Configuration

clush

clush.conf

The following configuration file defines system-wide default values for several clush tool parameters:

/etc/clustershell/clush.conf

clush settings might then be overridden (globally, or per user) if one of the following files is found, in priority order:

$XDG_CONFIG_HOME/clustershell/clush.conf
$HOME/.config/clustershell/clush.conf (only if $XDG_CONFIG_HOME is not defined)
{sys.prefix}/etc/clustershell/clush.conf
$HOME/.local/etc/clustershell/clush.conf
$HOME/.clush.conf (deprecated, for 1.6 compatibility only)

Note

The path using sys.prefix was added in version 1.9.1 and is useful for Python virtual environments.

In addition, if the environment variable $CLUSTERSHELL_CFGDIR is defined and valid, it will used instead. In such case, the following configuration file will be tried first for clush:

$CLUSTERSHELL_CFGDIR/clush.conf

The following table describes available clush config file settings.

Key Value
fanout Size of the sliding window of connectors (eg. max number of ssh(1) allowed to run at the same time).
confdir Optional list of directory paths where clush should look for .conf files which define run modes that can then be activated with --mode. All other clush config file settings defined in this table might be overriden in a run mode. Each mode section should have a name prefixed by "mode:" to clearly identify a section defining a mode. Duplicate modes are not allowed in those files. Configuration files that are not readable by the current user are ignored. The variable $CFGDIR is replaced by the path of the highest priority configuration directory found (where clush.conf resides). The default confdir value enables both system-wide and any installed user configuration (thanks to $CFGDIR). Duplicate directory paths are ignored.
connect_timeout Timeout in seconds to allow a connection to establish. This parameter is passed to ssh(1). If set to 0, no timeout occurs.
command_prefix Command prefix. Generally used for specific run modes, for example to implement sudo(8) support.
command_timeout Timeout in seconds to allow a command to complete since the connection has been established. This parameter is passed to ssh(1). In addition, the ClusterShell library ensures that any commands complete in less than (connect_timeout + command_timeout). If set to 0, no timeout occurs.
color Whether to use ANSI colors to surround node or nodeset prefix/header with escape sequences to display them in color on the terminal. Valid arguments are never, always or auto (which use color if standard output/error refer to a terminal). Colors are set to [34m (blue foreground text) for stdout and [31m (red foreground text) for stderr, and cannot be modified.
fd_max Maximum number of open file descriptors permitted per clush process (soft resource limit for open files). This limit can never exceed the system (hard) limit. The fd_max (soft) and system (hard) limits should be high enough to run clush, although their values depend on your fanout value.
history_size Set the maximum number of history entries saved in the GNU readline history list. Negative values imply unlimited history file size.
node_count Should clush display additional (node count) information in buffer header? (yes/no)
maxrc Should clush return the largest of command return codes? (yes/no) If set to no (the default), clush exit status gives no information about command return codes, but rather reports on clush execution itself (zero indicating a successful run).
password_prompt Enable password prompt and password forwarding to stdin? (yes/no) Generally used for specific run modes, for example to implement interactive sudo(8) support.
verbosity Set the verbosity level: 0 (quiet), 1 (default), 2 (verbose) or more (debug).
ssh_user Set the ssh(1) user to use for remote connection (default is to not specify).
ssh_path Set the ssh(1) binary path to use for remote connection (default is ssh).
ssh_options Set additional (raw) options to pass to the underlying ssh(1) command.
scp_path Set the scp(1) binary path to use for remote copy (default is scp).
scp_options Set additional options to pass to the underlying scp(1) command. If not specified, ssh_options are used instead.
rsh_path Set the rsh(1) binary path to use for remote connection (default is rsh). You could easily use mrsh or krsh by simply changing this value.
rcp_path Same as rsh_path but for rcp command (default is rcp).
rsh_options Set additional options to pass to the underlying rsh/rcp command.

Run modes

Since version 1.9, clush has support for run modes, which are special clush.conf settings with a given name. Two run modes are provided in example configuration files that can be copied and modified. They implement password-based authentication with sshpass(1) and support of interactive sudo(8) with password.

To use a run mode with clush --mode, install a configuration file in one of clush.conf's confdir (usually clush.conf.d). Only configuration files ending in .conf are scanned. If the user running clush doesn't have read access to a configuration file, it is ignored. When --mode is specified, you can display all available run modes for the current user by enabling debug mode (-d).

Example of a run mode configuration file (eg. /etc/clustershell/clush.conf.d/sudo.conf) to add support for interactive sudo:

[mode:sudo]
password_prompt: yes
command_prefix: /usr/bin/sudo -S -p "''"

System administrators or users can easly create additional run modes by adding configuration files to clush.conf's confdir.

More details about using run modes can be found here.

Node groups

ClusterShell defines a node group syntax to represent a collection of nodes. This is a convenient way to manipulate node sets, especially in HPC (High Performance Computing) or with large server farms. This section explains how to configure node group sources. Please see also nodeset node groups for specific usage examples.

groups.conf

ClusterShell loads groups.conf configuration files that define how to obtain node groups configuration, ie. the way the library should access file-based or external node group sources.

The following configuration file defines system-wide default values for groups.conf:

/etc/clustershell/groups.conf

groups.conf settings might then be overridden (globally, or per user) if one of the following files is found, in priority order:

$XDG_CONFIG_HOME/clustershell/groups.conf
$HOME/.config/clustershell/groups.conf (only if $XDG_CONFIG_HOME is not defined)
{sys.prefix}/etc/clustershell/groups.conf
$HOME/.local/etc/clustershell/groups.conf

Note

The path using sys.prefix was added in version 1.9.1 and is useful for Python virtual environments.

In addition, if the environment variable $CLUSTERSHELL_CFGDIR is defined and valid, it will used instead. In such case, the following configuration file will be tried first for groups.conf:

$CLUSTERSHELL_CFGDIR/groups.conf

This makes possible for an user to have its own node groups configuration. If no readable configuration file is found, group support will be disabled but other node set operations will still work.

groups.conf defines configuration sub-directories, but may also define source definitions by itself. These sources provide external calls that are detailed in External group sources.

The following example shows the content of a groups.conf file where node groups are bound to the source named genders by default:

[Main]
default: genders
confdir: /etc/clustershell/groups.conf.d $CFGDIR/groups.conf.d
autodir: /etc/clustershell/groups.d $CFGDIR/groups.d

[genders]
map: nodeattr -n $GROUP
all: nodeattr -n ALL
list: nodeattr -l

[slurm]
map: sinfo -h -o "%N" -p $GROUP
all: sinfo -h -o "%N"
list: sinfo -h -o "%P"
reverse: sinfo -h -N -o "%P" -n $NODE

The groups.conf files are parsed with Python's ConfigParser:

  • The first section whose name is Main accepts the following keywords:
    • default defines a default node group source (eg. by referencing a valid section header)
    • confdir defines an optional list of directory paths where the ClusterShell library should look for .conf files which define group sources to use. Each file in these directories with the .conf suffix should contain one or more node group source sections as documented below. These will be merged with the group sources defined in the main groups.conf to form the complete set of group sources to use. Duplicate group source sections are not allowed in those files. Configuration files that are not readable by the current user are ignored (except the one that defines the default group source). The variable $CFGDIR is replaced by the path of the highest priority configuration directory found (where groups.conf resides). The default confdir value enables both system-wide and any installed user configuration (thanks to $CFGDIR). Duplicate directory paths are ignored.
    • autodir defines an optional list of directories where the ClusterShell library should look for .yaml files that define in-file group dictionaries. No need to call external commands for these files, they are parsed by the ClusterShell library itself. Multiple group source definitions in the same file is supported. The variable $CFGDIR is replaced by the path of the highest priority configuration directory found (where groups.conf resides). The default confdir value enables both system-wide and any installed user configuration (thanks to $CFGDIR). Duplicate directory paths are ignored.
  • Each following section (genders, slurm) defines a group source. The map, all, list and reverse upcalls are explained below in Group source upcalls.

File-based group sources

Version 1.7 introduces support for native handling of flat files with different group sources to avoid the use of external upcalls for such static configuration. This can be achieved through the autodir feature and YAML files described below.

YAML group files

Cluster node groups can be defined in straightforward YAML files. In such a file, each YAML dictionary defines group to nodes mapping. Different dictionaries are handled as different group sources.

For compatibility reasons with previous versions of ClusterShell, this is not the default way to define node groups yet. So here are the steps needed to try this out:

Rename the following file:

/etc/clustershell/groups.d/cluster.yaml.example

to a file having the .yaml extension, for example:

/etc/clustershell/groups.d/cluster.yaml

Ensure that autodir is set in groups.conf:

autodir: /etc/clustershell/groups.d $CFGDIR/groups.d

In the following example, we also changed the default group source to roles in groups.conf (the first dictionary defined in the example), so that @roles:groupname can just be shorted @groupname.

Here is an example of /etc/clustershell/groups.d/cluster.yaml:

roles:
    adm: 'mgmt[1-2]'                 # define groups @roles:adm and @adm
    login: 'login[1-2]'
    compute: 'node[0001-0288]'
    gpu: 'node[0001-0008]'

    servers:                         # example of yaml list syntax for nodes
        - 'server001'                # in a group
        - 'server002,server101'
        - 'server[003-006]'

    cpu_only: '@compute!@gpu'        # example of inline set operation
                                     # define group @cpu_only with node[0009-0288]

    storage: '@lustre:mds,@lustre:oss' # example of external source reference

    all: '@login,@compute,@storage'  # special group used for clush/nodeset -a
                                     # only needed if not including all groups

lustre:
    mds: 'mds[1-4]'
    oss: 'oss[0-15]'
    rbh: 'rbh[1-2]'

Testing the syntax of your group file can be quickly performed through the -L or --list-all command of nodeset:

$ nodeset -LL
@adm mgmt[1-2]
@all login[1-2],mds[1-4],node[0001-0288],oss[0-15],rbh[1-2]
@compute node[0001-0288]
@cpu_only node[0009-0288]
@gpu node[0001-0008]
@login login[1-2]
@storage mds[1-4],oss[0-15],rbh[1-2]
@sysgrp sysgrp[1-4]
@lustre:mds mds[1-4]
@lustre:oss oss[0-15]
@lustre:rbh rbh[1-2]

External group sources

Group source upcalls

Each node group source is defined by a section name (source name) and up to four upcalls:

  • map: External shell command used to resolve a group name into a node set, list of nodes or list of node sets (separated by space characters or by carriage returns). The variable $GROUP is replaced before executing the command.
  • all: Optional external shell command that should return a node set, list of nodes or list of node sets of all nodes for this group source. If not specified, the library will try to resolve all nodes by using the list external command in the same group source followed by map for each available group. The notion of all nodes is used by clush -a and also by the special group name @* (or @source:*).
  • list: Optional external shell command that should return the list of all groups for this group source (separated by space characters or by carriage returns). If this upcall is not specified, ClusterShell won't be able to list any available groups (eg. with nodeset -l), so it is highly recommended to set it.
  • reverse: Optional external shell command used to find the group(s) of a single node. The variable $NODE is previously replaced. If this external call is not specified, the reverse operation is computed in memory by the library from the list and map external calls, if available. Also, if the number of nodes to reverse is greater than the number of available groups, the reverse external command is avoided automatically to reduce resolution time.

In addition to context-dependent $GROUP and $NODE variables described above, the two following variables are always available and also replaced before executing shell commands:

  • $CFGDIR is replaced by groups.conf base directory path
  • $SOURCE is replaced by current source name (see an usage example just below)

Caching considerations

External command results are cached in memory, for a limited amount of time, to avoid multiple similar calls.

The optional parameter cache_time, when specified within a group source section, defines the number of seconds each upcall result is kept in cache, in memory only. Please note that caching is actually only useful for long-running programs (like daemons) that are using node groups, not for one-shot commands like clush or cluset/nodeset.

The default value of cache_time is 3600 seconds.

Multiple sources section

Use a comma-separated list of source names in the section header if you want to define multiple group sources with similar upcall commands. The special variable $SOURCE is always replaced by the source name before command execution (here cluster, racks and cpu), for example:

[cluster,racks,cpu]
map: get_nodes_from_source.sh $SOURCE $GROUP
all: get_all_nodes_from_source.sh $SOURCE
list: list_nodes_from_source.sh $SOURCE

is equivalent to:

[cluster]
map: get_nodes_from_source.sh cluster $GROUP
all: get_all_nodes_from_source.sh cluster
list: list_nodes_from_source.sh cluster

[racks]
map: get_nodes_from_source.sh racks $GROUP
all: get_all_nodes_from_source.sh racks
list: list_nodes_from_source.sh racks

[cpu]
map: get_nodes_from_source.sh cpu $GROUP
all: get_all_nodes_from_source.sh cpu
list: list_nodes_from_source.sh cpu

Return code of external calls

Each external command might return a non-zero return code when the operation is not doable. But if the call return zero, for instance, for a non-existing group, the user will not receive any error when trying to resolve such unknown group. The desired behavior is up to the system administrator.

Slurm group bindings

Enable Slurm node group bindings by renaming the example configuration file usually installed as /etc/clustershell/groups.conf.d/slurm.conf.example to slurm.conf. Three group sources are defined in this file and are detailed below. Each section comes with a long and short names (for convenience), but actually defines a same group source.

While examples below are based on the nodeset tool, all Python tools using ClusterShell and the NodeSet class will automatically benefit from these additional node groups.

The first section slurmpart,sp defines a group source based on Slurm partitions. Each group is named after the partition name and contains the partition's nodes:

[slurmpart,sp]
map: sinfo -h -o "%N" -p $GROUP
all: sinfo -h -o "%N"
list: sinfo -h -o "%R"
reverse: sinfo -h -N -o "%R" -n $NODE

Example of use with nodeset on a cluster having two Slurm partitions named kepler and pascal:

$ nodeset -s sp -ll
@sp:kepler cluster-[0001-0065]
@sp:pascal cluster-[0066-0068]

The second section slurmstate,st defines a group source based on Slurm node states. Each group is based on a different state name and contains the nodes currently in that state:

[slurmstate,st]
map: sinfo -h -o "%N" -t $GROUP
all: sinfo -h -o "%N"
list: sinfo -h -o "%T" | tr -d '*~#$@+'
reverse: sinfo -h -N -o "%T" -n $NODE | tr -d '*~#$@+'
cache_time: 60

Here, cache_time is set to 60 seconds instead of the default (3600s) to avoid caching results in memory for too long, in case of state change (this is only useful for long-running processes, not one-shot commands).

Example of use with nodeset to get the current nodes that are in the Slurm state drained:

$ nodeset -f @st:drained
cluster-[0058,0067]

The third section slurmjob,sj defines a group source based on Slurm jobs. Each group is based on a running job ID and contains the nodes currently allocated for this job:

[slurmjob,sj]
map: squeue -h -j $GROUP -o "%N"
list: squeue -h -o "%i" -t R
reverse: squeue -h -w $NODE -o "%i"
cache_time: 60

The fourth section slurmuser,su defines a group source based on Slurm users. Each group is based on a username and contains the nodes currently allocated for jobs belonging to the username:

[slurmuser,su]
map: squeue -h -u $GROUP -o "%N" -t R
list: squeue -h -o "%u" -t R
reverse: squeue -h -w $NODE -o "%i"
cache_time: 60

Example of use with clush to execute a command on all nodes with running jobs of username:

$ clush -bw@su:username 'df -Ph /scratch'
$ clush -bw@su:username 'du -s /scratch/username'

cache_time is also set to 60 seconds instead of the default (3600s) to avoid caching results in memory for too long, because this group source is likely very dynamic (this is only useful for long-running processes, not one-shot commands).

You can then easily find nodes associated with a Slurm job ID:

$ nodeset -f @sj:686518
cluster-[0003,0005,0010,0012,0015,0017,0021,0055]

xCAT group bindings

Enable xCAT node group bindings by renaming the example configuration file usually installed as /etc/clustershell/groups.conf.d/xcat.conf.example to xcat.conf. A single group source is defined in this file and is detailed below.

Warning

xCAT installs its own nodeset command which usually takes precedence over ClusterShell's nodeset command. In that case, simply use cluset instead.

While examples below are based on the cluset tool, all Python tools using ClusterShell and the NodeSet class will automatically benefit from these additional node groups.

The section xcat defines a group source based on xCAT static node groups:

[xcat]

# list the nodes in the specified node group
map: lsdef -s -t node $GROUP | cut -d' ' -f1

# list all the nodes defined in the xCAT tables
all: lsdef -s -t node | cut -d' ' -f1

# list all groups
list: lsdef -t group | cut -d' ' -f1

Example of use with cluset:

$ lsdef -s -t node dtn
sh-dtn01  (node)
sh-dtn02  (node)

$ cluset -s xcat -f @dtn
sh-dtn[01-02]

Library Defaults

Warning

Modifying library defaults is for advanced users only as that could change the behavior of tools using ClusterShell. Moreover, tools are free to enforce their own defaults, so changing library defaults may not change a global behavior as expected.

Since version 1.7, most defaults of the ClusterShell library may be overridden in defaults.conf.

The following configuration file defines ClusterShell system-wide defaults:

/etc/clustershell/defaults.conf

defaults.conf settings might then be overridden (globally, or per user) if one of the following files is found, in priority order:

$XDG_CONFIG_HOME/clustershell/defaults.conf
$HOME/.config/clustershell/defaults.conf (only if $XDG_CONFIG_HOME is not defined)
{sys.prefix}/etc/clustershell/defaults.conf
$HOME/.local/etc/clustershell/defaults.conf

In addition, if the environment variable $CLUSTERSHELL_CFGDIR is defined and valid, it will used instead. In such case, the following configuration file will be tried first for ClusterShell defaults:

$CLUSTERSHELL_CFGDIR/defaults.conf

Use case: rsh

If your cluster uses a rsh variant like mrsh or krsh, you may want to change it in the library defaults.

An example file is usually available in /usr/share/doc/clustershell-*/examples/defaults.conf-rsh and could be copied to /etc/clustershell/defaults.conf or to an alternate path described above. Basically, the change consists in defining an alternate distant worker by Python module name as follow:

[task.default]
distant_workername: Rsh

Use case: Slurm

If your cluster naming scheme has multiple dimensions, as in node-93-02, we recommend that you disengage some nD folding when using Slurm, which is currently unable to detect some multidimensional node indexes when not explicitly enclosed with square brackets.

To do so, define fold_axis to -1 in the Library Defaults so that nD folding is only computed on the last axis (seems to work best with Slurm):

[nodeset]
fold_axis: -1

That way, node sets computed by ClusterShell tools can be passed to Slurm without error.