Release Notes

Version 1.8

This adaptive release is now compatible with both Python 2 and Python 3.

We hope this release will help you manage your clusters, server farms or cloud farms! Special thanks to the many of you that have sent us feedback on GitHub!


Support for Python 2.5 and below has been dropped in this version.

Version 1.8.1

This update contains a few bug fixes and some performance improvements of the NodeSet class.

The tree mode has been fixed to properly support offline gateways.

We added the following command line options:

  • --conf to specify alternative clush.conf (clush only)
  • --groupsconf to specify alternative groups.conf (all CLIs)

In EventHandler, we reinstated EventHandler.ev_error(): and EventHandler.ev_error(): (as deprecated) for compatibility purposes. Please see below for more details about important EventHandler changes in 1.8.

Finally, cluset/nodeset have been improved by adding support for:

  • litteral new line in -S
  • multiline shell variables in options

For more details, please have a look at GitHub Issues for 1.8.1 milestone.

Main changes in 1.8

For more details, please have a look at GitHub Issues for 1.8 milestone.

CLI (command line interface)

If you use the clush or cluset/nodeset tools, there are no major changes since 1.7, though a few bug fixes and improvements have been done:

  • It is now possible to work with numeric node names with cluset/nodeset:

    $ nodeset --fold 6704 6705 r931 r930
    $ squeue -h -o '%i' -u $USER | cluset -f

    As a reminder, cluset/nodeset has always had an option to switch to numerical cluster ranges (only), using -R/--rangeset:

    $ squeue -h -o '%i' -u $USER | cluset -f -R
  • Node group configuration is now loaded and processed only when required. This is actually an improvement of the NodeSet class that the tools readily benefit. This should improve both usability and performance.

  • YAML group files are now ignored for users that don’t have the permission to read them (see File-based group sources for more info about group files).

  • clush now use slightly different colors that are legible on dark backgrounds.

  • Tree execution mode:

    • Better detection of the Python executable, and, if needed, we added a new environment variable to override it, see Remote Python executable.
    • You must use the same major version of Python on the gateways and the root node.

Python library

If you’re a developer and use the ClusterShell Python library, please read below.

Python 3 support

Starting in 1.8, the library can also be used with Python 3. The code is compatible with both Python 2 and 3 at the same time. To make it possible, we performed a full code refactoring (without changing the behavior).


When using Python 3, we recommend Python 3.4 or any more recent version.

Improved Event API

We’ve made some changes to EventHandler, a class that defines a simple interface to handle events generated by Worker, EventTimer and EventPort objects.

Please note that all programs already based on EventHandler should work with this new version of ClusterShell without any code change (backward API compatibility across 1.x versions is enforced). We use object introspection, the ability to determine the type of an object at runtime, to make the Event API evolve smoothly. We do still recommend to change your code as soon as possible as we’ll break backward compatibility in the future major release 2.0.

The signatures of the following EventHandler methods changed in 1.8:

Both old and new signatures are supported in 1.8. The old signatures will be deprecated in a future 1.x release and removed in version 2.0.

The new methods aims to be more convenient to use by avoiding the need of accessing context-specific Worker attributes like worker.current_node (replaced with the node argument in that case).

Also, please note that the following EventHandler methods will be removed in 2.0:

  • EventHandler.ev_error(): its use should be replaced with EventHandler.ev_read() by comparing the stream name sname with Worker.SNAME_STDERR, like in the example below:

    class MyEventHandler(EventHandler):
        def ev_read(self, worker, node, sname, msg):
            if sname == worker.SNAME_STDERR:
                print('error from %s: %s' % (node, msg))
  • EventHandler.ev_timeout(): its use should be replaced with EventHandler.ev_close() by checking for the new timedout argument, which is set to True when a timeout occurred.

We recommend developers to start using the improved Event API now. Please don’t forget to update your packaging requirements to use ClusterShell 1.8 or later.

Task and standard input (stdin) and have a new stdin boolean argument which if set to False prevents the use of stdin by sending EOF at first read, like if it is connected to /dev/null.

If not specified, its value is managed by the Library Defaults. Its default value in Defaults is set to True for backward compatibility, but could change in a future major release.

If your program doesn’t plan to listen to stdin, it is recommended to set stdin=False when calling these two methods.

Packaging changes

We recommend that package maintainers use separate subpackages for Python 2 and Python 3, to install ClusterShell modules and related command line tools. The Python 2 and Python 3 stacks should be fully installable in parallel.

For the RPM packaging, there is now two subpackages python2-clustershell and python3-clustershell (or python34-clustershell in EPEL), each providing the library and tools for the corresponding version of Python.

The clustershell package includes the common configuration files and documentation and requires python2-clustershell, mainly because Python 2 is still the default interpreter on most operating systems.

vim-clustershell was confusing so we removed it and added the vim extensions to the main clustershell subpackage.

Version 1.8 should be readily available as RPMs in the following distributions or RPM repositories:

  • EPEL 6 and 7
  • Fedora 26 and 27
  • openSUSE Factory and Leap

On a supported environment, you can expect a smooth upgrade from version 1.6+.

We also expect the packaging to be updated for Debian.

Version 1.7

It’s just a small version bump from the well-known 1.6 version, but ClusterShell 1.7 comes with some nice new features that we hope you’ll enjoy! Most of these features have already been tested on some very large Linux production systems.

Version 1.7 and possible future minor versions 1.7.x are compatible with Python 2.4 up to Python 2.7 (for example: from RedHat EL5 to EL7). Upgrade from version 1.6 to 1.7 should be painless and is fully supported.

Version 1.7.3

This update contains a few bug fixes and some interesting performance improvements. This is also the first release published under the GNU Lesser General Public License, version 2.1 or later (LGPL v2.1+). Previous releases were published under the CeCILL-C V1.

Quite a bit of work has been done on the fanout of processes that the library uses to execute commands. We implemenented a basic per-worker fanout to fix the broken behaviour in tree mode. Thanks to this, it is now possible to use fanout=1 with gateways. The documentation has also been clarified.

An issue that led to broken pipe errors but also affected performance has been fixed in tree mode when copying files.

An issue with clush -L where nodes weren’t always properly sorted has been fixed.

The performance of MsgTree, the class used by the library to aggregate identical command outputs, has been improved. We have seen up to 75% speed improvement in some cases.

Finally, a cluset command has been added to avoid a conflict with xCAT nodeset command. It is the same command as nodeset.

For more details, please have a look at GitHub Issues for 1.7.3 milestone.

ClusterShell 1.7.3 is compatible with Python 2.4 up to Python 2.7 (for example: from RedHat EL5 to EL7). Upgrades from versions 1.6 or 1.7 are supported.

Version 1.7.2

This minor version fixes a defect in tree mode that led to broken pipe errors or unwanted backtraces.

The NodeSet class now supports the empty string as input. In practice, you may now safely reuse the output of a nodeset command as input argument for another nodeset command, even if the result is an empty string.

A new option --pick is available for clush and nodeset to pick N node(s) at random from the resulting node set.

For more details, please have a look at GitHub Issues for 1.7.2 milestone.

ClusterShell 1.7.2 is compatible with Python 2.4 up to Python 2.7 (for example: from RedHat EL5 to EL7). Upgrades from versions 1.6 or 1.7 are supported.

Version 1.7.1

This minor version contains a few bug fixes, mostly related to Node sets handling.

This version also contains bug fixes and performance improvements in tree propagation mode.

For more details, please have a look at GitHub Issues for 1.7.1 milestone.

ClusterShell 1.7.1 is compatible with Python 2.4 up to Python 2.7 (for example: from RedHat EL5 to EL7). Upgrades from versions 1.6 or 1.7 are supported.

Main changes in 1.7

This new version comes with a refreshed documentation, based on the Sphinx documentation generator, available on

The main new features of version 1.7 are described below.

Multidimensional nodesets

The NodeSet class and nodeset command-line have been improved to support multidimentional node sets with folding capability. The use of nD naming scheme is sometimes used to map node names to physical location like name-<rack>-<position> or node position within the cluster interconnect network topology.

A first example of 3D nodeset expansion is a good way to start:

$ nodeset -e gpu-[1,3]-[4-5]-[0-6/2]
gpu-1-4-0 gpu-1-4-2 gpu-1-4-4 gpu-1-4-6 gpu-1-5-0 gpu-1-5-2 gpu-1-5-4
gpu-1-5-6 gpu-3-4-0 gpu-3-4-2 gpu-3-4-4 gpu-3-4-6 gpu-3-5-0 gpu-3-5-2
gpu-3-5-4 gpu-3-5-6

You’ve probably noticed the /2 notation of the last dimension. It’s called a step and behaves as one would expect, and is fully supported with nD nodesets.

All other nodeset commands and options are supported with nD nodesets. For example, it’s always useful to have a quick way to count the number of nodes in a nodeset:

$ nodeset -c gpu-[1,3]-[4-5]-[0-6/2]

Then to show the most interesting new capability of the underlying NodeSet class in version 1.7, a folding example is probably appropriate:

$ nodeset -f compute-1-[1-34] compute-2-[1-34]

In the above example, nodeset will try to find a very compact nodesets representation whenever possible. ClusterShell is probably the first and only cluster tool capable of doing such complex nodeset folding.

Attention, as not all cluster tools are supporting this kind of complex nodesets, even for nodeset expansion, we added an --axis option to select to fold along some desired dimension:

$ nodeset --axis 2 -f compute-[1-2]-[1-34]

The last dimension can also be selected using -1:

$ nodeset --axis -1 -f compute-[1-2]-[1-34]

All set-like operations are also supported with several dimensions, for example difference (-x):

$ nodeset -f c-[1-10]-[1-44] -x c-[5-10]-[1-34]

Hard to follow? Don’t worry, ClusterShell does it for you!

File-based node groups

Cluster node groups have been a great success of previous version of ClusterShell and are now widely adopted. So we worked on improving it even more for version 1.7.

For those of you who use the file /etc/clustershell/group to describe node groups, that is still supported in 1.7 and upgrade from your 1.6 setup should work just fine. However, for new 1.7 installations, we have put this file in a different location by default:

$ vim /etc/clustershell/groups.d/local.cfg

Especially if you’re starting a new setup, you have also the choice to switch to a more advanced groups YAML configuration file that can define multiple sources in a single file (equivalent to separate namespaces for node groups). The YAML format possibly allows you to edit the file content with YAML tools but it’s also a file format convenient to edit just using the vim editor. To enable the example file, you need to rename it first as it needs to have the .yaml extension:

$ cd /etc/clustershell/groups.d
$ mv cluster.yaml.example cluster.yaml

You can make the first dictionary found on this file (named roles) to be the default source by changing default: local to default: roles in /etc/clustershell/groups.conf (main config file for groups).

For more info about the YAML group files, please see File-based group sources.

Please also see node groups configuration for node groups configuration in general.

nodeset -L/–list-all option

Additionally, the nodeset command also has a new option -L or --list-all to list groups from all sources (-l only lists groups from the default source). This can be useful when configuring ClusterShell and/or troubleshooting node group sources:

$ nodeset -LL
@adm example0
@all example[2,4-5,32-159]
@compute example[32-159]
@gpu example[156-159]
@io example[2,4-5]
@racks:new example[4-5,156-159]
@racks:old example[0,2,32-159]
@racks:rack1 example[0,2]
@racks:rack2 example[4-5]
@racks:rack3 example[32-159]
@racks:rack4 example[156-159]
@cpu:hsw example[64-159]
@cpu:ivy example[32-63]

Special group @*

The special group syntax @* (or @source:* if using explicit source selection) has been added and can be used in configuration files or with command line tools. This special group is always available for file-based node groups (return the content of the all group, or all groups from the source otherwise). For external sources, it is available when either the all upcall is defined or both map and list upcalls are defined. The all special group is also used by clush -a and nodeset -a. For example, the two following commands are equivalent:

$ nodeset -a -f

$ nodeset -f @*

Exec worker

Version 1.7 introduces a new generic execution worker named ExecWorker as the new base class for most exec()-based worker classes. In practice with clush, you can now specify the worker in command line using --worker or -R and use exec. It also supports special placeholders for the node (%h) or rank (%n). For example, the following command will execute ping commands in parallel, each with a different host from hosts cs01, etc. to cs05 as argument and then aggregate the results:

$ clush -R exec -w cs[01-05] -bL 'ping -c1 %h >/dev/null && echo ok'
cs[01-04]: ok
clush: cs05: exited with exit code 1

This feature allows the system administrator to use non cluster-aware tools in a more efficient way. You may also want to explicitly set the fanout (using -f) to limit the number of parallel local commands launched.

Please see also clush worker selection.

Rsh worker

Version 1.7 adds support for rsh or any of its variants like krsh or mrsh. rsh and ssh also share a lot of common mechanisms. Worker Rsh was added moving a lot of Worker Ssh code into it.

For clush, please see clush worker selection to enable rsh.

To use rsh by default instead of ssh at the library level, install the provided example file named defaults.conf-rsh to /etc/clustershell/defaults.conf.

Tree Propagation Mode

The ClusterShell Tree Mode allows you to send commands to target nodes through a set of predefined gateways (using ssh by default). It can be useful to access servers that are behind some other servers like bastion hosts, or to scale on very large clusters when the flat mode (eg. sliding window of ssh commands) is not enough anymore.

The tree mode is now documented, it has been improved and is enabled by default when a topology.conf file is found. While it is still a work in progress, the tree mode is known to work pretty well when all gateways are online. We’ll continue to improve it and make it more robust in the next versions.

Configuration files

When $XDG_CONFIG_HOME is defined, ClusterShell will use it to search for additional configuration files.

PIP user installation support

ClusterShell 1.7 is now fully compatible with PIP and supports user configuration files:

$ pip install --user clustershell

Please see Installing ClusterShell as user using PIP.