ubuntu 18.04.3 下安装启动VNC出现如下报错，
metacity-Message: 11:03:20.252: could not find XKB extension.
(metacity:9643): metacity-WARNING **: 11:03:20.256: Failed to create MetaCompositorXRender: Missing composite extension required for compositing
** (gnome-panel:9641): WARNING **: 11:03:20.291: Failed to register client: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.SessionManager was not provided by any .service files
** (gnome-panel:9641): WARNING **: 11:03:20.317: Error opening directory “/usr/share/gnome-panel/applets”: No such file or directory
** (nautilus:9644): WARNING **: 11:03:20.774: Unable to get contents of the bookmarks file: Error opening file /root/.gtk-bookmarks: Is a directory
** (nautilus:9644): WARNING **: 11:03:20.774: Unable to get contents of the bookmarks file: Error opening file /root/.gtk-bookmarks: Is a directory
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