd
/
root@sass60:/# ls
bin boot dev etc home lib lib32 lib64 libx32 lost+found media
mnt opt orighome proc root run sbin snap srv swap.img sys tmp
usr var
root@sass60:/# mkdir -pv dumbshit
mkdir: created directory 'dumbshit'
root@sass60:/# mount -t ext4 /dev/mapper/ubuntu-vg/home /dumbshit
mount: /dumbshit: special device /dev/mapper/ubuntu-vg/home does not exist.
root@sass60:/# mount -t ext4 /dev/ubuntu-vg/home /dumbshit
mount: /dumbshit: wrong fs type, bad option, bad superblock on
/dev/mapper/ubuntu--vg-home, missing codepage or helper program, or
other error.

_WTF??_

Howard

[Tilghman Lesher]

Did you remember to mkfs.ext4 (or whatever filesystem you wanted) on
/dev/mapper/ubuntu-vg/home ? If the last thing you did was simply to
create the lv, then it's just blank; there's no filesystem to mount.

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Tilghman

[Howard White]

Tilghman,

Miss one step and you don't get the pizza. No pizza for Howard...

D'oh!!!