[mythtv-users] FW: mythDVD playback problem

[Michael T. Dean]

Sperlongano Brian M NPRI wrote:

>1.) Power up the box.  "X" and "mythfrontend" are started via a respawn
>entry in my /etc/inittab
>  
>
Which means that you're not logging in to the myth box (i.e. 
/etc/profile, ~/.bash_profile, ~/.bash_login, and ~/.profile are not 
executed or whichever file(s) your shell uses).  Therefore, your 
environment is not properly configured (you get a PATH of 
/usr/local/sbin:/sbin:/bin:/usr/sbin:/usr/bin and no DISPLAY, etc.).  As 
a matter of fact you're probably not even running a shell (although it 
would be possible to have inittab start a shell that starts X, etc.).

>2.) Choose "Play DVD" command in mythtTV.  xine starts up, switches to
>full-screen black, X cursor appears for a second, then immediately
>returns to mythTV DVD menu.
>  
>
Probably giving the error "Cannot open display" or "command not found."  
You can find out by logging xine's output.  Use something like the 
following for your MythDVD playback command:

xine --no-splash -fg --auto-play --auto-scan dvd > /tmp/xine.log 2>&1

>3.) Press Alt+F1.  Login.  Type: export DISPLAY="localhost:0.0".  Run
>xine command (same as specified in DVD setup in mythTV).  Press Alt+F7
>(to go back to X).  DVD (audio AND video) are playing perfectly.
>  
>
Here you've logged in, so the environment is properly configured, and 
you have a proper shell running beneath xine.

So, to fix the problem, just make sure you log someone in (i.e. a user 
mythtv), who then automatically starts X which then automatically starts 
mythfrontend.  You can do this using GDM (as described in Jarod's guide 
http://www.wilsonet.com/mythtv/fcmyth.php#auto ) or KDM.

Or, if--like me--you don't want GNOME or KDE (and their multitudes of 
libraries) installed on your Myth box (which seems to be the case since 
you were trying to auto-start using inittab), write your own auto-login 
facility.  You can do so using the instructions at 
http://www.linuxgazette.com/issue72/chung.html .

I wanted a bit more control over the process (and error logging and 
fallback to (non-auto) login if an error occurs (instead of spawning 
millions of runaway autologin instances until init disabled the 
respawn)), so I modified the 1-line program Adrian Chung used (see 
attached).  The program can be compiled with:
gcc -o autologin autologin.c

There are several  places where my autologin could be improved, so if 
you add to it, please let me know.  :)  Also, there are several security 
weaknesses (and possibly some security holes), but, then again, 
autologin itself is a security weakness...

Mike


Using my program, the relevant line from /etc/inittab is (notice that, 
unlike with Adrian Chung's program, the username is not specified here):
1:2345:respawn:/sbin/agetty -n -l /bin/autologin tty1 9600


In my /etc/autologin, I put a single line with the username of the user 
who should automatically log in.  (Make sure this line is 
readable/writable only by root (i.e. chmod 600 /etc/autologin):
mythtv


In my mythtv user's ~/.bash_profile:
# If logging in on /dev/tty1, start X
if [ -z "$DISPLAY" ] && [ $(tty) == /dev/tty1 ]; then
  startx
fi


In my mythtv user's ~/.xinitrc (after taking care of other 
housekeeping--i.e. X resources, keyboard mappings, mouse acceleration 
and threshold, etc.):
# Start the window manager (change WM name as appropriate)
fluxbox & wmpid=$!

mythfrontend > /home/mythtv/logs/mythfrontend.log 2>&1

# Wait for the window manager to exit
# Comment out if you want X to exit when mythfrontend exits
#wait $wmpid

-------------- next part --------------
/*
 * $Header$
 * $Revision$
 * $Date$
 *
 * autologin
 *
 * Copyright 2004, Michael T. Dean
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

/* Location of commands/files used by autologin. */
const char* AUTOLOGIN="autologin";
const char* LOGIN_CMD="login";
const char* LOGIN_PREAUTH_ARG="-f";
const char* LOGGER_CMD="logger";
const char* AUTOLOGIN_FILE="/etc/autologin";

void login();
void autologin(const char* username);
void log_message(const char* message, int len);

int main() {
  FILE *file;
  char file_data[100];
  char username[100];

  /*
   *  Check to see if autologin is enabled.
   *  The existence of the file AUTOLOGIN_FILE indicates that we should
   *  proceed with autologin.
   */
  if(access(AUTOLOGIN_FILE, F_OK) == -1) {
    /*
     *  Autologin is disabled.  Call login without arguments.
     */
    login();
  } else {
    /*
     *  Proceed with autologin.
     *  Read the first line from the AUTOLOGIN_FILE and parse the first
     *  token (up to 99 characters) for use as the username.
     */
    if ((file = fopen(AUTOLOGIN_FILE, "r")) == NULL) {
      /* File could not be opened. Fall back to login. */
      login();
    } else {
      if (fgets(file_data, 99, file) == NULL) {
        /* File could not be read or contained no data. Fall back to login. */
        fclose(file);
        login();
      } else {
        fclose(file);
        /*
         *  Limit the allowable characters in the username to alphanumerics
         *  to try to prevent hijacking the execlp.  Any disallowed characters
         *  are truncated.
         */
        sscanf(file_data, "%[A-Za-z0-9]%*", username);
        autologin(username);
      }
    }
  }
}

void login() {
  execlp(LOGIN_CMD, LOGIN_CMD, NULL);
  /* If execlp returns, an error has occurred.*/
  char message[500];
  sprintf((char *)message, "autologin: \'%s\' failed.\n", LOGIN_CMD);
  log_message((char *)message, 500);
  sprintf((char *)message, "autologin: %s\n", strerror(errno));
  log_message((char *)message, 500);
}

void autologin(const char *username) {
  if (strnlen(username,99)) {
    execlp(LOGIN_CMD, LOGIN_CMD, LOGIN_PREAUTH_ARG, username, NULL);
    /* If execlp returns, an error has occurred.*/
    char message[500];
    sprintf((char *)message, "autologin: \'%s %s %s\' failed.\n",
            LOGIN_CMD, LOGIN_PREAUTH_ARG, username);
    log_message((char *)message, 500);
    sprintf((char *)message, "autologin: %s\n", strerror(errno));
    log_message((char *)message, 500);
  }
  /*
   *  No username specified or execlp for autologin returned.
   *  Fall back to login.
   */
  login();
}

void log_message(const char *message, int len) {
  char logcmd[300 + strnlen(message, len)];
  sprintf((char *)logcmd, "%s \"%s\"", LOGGER_CMD, message);
  system(logcmd);
}