How mount secondary disk

trying mount disk via fstab, but after reboot fstab is clean

cat /etc/*release
NAME="k3OS"
VERSION="k3OS v0.1.3-dirty"
ID=k3os
ID_LIKE=alpine
PRETTY_NAME="k3OS v0.1.3-dirty"
VERSION_ID="v0.1.3-dirty"
HOME_URL="https://k3os.io/"
SUPPORT_URL="https://k3os.io/"
BUG_REPORT_URL="https://github.com/rancher/k3os/issues"
ISO_URL="https://github.com/rancher/k3os/releases/download/v0.1.3-dirty/k3os-amd64.iso"

harvester-52cj6 [~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
loop1 7:1 0 46.7M 1 loop /usr
loop2 7:2 0 290M 0 loop /usr/src
sda 8:0 0 446.6G 0 disk
├─sda1 8:1 0 47M 0 part
└─sda2 8:2 0 446.6G 0 part /k3os/system
sdb 8:16 0 16.4T 0 disk
└─sdb1 8:17 0 16.4T 0 part
sdc 8:32 0 20G 0 disk /var/lib/kubelet/pods/8e9d4cc3-7d44-43d9-8b54-f652fdfd71dc/volumes/kubernetes.io~csi/pvc-ceb5c8eb-7fa0-4f01-ac4b-14c95a7b3796/mount