add ubuntu-init-switch module for testing systemd.

The module is useful primarily for testing in Ubuntu's transition to systemd.
It should be very harmless elsewhere as it defaults to doing nothing,
and will only run if configured as 'ubuntu' distro *and* 'dpkg' is available.

3 files changed, 152 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 3ec4eb1a..296a15cd 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -15,6 +15,7 @@
    [Dimitri John Ledkov]
  - SeLinuxGuard: remove invalid check that looked for stat.st_mode in os.lstat.
  - do not write comments in /etc/timezone (LP: #1341710)
+ - ubuntu: provide 'ubuntu-init-switch' module to aid in systemd testing.
 0.7.5:
  - open 0.7.5
  - Add a debug log message around import failures
diff --git a/cloudinit/config/cc_ubuntu_init_switch.py b/cloudinit/config/cc_ubuntu_init_switch.py
new file mode 100644
index 00000000..485c46a4
--- /dev/null
+++ b/cloudinit/config/cc_ubuntu_init_switch.py
@@ -0,0 +1,150 @@
+# vi: ts=4 expandtab
+#
+#    Copyright (C) 2014 Canonical Ltd.
+#
+#    Author: Scott Moser <scott.moser@canonical.com>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License version 3, as
+#    published by the Free Software Foundation.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""
+ubuntu_init_switch: reboot system into another init
+
+This provides a way for the user to boot with systemd even if the
+image is set to boot with upstart.  It should be run as one of the first
+cloud_init_modules, and will switch the init system and then issue a reboot.
+The next boot will come up in the target init system and no action will
+be taken.
+
+This should be inert on non-ubuntu systems, and also exit quickly.
+
+config is comes under the top level 'init_switch' dictionary.
+
+#cloud-config
+init_switch:
+ target: systemd
+
+'target' can be 'systemd' or 'upstart'.  Best effort is made, but its possible
+this system will break, and probably won't interact well with any other
+mechanism you've used to switch the init system.
+"""
+
+from cloudinit.settings import PER_INSTANCE
+from cloudinit import log as logging
+from cloudinit import util
+from cloudinit.distros import ubuntu
+
+import os
+import time
+
+frequency = PER_INSTANCE
+REBOOT_CMD = ["/sbin/reboot"]
+
+DEFAULT_CONFIG = {
+    'init_switch': {'target': None}
+}
+
+SWITCH_INIT = """
+#!/bin/sh
+# switch_init: [upstart | systemd]
+
+is_systemd() {
+   [ "$(dpkg-divert --listpackage /sbin/init)" = "systemd-sysv" ]
+}
+debug() { echo "$@" 1>&2; }
+fail() { echo "$@" 1>&2; exit 1; }
+
+if [ "$1" = "systemd" ]; then
+   if is_systemd; then
+      debug "already systemd, nothing to do"
+   else
+      [ -f /lib/systemd/systemd ] || fail "no systemd available";
+      dpkg-divert --package systemd-sysv --divert /sbin/init.diverted \\
+          --rename /sbin/init
+   fi
+   [ -f /sbin/init ] || ln /lib/systemd/systemd /sbin/init
+elif [ "$1" = "upstart" ]; then
+   if is_systemd; then
+      rm -f /sbin/init
+      dpkg-divert --package systemd-sysv --rename --remove /sbin/init
+   else
+      debug "already upstart, nothing to do."
+   fi
+else
+  fail "Error. expect 'upstart' or 'systemd'"
+fi
+"""
+
+
+def handle(name, cfg, cloud, log, args):
+
+    if not isinstance(cloud.distro, ubuntu.Distro):
+        log.debug("%s: distro is '%s', not ubuntu. returning",
+                  name, cloud.distro.__class__)
+        return
+
+    cfg = util.mergemanydict([cfg, DEFAULT_CONFIG])
+    target = cfg['init_switch']['target']
+
+    if len(args) != 0:
+        target = args[0]
+
+    if not target:
+        log.debug("%s: target=%s. nothing to do", name, target)
+        return
+
+    if not util.which('dpkg'):
+        log.warn("%s: 'dpkg' not available. Assuming not ubuntu", name)
+        return
+
+    supported = ('upstart', 'systemd')
+    if target not in supported:
+        log.warn("%s: target set to %s, expected one of: %s",
+                 name, target, str(supported))
+
+    if os.path.exists("/run/systemd"):
+        current = "systemd"
+    else:
+        current = "upstart"
+
+    if current == target:
+        log.debug("%s: current = target = %s. nothing to do", name, target)
+        return
+
+    try:
+        util.subp(['sh', '-c', SWITCH_INIT, '--', target])
+    except util.ProcessExecutionError as e:
+        log.warn("%s: Failed to switch to init '%s'. %s", name, target, e)
+        return
+
+    try:
+        log.warn("%s: rebooting from '%s' to '%s'", name, current, target)
+        logging.flushLoggers(log)
+        _fire_reboot(log, initial_sleep=4)
+    except Exception as e:
+        util.logexc(log, "Requested reboot did not happen!")
+        raise
+
+
+def _fire_reboot(log, wait_attempts=6, initial_sleep=1, backoff=2):
+    util.subp(REBOOT_CMD)
+    start = time.time()
+    wait_time = initial_sleep
+    for _i in range(0, wait_attempts):
+        time.sleep(wait_time)
+        wait_time *= backoff
+        elapsed = time.time() - start
+        log.debug("Rebooted, but still running after %s seconds", int(elapsed))
+    # If we got here, not good
+    elapsed = time.time() - start
+    raise RuntimeError(("Reboot did not happen"
+                        " after %s seconds!") % (int(elapsed)))
diff --git a/config/cloud.cfg b/config/cloud.cfg
index b746e3db..200050d3 100644
--- a/config/cloud.cfg
+++ b/config/cloud.cfg
@@ -24,6 +24,7 @@ preserve_hostname: false
 # The modules that run in the 'init' stage
 cloud_init_modules:
  - migrator
+ - ubuntu-init-switch
  - seed_random
  - bootcmd
  - write-files