Installation tools

📷Steve Johnson

OVH recently announced that it will not offer the option of Arch Linux and FreeBSD for new installations. Although they recommend that you upload your own image if you are using its Public Cloud, this option is not available to VPS users.

Not a problem though. There are a few ways to install any OS you want and they seem ok with it.

Use a cloud image

I have tested this method with Arch and Debian bullseye images and everything worked fine, including IPv6 configured out of the box. The following steps describe an Arch installation but, with small adjustments, they should work for other distributions as well.

Install any available distribution such as e.g. Debian.

Log in the manager and reboot in rescue mode. The rescue system is Debian based and includes backports and ZFS packages if you ever need them.

Use lsblk to orient yourself. The Debian based rescue disk should be mounted at /dev/sda while your target disk is at /dev/sdb.

Make some extra room for the image:

mkdir /tmp/mnt
mount -t tmpfs tmpfs /tmp/mnt
cd /tmp/mnt

Download the image with wget:

We need qemu-img from qemu-utils:

apt install qemu-utils

Overwrite your target disk /dev/sdb with the image as shown in the arch wiki. Notice we are overwriting the whole disk, not just a partition:

qemu-img convert -f qcow2 -O raw Arch-Linux-x86_64-cloudimg-20210315.17387.qcow2 /dev/sdb

The Arch Linux image uses a GPT partitioning scheme, a btrfs partition compressed with zstd and a BIOS compatibility partition.

To make sure you are able to login after reboot, it’s a good idea to setup a user with sudo abilities and a known password. You may also copy your ssh public key manually.

sfdisk -l /dev/sdb
mount -t btrfs /dev/sdbX /mnt
chroot /mnt
useradd -m -s /bin/bash -G wheel arch
passwd arch
echo "arch ALL=(ALL) NOPASSWD:ALL" > /etc/sudoers.d/arch

Finally use the manager to reboot the virtual machine in normal mode.

Cloud images contain cloud-guest-utils which should take of resizing the partition table to fill the disk, setup networking etc. If for some reason you can’t connect with ssh, you can still try KVM to login.

If you got so far, then it’s time to secure the installation:

Final tuning

OVH recommends that cloud-guest-utils and qemu-guest-agent are installed when using a custom image. cloud-guest-utils are already installed, so:

sudo pacman -S qemu-guest-agent
sudo systemctl enable --now qemu-guest-agent.service

Have a look at /etc/default/grub.

  • To have KVM console work, we need to add console=ttyS0 to boot parameters.
  • To improve performance, you may be interested in disabling compression by removing rootflags=compress-force=zstd.
  • Provide some entropy to the kernel’s random number generator. You may decide that you’d rather trust the CPU manufacturer’s random number generator rather than get warnings in boot messages about using an uninitialized urandom.

These are just some recommendations. So, let’s modify /etc/default/grub to look like this:

GRUB_CMDLINE_LINUX="net.ifnames=0 console=ttyS0"

And then we can apply the changes.

sudo grub-mkconfig -o /boot/grub/grub.cfg
sudo reboot
sudo btrfs filesystem defragment -r /

Perhaps you are interested in converting the system to use a flat hierarchy of subvolumes by using steps similar to the ones described here.

Here is a benchmark comparing the performance of Postgresql on btrfs and other filesystems.