OMV serial console access [putty | GNU screen ]

    • OMV 1.0
    • core

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    • OMV serial console access [putty | GNU screen ]

      OMV serial console access [putty | GNU screen ]

      Intro
      In NAS headless systems sometimes we loose network connectivity or the kernel boot stops in some error, for that purposes and having no monitor available we can always use the serial console available in every motherboard.

      Prerequisites
      Openmediavault 1.0
      SSH access
      Serial port in motherboard and USB to serial cable

      Some mobo's don't have the DB9 port on the back, but they all have it inside, this is what it looks like:

      mobo.jpg 8.jpg
      That's a 9 pin header com

      With the help of this accessory we can bring the header to the outside of the case with a nice DB9 male connector.

      SERIAL.jpg

      Then with a USB to DB9 (serial) cable, we can output the console text to a computer or if we want we can redirect it to a network socket. This is interactive, we can send commands also.

      cable.jpg

      Start:

      We are enabling the serial console for:
      1. grub boot menu
      2. boot sequence (kernel load and daemon starts)
      3. login tty, this is for login and command posting
      We set grub options for serial, so we edit the default file

      nano /etc/default/grub

      This two lines are for grub boot menu, you will be able to select kernel or other OS
      GRUB_TERMINAL=serial
      GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"

      The following are kernel boot parameters, with these you will monitor the whole boot sequence, and press some ctrl-D if necessary
      GRUB_CMDLINE_LINUX_DEFAULT="console=tty0 console=ttyS0,115200n8"

      When you finish run update-grub2

      Now for the login tty we edit inittab and add the ttyS0 (serial) line after the getty's runlevel set.

      nano /etc/inittab
      look for this line 6:23:respawn:/sbin/getty 38400 tty6, and after that add

      Source Code

      1. T0:23:respawn:/sbin/getty -L ttyS0 115200 vt100
      this will give you a login tty prompt after the boot sequence is finished.

      Connecting

      The most common program for this is our old good putty, watch the COM port and check that at device management in windows is set correctly.

      Capture.PNG

      Capture2.PNG

      Capture1.PNG

      From a linux client you can access with GNU screen

      screen /dev/ttyUSB0 115200


      Notes
      - I'd recommend to buy a good serial cable, one with an FTDI chip. The prolific ones are just pure sh*t, tons of fake chips coming from china, drivers won't load, gibberish in the screen.
      -This is valid only for OMV 1.0, Debian Squeeze might have a slight difference in grub syntax, also never achieved 115200bps back then.
      - If 115200bps doesn't work, start by setting a 9600bps speed, and keep increasing until you find the one that works for you.
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      The post was edited 29 times, last by subzero79 ().