( Is common for VMs with full virtual disks to come up with their user-space file-systems mount as ro (read-only). )
Check where the root or the file-system that you want to mount as read-write(rw) is mounted.
# mount /dev/sda1 on / type ext3 (rw) ...
/proc/mounts and the mount command may report rw even if the file-system is mounted as ro.
Remount root as read-write.
# mount -o remount,rw /dev/sda1 /
Remount as read-write a filesystem in linux