Error Starting Proxmox VM: pve-ssl.pem is empty

Got following error when starting a Proxmox VM with Spice driver.

kvm: warning: Spice: reds.c:2893:reds_init_ssl: Could not load certificates from /etc/pve/local/pve-ssl.pem
kvm: warning: Spice: error:0909006C:PEM routines:get_name:no start line
kvm: warning: Spice: error:140DC009:SSL routines:use_certificate_chain_file:PEM lib
kvm: failed to initialize spice server
TASK ERROR: start failed: QEMU exited with code 1

pve-ssl.pem size

The file size of /etc/pve/local/pve-ssl.pem is 0.

Fix

Standalone server

Regenerate following files using method stated in https://pve.proxmox.com/wiki/Proxmox_SSL_Error_Fixing

/etc/pve/pve-root-ca.pem
/etc/pve/local/pve-ssl.key
/etc/pve/local/pve-ssl.pem

Cluster node

Copy following files from other Proxmox node, normally, /etc/pve/pve-root-ca.pem files are the same.

/etc/pve/nodes/<node_name>/pve-ssl.key
/etc/pve/nodes/<node_name>/pve-ssl.pem

Note: These certificates can be used for all nodes.
Note: /etc/pve/local is a link to nodes/<node_name>

References

Proxmox SSL Error Fixing