xserver-nodm-init: Use useradd to add the xuser for rootless X

This also address an issue with dbus and connman, since connmand
needs to start as the xuser in the rootless X situation.

Fixes: [YOCTO #1699]

(From OE-Core rev: 6823a32035de5d0bcd82a3b41a6ad536aaddbc58)

(From OE-Core rev: 26573a84583793f64979100c2b89a95146d38dd1)

Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-graphics/x11-common/xserver-nodm-init.bb

@@ -2,7 +2,7 @@ DESCRIPTION = "Simple Xserver Init Script (no dm)"
 LICENSE = "GPLv2"
 LIC_FILES_CHKSUM = "file://COPYING;md5=751419260aa954499f7abaabaa882bbe"
 SECTION = "x11"
-PR = "r26"
+PR = "r28"
 RDEPENDS_${PN} = "sudo"
 
 SRC_URI = "file://xserver-nodm \
@@ -23,23 +23,15 @@ do_install() {
     fi
 }
 
-pkg_postinst_${PN} () {
-    if [ "x$D" != "x" ] ; then
-        exit 1
-    fi
-
-    if [ -f /etc/X11/Xusername ]; then
-        # create the rootless X user, and add user to group tty, video, audio
-        username=`cat /etc/X11/Xusername`
-        adduser --disabled-password $username
-        # FIXME: use addgroup if busybox addgroup is ready
-        sed -i -e "s/^video:.*/&${username}/g" /etc/group
-        sed -i -e "s/^tty:.*/&${username}/g" /etc/group
-        sed -i -e "s/^audio:.*/&${username}/g" /etc/group
-    fi
-}
-
-inherit update-rc.d
+inherit update-rc.d useradd
 
 INITSCRIPT_NAME = "xserver-nodm"
 INITSCRIPT_PARAMS = "start 9 5 2 . stop 20 0 1 6 ."
+
+# Use fixed Xusername of xuser for now, this will need to be
+# fixed if the Xusername changes from xuser
+USERADD_PACKAGES = "${PN}"
+USERADD_PARAM_${PN} = "--system --no-create-home \
+                       --shell /bin/false --groups video,tty,audio \
+                       --user-group xuser"
+