The message is more generic than talking of the root Ram disk only.
Login to the NAS Linux shell from your computer (Windows: puTTY, OS X Terminal app: $ ssh admin@[NAS-IP-address]) using the admin credentials. There you can enter the commands (the [~] shows just the current directory, the # is the prompt.
Run these commands as the shell prompt, post the output to the forum:
Example output:
[~] # mount
/proc on /proc type proc (rw)
none on /dev/pts type devpts (rw,gid=5,mode=620)
sysfs on /sys type sysfs (rw)
tmpfs on /tmp type tmpfs (rw,size=32M)
none on /proc/bus/usb type usbfs (rw)
/dev/sda4 on /mnt/ext type ext3 (rw)
/dev/md9 on /mnt/HDA_ROOT type ext3 (rw,data=ordered)
/dev/sda3 on /share/HDA_DATA type ext4 (rw,usrjquota=aquota.user,jqfmt=vfsv0,user_xattr,data=ordered,delalloc,acl)
nfsd on /proc/fs/nfsd type nfsd (rw)
tmpfs on /.eaccelerator.tmp type tmpfs (rw,size=32M)
[~] # df
Filesystem Size Used Available Use% Mounted on
/dev/ram0 32.9M 15.9M 17.0M 48% /
tmpfs 32.0M 2.2M 29.8M 7% /tmp
/dev/sda4 364.2M 345.0M 19.2M 95% /mnt/ext
/dev/md9 509.5M 141.6M 367.9M 28% /mnt/HDA_ROOT
/dev/sda3 457.0G 38.7G 417.8G 8% /share/HDA_DATA
tmpfs 32.0M 0 32.0M 0% /.eaccelerator.tmp
Following a potential free-up (wont work otherwise I'd guess), copy the firmware image i.e. to the Public shared folder, use the process here
http://wiki.qnap.com/wiki/Manually_Updating_Firmware (for the move [mv] or better us copy # cp /share/Public/TS....img ...).