ttyS − serial terminal lines
ttyS[0−3] are character devices for the serial terminal lines.
They are typically created by:
mknod −m
660 /dev/ttyS0 c 4 64 # base address 0x3f8
mknod −m 660 /dev/ttyS1 c 4 65 # base address 0x2f8
mknod −m 660 /dev/ttyS2 c 4 66 # base address 0x3e8
mknod −m 660 /dev/ttyS3 c 4 67 # base address 0x2e8
chown root:tty /dev/ttyS[0−3]
/dev/ttyS[0−3]
chown(1), mknod(1), tty(4), agetty(8), mingetty(8), setserial(8)