Installation - yi-hsuan/Proxmox GitHub Wiki
Modify existing lvm storage
This step removes the 'local-lvm' partition originally created by the ProxMox install and expands the 'local' partition to fill the free space.
At the command line.
Disable the data lvm
lvchange -an /dev/pve/data
This step may fail as the last step in the previous section may disable the data lvm for you. If so skip to the next step.
Remove the data lvm
lvremove /dev/pve/data
Extend the root lvm
lvextend -l +100%FREE /dev/pve/root
Resize the root file system
resize2fs /dev/pve/root