Use thinly-provisioned LVM in Kubuntu

[quaksoul1]

When installing Kubuntu and you want to create manual LVM. But LVM you want to create is thin. Open Live Session. Make sure you have network access.

Install thin-provisioning-tools:

# apt-get install thin-provisioning-tools .....<-- you may need to enable "universe" repository in /etc/apt/sources.list

Now install as usual. First create LVM thin pool and thin volumes as you need:

# pvcreate /dev/sda5 ......(for example)
# vgcreate kubuntu /dev/sda5 ......(again, example)
# lvcreate kubuntu --thinpool thin -L size .....<-- "thin" is volume name

# lvcreate -T kubuntu/thinpool -n root -V 15G
# lvcreate -T kubuntu/thinpool -n home -V 30G .....<-- V specifies virtual size, may be bigger than -L size.

Now make filesystems manually or proceed with installation:

# mkfs.ext3 /dev/kubuntu/root
# mkfs.ext3 /dev/kubuntu/home

Install Kubuntu. Use LVM volumes for root, home, etc.

Wait till install is finished. Go back to root shell.

Chroot into /target:

# cd /target
# mount --bind /dev dev
# mount --bind /sys sys
# mount --bind /proc proc
# chroot .

Forget! Apt-get won't work in chroot. Go into other root shell (press ctrl-shift-T in Konsole, sudo su). Go to /var/cache/apt/archives.

# cp /var/cache/apt/archives/* /target/tmp

Back to first chroot shell:

# dpkg -i /tmp/*.deb

This will install thin-provisioning-tools in target system.

Now create /etc/initramfs-tools/hooks/thin-provisioning-tools with content:

#!/bin/sh

PREREQ="lvm2"

prereqs()
{
    echo ""
}

case $1 in
prereqs)
    prereqs
    exit 0
    ;;
esac

. /usr/share/initramfs-tools/hook-functions

copy_exec /usr/sbin/thin_check
copy_exec /usr/sbin/thin_dump
copy_exec /usr/sbin/thin_repair
copy_exec /usr/sbin/thin_restore
copy_exec /sbin/dmeventd


manual_add_modules dm_thin_pool

Change perms:

# chmod /etc/initramfs-tools/hooks/thin-provisioning-tools

Run update-initramfs-tools:

# update-initramfs-tools -u

Presto! On reboot will work, otherwise won't work.

Check initramfs for test:

# lsinitramfs /initrd.img | grep thin

usr/sbin/thin_dump
usr/sbin/thin_restore
usr/sbin/thin_check
usr/sbin/thin_repair
lib/modules/x.y.z-a-generic/kernel/drivers/md/dm-thin-pool.ko
lib/modules/x.y.z-a-generic/kernel/drivers/hid/hid-thingm.ko

Is included in initramfs now. Boot should work.

Otherwise won't load LVM & kernel panic.

Good luck!

[quaksoul1]

I was mistaken about one thing:

Grub does not understand thin LVM volumes. It will see them but won't be able to access them. Then grub-probe will fail when doing update-grub. This only applies to the mounted root filesystem. Your root cannot be on thin LVM for update-grub to work. If you have separate boot partition, however, grub-install will still work fine (if you have self-maintained grub config file).

:

* you cannot use thin LVM for root and have a normally functioning grub-update system
* hence, you also cannot use thin LVM for boot partition
* if your root is also your boot, that means grub won't be able to read boot files from your /boot if root is thin

* you CAN use thin LVM for everything other than root (grub won't complain about other mounted partitions)
* only boot and root are excluded.

[claydoh]

Soooooo...... what is a thinly-provisioned LVM, and what would it's use case be?
(And yes, I did search for it. Still not clear on it)
A brief summary of what it is and what it is used for may make it more useful to the readers.

[Snowhog]

See https://www.kernel.org/doc/Documenta...ovisioning.txt

[claydoh]

Yes, I have already read that, and it still makes little sense.

There was a post in recent months asking a question about thin provisioning, but it received zero response, possibly due to lack of anyone knowing anything about the topic.

A brief description of what this is, how why and where it is used would be very useful for a posting in our how-to section.

Sent from my LG G4

[Snowhog]

Then maybe https://access.redhat.com/documentat...d_volumes.html