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clush - execute shell commands on a cluster


clush -a | -g group | -w nodes [OPTIONS]

clush -a | -g group | -w nodes [OPTIONS] command

clush -a | -g group | -w nodes [OPTIONS] --copy file | dir [ file | dir ...] [ --dest
path ]

clush -a | -g group | -w nodes [OPTIONS] --rcopy file | dir [ file | dir ...] [ --dest
path ]


clush is a program for executing commands in parallel on a cluster and for gathering their
results. clush executes commands interactively or can be used within shell scripts and
other applications. It is a partial front-end to the ClusterShell library that ensures a
light, unified and robust parallel command execution framework. Thus, it allows
traditional shell scripts to benefit from some of the library features. clush currently
makes use of the Ssh worker of ClusterShell, by default, that only requires ssh(1)
(OpenSSH SSH client).


clush can be started non-interactively to run a shell command, or can be invoked as an
interactive shell. To start a clush interactive session, invoke the clush command without
providing command.

Non-interactive mode
When clush is started non-interactively, the command is executed on the specified
remote hosts in parallel. If option -b or --dshbak is specified, clush waits for
command completion and then displays gathered output results.

The -w option allows you to specify remote hosts by using ClusterShell NodeSet
syntax, including the node groups @group special syntax and the Extended Patterns
syntax to benefits from NodeSet basic arithmetics (like @Agroup\&@Bgroup). See
EXTENDED PATTERNS in nodeset(1) and also groups.conf(5) for more information.

Unless option --nostdin is specified, clush detects when its standard input is
connected to a terminal (as determined by isatty(3)). If actually connected to a
terminal, clush listens to standard input when commands are running, waiting for an
Enter key press. Doing so will display the status of current nodes. If standard
input is not connected to a terminal, and unless option --nostdin is specified,
clush binds the standard input of the remote commands to its own standard input,
allowing scripting methods like:
# echo foo | clush -w node[40-42] -b cat

Please see some other great examples in the EXAMPLES section below.

Interactive session
If a command is not specified, and its standard input is connected to a terminal,
clush runs interactively. In this mode, clush uses the GNU readline library to read
command lines. Readline provides commands for searching through the command history
for lines containing a specified string. For instance, type Control-R to search in
the history for the next entry matching the search string typed so far. clush also
recognizes special single-character prefixes that allows the user to see and modify
the current nodeset (the nodes where the commands are executed).

Single-character interactive commands are:

clush> ?
show current nodeset

clush> =<NODESET>
set current nodeset

clush> +<NODESET>
add nodes to current nodeset

clush> -<NODESET>
remove nodes from current nodeset

clush> !COMMAND
execute COMMAND on the local system

clush> =
toggle the output format (gathered or standard mode)

To leave an interactive session, type quit or Control-D.

Local execution ( --worker=exec or -R exec )
Instead of running provided command on remote nodes, clush can use the dedicated
exec worker to launch the command locally, for each node. Some parameters could be
used in the command line to make a different command for each node. %h or %host
will be replaced by node name and %r or %rank by the remote rank [0-N] (to get a
literal % use %%)

File copying mode ( --copy )
When clush is started with the -c or --copy option, it will attempt to copy
specified file and/or dir to the provided target cluster nodes. If the --dest
option is specified, it will put the copied files there.

Reverse file copying mode ( --rcopy )
When clush is started with the --rcopy option, it will attempt to retrieve
specified file and/or dir from provided cluster nodes. If the --dest option is
specified, it must be a directory path where the files will be stored with their
hostname appended. If the destination path is not specified, it will take the first
file or dir basename directory as the local destination.


show clush version number and exit

optional groups.conf(5) group source to use

do not watch for possible input from stdin

-O <KEY=VALUE>, --option=<KEY=VALUE>
override any key=value clush.conf(5) options (repeat as needed)

Selecting target nodes:

nodes where to run the command

exclude nodes from the node list

-a, --all
run command on all nodes

-g GROUP, --group=GROUP
run command on a group of nodes

exclude nodes from this group

--hostfile=FILE, --machinefile=FILE
path to a file containing a list of single hosts, node sets or node groups,
separated by spaces and lines (may be specified multiple times, one per

topology configuration file to use for tree mode

Output behaviour:

-q, --quiet
be quiet, print essential output only

-v, --verbose
be verbose, print informative messages

-d, --debug
output more messages for debugging purpose

-G, --groupbase
do not display group source prefix

-L disable header block and order output by nodes; additionally, when used in
conjunction with -b/-B, it will enable "life gathering" of results by line
mode, such as the next line is displayed as soon as possible (eg. when all
nodes have sent the line)

-N disable labeling of command line

-P, --progress
show progress during command execution; if writing is performed to standard
input, the live progress indicator will display the global bandwidth of data
written to the target nodes

-b, --dshbak
display gathered results in a dshbak-like way

-B like -b but including standard error

-r, --regroup
fold nodeset using node groups

-S return the largest of command return codes

whether to use ANSI colors to surround node or nodeset prefix/header with
escape sequences to display them in color on the terminal. WHENCOLOR is
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.

--diff show diff between common outputs (find the best reference output by focusing
on largest nodeset and also smaller command return code)

File copying:

-c, --copy
copy local file or directory to remote nodes

copy file or directory from remote nodes

destination file or directory on the nodes (optional: use the first source
directory path when not specified)

-p preserve modification times and modes

Connection options:

-f FANOUT, --fanout=FANOUT
use a specified maximum fanout size (ie. do not execute more than FANOUT
commands at the same time, useful to limit resource usage)

-l USER, --user=USER
execute remote command as user

-o OPTIONS, --options=OPTIONS
can be used to give ssh options, eg. -o "-p 2022 -i ~/.ssh/myidrsa"; these
options are added first to ssh and override default ones

limit time to connect to a node

limit time for command to run on the node

-R WORKER, --worker=WORKER
worker name to use for connection (exec, ssh, rsh, pdsh), default is ssh

For a short explanation of these options, see -h, --help.


By default, an exit status of zero indicates success of the clush command but gives no
information about the remote commands exit status. However, when the -S option is
specified, the exit status of clush is the largest value of the remote commands return

For failed remote commands whose exit status is non-zero, and unless the combination of
options -qS is specified, clush displays messages similar to:

clush: node[40-42]: exited with exit code 1


Remote parallel execution
# clush -w node[3-5,62] uname -r
Run command uname -r in parallel on nodes: node3, node4, node5 and node62

Local parallel execution
# clush -w node[1-3] --worker=exec ping -c1 %host
Run locally, in parallel, a ping command for nodes: node1, node2 and node3. You
may also use -R exec as the shorter and pdsh compatible option.

Display features
# clush -w node[3-5,62] -b uname -r
Run command uname -r on nodes[3-5,62] and display gathered output results
(integrated dshbak-like).

# clush -w node[3-5,62] -bL uname -r
Line mode: run command uname -r on nodes[3-5,62] and display gathered output
results without default header block.

# ssh node32 find /etc/yum.repos.d -type f | clush -w node[40-42] -b xargs ls -l
Search some files on node32 in /etc/yum.repos.d and use clush to list the matching
ones on node[40-42], and use -b to display gathered results.

# clush -w node[3-5,62] --diff dmidecode -s bios-version
Run this Linux command to get BIOS version on nodes[3-5,62] and show version
differences (if any).

All nodes
# clush -a uname -r
Run command uname -r on all cluster nodes, see groups.conf(5) to setup all cluster
nodes (all: field).

# clush -a -x node[5,7] uname -r
Run command uname -r on all cluster nodes except on nodes node5 and node7.

# clush -a --diff cat /some/file
Run command cat /some/file on all cluster nodes and show differences (if any), line
by line, between common outputs.

Node groups
# clush -w @oss modprobe lustre
Run command modprobe lustre on nodes from node group named oss, see groups.conf(5)
to setup node groups (map: field).

# clush -g oss modprobe lustre
Same as previous example but using -g to avoid @ group prefix.

# clush -w @mds,@oss modprobe lustre
You may specify several node groups by separating them with commas (please see
EXTENDED PATTERNS in nodeset(1) and also groups.conf(5) for more information).

Copy files
# clush -w node[3-5,62] --copy /etc/motd
Copy local file /etc/motd to remote nodes node[3-5,62].

# clush -w node[3-5,62] --copy /etc/motd --dest /tmp/motd2
Copy local file /etc/motd to remote nodes node[3-5,62] at path /tmp/motd2.

# clush -w node[3-5,62] -c /usr/share/doc/clustershell
Recursively copy local directory /usr/share/doc/clustershell to the same path on
remote nodes node[3-5,62].

# clush -w node[3-5,62] --rcopy /etc/motd --dest /tmp
Copy /etc/motd from remote nodes node[3-5,62] to local /tmp directory, each file
having their remote hostname appended, eg. /tmp/motd.node3.

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