[PVE-User] why /etc/pve/storage.cfg is read-only?

[para zheng]

Dear all:

     When adding CEPH as the storage, i want to add configs in the
/etc/pve/storage.cfg, but I found these files are read-only.

# ls -l storage.cfg
-r--r----- 1 root www-data 357 Jun 25 12:35 storage.cfg

Then I use "mount -o rw" remount it to make it wriable, but it does
not make any sense.

And use df comand, found :
# df -h | grep /etc/pve
/dev/fuse              30M   72K   30M   1% /etc/pve

here are pve version:

#peversion -v
pve-manager: 2.2-21 (pve-manager/2.2/8f343d5a)
running kernel: 2.6.32-16-pve
proxmox-ve-2.6.32: 2.2-79
pve-kernel-2.6.32-11-pve: 2.6.32-66
pve-kernel-2.6.32-16-pve: 2.6.32-79
pve-kernel-2.6.32-12-pve: 2.6.32-68
lvm2: 2.02.95-1pve2
clvm: 2.02.95-1pve2
corosync-pve: 1.4.4-1
openais-pve: 1.1.4-2
libqb: 0.10.1-2
redhat-cluster-pve: 3.1.93-1
resource-agents-pve: 3.9.2-3
fence-agents-pve: 3.1.9-1
pve-cluster: 1.0-28
qemu-server: 2.0-59
pve-firmware: 1.0-20
libpve-common-perl: 1.0-35
libpve-access-control: 1.0-25
libpve-storage-perl: 2.0-33
vncterm: 1.0-3
vzctl: 4.0-1pve2
vzprocps: 2.0.11-2
vzquota: 3.1-1
pve-qemu-kvm: 1.2-6
ksm-control-daemon: 1.1-1

I do not know why this happen. I had used to test ceph in VE few days ago.
Thanks for your replies and free sharing.