Connecter au serveur de console

Required

• SSH Client
• Access Credentials

Cereal and usb adapters

Connecting

Connect to the console switch using your username, password and port number

1. Using your SSH client, connect to the desired serial console and port.

   ssh user@cs0.koumbit.net

2. You need to become root to access cereal

   sudo su

3. To liste all available connections:

   cereal-admin list

4. Connect to the desired console:

   cereal attach <NAME>

5. If desired port is down, start it:

   cereal-admin start <NAME>

Older HP serial consoles

Connecting

Connect to the console switch using your username, password and port number

1. Using your SSH client, connect to the desired serial console and port.

   ssh user@cs2.koumbit.net -p 3101

2. Enter your password.

   user@cs2.koumbit.net's password:

3. Assuming your password is correct, you will be re-directed and automatically connected to the port specified earlier.

   Hewlett-Packard HPSCS16 S/W Version 1.9
   Connected to Port: 2 115200,8,N,1,NONE
   61 bytes available in history buffer
   
   Debian GNU/Linux 5.0 shell.koumbit.net tty1
   
   shell.koumbit.net login: 

export TERM=screen

Disconnecting

Disconnecting from your session

1. When you wish to disconnect, you may either close your SSH client (the serial console will eventually figure out the hanging terminal and end the session) or press Control+D, then enter quit at the > prompt.

   shell.koumbit.net login: <Control+D>
   Entering Command Mode
   > quit
   
   Session Terminated

For additional information, refer to ConsoleSérieService/hp-scs-users-guide.pdf

Hard resets

Sending the Skinny Elephants signals can be done by sending a break signal to the serial console. On the HP serial console devices, you can send a break signal with ctrl-D followed by port break followed by resume. Do these in rapid succession so you can send the control character quickly thereafter. You might prefer to write all your commands into a text file and then copy/paste to the ssh session.

Here is an example of serial console output sending h after the magic sysrq (to get a help listing):

monkey login: 
Entering Command Mode
> port break
> resume
Connected to Port: 1 115200,8,N,1,NONE
63310 bytes available in history buffer
[ 1268.051544] SysRq : HELP : loglevel(0-9) reBoot Crash terminate-all-tasks(E) memory-full-oom-kill(F) kill-all-tasks(I) thaw-filesystems(J) saK show-backtrace-all-active-cpus(L) show-memory-usage(M) nice-all-RT-tasks(N) powerOff show-registers(P) show-all-timers(Q) unRaw Sync show-task-states(T) Unmount show-blocked-tasks(W) dump-ftrace-buffer(Z) 

Debian GNU/Linux 6.0 monkey ttyS0

monkey login:

See HardReset for the details of the specific signals you can send.

In cereal, its C-\ C-b .

How to configure your server to be accessible through the a serial console

Linux servers

There is an excellent howto about remote serial consoles, however it covers more stuff than what we actually need. The breakdown is actually quite simple. there are three different parts (ignoring the BIOS here): the console (the login prompt you usually see when you boot your OS), the kernel (linux here) and the boot loader (grub).

Operating system with systemd

If the serial port connected is ttyS0, you can run the following commands, but make sure that the kernel has already been configure to output to the serial console.

# systemctl enable serial-getty@ttyS0.service
# systemctl start serial-getty@ttyS0.service

To get the status on the port:

# systemctl status serial-getty@ttyS0.service

We can specified the speed of the port in this file

/etc/systemd/system/getty.target.wants/serial-getty\@ttyS0.service

Ref

http://0pointer.de/blog/projects/serial-console.html

Console with systemd gives out garbage with proprietary console server

This is because the proprietary console servers don't like terminal type vt102, which is set by default by systemd and require type vt100.

In order to change that you need to create a "drop-in". In this example the terminal port that's used is ttyS1, you should adapt to the device that's right for your setup.

First create a directory:

mkdir /etc/systemd/system/serial-getty@ttyS1.service.d

then create file /etc/systemd/system/serial-getty@ttyS1.service.d/force-term-type.conf set its contents to the following:

# Redefine service call to force terminal speed.
[Service]
Environment=TERM=vt100

Finally to make that effective, run systemctl daemon-reload. Then when running systemctl status serial-getty@ttyS1.service the output should tell you that there is an effective drop-in at the path where you just created the file. Restart the service and the console should be showing getty's output correctly.

Operating system without systemd

Configure the console tty

This configures a login terminal to popup on the serial console port.

Add this line (or uncomment) in /etc/inittab:

T0:23:respawn:/sbin/getty -L ttyS0 115200 vt100

T2:23:respawn:/sbin/getty -L hvc0 115200 vt100

Then use the traditionnal kill -1 1 to tell init to reload inittab.

Vérifier avec la commande :

# ps -ax | grep getty

Full article

Configure the kernel

Then you configure the kernel to also show up on the serial console. The argument to pass the kernel is console=tty0 console=ttyS0,115200n8, for the console to appear both on the serial console and regular VGA console.

Make sure those lines are present in /etc/default/grub:

On the servers that the console works on ttyS0, like vandales, there is:

# next line for single user mode (recovery)
GRUB_CMDLINE_LINUX="console=ttyS0,115200n8"
# for normal boot
GRUB_CMDLINE_LINUX_DEFAULT="console=hvc0 console=tty0 earlyprintk=xen"
# for normal boot
GRUB_CMDLINE_XEN_DEFAULT="dom0_mem=1024M,max:1024M com1=115200,8n1 console=com1,vga"

Then rerun update-grub2.

Archive: In grub 1

In /boot/grub/menu.list, you need to add console=tty0 console=ttyS0,115200n8 on the kernel line:

  kernel /vmlinuz-2.4.9-21 ro root=/dev/hda6 console=tty0 console=ttyS0,115200n8

For this to survive Debian kernel upgrades, you also need to add those to the kopt line in /boot/grub/menu.list:

# kopt=root=/dev/mapper/ceres-root ro console=tty0 console=ttyS0,115200n8

Then run update-grub to apply the new parameters to the current kernel installed in the grub menu.lst

Full article

Configure the bootloader

To configure grub to show up on the serial console, add this to /etc/default/grub:

# Uncomment to disable graphical terminal (grub-pc only)
GRUB_TERMINAL="serial console"
GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"

• Les options pour GRUB_TERMINAL

  • serial pour avoir le menu de grub sur le port serie

  • console pour avoir le menu de grub AUSSI sur l'écran

GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=1 --word=8 --parity=no --stop=1"

après ça, n'oubliez pas d'exécuter update-grub à nouveau

Archive: Grub 1

Add this on top of /boot/grub/menu.list:

serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
terminal --timeout=10 serial console

Full article

Configure the BIOS

Configuring the BIOS and other operating systems is not covered here yet.

Ensuite, certains serveurs offrent la possibilité d'envoyer le output du bios vers le port série, c'est a vérifier cas par cas dans le bios de chaque machine.

FreeBSD

As documented in the advanced guide, we can easily configure FreeBSD to boot from the serial console, which will just show up in the terminal in qemu, very handy.

1. Enable serial console in /etc/ttys by editing the ttyu0 entry. The ttyu0 line should appear like the following;

   • ttyu0   "/usr/libexec/getty std.115200"   vt100   on secure

   • Be sure to disable the other tty's listed by changing the value on to off otherwise you'll see errors when booting.

2. Edit /boot/loader.conf (It may be empty) and add the following;

   • boot_multicons="YES"
     boot_serial="YES"
     comconsole_speed="115200"
     console="comconsole,vidconsole"

3. add the following line to /boot.config (you may need to create the file):

   • -D -S115200

4. reboot. the new console will not start automatically, plus you want to test the bootloader options.

memtest86

To run memtest86+ on the serial console, you need to add this parameter: console=ttyS0,115200n8, for example, in grub:

menuentry "Memory test (memtest86+, serial console 115200)" {
    linux16 /boot/memtest86+.bin console=ttyS0,115200n8
}

How to access a console using the USB port

With cereal, you need to set an environment variable to your ssh connection in order to chose which session (e.g. which machine) to connect to:

TARGET="SERVERNAME" ssh -o SendEnv=TARGET -v USERNAME@cs0.koumbit.net 

The SERVERNAME, USERNAME and password will need to be given to you by a sysadmin who has done the creation of a cereal session for your server.

The password for this ssh login is managed through your account at collectif.koumbit.net

connexion avec screen (ancienne methode)

1. D'abord vérifier s'il y a une session entamé avec cereal et prendre en note le path du tty si présent:

   cereal-admin list

2. Fermer et détruire la session cereal:

   cereal-admin stop SESSION ; cereal-admin destroy SESSION

3. se connecter avec screen:

   screen /dev/serial/by-id/usb-FTDI_FT232R_USB_UART_ST162110-if00-port0 115200

un autre exemple à partir du serveur de console:

screen /dev/ttyUSB0 115200

Pour détacher et détruire la session screen:

<CTRL+a> <k>

Having two screen sessions connected to the same serial console device creates weird conflits that break screen feedback and keyboard interactivity. In order to avoid those issues you can use the following command, which will create a screen session only if there's none, otherwise you'll be reconnected to the current screen session:

devnum=2; if fuser -s /dev/ttyUSB$devnum; then screen -x; else screen /dev/ttyUSB$devnum 115200; fi

CategoryGuide CategoryConsoleServer