#!/bin/sh
# Script to allow starting an X server inside an LXC container on ubuntu 16.04
# Run once OUTSIDE the container like this:
#   $0 host containername
# and once INSIDE the container like this:
#   $0 guest

# cf.
# http://unix.stackexchange.com/questions/18003/linux-lxc-deploying-images-with-tiniest-possible-x11
# https://mraw.org/blog/2011/04/05/Running_X_from_LXC/
# http://unix.stackexchange.com/questions/191289/docker-how-to-run-x-desktop-in-a-container
# https://github.com/ustuehler/lxc-desktop/blob/master/usr/share/lxc/hooks/desktop-autodev
# http://www.joshh.info/2016/01/running-x-server-inside-docker-container.html

set -x

do_host() {
    container=$1; shift

    # Pass the devices through
    tee -a /var/lib/lxc/$container/config <<_EOF_
# Added by install-x.sh
# Do not edit next line, the value of #use_x is sensed by bvslave-lxc.sh
#use_x=1
lxc.cgroup.devices.allow = c 4:9 rwm  # /dev/tty9 X Desktop
lxc.cgroup.devices.allow = c 10:63 rwm  # /dev/vga_arbiter
lxc.cgroup.devices.allow = c 13:* rwm  # /dev/input/* input devices
lxc.cgroup.devices.allow = c 29:0 rwm  # /dev/fb0
lxc.cgroup.devices.allow = c 226:0 rwm # /dev/dri/card0
lxc.cgroup.devices.allow = c 226:64 rwm # /dev/dri/controlD64
lxc.cgroup.devices.allow = c 226:128 rwm # /dev/dri/renderD128
# Proprietary drivers
lxc.cgroup.devices.allow = c 195:* rwm # /dev/nvidia Graphics card
_EOF_
}

do_guest() {
    # Create entries for the devices
    mknod -m 666 /dev/tty9 c 4 9
    mknod -m 666 /dev/vga_arbiter c 10 63
    mkdir -p /dev/input
    chmod 755 /dev/input
    mknod -m 666 /dev/input/mice c 13 63
    mknod -m 666 /dev/input/event0 c 13 64
    mknod -m 666 /dev/input/event1 c 13 65
    mknod -m 666 /dev/input/event2 c 13 66
    mknod -m 666 /dev/input/event3 c 13 67
    mknod -m 666 /dev/input/event4 c 13 68
    mknod -m 666 /dev/input/event5 c 13 69
    mknod -m 666 /dev/input/event6 c 13 70
    mknod -m 666 /dev/input/event7 c 13 71
    mknod -m 666 /dev/input/event8 c 13 72
    mknod -m 666 /dev/input/event9 c 13 73
    mknod -m 666 /dev/fb0 c 29 0
    mkdir -p /dev/dri
    chmod 755 /dev/dri
    mknod -m 666 /dev/dri/card0 c 226 0
    mknod -m 666 /dev/dri/controlD64 c 226 64
    mknod -m 666 /dev/dri/renderD128 c 226 128
    # Proprietary drivers
    mknod -m 666 /dev/nvidia0 c 195 0
    mknod -m 666 /dev/nvidiactl c 195 255

    set -e

    # Now install X... all the X.  Well, all the free X.
    apt-get install -y \
       pciutils \
       mesa-utils \
       xinit \
       xterm \
       xserver-xorg-input-evdev \
       xserver-xorg-video-intel-dbg \
       xserver-xorg-video-radeon-dbg \
       xserver-xorg-video-amdgpu-dbg \
       #

    if lspci | egrep -i "vga.*amd"
    then
        # On ati, we have to run X as root (so it can have at /proc/mtrr?), see
        # https://lists.linuxcontainers.org/pipermail/lxc-users/2016-September/012285.html
        # Setuid root xorg is still supported, but off to the side in xserver-xorg-legacy
        # So make sure that's installed, and
        # /etc/X11/Xwrapper.config is set to run X as root.
        if ! test -f /etc/X11/Xwrapper.config
        then
            sudo apt-get install -y xserver-xorg-legacy
        fi
        if ! grep "needs_root_rights = yes" /etc/X11/Xwrapper.config
        then
            cat > lines.txt.tmp <<_EOF_
allowed_users = anybody
needs_root_rights = yes
_EOF_
            sudo cat lines.txt.tmp >> /etc/X11/Xwrapper.config
        fi
    fi

    cat > /usr/share/X11/xorg.conf.d/10-lxc-input.conf <<_EOF_
Section "ServerFlags"
     Option "AutoAddDevices" "False"
EndSection
_EOF_

    (
     cd /dev/input
     for input in event*
     do
        cat >> /usr/share/X11/xorg.conf.d/10-lxc-input.conf <<_EOF_
Section "InputDevice"
    Identifier "$input"
    Option "Device" "/dev/input/$input"
    Option "AutoServerLayout" "true"
    Driver "evdev"
EndSection
_EOF_
    done
    )
    echo "Test mouse input with 'cat /dev/input/mice' to verify you get garbage when the mouse moves."

    echo "Then create ~/.xinitrc containing the line 'exec xterm'"
    echo "Then start X with 'startx -- vt9'"
    echo "See https://lists.linuxcontainers.org/pipermail/lxc-users/2011-April/001817.html for more tips."

    echo "Problem: for some reason, with radeon, starting X inside lxc fails with"
    echo "  Fatal server error: AddScreen/ScreenInit failed for driver 0"
    echo "Running startx as root works around this, but that's ugly."
}

case "$1" in
host) shift; lxcname=$1; shift; do_host $lxcname;;
guest) do_guest;;
*) echo "usage: $0 [host lxc-container-name|guest]"
esac