Add a getty/login prompt on ttyS0 cloud images

[Alessandro Pilotti]

Most hypervisors have the option to connect to guests via serial port. Adding a console on ttyS0 is particularly helpful for troubleshooting purposes.

Example:

/bin/sed -i 's/rhgb quiet/quiet console=tty0 console=ttyS0,115200n8/g' /boot/grub/grub.conf

/bin/sed -i 's/^hiddenmenu$/hiddenmenu\nserial\ --unit=0\ --speed=115200\ --word=8\ --parity=no\ --stop=1\nterminal\ --timeout=5\ console\ serial/g' /boot/grub/grub.conf

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[Ben Howard (darkmuggle-deactivatedaccount)]

The problem here is that if you configure grub for the serial console, you don't get it for on the terminal. I am not opposed to making the change, but this would enable some users at the risk of breaking others.

http://www.gnu.org/software/grub/manual/html_node/Serial-terminal.html

Indicates that you can have both, but "In this case, a terminal in which you press any key will be selected as a GRUB terminal. "

With out testing, I'm not sure that we can it both ways with out breaking a user.

[Ben Howard (darkmuggle-deactivatedaccount)]

Also, I might add that starting with 12.10, the Cloud Images are configured in appliance mode -- unless there is a problem, the images will boot immediately with out a grub timeout unless there is a problem.

[Robert C Jennings (rcj)]

I believe that this could work if we launch getty with something like this in /etc/init/ttyS0.conf :
# ttyS01 - getty
#
# This service maintains a getty on ttyS01 from the point the system is
# started until it is shut down again.

start on stopped rc RUNLEVEL=[2345] and (
            not-container or
            container CONTAINER=lxc or
            container CONTAINER=lxc-libvirt)

stop on runlevel [!2345]

pre-start script
  # getty will not be started if the serial console is not present
  stty -F /dev/ttyS0 -a 2> /dev/null > /dev/null || { stop ; exit 0; }
end script

respawn
script
  exec /sbin/getty -L 115200 ttyS01
end script

Without the pre-start, configuring a console on ttyS0 for upstart in /etc/init/ttyS0.conf for instances that do not have a serial console present will result in getty repeatedly failing and respawning and the failures would clutter up /var/log/auth.log with messages like:

Jan 10 21:34:22 test-system getty[1163]: /dev/ttyS0: not a character device
Jan 10 21:34:33 test-system getty[1186]: /dev/ttyS0: not a character device
Jan 10 21:34:43 test-system getty[1200]: /dev/ttyS0: not a character device
Jan 10 21:34:53 test-system getty[1211]: /dev/ttyS0: not a character device
Jan 10 21:35:03 test-system getty[1223]: /dev/ttyS0: not a character device
Jan 10 21:35:13 test-system getty[1235]: /dev/ttyS0: not a character device

[Robert C Jennings (rcj)]

Adding this for Trusty in x86/amd64. Testing the patch now.

[Robert C Jennings (rcj)]

Fix merged and awaiting next image build to verify release.

[Ben Howard (darkmuggle-deactivatedaccount)]

Validated 14.04 daily build in both EC2 and in KVM. I've confirmed that ttyS0 is present on systems with a serial console, while not doing anything on systems with out a ttyS0.

This fix should roll out to 12.04 released images in the next few weeks. Marking as "fix released."

[Vincent Bernat (vbernat)]

Ben, I am looking at the latest 12.04 cloud images and it doesn't seem to have that. Could you check?

[Ben Howard (darkmuggle-deactivatedaccount)]

Vincent, can you provide more information? ttyS0 will appear if the device is found. After smoke-checking, it should indeed be there. Can you provide a console log and the cloud where you are seeing this (if its a public cloud) or the hypervisor?