cloud-init for hetzner debian with 25% / ext4 and 75% /data xfs

cloud-init-10g-30g-debian.yaml

#cloud-config
resize_rootfs: false

disk_setup:
  /dev/sda:
    table_type: 'mbr'
    layout:
      - 25
      - 75
    overwrite: true

fs_setup:
  - label: root_fs
    filesystem: 'ext4'
    device: /dev/sda
    partition: sda1
    overwrite: true
#  - label: data
#    filesystem: 'xfs'
#    device: /dev/sda
#    partition: sda2
#    overwrite: true

packages:
  - xfsprogs
  - parted
  - lvm2

# now we attach the settings
runcmd:
  - [ partx, --update, /dev/sda ]
  - [ partprobe ]
  - parted /dev/sda set 1 boot on p
  - resize2fs /dev/sda1
  - [ pvcreate, /dev/sda2 ]
  - [ vgcreate, vg_data, /dev/sda2 ]
  - [ lvcreate, -l, 100%FREE, -n, lv_data, vg_data ]
  - echo sleep 10
  - sleep 10
  - [ mkfs.xfs, /dev/vg_data/lv_data ]
  - [ mount, /dev/vg_data/lv_data, /data/ ]

mounts:
  - ["/dev/sda1", "/"]
  - ["/dev/vg_data/lv_data", "/data"]

extend by resizing existing disk:

pvresize /dev/sdb
lvresize /dev/vg_data/lv_data /dev/sdb
xfs_growfs /data/