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Old 05-07-2017, 10:54 AM   #1
hellscream
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Registered: May 2017
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Unhappy Serial over SSH Not working


Hi I am trying to setup a serial connection over SSH
on RedHat7.1

GRUB_TIMEOUT=10
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL="serial" #I have to put this line as it was missing
GRUB_TERMINAL_OUTPUT="console" # I dont know if to change console to serial
GRUB_CMDLINE_LINUX="rd.lvm.lv=rhel/swap crashkernel=auto rd.lvm.lv=rhel/root rhgb quiet # I have added the following (console=tty0 console=ttyS0,115200"
GRUB_DISABLE_RECOVERY="true") but still not working
GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1 vga=normal nomodeset"

then grub2-mkconfig -o /boot/grub2/grub.cfg

and reboot the system
I get the console up to the moment that redhat first line then I never get console again, therfore I think my problem is with y lines above
hope you can help
Best regards

Last edited by hellscream; 05-07-2017 at 10:55 AM.
 
Old 05-07-2017, 11:15 AM   #2
michaelk
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Welcome to LinuxQuestions

By default boot up messages are displayed on the first virtual terminal i.e tty0. A serial console is a way of displaying boot up messages using RS-232 to another computer, terminal, teletype etc. So once the console is reconfigured you will not see anything unless you connect something to the serial port or go back to using tty0.

ssh is a way to login over a TCP/IP network and unrelated to a remote serial console.
 
Old 05-07-2017, 03:42 PM   #3
hellscream
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Registered: May 2017
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Thank you MichaelK
I don’t have any cables connected to the serial port.
I have configured in the BIOS for Console redirection over SSH?
So during boot up I can see the whole POST (no cables)
Forgot to mention this is a Dell server, during post I connect to the iDRAC similar to ILO from HP.
This is an out-of-band controller, I ssh to this IP and get two options from admin.
I can type racadm or console com2
I type console com2 and it redirects me to a virtual serial connection (I can see POST)but as soon as I RedHat command line appears the whole thing dies...
I have been told that the console should continue open.
Have spent over 2 weekends trying to make this work but bashing my head against the wall...
 
Old 05-07-2017, 04:22 PM   #4
michaelk
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Oh, sorry I should of guessed that.

I assume the iDRAC BIOS settings are enabled and configured for the proper settings for racadm have been set to enable ssh.

I've never had the need to configure a serial console with systemd but according to Arch wiki the configuration settings are:

GRUB_CMDLINE_LINUX_DEFAULT="console=tty0 console=ttyS0,38400n8"
GRUB_TERMINAL=serial
GRUB_SERIAL_COMMAND="serial --speed=38400 --unit=0 --word=8 --parity=no --stop=1"

Don't know what bugs or cavaets still exist with systemd and a using serial console so contacting Redhat might be a good idea.
 
Old 05-08-2017, 03:52 PM   #5
hellscream
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Thank you MichaelK
will check those settings tonight
best regards
 
  


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