Expand Hetzner disk / volume
Scan for disk-changes if those happened in a vm-environment by $host
echo 1 > /sys/block/sda/device/rescan
Install cloud-guest-utils which provide growpart
apk add cloud-utils-growpart
# or: yum install cloud-utils-growpart
Extend partition to maximum available size
Check with lsblk if the disk is already expanded and if not, which partition to expand.
For example, if the disk is /dev/sda and the partition is /dev/sda1 run:
growpart /dev/sda 1
Extend ext4 filesystem to maximum available size
When using ext4 filesystem, run:
resize2fs /dev/sda1