With a PVC mounted to /var/lib/postgresql and using Alpine based image, the initialisation process creates a new mount /var/lib/postgresql/data to the OS disk. This leads to data loss when pod is recycled
$ grep image statefulset.yaml | grep -v \#
image: postgres:15.0-alpine
$ kubectl apply -k .
namespace/test created
statefulset.apps/postgres created
$ kubectl exec -it -n test statefulset/postgres -- bash
bash-5.1# df -h
Filesystem Size Used Available Use% Mounted on
overlay 125.4G 33.0G 86.7G 28% /
tmpfs 64.0M 0 64.0M 0% /dev
/dev/mapper/rl-root 125.4G 33.0G 86.7G 28% /etc/hosts
/dev/mapper/rl-root 125.4G 33.0G 86.7G 28% /dev/termination-log
/dev/mapper/rl-root 125.4G 33.0G 86.7G 28% /etc/hostname
/dev/mapper/rl-root 125.4G 33.0G 86.7G 28% /etc/resolv.conf
shm 64.0M 1.0M 63.0M 2% /dev/shm
/dev/longhorn/pvc-7a73320e-4498-403a-a5ec-33d3c4f8ae76
7.8G 28.0K 7.8G 0% /var/lib/postgresql
/dev/mapper/rl-root 125.4G 33.0G 86.7G 28% /var/lib/postgresql/data
...
bash-5.1# exit
command terminated with exit code 1
$ kubectl delete -k .
namespace "test" deleted
statefulset.apps "postgres" deleted
With Debian based image the problem does not exist.
$ grep image statefulset.yaml | grep -v \#
image: postgres:15.0
$ kubectl apply -k .
namespace/test created
statefulset.apps/postgres created
$ kubectl exec -it -n test statefulset/postgres -- bash
bash-5.1# df -h
Filesystem Size Used Avail Use% Mounted on
overlay 126G 34G 87G 28% /
tmpfs 64M 0 64M 0% /dev
/dev/mapper/rl-root 126G 34G 87G 28% /etc/hosts
shm 64M 1.1M 63M 2% /dev/shm
/dev/longhorn/pvc-7eab52f7-918e-4791-a924-74072998cd26 7.8G 28K 7.8G 1% /var/lib/postgresql
...
bash-5.1# exit
command terminated with exit code 1
$ kubectl delete -k .
namespace "test" deleted
statefulset.apps "postgres" deleted