Small script to automatically format and mount virtio disks

auto-format-mount.py

#!/usr/bin/env python3

import glob
import json
import os
import subprocess

prefix = "/dev/disk/by-id/virtio-"

for disk in glob.glob(f"{prefix}*"):
    name = disk.removeprefix(prefix)

    if name.startswith("boot"):
        continue

    print(f"Checking disk {disk}")

    # check if the disk is already formatted

    blockdevice = json.loads(subprocess.check_output(["lsblk", "-f", disk, "--json"]))[
        "blockdevices"
    ][0]

    if blockdevice["fstype"] is None:
        print(f"  Formatting disk")

        subprocess.run(["mkfs.ext4", disk], check=True)
    else:
        print(f"  Disk already formatted")

    # check / update fstab

    with open("/etc/fstab") as f:
        fstab = f.read()

    mountpoint = f"/mnt/disk-{name}"

    if disk in fstab:
        print(f"  Disk already setup in fstab. Expected mounted at {mountpoint}")
    else:
        print(f"  Mounting at {mountpoint}")

        os.makedirs(mountpoint, exist_ok=True)

        # make the mountpoint immutable to prevent accidentally writing files to the unmounted mountpoint
        subprocess.run(["chattr", "+i", mountpoint], check=True)

        with open("/etc/fstab", "a") as f:
            f.write(f"{disk}  {mountpoint}  ext4  defaults,nofail  0  2\n")


# reload fstab

print("")
print("Reloading all mountpoints")

subprocess.run(["mount", "-a"], check=True)

Usage:

sudo wget -O /usr/local/bin/auto-format-mount https://gist.github.com/skirsten/e5aa8f739afbfc6b1e230bc96509620f/raw/auto-format-mount.py

sudo chmod +x /usr/local/bin/auto-format-mount

sudo auto-format-mount # run this after attaching a new volume or run it periodically