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Autologin with mingetty

By John Kodis

In Issue 26 of the Linux Gazette, Todd Blake, tbb@enterprise.aacc.cc.md.us, wrote in to ask:

"I like most people am the only person to use my linux system at home. What I'd like to do is when my system is done booting to have me automatically login as my main user account (not as root though) on one virtual console (the first) and leave all other consoles and virtual consoles alone, so that someone telneting in will get a login prompt like normal, just that I won't. I'd still like the other VC's have logins for others to login and other reasons. I've tried just putting /bin/sh in /etc/inittab and that didn't work, and I'm stumped. Does anyone have any ideas on this?"
I was in the same situation. I saw this question come up regularly in various newsgroups, but never with a satisfactory solution being proposed. Recently I came up with a solution that does just what Mr. Blake requested. I did this by making a few changes to Florian LaRoche's mingetty program, which is used issue the login prompt on virtual consoles in most Linux distributions. These changes allow a user to be automatically logged onto the console terminal as soon as the system boots. I got the idea for this patch after reading about a similar feature provided on SGI's Irix operating system.

Here's the description of the autologin feature that I've added to the mingetty.8 man page:

--autologin username Log the specified user onto the console (normally /dev/tty1) when the system is first booted without prompting for a username or password.

When the autologin option is supplied, mingetty will check that the controlling terminal is the console (normally /dev/tty1), that a reasonable username has been supplied, and that this is the first autologin request since the system has booted. If all of these conditions have been met, a request for an unauthenticated login is passed to the login program. Otherwise, a normal interactive login is performed.

The login program may deny the request for an unau- thenticated login. Typically this will happen when the user is root, has a UID of 0, or whenever a normal interactive login would be denied due to the access restrictions specified in the nologin, usertty, or securetty files.

Only a single autologin request will be issued after a system boot. If the automated login request is denied, or if the user logs out, mingetty will revert to performing normal interac- tive logins for all subsequent login requests.

I've placed unified diffs against the mingetty-0.9.4 version of mingetty.c and mingetty.8 on my web page at http://www5.jagunet.com/~kodis/. The patched version of mingetty logs me in on the first virtual console when my computer first boots, while leaving all the normal Unix security measures in effect for all but this one specific console login.

To use this patch, you'll have to first obtain the sources for the mingetty program, preferably with any patches used in your Linux distribution. After applying the patch file from my web page, you will have to rebuild the mingetty program, and install it and the patched mingetty.8 man page in the appropriate directories after saving the original versions.

The inittab entry for the first VC will then have to be modified to put the autologin feature into effect. In my /etc/inittab file, this line now reads:

    1:12345:respawn:/sbin/mingetty --noclear --autologin kodis tty1
Rebooting after making these changes will insure that init has spawned the new version of mingetty, and if all is well, will automatically log you on to the console.

Since I normally use X whenever I'm logged in at the console, I've added the following few lines of code to my .zlogin and .bash_profile scripts. This code queries "Start X [Yn]? " when initially logged in from the first virtual console, and waits 10 seconds for a response. Entering Y or allowing the timeout to occur results in X being started. On exiting X, a similar timed query asking "Log out [Yn]? " is issued, giving the option of logging out or being dropped into a text console.

case `tty` in 
        echo -n "Start X [Yn]? "
        expect \
	    -c 'stty raw' \
	    -c 'set timeout 10' \
	    -c 'expect -nocase n {exit 1} -re . {exit 0}'
        if [ $? = 0 ] ; then
            echo -n "Log out [Yn]? "
            expect \
	        -c 'stty raw' \
	        -c 'set timeout 10' \
	        -c 'expect -nocase n {exit 1} -re . {exit 0}'
	    if [ $? = 0 ] ; then
These few changes combine to make getting logged on and running X on a Linux box as easy as turning the power on. Here's hoping that this proves useful for Mr. Blake and any of your other readers who find themselves in this situation.

Copyright © 1998, John Kodis
Published in Issue 27 of Linux Gazette, April 1998