Recover from Unmounted VI : rc.conf Mistakenly Typed

Reboot your System.

Choose Single User mode from list. (Press F4)

now your single usermode is enable.
Now the problem is even entered /bin/sh, still do not have any function can
change this configuration file, even “vi” is not available

After entering the single user mode, only your root filesystem
is mounted. If /usr (vi lives in /usr/bin) is a separate
filesystem, you have to mount it first. Try

Change your /etc/rc.conf

reboot your system after cleaning your file.

Cheers!!