Serial console shenanigans

[decuser]

I'm reading Chapter 4 of Michael Lucas's great book, Absolute FreeBSD on startup and he's talking about connecting to the serial console of the FreeBSD machine... so, of course, I have to go digging for null modem cables, usb-db9 cables, and hook it up to try out what he's talking about. At first, no luck, then a couple of hours later and swapping this cable for that one, I got it working and it's glorious. Watching the machine boot is so much more fun on the serial console - lots of additional info, but it's in a terminal window where I can easily scroll. I definitely should have done this sooner - oh, wait, I did, about 10 years ago when my laptop had a serial port... I remember it being a week or two of experimentation, apparently I've picked up a lot of know-how since then. Anyway, here's what I did. I have some questions and would appreciate any tips on doing it the "right" way y'all might have.

1. Get a USB to DB9 (male) cuz my T430 doesn't have a serial port . I tried two different prolific chipset cables and they both worked fine. I don't have an FTDI version, but one of these days...

2. Get a Null Modem Female DB9 to Female DB9 (my m92p has a Male DB9 serial port)

3. Connect them to each other and connect them to the host and client

# on the client (USB side)
4. See what the kernel picks up (dmesg):

ugen0.2: <Prolific Technology Inc. USB-Serial Controller> at usbus0

uplcom0 on uhub1

uplcom0: <Prolific Technology Inc. USB-Serial Controller, class 0/0, rev 2.00/3.00, addr 6> on usbus0

5. start a session (this is voodoo, but it works, 9600 was slow, but 115200 is quick)

# cu session

sudo cu -l /dev/cuaU0 -s 115200
or
sudo cu -l /dev/ttyU0 -s 115200
dunno how to exit, but disconnecting the cable works

# screen (pretty and kinda like tmux... makes me wonder if tmux would work)

sudo screen /dev/ttyU0 115200
or
sudo screen /dev/cuaU0 115200
CTL-a CTL-\ to exit

Note: I did a google search to figure out what device it would be on, these work:

crw-rw----  1 uucp dialer 0x202 Feb 11 19:23 /dev/cuaU0
crw-------  1 root wheel  0x1ff Feb 11 19:23 /dev/ttyU0

# on the host (Null Modem DB9 side)
6. configure loader.conf (another bit of voodoo, took several tries to find an incantation that worked

vi /boot/loader.conf
boot_multicons="YES"
boot_serial="YES"
comconsole_speed=""115200
console="comconsole,efi"

7. configure ttys (more voodoo and googlefu)

vi /etc/ttys
ttyu0  "/usr/libexec/getty 3wire"      vt100   onifconsole secure

8. Reboot host and watch the magic

\  ______               ____   _____ _____
  |  ____|             |  _ \ / ____|  __ \
  | |___ _ __ ___  ___ | |_) | (___ | |  | |
  |  ___| '__/ _ \/ _ \|  _ < \___ \| |  | |
  | |   | | |  __/  __/| |_) |____) | |__| |
  | |   | | |    |    ||     |      |      |
  |_|   |_|  \___|\___||____/|_____/|_____/      ```                        `
                                                s` `.....---.......--.```   -/
 +---------- Welcome to FreeBSD -----------+    +o   .--`         /y:`      +.
 |                                         |     yo`:.            :o      `+-
 |  1. Boot Multi user [Enter]             |      y/               -/`   -o/
 |  2. Boot Single user                    |     .-                  ::/sy+:.
 |  3. Escape to loader prompt             |     /                     `--  /
 |  4. Reboot                              |    `:                          :`
 |  5. Cons: Dual (Serial primary)         |    `:                          :`
 |                                         |     /                          /
 |  Options:                               |     .-                        -.
 |  6. Kernel: default/kernel (1 of 2)     |      --                      -.
 |  7. Boot Options                        |       `:`                  `:`
 |  8. Boot Environments                   |         .--             `--.
 |                                         |            .---.....----.
 +-----------------------------------------+
   Autoboot in 1 seconds. [Space] to pause
   Autoboot in 0 seconds. [Space] to pause
Loading kernel...

My questions are:

1. what's the difference between /dev/cuaXXX and /dev/ttyXXX?
2. is the ttys stuff necessary/correct? in that file it's listed as /dev/ttyu0, but the dev is /dev/ttyU0 (or /dev/cuaU0)
3. how do you exit cu? I just pulled the usb cable... seems drastic.
4. the book and online sources talk about using tip, how does that work (I tried a bunch of stuff to no avail)?
5. how do I know that uplcom0 is attached to /dev/ttyU0? or how do I figure it out other than trial and error.

Thanks!

 

[richardtoohey2]

3. how do you exit cu? I just pulled the usb cable... seems drastic.

Solved - How to get out of a cu connection

Hi all, I needed to have a look at the vlan on my Cisco switch so I switched to F1 logged in as root and executed cu -l cuau0 No problem, I got my switch> prompt and did my task on the switch. Now I can't get cu to let go of the switch and return to the root prompt. I can execute the quit...

forums.freebsd.org

~.

 

[decuser]

Solved - How to get out of a cu connection

Hi all, I needed to have a look at the vlan on my Cisco switch so I switched to F1 logged in as root and executed cu -l cuau0 No problem, I got my switch> prompt and did my task on the switch. Now I can't get cu to let go of the switch and return to the root prompt. I can execute the quit...

forums.freebsd.org

~.

It's finicky, but the <enter>~. thing works, but if you type ~ twice it escapes the tilde and then you need to press enter again. Weird, but workable!

 

[decuser]

4. the book and online sources talk about using tip, how does that work (I tried a bunch of stuff to no avail)?

Figured this one out after rereading the chapter some more and thinking things through..

vi /etc/remote
#modify the line pertaining to /dev/cuaU0
ucom1:dv=/dev/cuaU0:br#115200:pa=none:

Then, just use the shortcut ucom1 for tip:

tip ucom1

And

~.

to exit tip.