mingetty is designed to be a minimal getty for the virtual terminals on the the workstation's monitor and keyboard. It has no support for serial lines.
You must not use mingetty for the serial line in /etc/inittab, but the current mingetty entries for the virtual terminals can remain.
Each virtual terminal uses about 8KB of kernel memory. If this matters, it is easy to allocate fewer virtual terminals. In the Linux 2.4 kernel virtual terminals are created on demand, so not starting mingetty on the virtual terminal will not create the virtual terminal. If the machine does not have a video card then remove all the mingetty entries from /etc/inittab.
Figure 6-9. Fewer virtual terminals. Removing mingetty entries from /etc/inittab
1:2345:respawn:/sbin/mingetty tty1 # Additional virtual terminals are not used 2:2345:off:/sbin/mingetty tty2 3:2345:off:/sbin/mingetty tty3 4:2345:off:/sbin/mingetty tty4 5:2345:off:/sbin/mingetty tty5 6:2345:off:/sbin/mingetty tty6
After restarting init it would be wise to remove the unused device files.