Clean Core

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Revision as of 18:08, 12 June 2008 by Langstonius (Talk | contribs)

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Introduction

This page is meant to document the efforts to turn the LinuxMCE core into one or more Linux "services" that are automaticly started at boot time. In other words we would like to be able to boot a dedicated LinuxMCE Core server without using the Launch Manager application and without the dependency upon a graphic environment.

Please don't be shy to add any related knowledge you have.

Runlevels

Runlevels are an easy way to change how the system boots. LinuxMCE (as Kubuntu) uses runlevel 2 for normal operation (depending on the selections you made during installation) and runlevel 1 is used for rescue mode. The runlevels 0 and 6 are used for doing a shutdown or a reboot. Which leaves the runlevels 3, 4 and 5 free for us to experiment with.

As an example we will be setting up the following scheme in this document:

  1. rescue (as it is now)
  2. KDE (as installed by Kubuntu, like mainly-PC is now)
  3. Core (as in textmode, ideal for headless systems)
  4. Core + KDE (best of both worlds)
  5. LaunchManager (as the classic dedicated-MC setup is now)

Of course you can just adapt the example to your specific wishes or needs.

Starting another runlevel

If you just want to start a different runlevel once without modifying your startup scripts to much (as described below) You can simply boot into rescue mode by pressing [Esc] if grub tells you to and selecting it from the boot menu. That should boot up to a text console in single user mode, from there you can easily switch to another runlevel, for example runlevel 3: 

telinit 3

The "runlevel" command will show you the previous and current runlevel.

Setting up the runlevels

Traditionally the runlevels are controlled by manipulating a set of "symbolic links" in the /etc/rcX.d/ directory, where X is the runlevel (0-6,S), however the Kubuntu system uses upstart, which has other ways as well.

When you are done with this you can switch to a different runlevel using one of the methods described elsewhere in this document, be sure to reboot in order to make a clean start.

Before starting it is always wise to make a backup of a few things, just in case: 

tar cjvf ~/backup-`date '+%Y%m%d:%H%M'`.tar.bz2 /etc/init.d /etc/rc*.d

Preparation

Here are additional scripts needed to start the core devices, normally these task are performed by the launch-manager and it's startup script.

First a script for init (upstart): 

cd /
cat >etc/init.d/core <<"EOF"
#!/bin/sh

case "$1" in
        start)
                /usr/pluto/bin/startCore.sh
                ;;
        stop)

                /usr/pluto/bin/StopCoreServices.sh
                ;;

        *)
                echo "Usage: /etc/init.d/core {start|stop}"
                exit 1
                ;;
esac

exit 0
EOF
chmod +x etc/init.d/core

Which calls a script that determines the device number of the core device: 

cd /
cat >usr/pluto/bin/startCore.sh <<"EOF"
#!/bin/sh

BASEDIR=/usr/pluto/bin
DeviceTemplate_Core=7

source $BASEDIR/SQL_Ops.sh

$BASEDIR/Config_Device_Changes.sh
$BASEDIR/Start_OrbiterGen.sh
$BASEDIR/UpdateMediaDaemonControl.sh -enable

$BASEDIR/Start_DCERouter.sh


QUERY="SELECT PK_Device FROM Device JOIN DeviceTemplate ON Device.FK_DeviceTemplate=DeviceTemplate.PK_DeviceTemplate WHERE PK_DeviceTemplate=${DeviceTemplate_Core}"
RESULT=$(RunSQL "$QUERY")
for ROW in $RESULT
do
        CoreDev=$(Field 1 "$ROW")
        $BASEDIR/startDevices.sh $CoreDev
done

EOF
chmod +x usr/pluto/bin/startCore.sh

And in turn calls this script to start the whole device family, excluding any media directors: 

cd /
cat >usr/pluto/bin/startDevices.sh <<"EOF"
#!/bin/sh


BASEDIR=/usr/pluto/bin
DeviceTemplate_MeDi=28

source $BASEDIR/SQL_Ops.sh


DEVICES=$*


for DEVICE in $DEVICES
do


       QUERY="SELECT ImplementsDCE, IsPlugin, Disabled, IF(PK_DeviceTemplate=${DeviceTemplate_MeDi},1,0) AS IsMeDi, REPLACE(DeviceTemplate.Description,' ','_') AS Description, CommandLine FROM Device JOIN DeviceTemplate ON Device.FK_DeviceTemplate=DeviceTemplate.PK_DeviceTemplate WHERE PK_Device=${DEVICE}"

       RESULT=$(RunSQL "$QUERY")
       for ROW in $RESULT
       do
               IMPLEMENTSDCE=$(Field 1 "$ROW")
               ISPLUGIN=$(Field 2 "$ROW")
               DISABLED=$(Field 3 "$ROW")
               ISMEDI=$(Field 4 "$ROW")
               DESCRIPTION=$(Field 5 "$ROW")
               COMMANDLINE=$(Field 6 "$ROW")

#              echo $RESULT, $IMPLEMENTSDCE $ISPLUGIN $DISABLED $ISMEDI $DESCRIPTION \"$COMMANDLINE\"

               if [ "$ISMEDI" != "0" ]
               then
                       echo "Device $DEVICE ($DESCRIPTION) is a Media Director"
                       continue
               fi



               if [ "$IMPLEMENTSDCE" = "0" ]
               then

                       echo "Device $DEVICE ($DESCRIPTION) no DCE, going after the children"

                       CHILDREN=""
                       QUERY="SELECT PK_Device FROM Device WHERE FK_Device_ControlledVia=$DEVICE"
                       RESULT=$(RunSQL "$QUERY")
                       for ROW in $RESULT
                       do
                               CHILD=$(Field 1 "$ROW")
                               CHILDREN="$CHILDREN $CHILD"
                       done


                       if [ "$CHILDREN" ]
                       then

                               $0 $CHILDREN
                       else
                               echo "Device $DEVICE ($DESCRIPTION) has no children"
                       fi

               else

                       if [ "$ISPLUGIN" = "0" ]
                       then

                               if [ "$DISABLED" = "0" ]
                               then

                                       if [ -z "$COMMANDLINE" ]
                                       then
                                               COMMANDLINE=$DESCRIPTION
                                       fi

                                       if [ -x "$BASEDIR/${COMMANDLINE}" ]
                                       then

#                                               echo "/usr/bin/screen -d -m -S ${DESCRIPTION}-${DEVICE} $BASEDIR/Spawn_Device.sh ${DEVICE} ${DCERouter} ${COMMANDLINE}"
                                               /usr/bin/screen -d -m -S ${DESCRIPTION}-${DEVICE} $BASEDIR/Spawn_Device.sh ${DEVICE} ${DCERouter} ${COMMANDLINE}
                                               echo "Device $DEVICE ($DESCRIPTION) started  ${COMMANDLINE}"

                                       else
                                               echo "Device $DEVICE ($DESCRIPTION) unable to start ${COMMANDLINE}"
                                       fi



                               else
                                       echo "Device $DEVICE ($DESCRIPTION) is disabled"
                               fi


                       else
                               echo "Device $DEVICE ($DESCRIPTION) is a plugin"
                       fi

               fi

       done

done

EOF
chmod +x usr/pluto/bin/startDevices.sh
On a Mainly Personal Computer installation

If you chose this install type you will need to create an extra startup script. In other words: when your core machine starts up with a KDE desktop. Here is a slightly simplified version of the one included in the "Dedicated Media Center" install type: 

cd /
cat >etc/init.d/launch-manager <<"EOF"
#!/bin/sh
if [ "$1" == "start" ]
then
        /usr/pluto/bin/Startup_Core-Hybrid.sh
fi

EOF
chmod +x etc/init.d/launch-manager
On a Dedicated Media Center installation

To make things a little bit easier for ourselves we're going to move a few things around a bit, this should give us about the same starting point as when using a "Mainly Personal Computer" setup. Do this if your core machine normally starts up with the launch manager: 

cd /
mv -iv etc/init.d/kdm etc/init.d/launch-manager
cp -iv etc/init.d/kdm.saved etc/init.d/kdm

Changing the symlinks

In order to make the system boot only the core in runlevel 3, simply copy the symlinks of runlevel 2 and replace the ones that start KDE and the AVWizard with a symlink to the init script we created earlier during the preparations: 

cd /
rm -rfv etc/rc3.d/*
cp -av etc/rc2.d/* etc/rc3.d/
ln -sfv ../init.d/core etc/rc3.d/S99core
rm -fv etc/rc3.d/S99kdm etc/rc3.d/S990start_avwizard

Making the system boot the core + KDE in runlevel 4 is even simpeler as we don't even have to remove the symlinks: 

cd /
rm -rfv etc/rc4.d/*
cp -av etc/rc2.d/* etc/rc4.d/
ln -sfv ../init.d/core etc/rc4.d/S99core

Starting the launchmanager in runlevel 5: 

cd /
rm -rfv etc/rc5.d/*
cp -av etc/rc2.d/* etc/rc5.d/
ln -sfv ../init.d/launch-manager etc/rc5.d/S99launch-manager
rm -fv etc/rc5.d/S99kdm

Additional upstart files to modify

You can edit these with your favorite text editor. In this example they are changed to start in runlevels 3-5 as well.

/etc/event.d/media-center-startup 

start on runlevel 2
start on runlevel 3
start on runlevel 4
start on runlevel 5

stop on shutdown

script
/usr/pluto/bin/startup-script.sh
end script

/etc/event.d/pluto-dhcpd-plugin 

start on runlevel 2
start on runlevel 3
start on runlevel 4
start on runlevel 5

stop on shutdown

script
screen -d -m -S DhcpdPlugin /usr/pluto/bin/Dhcpd-Plugin.sh
end script

On a sidenote: /etc/event.d/pluto-dhcpd-plugin seems redundant as it appears to be started from /usr/pluto/bin/startup-script.sh as well.

Changing the default runlevel

The default runlevel is 2, unless specified otherwise in the /etc/inittab file, here is an example on how to create such a file (it will override an existing one): 

cd /
cat >etc/inittab <<"EOF"
# WARNING: Do NOT set the default runlevel to 0 (shutdown) or 6 (reboot).
id:2:initdefault: # KDE
#id:3:initdefault: # Core
#id:4:initdefault: # Core + KDE
#id:5:initdefault: # Launch Manager
EOF

This specifies a default runlevel 2 (which it already was without this file anyway), you can use your favorite text editor to edit it to your desire when you permanently want to switch.

Note that the runlevel= options specified in the grub menu override this, at least if you have updated the /etc/event.d/rc-default file as described below.

Selecting a runlevel at boot time

This is a convenient way to experiment by simply selecting an alternative target from the boot-menu. If it doesn't work out you can always simply reboot to another runlevel.

First we need to replace one of upstart's files, /etc/event.d/rc-default. (It wasn't a big addition, but I didn't like the inconsistent way it was written originally, so I just cleaned it up a bit.) 

cd /
cat >etc/event.d/rc-default <<"EOF"
# rc - runlevel compatibility
#
# This task guesses what the "default runlevel" should be and starts the
# appropriate script.

start on stopped rcS

script
        runlevel --reboot || true


        if grep -q -w -- "-s\|single\|S" /proc/cmdline
        then
                RL="S"
        else
                RL="$(sed -n -e "s/.*runlevel=\([1-5]\).*/\1/p" /proc/cmdline || true)"
        fi

        if [ -z "$RL" -a -r /etc/inittab ]
        then
                RL="$(sed -n -e 's/^id:\([1-5]\):initdefault:.*/\1/p' /etc/inittab || true)"
        fi

        if [ -z "$RL" ]
        then
                RL="2"
        fi

        telinit $RL

end script
EOF

Now edit /boot/grub/menu.lst with your favorite text editor as follows:

Comment out the "hiddenmenu" option as follows (this will show you the boot menu without having to press [Esc]): 

## hiddenmenu   
# Hides the menu by default (press ESC to see the menu)
#hiddenmenu

Copy the first boot target once for every runlevel you want to be able to start, and modify it to look something like this: 

title           LMCE 1.1 (0704) KDE
root            (hd#,#)
kernel          /boot/vmlinuz-2.6.20-15-generic root=UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx ro quiet splash runlevel=2
initrd          /boot/initrd.img-2.6.20-15-generic
quiet
savedefault

title           LMCE 1.1 (0704) Core
root            (hd#,#)
kernel          /boot/vmlinuz-2.6.20-15-generic root=UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx ro quiet splash runlevel=3
initrd          /boot/initrd.img-2.6.20-15-generic
quiet
savedefault

title           Ubuntu, kernel 2.6.20-15-generic
root            (hd#,#)
kernel          /boot/vmlinuz-2.6.20-15-generic root=UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx ro quiet splash 
initrd          /boot/initrd.img-2.6.20-15-generic
quiet
savedefault

The last one is the original boot target, this will start whatever runlevel is set as the default (or runlevel 2 if none specified in /etc/inittab). It shouldn't take to much imagination to add targets for runlevels 4 and 5 as well.

You can also remove the quiet splash part if you want to see what is going on during boot.

Another section of interest could be: 

## default num
# Set the default entry to the entry number NUM. Numbering starts from 0, and
# the entry number 0 is the default if the command is not used.
#
# You can specify 'saved' instead of a number. In this case, the default entry
# is the entry saved with the command 'savedefault'.
# WARNING: If you are using dmraid do not change this entry to 'saved' or your
# array will desync and will not let you boot your system.
default         0

Personal experience

Moved to the discussion/talk page.

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