From EECS

Some notes on UML setup on fruit

We have been using kernel version 2.6.11.6-skas3-v8 for the host. The guests used kernel versions 2.6.11.11 or 2.4.27.

The guest UMls were chroot-ed and chuid-ed to make the setup more secure. The conosole of a UML guest was put into a (detached) screen session. This could then be easily re-attached if one needed access the UM console (i.e. in case network broke down).

The init.d script to start/stop uml looked as follows:

set -e

PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
UML="kiwi"
DESC="uml $UML"
NAME="uml-$UML"
#DAEMON=/usr/bin/linux
#DAEMON=/usr/bin/linux-2.4.27
DAEMON=/linux
#DAEMON=/usr/bin/linux-2.6.10
PIDFILE=/var/run/$NAME.pid
SCRIPTNAME=/etc/init.d/$NAME
CHROOT=/uml/$UML
#DAEMON=$CHROOT/linux

# Gracefully exit if the package has been removed.
#test -x $DAEMON || exit 0
#test -x $CHROOT/$DAEMON || exit 0

# Read config file if it is present.
if [ -r /etc/default/$NAME ]
then
       . /etc/default/$NAME
fi

# using uml_switch daemon
#OPTIONS="umid=$UML eth0=daemon,,unix,/var/run/uml-utilities/uml_switch.ctl con0=tty:$TTY ubd0=/uml/$UML/root_fs uml_dir=/tmp/uml"
OPTIONS="umid=$UML uml_dir=/tmp eth0=daemon,,unix,/var/uml_switch.ctl ubd0=/root.ext2 mem=32M"

# using tap0 directly
#OPTIONS="umid=peach eth0=tuntap,tap0 con0=tty:$TTY ubd0=/uml/$UML/root_fs"

#
#      Function that starts the daemon/service.
#
d_start() {
       mount -o bind /proc/mm $CHROOT/proc/mm
       mount --bind /var/run/uml-utilities/ $CHROOT/var/
       mkdir -p /tmp/uml
       chmod 770 /tmp/uml
       chown root:uml /tmp/uml
       screen -d -m -S $UML \
               compartment --user $UML --group uml \
                       --chroot $CHROOT \
                       $DAEMON $OPTIONS
}

#
#      Function that stops the daemon/service.
#
d_stop() {
#      start-stop-daemon --stop --quiet --pidfile $PIDFILE \
#              --name $NAME
#      compartment --user orange --group uml \
#              --chroot $CHROOT \
       uml_mconsole /uml/$UML/tmp/$UML/mconsole cad
       echo -n " waiting for uml to halt..."
       sleep 15
       umount $CHROOT/proc/mm
       umount $CHROOT/var/
}

#
#      Function that sends a SIGHUP to the daemon/service.
#
d_reload() {
       start-stop-daemon --stop --quiet --pidfile $PIDFILE \
               --name $NAME --signal 1
}

case "$1" in
  start)
       echo -n "Starting $DESC: $NAME"
       d_start
       echo "."
       ;;
  single)
       echo -n "Starting $DESC: $NAME (single user)"
       OPTIONS="$OPTIONS single"
       d_start
       echo "."
       ;;
  stop)
       echo -n "Stopping $DESC: $NAME"
       d_stop
       echo "."
       ;;
  #reload)
       #
       #       If the daemon can reload its configuration without
       #       restarting (for example, when it is sent a SIGHUP),
       #       then implement that here.
       #
       #       If the daemon responds to changes in its config file
       #       directly anyway, make this an "exit 0".
       #
       # echo -n "Reloading $DESC configuration..."
       # d_reload
       # echo "done."
  #;;
  restart|force-reload)
       #
       #       If the "reload" option is implemented, move the "force-reload"
       #       option to the "reload" entry above. If not, "force-reload" is
       #       just the same as "restart".
       #
       echo -n "Restarting $DESC: $NAME"
       d_stop
       sleep 1
       d_start
       echo "."
       ;;
  *)
       # echo "Usage: $SCRIPTNAME {start|stop|single|restart|reload|force-reload}" >&2
       echo "Usage: $SCRIPTNAME {start|stop|single|restart|force-reload}" >&2
       exit 1
       ;;
esac

exit 0

The networking was done by bridging eth0 with tap0, to which the UMls were attching. /etc/network/interfaces:

# The loopback network interface
auto lo
iface lo inet loopback

# tun/tap device for umls
auto tap0
iface tap0 inet static
    address 192.168.0.1
    netmask 255.255.255.0
    tunctl_user uml-net

# bridge for UMLs
auto br0
iface br0 inet static
    address 212.201.49.185
    netmask 255.255.254.0
    gateway 212.201.49.250
    bridge_ports eth0 tap0

iface br0 inet6 static
    address 2001:638:709:4::2
     netmask 64 

auto eth1
iface eth1 inet static
    address 192.168.1.67
    netmask 255.255.255.0

The following files/devices are needed in a UML chroot

uml-skeleton/
uml-skeleton/linux
uml-skeleton/proc/
uml-skeleton/proc/mm - I think this was a copy of the real file
uml-skeleton/proc/cpuinfo - this was a copy of the real file or a link (symlink) to the real /proc file
uml-skeleton/tmp/
uml-skeleton/dev/
uml-skeleton/dev/net/
uml-skeleton/dev/net/tun - character device with major 10, minor 200
uml-skeleton/var/
uml-skeleton/root.ext2