d/xen-utils-common.xen.init: multi-version comment

Having the init script in a -common package (of which the version is
installed that matches the newest installed versioned other xen
packages) means that it also has to be able to deal with older Xen
versions.

Add a little reminder of this fact, because this can be a bit of a
surprise if you didn't realize yet.

Signed-off-by: Hans van Kranenburg <hans@knorrie.org>

diff --git a/debian/xen-utils-common.xen.init b/debian/xen-utils-common.xen.init
index 05521733494ee8f7db1df5d35cc52ee4e926512c..54aaba89d320de9e510c821e7f3b44b9e8cd545f 100644 (file)
--- a/debian/xen-utils-common.xen.init
+++ b/debian/xen-utils-common.xen.init
@@ -9,6 +9,27 @@
 # Description:       Xen daemons
 ### END INIT INFO
 
+# Important notes to keep in mind when changing this script:
+#
+# * This init script is part of the xen-utils-common package.
+# * It is *not* called from xen-utils-common maintscripts, but from the
+#   xen-utils-V package maintscripts instead, and only if V is equal to the
+#   currently running version of Xen.
+# * The xen-utils-V package has a dependency on xen-utils-common >= V.
+# * So, while there can be multiple xen-utils-V packages installed, there is
+#   still only a single xen-utils-common package installed, which matches the
+#   newest installed Xen version.
+# * This means that this script has to be compatible with the other packages
+#   for any older Xen version that was available in the current and previous
+#   Debian release.
+#
+# Example scenarios in which this is needed:
+#
+# * After upgrading to a new Xen version, the new init script will already be
+#   used for shutting down the system before reboot.
+# * If the user encounters problems and reboots back into the old Xen version,
+#   this init script will also be used.
+
 . /lib/init/vars.sh
 . /lib/lsb/init-functions