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I installed a linaro system on my ARM chromebook, and it seems to autoboot to a root prompt. I've set a user password, and use it to login to the GUI, but with a simple Ctrl+Alt+F1, I can get to a logged in root prompt.
Setting a new root password with passwd does not help. I cannot logout of the root shell, it just returns me to a new login root shell.
Ok, I figured it out. So this is how login works. There is an init script in /etc/init/tty1.conf which runs getty. Getty is a program that waits for login connections, and then authenticates a user. I initially thought getty was being run with autologin, and so I looked for a line in /etc/init/tty1.conf like
exec /sbin/getty -8 38400 -a root tty1
which means, open an 8bit terminal at 38400 baud and autologin the root user into tty1. But when I looked at the file, there was no -a option to autologin the root user. I'm stating this because /etc/init/tty1.conf should be the first place to look if others face the same issue.
Then I looked through the /etc/init/ directory and found a file called openvt.conf. This had the following line:
exec /bin/login -f root
This was the culprit. The login command with the -f option automatically logs the user in without authentication.
Since the openvt.conf file is intended to be an upstart service, it has to be disabled in a particular way, although one can also simply delete the file. See this askubuntu post about upstart. In short, either delete the openvt.conf file, or run
echo manual | sudo tee /etc/init/openvt.override
and then root is no longer logged in automatically.
