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OS X:Terminal Break for Serial Console on OS X

15 May 2009 By Greg Ferro 5 Comments

In a previous post Serial Console on OS X I wrote about how to connect a USB-Serial converter to console into Cisco router and use the ‘screen’ command.

To perform a password recovery on a Cisco router you need to issue a “terminal break” character to interrupt the boot process. The Cisco page on terminal break shows a lot of break sequences.

The break sequence for “screen” is to use Ctrl-A and then Ctrl-B. The Ctrl-A shifts the focus back to the screen process (away from the serial console) and the Ctrl-B issues the break sequence.

You may need to break more than once. This is done by Ctrl-A, Ctrl-B, Ctrl-B, Ctrl-B.

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About Greg Ferro
Greg is a Network and Security Architect / Designer / Engineer working freelance in the UK and worked for Resellers, DotCom's, Large Corporate's and Service Providers across a variety of products & Vendors. He prefers to work for end users, believes in the life cycle, total cost of ownership and that near enough is often good enough. He likes talking about himself in the first person to feel "royal", even when hosting the Packet Pushers Podcast on Data Networking. More about Greg at http://etherealmind.com/who-am-i/ and you can follow him on Twitter.

Comments

  1. Dmitri says:
    15 May 2009 at 10:51 +0000

    …and if it works for you – you’re lucky, because not very many USB to Serial adapters pass “break”.

    Reply
  2. Marko Milivojevic says:
    15 May 2009 at 14:04 +0000

    I believe that the problem with break on OSX is with Prolific driver. You may wish to try open source one. I had no luck with it (didn’t handle large buffers when pasting) and I’m stuck with Prolific driver.

    Reply
  3. Gary Smith says:
    7 October 2009 at 16:56 +0000

    I think it does depend on the chipset of the convertor – I’ve got a PL2303 based unit here and I’ve been struggling to find a way to issue a break with it. I don’t believe it’s possible to do, although there’s been many rumours about the functionality being added in to a later release of the driver.

    Cheers,

    Gary Smith

    Reply
  4. Chris Welsh says:
    1 July 2010 at 22:23 +0000

    IT WORKED FOR ME – I’m using iTerm though, rather than the built in Apple Terminal program.

    Thanks Greg.

    Reply
    • Joe Finley says:
      6 July 2010 at 18:44 +0000

      Ok, here’s what I did.

      download – Installed ITERM
      download – install the opensource PROLIFIC drivers
      ——Not sure if this made any difference——
      Open Network Interfaces – Selected USB-Serial D2″, created a new profile “SERIAL”
      Clicked Advanced.. “Modem – Vendor Null Modem” Model “9600″ (OK)
      Clicked on the USB-Seral D1 to “Default”
      ———————————————-

      Open iTerm, typed “ls -la /dev/tty.*”

      crw-rw-rw- 1 root wheel 11, 4 Jul 6 13:22 /dev/tty.Bluetooth-Modem
      crw-rw-rw- 1 root wheel 11, 0 Jul 6 13:21 /dev/tty.Bluetooth-PDA-Sync
      crw-rw-rw- 1 root wheel 11, 12 Jul 6 13:35 /dev/tty.PL2303-00301124
      crw-rw-rw- 1 root wheel 11, 2 Jul 6 13:21 /dev/tty.jfinleysiphone-Wireless
      crw-rw-rw- 1 root wheel 11, 10 Jul 6 13:27 /dev/tty.usbserial

      Then I typed screen “/dev/tty.PL2303-00301124 9600″
      Assuming the opensource is “PL2303-00301124″
      Powercycled the router & hit control-a & control-b many times

      Finally received the ROM-MON!

      Reply

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