So unmount /alma2, rename and mount again.
Code:
mount /dev/sda5 /almacen
I take it /alma2 is not your root directory but some data or home directory. Su to root first, don't do it as sudo. You want to have your home directory on /root. (maybe not strictly necessary)
Edit your /etc/fstab and change the mount point for /dev/sda5 to /alamcen.
jlinkels