Synnefo » snf-ganeti » ganeti-local

News

====

Version 2.1.1

-------------

During the 2.1.0 long release candidate cycle, a lot of improvements and

changes have accumulated with were released later as 2.1.1.

Major changes

~~~~~~~~~~~~~

The node evacuate command (``gnt-node evacuate``) was significantly

rewritten, and as such the IAllocator protocol was changed - a new

request type has been added. This unfortunate change during a stable

series is designed to improve performance of node evacuations; on

clusters with more than about five nodes and which are well-balanced,

evacuation should proceed in parallel for all instances of the node

being evacuated. As such, any existing IAllocator scripts need to be

updated, otherwise the above command will fail due to the unknown

request. The provided "dumb" allocator has not been updated; but the

ganeti-htools package supports the new protocol since version 0.2.4.

Another important change is increased validation of node and instance

names. This might create problems in special cases, if invalid host

names are being used.

Also, a new layer of hypervisor parameters has been added, that sits at

OS level between the cluster defaults and the instance ones. This allows

customisation of virtualization parameters depending on the installed

OS. For example instances with OS 'X' may have a different KVM kernel

(or any other parameter) than the cluster defaults. This is intended to

help managing a multiple OSes on the same cluster, without manual

modification of each instance's parameters.

A tool for merging clusters, ``cluster-merge``, has been added in the

tools sub-directory.

Bug fixes

~~~~~~~~~

- Improved the int/float conversions that should make the code more

  robust in face of errors from the node daemons

- Fixed the remove node code in case of internal configuration errors

- Fixed the node daemon behaviour in face of inconsistent queue

  directory (e.g. read-only file-system where we can't open the files

  read-write, etc.)

- Fixed the behaviour of gnt-node modify for master candidate demotion;

  now it either aborts cleanly or, if given the new “auto_promote”

  parameter, will automatically promote other nodes as needed

- Fixed compatibility with (unreleased yet) Python 2.6.5 that would

  completely prevent Ganeti from working

- Fixed bug for instance export when not all disks were successfully

  exported

- Fixed behaviour of node add when the new node is slow in starting up

  the node daemon

- Fixed handling of signals in the LUXI client, which should improve

  behaviour of command-line scripts

- Added checks for invalid node/instance names in the configuration (now

  flagged during cluster verify)

- Fixed watcher behaviour for disk activation errors

- Fixed two potentially endless loops in http library, which led to the

  RAPI daemon hanging and consuming 100% CPU in some cases

- Fixed bug in RAPI daemon related to hashed passwords

- Fixed bug for unintended qemu-level bridging of multi-NIC KVM

  instances

- Enhanced compatibility with non-Debian OSes, but not using absolute

  path in some commands and allowing customisation of the ssh

  configuration directory

- Fixed possible future issue with new Python versions by abiding to the

  proper use of ``__slots__`` attribute on classes

- Added checks that should prevent directory traversal attacks

- Many documentation fixes based on feedback from users

New features

~~~~~~~~~~~~

- Added an “early_release” more for instance replace disks and node

  evacuate, where we release locks earlier and thus allow higher

  parallelism within the cluster

- Added watcher hooks, intended to allow the watcher to restart other

  daemons (e.g. from the ganeti-nbma project), but they can be used of

  course for any other purpose

- Added a compile-time disable for DRBD barriers, to increase

  performance if the administrator trusts the power supply or the

  storage system to not lose writes

- Added the option of using syslog for logging instead of, or in

  addition to, Ganeti's own log files

- Removed boot restriction for paravirtual NICs for KVM, recent versions

  can indeed boot from a paravirtual NIC

- Added a generic debug level for many operations; while this is not

  used widely yet, it allows one to pass the debug value all the way to

  the OS scripts

- Enhanced the hooks environment for instance moves (failovers,

  migrations) where the primary/secondary nodes changed during the

  operation, by adding {NEW,OLD}_{PRIMARY,SECONDARY} vars

- Enhanced data validations for many user-supplied values; one important

  item is the restrictions imposed on instance and node names, which

  might reject some (invalid) host names

- Add a configure-time option to disable file-based storage, if it's not

  needed; this allows greater security separation between the master

  node and the other nodes from the point of view of the inter-node RPC

  protocol

- Added user notification in interactive tools if job is waiting in the

  job queue or trying to acquire locks

- Added log messages when a job is waiting for locks

- Added filtering by node tags in instance operations which admit

  multiple instances (start, stop, reboot, reinstall)

- Added a new tool for cluster mergers, ``cluster-merge``

- Parameters from command line which are of the form ``a=b,c=d`` can now

  use backslash escapes to pass in values which contain commas,

  e.g. ``a=b\\c,d=e`` where the 'a' parameter would get the value

  ``b,c``

- For KVM, the instance name is the first parameter passed to KVM, so

  that it's more visible in the process list

Version 2.1.0

-------------

Ganeti 2.1 brings many improvements with it. Major changes:

- Added infrastructure to ease automated disk repairs

- Added new daemon to export configuration data in a cheaper way than

  using the remote API

- Instance NICs can now be routed instead of being associated with a

  networking bridge

- Improved job locking logic to reduce impact of jobs acquiring multiple

  locks waiting for other long-running jobs

In-depth implementation details can be found in the Ganeti 2.1 design

document.

Details

~~~~~~~

- Added chroot hypervisor

- Added more options to xen-hvm hypervisor (``kernel_path`` and

  ``device_model``)

- Added more options to xen-pvm hypervisor (``use_bootloader``,

  ``bootloader_path`` and ``bootloader_args``)

- Added the ``use_localtime`` option for the xen-hvm and kvm

  hypervisors, and the default value for this has changed to false (in

  2.0 xen-hvm always enabled it)

- Added luxi call to submit multiple jobs in one go

- Added cluster initialization option to not modify ``/etc/hosts``

  file on nodes

- Added network interface parameters

- Added dry run mode to some LUs

- Added RAPI resources:

  - ``/2/instances/[instance_name]/info``

  - ``/2/instances/[instance_name]/replace-disks``

  - ``/2/nodes/[node_name]/evacuate``

  - ``/2/nodes/[node_name]/migrate``

  - ``/2/nodes/[node_name]/role``

  - ``/2/nodes/[node_name]/storage``

  - ``/2/nodes/[node_name]/storage/modify``

  - ``/2/nodes/[node_name]/storage/repair``

- Added OpCodes to evacuate or migrate all instances on a node

- Added new command to list storage elements on nodes (``gnt-node

  list-storage``) and modify them (``gnt-node modify-storage``)

- Added new ssconf files with master candidate IP address

  (``ssconf_master_candidates_ips``), node primary IP address

  (``ssconf_node_primary_ips``) and node secondary IP address

  (``ssconf_node_secondary_ips``)

- Added ``ganeti-confd`` and a client library to query the Ganeti

  configuration via UDP

- Added ability to run hooks after cluster initialization and before

  cluster destruction

- Added automatic mode for disk replace (``gnt-instance replace-disks

  --auto``)

- Added ``gnt-instance recreate-disks`` to re-create (empty) disks

  after catastrophic data-loss

- Added ``gnt-node repair-storage`` command to repair damaged LVM volume

  groups

- Added ``gnt-instance move`` command to move instances

- Added ``gnt-cluster watcher`` command to control watcher

- Added ``gnt-node powercycle`` command to powercycle nodes

- Added new job status field ``lock_status``

- Added parseable error codes to cluster verification (``gnt-cluster

  verify --error-codes``) and made output less verbose (use

  ``--verbose`` to restore previous behaviour)

- Added UUIDs to the main config entities (cluster, nodes, instances)

- Added support for OS variants

- Added support for hashed passwords in the Ganeti remote API users file

  (``rapi_users``)

- Added option to specify maximum timeout on instance shutdown

- Added ``--no-ssh-init`` option to ``gnt-cluster init``

- Added new helper script to start and stop Ganeti daemons

  (``daemon-util``), with the intent to reduce the work necessary to

  adjust Ganeti for non-Debian distributions and to start/stop daemons

  from one place

- Added more unittests

- Fixed critical bug in ganeti-masterd startup

- Removed the configure-time ``kvm-migration-port`` parameter, this is

  now customisable at the cluster level for both the KVM and Xen

  hypervisors using the new ``migration_port`` parameter

- Pass ``INSTANCE_REINSTALL`` variable to OS installation script when

  reinstalling an instance

- Allowed ``@`` in tag names

- Migrated to Sphinx (http://sphinx.pocoo.org/) for documentation

- Many documentation updates

- Distribute hypervisor files on ``gnt-cluster redist-conf``

- ``gnt-instance reinstall`` can now reinstall multiple instances

- Updated many command line parameters

- Introduced new OS API version 15

- No longer support a default hypervisor

- Treat virtual LVs as inexistent

- Improved job locking logic to reduce lock contention

- Match instance and node names case insensitively

- Reimplemented bash completion script to be more complete

- Improved burnin

Version 2.0.6

-------------

- Fix cleaner behaviour on nodes not in a cluster (Debian bug 568105)

- Fix a string formatting bug

- Improve safety of the code in some error paths

- Improve data validation in the master of values returned from nodes

Version 2.0.5

-------------

- Fix security issue due to missing validation of iallocator names; this

  allows local and remote execution of arbitrary executables

- Fix failure of gnt-node list during instance removal

- Ship the RAPI documentation in the archive

Version 2.0.4

-------------

- Fixed many wrong messages

- Fixed a few bugs related to the locking library

- Fixed MAC checking at instance creation time

- Fixed a DRBD parsing bug related to gaps in /proc/drbd

- Fixed a few issues related to signal handling in both daemons and

  scripts

- Fixed the example startup script provided

- Fixed insserv dependencies in the example startup script (patch from

  Debian)

- Fixed handling of drained nodes in the iallocator framework

- Fixed handling of KERNEL_PATH parameter for xen-hvm (Debian bug

  #528618)

- Fixed error related to invalid job IDs in job polling

- Fixed job/opcode persistence on unclean master shutdown

- Fixed handling of partial job processing after unclean master

  shutdown

- Fixed error reporting from LUs, previously all errors were converted

  into execution errors

- Fixed error reporting from burnin

- Decreased significantly the memory usage of the job queue

- Optimised slightly multi-job submission

- Optimised slightly opcode loading

- Backported the multi-job submit framework from the development

  branch; multi-instance start and stop should be faster

- Added script to clean archived jobs after 21 days; this will reduce

  the size of the queue directory

- Added some extra checks in disk size tracking

- Added an example ethers hook script

- Added a cluster parameter that prevents Ganeti from modifying of

  /etc/hosts

- Added more node information to RAPI responses

- Added a ``gnt-job watch`` command that allows following the ouput of a

  job

- Added a bind-address option to ganeti-rapi

- Added more checks to the configuration verify

- Enhanced the burnin script such that some operations can be retried

  automatically

- Converted instance reinstall to multi-instance model

Version 2.0.3

-------------

- Added ``--ignore-size`` to the ``gnt-instance activate-disks`` command

  to allow using the pre-2.0.2 behaviour in activation, if any existing

  instances have mismatched disk sizes in the configuration

- Added ``gnt-cluster repair-disk-sizes`` command to check and update

  any configuration mismatches for disk sizes

- Added ``gnt-master cluste-failover --no-voting`` to allow master

  failover to work on two-node clusters

- Fixed the ``--net`` option of ``gnt-backup import``, which was

  unusable

- Fixed detection of OS script errors in ``gnt-backup export``

- Fixed exit code of ``gnt-backup export``

Version 2.0.2

-------------

- Added experimental support for stripped logical volumes; this should

  enhance performance but comes with a higher complexity in the block

  device handling; stripping is only enabled when passing

  ``--with-lvm-stripecount=N`` to ``configure``, but codepaths are

  affected even in the non-stripped mode

- Improved resiliency against transient failures at the end of DRBD

  resyncs, and in general of DRBD resync checks

- Fixed a couple of issues with exports and snapshot errors

- Fixed a couple of issues in instance listing

- Added display of the disk size in ``gnt-instance info``

- Fixed checking for valid OSes in instance creation

- Fixed handling of the "vcpus" parameter in instance listing and in

  general of invalid parameters

- Fixed http server library, and thus RAPI, to handle invalid

  username/password combinations correctly; this means that now they

  report unauthorized for queries too, not only for modifications,

  allowing earlier detect of configuration problems

- Added a new "role" node list field, equivalent to the master/master

  candidate/drained/offline flags combinations

- Fixed cluster modify and changes of candidate pool size

- Fixed cluster verify error messages for wrong files on regular nodes

- Fixed a couple of issues with node demotion from master candidate role

- Fixed node readd issues

- Added non-interactive mode for ``ganeti-masterd --no-voting`` startup

- Added a new ``--no-voting`` option for masterfailover to fix failover

  on two-nodes clusters when the former master node is unreachable

- Added instance reinstall over RAPI

Version 2.0.1

-------------

- added ``-H``/``-B`` startup parameters to ``gnt-instance``, which will

  allow re-adding the start in single-user option (regression from 1.2)

- the watcher writes the instance status to a file, to allow monitoring

  to report the instance status (from the master) based on cached

  results of the watcher's queries; while this can get stale if the

  watcher is being locked due to other work on the cluster, this is

  still an improvement

- the watcher now also restarts the node daemon and the rapi daemon if

  they died

- fixed the watcher to handle full and drained queue cases

- hooks export more instance data in the environment, which helps if

  hook scripts need to take action based on the instance's properties

  (no longer need to query back into ganeti)

- instance failovers when the instance is stopped do not check for free

  RAM, so that failing over a stopped instance is possible in low memory

  situations

- rapi uses queries for tags instead of jobs (for less job traffic), and

  for cluster tags it won't talk to masterd at all but read them from

  ssconf

- a couple of error handling fixes in RAPI

- drbd handling: improved the error handling of inconsistent disks after

  resync to reduce the frequency of "there are some degraded disks for

  this instance" messages

- fixed a bug in live migration when DRBD doesn't want to reconnect (the

  error handling path called a wrong function name)

Version 2.0.0 final

-------------------

- no changes from rc5

Version 2.0 release candidate 5

-------------------------------

- fix a couple of bugs (validation, argument checks)

- fix ``gnt-cluster getmaster`` on non-master nodes (regression)

- some small improvements to RAPI and IAllocator

- make watcher automatically start the master daemon if down

Version 2.0 release candidate 4

-------------------------------

- change the OS list to not require locks; this helps with big clusters

- fix ``gnt-cluster verify`` and ``gnt-cluster verify-disks`` when the

  volume group is broken

- ``gnt-instance info``, without any arguments, doesn't run for all

  instances anymore; either pass ``--all`` or pass the desired

  instances; this helps against mistakes on big clusters where listing

  the information for all instances takes a long time

- miscellaneous doc and man pages fixes

Version 2.0 release candidate 3

-------------------------------

- Change the internal locking model of some ``gnt-node`` commands, in

  order to reduce contention (and blocking of master daemon) when

  batching many creation/reinstall jobs

- Fixes to Xen soft reboot

- No longer build documentation at build time, instead distribute it in

  the archive, in order to reduce the need for the whole docbook/rst

  toolchains

Version 2.0 release candidate 2

-------------------------------

- Now the cfgupgrade scripts works and can upgrade 1.2.7 clusters to 2.0

- Fix watcher startup sequence, improves the behaviour of busy clusters

- Some other fixes in ``gnt-cluster verify``, ``gnt-instance

  replace-disks``, ``gnt-instance add``, ``gnt-cluster queue``, KVM VNC

  bind address and other places

- Some documentation fixes and updates

Version 2.0 release candidate 1

-------------------------------

- More documentation updates, now all docs should be more-or-less

  up-to-date

- A couple of small fixes (mixed hypervisor clusters, offline nodes,

  etc.)

- Added a customizable HV_KERNEL_ARGS hypervisor parameter (for Xen PVM

  and KVM)

- Fix an issue related to $libdir/run/ganeti and cluster creation

Version 2.0 beta 2

------------------

- Xen PVM and KVM have switched the default value for the instance root

  disk to the first partition on the first drive, instead of the whole

  drive; this means that the OS installation scripts must be changed

  accordingly

- Man pages have been updated

- RAPI has been switched by default to HTTPS, and the exported functions

  should all work correctly

- RAPI v1 has been removed

- Many improvements to the KVM hypervisor

- Block device errors are now better reported

- Many other bugfixes and small improvements

Version 2.0 beta 1

------------------

- Version 2 is a general rewrite of the code and therefore the

  differences are too many to list, see the design document for 2.0 in

  the ``doc/`` subdirectory for more details

- In this beta version there is not yet a migration path from 1.2 (there

  will be one in the final 2.0 release)

- A few significant changes are:

  - all commands are executed by a daemon (``ganeti-masterd``) and the

    various ``gnt-*`` commands are just front-ends to it

  - all the commands are entered into, and executed from a job queue,

    see the ``gnt-job(8)`` manpage

  - the RAPI daemon supports read-write operations, secured by basic

    HTTP authentication on top of HTTPS

  - DRBD version 0.7 support has been removed, DRBD 8 is the only

    supported version (when migrating from Ganeti 1.2 to 2.0, you need

    to migrate to DRBD 8 first while still running Ganeti 1.2)

  - DRBD devices are using statically allocated minor numbers, which

    will be assigned to existing instances during the migration process

  - there is support for both Xen PVM and Xen HVM instances running on

    the same cluster

  - KVM virtualization is supported too

  - file-based storage has been implemented, which means that it is

    possible to run the cluster without LVM and DRBD storage, for

    example using a shared filesystem exported from shared storage (and

    still have live migration)

Version 1.2.7

-------------

- Change the default reboot type in ``gnt-instance reboot`` to "hard"

- Reuse the old instance mac address by default on instance import, if

  the instance name is the same.

- Handle situations in which the node info rpc returns incomplete

  results (issue 46)

- Add checks for tcp/udp ports collisions in ``gnt-cluster verify``

- Improved version of batcher:

  - state file support

  - instance mac address support

  - support for HVM clusters/instances

- Add an option to show the number of cpu sockets and nodes in

  ``gnt-node list``

- Support OSes that handle more than one version of the OS api (but do

  not change the current API in any other way)

- Fix ``gnt-node migrate``

- ``gnt-debug`` man page

- Fixes various more typos and small issues

- Increase disk resync maximum speed to 60MB/s (from 30MB/s)

Version 1.2.6

-------------

- new ``--hvm-nic-type`` and ``--hvm-disk-type`` flags to control the

  type of disk exported to fully virtualized instances.

- provide access to the serial console of HVM instances

- instance auto_balance flag, set by default. If turned off it will

  avoid warnings on cluster verify if there is not enough memory to fail

  over an instance. in the future it will prevent automatically failing

  it over when we will support that.

- batcher tool for instance creation, see ``tools/README.batcher``

- ``gnt-instance reinstall --select-os`` to interactively select a new

  operating system when reinstalling an instance.

- when changing the memory amount on instance modify a check has been

  added that the instance will be able to start. also warnings are

  emitted if the instance will not be able to fail over, if auto_balance

  is true.

- documentation fixes

- sync fields between ``gnt-instance list/modify/add/import``

- fix a race condition in drbd when the sync speed was set after giving

  the device a remote peer.

Version 1.2.5

-------------

- note: the allowed size and number of tags per object were reduced

- fix a bug in ``gnt-cluster verify`` with inconsistent volume groups

- fixed twisted 8.x compatibility

- fixed ``gnt-instance replace-disks`` with iallocator

- add TCP keepalives on twisted connections to detect restarted nodes

- disk increase support, see ``gnt-instance grow-disk``

- implement bulk node/instance query for RAPI

- add tags in node/instance listing (optional)

- experimental migration (and live migration) support, read the man page

  for ``gnt-instance migrate``

- the ``ganeti-watcher`` logs are now timestamped, and the watcher also

  has some small improvements in handling its state file

Version 1.2.4

-------------

- Experimental readonly, REST-based remote API implementation;

  automatically started on master node, TCP port 5080, if enabled by

  ``--enable-rapi`` parameter to configure script.

- Instance allocator support. Add and import instance accept a

  ``--iallocator`` parameter, and call that instance allocator to decide

  which node to use for the instance. The iallocator document describes

  what's expected from an allocator script.

- ``gnt-cluster verify`` N+1 memory redundancy checks: Unless passed the

  ``--no-nplus1-mem`` option ``gnt-cluster verify`` now checks that if a

  node is lost there is still enough memory to fail over the instances

  that reside on it.

- ``gnt-cluster verify`` hooks: it is now possible to add post-hooks to

  ``gnt-cluster verify``, to check for site-specific compliance. All the

  hooks will run, and their output, if any, will be displayed. Any

  failing hook will make the verification return an error value.

- ``gnt-cluster verify`` now checks that its peers are reachable on the

  primary and secondary interfaces

- ``gnt-node add`` now supports the ``--readd`` option, to readd a node

  that is still declared as part of the cluster and has failed.

- ``gnt-* list`` commands now accept a new ``-o +field`` way of

  specifying output fields, that just adds the chosen fields to the

  default ones.

- ``gnt-backup`` now has a new ``remove`` command to delete an existing

  export from the filesystem.

- New per-instance parameters hvm_acpi, hvm_pae and hvm_cdrom_image_path

  have been added. Using them you can enable/disable acpi and pae

  support, and specify a path for a cd image to be exported to the

  instance. These parameters as the name suggest only work on HVM

  clusters.

- When upgrading an HVM cluster to Ganeti 1.2.4, the values for ACPI and

  PAE support will be set to the previously hardcoded values, but the

  (previously hardcoded) path to the CDROM ISO image will be unset and

  if required, needs to be set manually with ``gnt-instance modify``

  after the upgrade.

- The address to which an instance's VNC console is bound is now

  selectable per-instance, rather than being cluster wide. Of course

  this only applies to instances controlled via VNC, so currently just

  applies to HVM clusters.

Version 1.2.3

-------------

- more tweaks to the disk activation code (especially helpful for DRBD)

- change the default ``gnt-instance list`` output format, now there is

  one combined status field (see the manpage for the exact values this

  field will have)

- some more fixes for the mac export to hooks change

- make Ganeti not break with DRBD 8.2.x (which changed the version

  format in ``/proc/drbd``) (issue 24)

- add an upgrade tool from "remote_raid1" disk template to "drbd" disk

  template, allowing migration from DRBD0.7+MD to DRBD8

Version 1.2.2

-------------

- fix ``gnt-instance modify`` breakage introduced in 1.2.1 with the HVM

  support (issue 23)

- add command aliases infrastructure and a few aliases

- allow listing of VCPUs in the ``gnt-instance list`` and improve the

  man pages and the ``--help`` option of ``gnt-node

  list``/``gnt-instance list``

- fix ``gnt-backup list`` with down nodes (issue 21)

- change the tools location (move from $pkgdatadir to $pkglibdir/tools)

- fix the dist archive and add a check for including svn/git files in

  the future

- some developer-related changes: improve the burnin and the QA suite,

  add an upload script for testing during development

Version 1.2.1

-------------

- experimental HVM support, read the install document, section

  "Initializing the cluster"

- allow for the PVM hypervisor per-instance kernel and initrd paths

- add a new command ``gnt-cluster verify-disks`` which uses a new

  algorithm to improve the reconnection of the DRBD pairs if the device

  on the secondary node has gone away

- make logical volume code auto-activate LVs at disk activation time

- slightly improve the speed of activating disks

- allow specification of the MAC address at instance creation time, and

  changing it later via ``gnt-instance modify``

- fix handling of external commands that generate lots of output on

  stderr

- update documentation with regard to minimum version of DRBD8 supported

Version 1.2.0

-------------

- Log the ``xm create`` output to the node daemon log on failure (to

  help diagnosing the error)

- In debug mode, log all external commands output if failed to the logs

- Change parsing of lvm commands to ignore stderr

Version 1.2b3

-------------

- Another round of updates to the DRBD 8 code to deal with more failures

  in the replace secondary node operation

- Some more logging of failures in disk operations (lvm, drbd)

- A few documentation updates

- QA updates

Version 1.2b2

-------------

- Change configuration file format from Python's Pickle to JSON.

  Upgrading is possible using the cfgupgrade utility.

- Add support for DRBD 8.0 (new disk template ``drbd``) which allows for

  faster replace disks and is more stable (DRBD 8 has many improvements

  compared to DRBD 0.7)

- Added command line tags support (see man pages for ``gnt-instance``,

  ``gnt-node``, ``gnt-cluster``)

- Added instance rename support

- Added multi-instance startup/shutdown

- Added cluster rename support

- Added ``gnt-node evacuate`` to simplify some node operations

- Added instance reboot operation that can speedup reboot as compared to

  stop and start

- Soften the requirement that hostnames are in FQDN format

- The ``ganeti-watcher`` now activates drbd pairs after secondary node

  reboots

- Removed dependency on debian's patched fping that uses the

  non-standard ``-S`` option

- Now the OS definitions are searched for in multiple, configurable

  paths (easier for distros to package)

- Some changes to the hooks infrastructure (especially the new

  post-configuration update hook)

- Other small bugfixes

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