FreeBSD installer memstick does not have serial console enabled by default. But for some hardware, it’s not convenient to access the VGA console. This article described how to enable serial console by modifying /memstick/boot/loader.conf on a memstick.
This work on FreeBSD-13.1-RELEASE-amd64-memstick.img
First, find a FreeBSD machine and mount the memstick
mkdir /memstick mount /dev/da0s2a /memstick
And add the following lines to /memstick/boot/loader.conf
boot_multicons="YES"
boot_serial="YES"
comconsole_speed="115200"
comconsole_port="0x3F8" # ttyu0 ttyS0
# comconsole_port="0x2F8" # ttyu1 ttyS1
# comconsole_port="0x3E8" # ttyu2 ttyS2
# comconsole_port="0x2E8" # ttyu3 ttyS3
console="comconsole,vidconsole" # legacy boot
# console="comconsole,efi" # UEFI ("vidconsole" is not a valid option for UEFI boot)
And then umount /memstick
For detail, check loader.conf
Note: to find out the “port” number on a recent Linux version (e.g. kernel 5.15), try
Linux$ udevadm info -q all -n /dev/ttyS0 | grep DEVPATH E: DEVPATH=/devices/platform/serial8250/tty/ttyS0 Linux$ cat /sys/devices/platform/serial8250/tty/ttyS0/port 0x3F8
On an older Linux (kernel 2.6), try
Linux$ udevadm info -q all -n /dev/ttyS0 | grep DEVPATH E: DEVPATH=/devices/pnp0/00:07/tty/ttyS0 Linux$ cat /sys/devices/pnp0/00:07/tty/ttyS0/device/resources state = active io 0x3f8-0x3ff irq 4