As an example of a Logical Volume Manager ( LVM ) setup on Azure, let me show you a real-world use case. Say we want to run a Pulp 3 container to host an rpm repo on Azure. As the base image let’s choose Rocky Linux 9.
The machine that we provision will have two extra hard drives, one for the Docker overlay and one for the Pulp 3 repo data. Thanks to LVM, if in the future the repo needs to grow, we can simply add a disk and resize the volume group.
The first problem that we encounter is that Rocky’s default rpm mirrors are too slow to install even a single package: to overcome this issue it’s enough to add
/etc/dnf/dnf.conf and run
To use LVM we need to install the
sudo dnf install lvm2
For our setup we’ll use the disks
sdd for our lvm volumes.
lsblk -o NAME,HCTL,SIZE,MOUNTPOINT | grep -i "sd" sda 0:0:0:0 10G ├─sda1 100M /boot/efi ├─sda2 1000M /boot ├─sda3 7.8G / ├─sda4 4M └─sda5 1M sdb 0:0:0:1 8G └─sdb1 8G /mnt sdc 1:0:0:0 32G sdd 1:0:0:1 64G
First let’s create the physical volumes:
sudo pvcreate /dev/sdc sudo pvcreate /dev/sdd
And then create the volume groups:
vgcreate docker_overlay_vg /dev/sdc vgcreate pulp3_vg /dev/sdd
Now let’s create logical volumes and set them to use all the available space on their respective volume groups:
lvcreate -l +100%free -n docker_overalay_lv docker_overlay_vg lvcreate -l +100%free -n pulp3_lv pulp3_vg
Finally, we can create the file systems on the logical volumes, in our case we choose xfs:
mkfs.xfs /dev/docker_overlay_vg/docker_overlay_lv mkfs.xfs /dev/pulp3_vg/pulp3_lv
The last step is to mount the newly created volumes to the correct location and add them to fstabs. I’ll just show the procedure for one volume, since it’s the same for both.
First, let’s create the mount point for the Docker storage location and get the UID of the Docker logical volume:
mkdir /var/lib/docker blkid | grep overlay /dev/mapper/docker_overlay_vg-docker_overlay_lv: UUID="46c7eb1e-5b10-4f17-9d7b-d59995574ffb" TYPE="xfs"
Next, let’s append the mount point using the uid to /etc/fstabs:
UUID=46c7eb1e-5b10-4f17-9d7b-d59995574ffb /var/lib/docker defaults 0 0
and finally reboot. Now we see:
df -h Filesystem Size Used Avail Use% Mounted on [..] /dev/mapper/docker_overlay_vg-docker_overlay_lv 32G 261M 32G 1% /var/lib/docker [..]
More advanced solutions for Docker storage and LVM, such as using LVM thin provisioning, could be used but are outside of the scope of this blog post.
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