PSSH

Linux.com Parallel SSH execution and a single shell to control them all

Many people use SSH to log in to remote machines, copy files around, and perform general system administration. If you want to increase your productivity with SSH, you can try a tool that lets you run commands on more than one remote machine at the same time. Parallel ssh, Cluster SSH, and ClusterIt let you specify commands in a single terminal window and send them to a collection of remote machines where they can be executed.

Why you would need a utility like this when, using openSSH, you can create a file containing your commands and use a bash for loop to run it on a list of remote hosts, one at a time? One advantage of a parallel SSH utility is that commands can be run on several hosts at the same time. For a short-running task this might not matter much, but if a task needs an hour to complete and you need to run it on 20 hosts, parallel execution beats serial by a mile. Also, if you want to interactively edit the same file on multiple machines, it might be quicker to use a parallel SSH utility and edit the file on all nodes with vi rather than concoct a script to do the same edit.

Many of these parallel SSH tools include support for copying to many hosts at once (a parallel version of scp) or using rsync on a collection of hosts at once. Because the parallel SSH implementations know about all the hosts in a group, some of them also offer the ability to execute a command "on one host" and will work out which host to pick using load balancing. Finally, some parallel SSH projects let you use barriers so that you can execute a collection of commands and explicitly have each node in the group wait until all the nodes have completed a stage before moving on to the next stage of processing.

Parallel ssh (pssh)

The Parallel ssh project includes parallel versions of the shell (pssh), scp (pscp), rsync (prsync), and kill (pnuke).

pssh is packaged for openSUSE as a 1-Click install, is available in Ubuntu Hardy Universe and the Fedora 9 repositories. I used the 64-bit package from the Fedora 9 repositories.

All of the Parallel ssh commands have the form command -h hosts-file options, where the hosts-file contains a list of all the hosts that you want to have the command executed on. For example, the first pssh command below will execute the date command on p1 and p2 as the ben user. The optional -l argument specifies the username that should be used to log in to the remote machines.

# cat hosts-file p1 p2 # pssh -h hosts-file -l ben date [1] 21:12:55 [SUCCESS] p2 22 [2] 21:12:55 [SUCCESS] p1 22 # pssh -h hosts-file -l ben -P date p2: Thu Oct 16 21:14:02 EST 2008 p2: [1] 21:13:00 [SUCCESS] p2 22 p1: Thu Sep 25 15:44:36 EST 2008 p1: [2] 21:13:00 [SUCCESS] p1 22

Normally the standard output from the remote hosts is not shown to you. The -P option in the last invocation displays the output from both remote hosts as well as the exit status. If you are running more complex commands you might like to use -i instead to see each remote host's output grouped nicely under its hostname rather than mixed up as the output comes in from the hosts. You can also use the --outdir pssh option to specify the path of a directory that should be used to save the output from each remote host. The output for each host is saved in separate file named with the remote machine's hostname.

You can use the --timeout option to specify how long a command can take. It defaults to 60 seconds. This means that if your command fails to complete within 60 seconds on a host, pssh will consider it an error and report it as such, as shown below. You can increase the timeout to something well above what might be acceptable (for example to 24 hours) to avoid this problem.

# pssh -h hosts-file -l ben -i "sleep 65; date" [1] 21:19:26 [FAILURE] p1 22 Timeout [2] 21:19:26 [FAILURE] p2 22 (4, 'Interrupted system call')

The pscp command takes the same -h, -l, and --timeout options and includes a --recursive option to enable deep copying from the local host. At the end of the command you supply the local and remote paths you would like to copy. The first pscp command in the example below copies a single file to two remote hosts in parallel. The following ssh command checks that the file exists on the p1 machine. The second pscp command fails in a verbose manner without really telling you the simple reason why. Knowing that I was trying to copy a directory over, I added the --recursive option to the command and it executed perfectly. The final ssh command verifies that the directory now exists on the p1 remote host.

$ mkdir example-tree $ date > example-tree/df1.txt $ date > example-tree/df2.txt $ mkdir example-tree/subdir1 $ date > example-tree/subdir1/df3.txt $ pscp -h hosts-file -l ben example-tree/df1.txt /tmp/df1.txt [1] 21:28:36 [SUCCESS] p1 22 [2] 21:28:36 [SUCCESS] p2 22 $ ssh p1 "cat /tmp/df1.txt" Thu Oct 16 21:27:25 EST 2008 $ pscp -h hosts-file -l ben example-tree /tmp/example-tree ... python: Python/ceval.c:2918: set_exc_info: Assertion `frame != ((void *)0)' failed. Aborted $ pscp -h hosts-file -l ben --recursive example-tree /tmp/example-tree [1] 21:29:57 [SUCCESS] p1 22 [2] 21:29:57 [SUCCESS] p2 22 $ ssh p1 "ls -l /tmp/example-tree" total 24 -rw-r--r-- 1 ben ben 29 2008-09-25 16:01 df1.txt -rw-r--r-- 1 ben ben 29 2008-09-25 16:01 df2.txt drwxr-xr-x 2 ben ben 4096 2008-09-25 16:01 subdir1

The prsync command uses only a handful of the command-line options from rsync. In particular, you cannot use the verbose or dry-run options to get details or see what would have been done. The command shown below will rsync the example-tree into /tmp/example-tree on the remote hosts in a manner similar to the final command in the pscp example.

$ prsync -h hosts-file -l ben -a --recursive example-tree /tmp

The main gain of the prsync command over using the normal rsync command with pssh is that prsync gives a simpler command line and lets you sync from the local machine to the remote hosts directly. Using pssh and rsync, you are running the rsync command on each remote machine, so the remote machine will need to connect back to the local machine in order to sync.

The pslurp command is sort of the opposite to the pscp in that it grabs a file or directory off all the remote machines and copies it to the local machine. The below command grabs the example-tree directory from both p1 and p2 and stores them into /tmp/outdir. The -r option is shorthand for --recursive. As you can see, for each remote host a new directory is created with the name of the host, and inside that directory a copy of example-tree is made using the local directory name supplied as the last argument to pslurp.

# mkdir /tmp/outdir # pslurp -h hosts-file -L /tmp/outdir -l ben -r /tmp/example-tree example-tree # l /tmp/outdir drwxr-xr-x 3 root root 4.0K 2008-10-16 21:47 p1/ drwxr-xr-x 3 root root 4.0K 2008-10-16 21:47 p2/ # l /tmp/outdir/p2 drwxr-xr-x 3 root root 4.0K 2008-10-16 21:47 example-tree/ # l /tmp/outdir/p2/example-tree/ -rw-r--r-- 1 root root 29 2008-10-16 21:47 df10.txt -rw-r--r-- 1 root root 29 2008-10-16 21:47 df1.txt ... drwxr-xr-x 2 root root 4.0K 2008-10-16 21:47 subdir1/

You can use environment variables to make things easier with Parallel ssh. You can use the PSSH_HOSTS variable to name the hosts file instead of using the -h option. Likewise, the PSSH_USER environment variable lets you set the username to log in as, like the -l pssh command line option.

 

pssh provides a number of commands for executing against a group of computers, using SSH. It’s most useful for operating on clusters of homogenously-configured hosts.

The package contains:

• Parallel ssh (pssh), executes commands on multiple hosts in parallel
• Parallel scp (pscp), copies files to multiple remote hosts in parallel
• Parallel rsync (prsync), efficiently copies files to multiple hosts in parallel
• Parallel nuke (pnuke), kills processes on multiple remote hosts in parallel
• Parallel slurp (pslurp), copies files from multiple remote hosts to a central host in parallel

These tools are good for controlling large collections of nodes, where faster alternatives

pssh Syntax

pssh command -h hosts-file options

-h –hosts   hosts file (each line “host[:port] [user]“)
-l –user    username (OPTIONAL)
-p –par     max number of parallel threads (OPTIONAL)
-o –outdir  output directory for stdout files (OPTIONAL)
-t –timeout timeout in seconds to do ssh to a host (OPTIONAL)
-v –verbose turn on warning and diagnostic messages (OPTIONAL)
-O –options SSH options (OPTIONAL)

where the hosts-file contains a list of all the hosts that you want to have the command executed on.

pssh Examples

The following example runs hostname on three machines (IPs or hostnames) specified in the file ips.txt using login irb2 and saves the output in /tmp/foo.

sudo cat ips.txt
128.112.152.122
18.31.0.190
128.232.103.201

sudo pssh -h ips.txt -l irb2 -o /tmp/foo hostname

Success on 128.112.152.122:22
Success on 18.31.0.190:22
Success on 128.232.103.201:22

sudo ls /tmp/foo

128.112.152.122  128.232.103.201  18.31.0.190

sudo cat /tmp/foo/*

planetlab-1.cs.princeton.edu
planetlab1.xeno.cl.cam.ac.uk
planetlab1.lcs.mit.edu

By default, pssh uses at most 32 ssh processes in parallel to ssh to the various nodes. (This is somewhat important if you’re controlling hundreds or thousands of machines.) By default, it also uses a timeout of one minute to ssh to a node and obtain a result. For ssh commands that take longer than this (e.g., sleep 61), the -t option can be used. Note that pssh and pnuke have a default timeout of one minute. pscp and prsync have no default timeout, but one can be specified using the -t option.

pscp

Here’s an example of using pscp to copy files in parallel to a set of machines.

sudo  pscp -h ips.txt -l irb2 /etc/hosts /tmp/hosts

Success on 128.112.152.122:22
Success on 18.31.0.190:22
Success on 128.232.103.201:22

Using the -r option will perform a recursive copy for copying entire directories.

NEWS CONTENTS

• 20200323 : Pscp - Transfer-Copy Files to Multiple Linux Servers Using Single Shell by Ravi Saive ( Dec 05, 2015 , www.tecmint.com )
• 20181108 : How to use parallel ssh (PSSH) for executing ssh in parallel on a number of Linux-Unix-BSD servers ( Nov 08, 2018 , www.cyberciti.biz )
• 20181013 : 4 Useful Tools to Run Commands on Multiple Linux Servers ( Oct 13, 2018 , www.tecmint.com )
• 20180807 : Managing Multiple Linux Servers with ClusterSSH Linux.com The source for Linux information ( Aug 07, 2018 , www.linux.com )
• 20170212 : Linux Server Hacks, Volume Two ( Feb 12, 2017 , www.amazon.com )
• 20141218 : Execute commands simultaneously on multiple servers Using PSSH/Cluster SSH/Multixterm ( Execute commands simultaneously on multiple servers Using PSSH/Cluster SSH/Multixterm, Dec 18, 2014 )
• 20100706 : What is a good modern parallel SSH tool - Server Fault ( What is a good modern parallel SSH tool - Server Fault, Jul 06, 2010 )
• 20100705 : parallel-ssh - Project Hosting on Google Code ( parallel-ssh - Project Hosting on Google Code, Jul 05, 2010 )
• 20100705 : Save time managing multiple systems with Parallel SSH Linux and Open Source ( TechRepublic.com )

Old News ;-)

[Mar 23, 2020] Pscp - Transfer-Copy Files to Multiple Linux Servers Using Single Shell by Ravi Saive

Dec 05, 2015 | www.tecmint.com

Pscp utility allows you to transfer/copy files to multiple remote Linux servers using single terminal with one single command, this tool is a part of Pssh (Parallel SSH Tools), which provides parallel versions of OpenSSH and other similar tools such as:

1. pscp – is utility for copying files in parallel to a number of hosts.
2. prsync – is a utility for efficiently copying files to multiple hosts in parallel.
3. pnuke – it helps to kills processes on multiple remote hosts in parallel.
4. pslurp – it helps to copy files from multiple remote hosts to a central host in parallel.

When working in a network environment where there are multiple hosts on the network, a System Administrator may find these tools listed above very useful. When working in a network environment where there are multiple hosts on the network, a System Administrator may find these tools listed above very useful.

Pscp – Copy Files to Multiple Linux Servers In this article, we shall look at some useful examples of Pscp utility to transfer/copy files to multiple Linux hosts on a network. To use the pscp tool, you need to install the PSSH utility on your Linux system, for installation of PSSH you can read this article. Pscp – Copy Files to Multiple Linux Servers In this article, we shall look at some useful examples of Pscp utility to transfer/copy files to multiple Linux hosts on a network. To use the pscp tool, you need to install the PSSH utility on your Linux system, for installation of PSSH you can read this article. In this article, we shall look at some useful examples of Pscp utility to transfer/copy files to multiple Linux hosts on a network. To use the pscp tool, you need to install the PSSH utility on your Linux system, for installation of PSSH you can read this article. To use the pscp tool, you need to install the PSSH utility on your Linux system, for installation of PSSH you can read this article. To use the pscp tool, you need to install the PSSH utility on your Linux system, for installation of PSSH you can read this article.

1. How to Install Pssh Tool to Execute Commands on Multiple Linux Servers

Almost all the different options used with these tools are the same except for few that are related to the specific functionality of a given utility. Almost all the different options used with these tools are the same except for few that are related to the specific functionality of a given utility. How to Use Pscp to Transfer/Copy Files to Multiple Linux Servers While using pscp you need to create a separate file that includes the number of Linux server IP address and SSH port number that you need to connect to the server. While using pscp you need to create a separate file that includes the number of Linux server IP address and SSH port number that you need to connect to the server. Copy Files to Multiple Linux Servers Let's create a new file called " myscphosts.txt " and add the list of Linux hosts IP address and SSH port (default 22 ) number as shown. Let's create a new file called " myscphosts.txt " and add the list of Linux hosts IP address and SSH port (default 22 ) number as shown.

192.168.0.3:22
192.168.0.9:22

Once you've added hosts to the file, it's time to copy files from local machine to multiple Linux hosts under /tmp directory with the help of following command. Once you've added hosts to the file, it's time to copy files from local machine to multiple Linux hosts under /tmp directory with the help of following command.

# pscp -h myscphosts.txt -l tecmint -Av wine-1.7.55.tar.bz2 /tmp/
OR
# pscp.pssh -h myscphosts.txt -l tecmint -Av wine-1.7.55.tar.bz2 /tmp/

Sample Output

Warning: do not enter your password if anyone else has superuser
privileges or access to your account.
Password: 
[1] 17:48:25 [SUCCESS] 192.168.0.3:22
[2] 17:48:35 [SUCCESS] 192.168.0.9:22

Explanation about the options used in the above command. Explanation about the options used in the above command.

1. -h switch used to read a hosts from a given file and location.
2. -l switch reads a default username on all hosts that do not define a specific user.
3. -A switch tells pscp ask for a password and send to ssh.
4. -v switch is used to run pscp in verbose mode.

Copy Directories to Multiple Linux Servers If you want to copy entire directory use -r option, which will recursively copy entire directories as shown. If you want to copy entire directory use -r option, which will recursively copy entire directories as shown.

# pscp -h myscphosts.txt -l tecmint -Av -r Android\ Games/ /tmp/
OR
# pscp.pssh -h myscphosts.txt -l tecmint -Av -r Android\ Games/ /tmp/

Sample Output

Warning: do not enter your password if anyone else has superuser
privileges or access to your account.
Password: 
[1] 17:48:25 [SUCCESS] 192.168.0.3:22
[2] 17:48:35 [SUCCESS] 192.168.0.9:22

You can view the manual entry page for the pscp or use pscp --help command to seek for help.

1. Ashwini R says: January 24, 2019 at 7:13 pm

   It didn't work for me as well. I can get into the machine through same ip and port as I've inserted into hosts.txt file. Still i get the below messages:

   [root@node1 ~]# pscp -h myscphosts.txt root -Av LoadKafkaRN.jar /home/
   [1] 13:37:42 [FAILURE] 173.37.29.85:22 Exited with error code 1
   [2] 13:37:42 [FAILURE] 173.37.29.2:22 Exited with error code 1
   [3] 13:37:42 [FAILURE] 173.37.28.176:22 Exited with error code 1
   [4] 13:37:42 [FAILURE] 173.37.28.121:22 Exited with error code 1
   

   • Cody says: April 5, 2019 at 7:52 pm

     did you find an answer for this issue? I'm having the same problem

2. Ankit Tiwari says: November 28, 2016 at 11:26 am

   Hi,

   I am following this tutorial to copy a file to multiple system but its giving error. The code i am using is

   pscp -h myhost.txt -l zabbix -Av show-image-1920×1080.jpg /home/zabbix/

   but it gives error

   [1] 11:18:50 [FAILURE] 192.168.0.244:22 Exited with error code 1

   • Ravi Saive says: November 28, 2016 at 1:00 pm

     @Ankit,

     Have you placed correct remote SSH host IP address and port number in the myscphosts.txt file? please confirm and add correct values and then try again..

   jHz says: September 7, 2016 at 7:18 am

   Hi,

   I am trying to copy one file from 30 hosts to one central computer by following you article but no success.
   I am using pscp command for this purpose:

   pscp -h hosts.txt /camera/1.jpg /camera/1.jpg

   where camera directory has been created already in which 1.jpg exists. It always give me error:

   Exited with error code 1

   I have also tried pscp command to copy file from one host to server:

   pscp -H "192.168.0.101" /camera/1.jpg /camera/1.jpg

   but it also returned me with the same error.

   Any help will be much appreciated.
   Thanks in advance.

[Nov 08, 2018] How to use parallel ssh (PSSH) for executing ssh in parallel on a number of Linux-Unix-BSD servers

Looks like -h option is slightly more convenient then -w option.

Notable quotes:

"... Each line in the host file are of the form [user@]host[:port] and can include blank lines and comments lines beginning with "#". ..."

Nov 08, 2018 | www.cyberciti.biz

First you need to create a text file called hosts file from which pssh read hosts names. The syntax is pretty simple.

Each line in the host file are of the form [user@]host[:port] and can include blank lines and comments lines beginning with "#".

Here is my sample file named ~/.pssh_hosts_files:
$ cat ~/.pssh_hosts_files
vivek@dellm6700
[email protected]
[email protected]
[email protected]
Run the date command all hosts:
$ pssh -i -h ~/.pssh_hosts_files date
Sample outputs:

[1] 18:10:10 [SUCCESS] [email protected]
Sun Feb 26 18:10:10 IST 2017
[2] 18:10:10 [SUCCESS] vivek@dellm6700
Sun Feb 26 18:10:10 IST 2017
[3] 18:10:10 [SUCCESS] [email protected]
Sun Feb 26 18:10:10 IST 2017
[4] 18:10:10 [SUCCESS] [email protected]
Sun Feb 26 18:10:10 IST 2017

Run the uptime command on each host:
$ pssh -i -h ~/.pssh_hosts_files uptime
Sample outputs:

[1] 18:11:15 [SUCCESS] [email protected]
 18:11:15 up  2:29,  0 users,  load average: 0.00, 0.00, 0.00
[2] 18:11:15 [SUCCESS] vivek@dellm6700
 18:11:15 up 19:06,  0 users,  load average: 0.13, 0.25, 0.27
[3] 18:11:15 [SUCCESS] [email protected]
 18:11:15 up  1:55,  0 users,  load average: 0.00, 0.00, 0.00
[4] 18:11:15 [SUCCESS] [email protected]
 6:11PM  up 1 day, 21:38, 0 users, load averages: 0.12, 0.14, 0.09

You can now automate common sysadmin tasks such as patching all servers:
$ pssh -h ~/.pssh_hosts_files -- sudo yum -y update
OR
$ pssh -h ~/.pssh_hosts_files -- sudo apt-get -y update
$ pssh -h ~/.pssh_hosts_files -- sudo apt-get -y upgrade

How do I use pssh to copy file to all servers?

The syntax is:
pscp -h ~/.pssh_hosts_files src dest
To copy $HOME/demo.txt to /tmp/ on all servers, enter:
$ pscp -h ~/.pssh_hosts_files $HOME/demo.txt /tmp/
Sample outputs:

[1] 18:17:35 [SUCCESS] vivek@dellm6700
[2] 18:17:35 [SUCCESS] [email protected]
[3] 18:17:35 [SUCCESS] [email protected]
[4] 18:17:35 [SUCCESS] [email protected]

Or use the prsync command for efficient copying of files:
$ prsync -h ~/.pssh_hosts_files /etc/passwd /tmp/
$ prsync -h ~/.pssh_hosts_files *.html /var/www/html/

How do I kill processes in parallel on a number of hosts?

Use the pnuke command for killing processes in parallel on a number of hosts. The syntax is:
$ pnuke -h .pssh_hosts_files process_name
### kill nginx and firefox on hosts:
$ pnuke -h ~/.pssh_hosts_files firefox
$ pnuke -h ~/.pssh_hosts_files nginx
See pssh/pscp command man pages for more information.

[Oct 13, 2018] 4 Useful Tools to Run Commands on Multiple Linux Servers

Oct 13, 2018 | www.tecmint.com

1. John west says: October 12, 2018 at 5:02 pm

   Xcat project spawned psh and dsh . Older version of psh had an option to use nodelist.tab file that contained:

   Host01 group1,webserver,rhel7
   Host02 group1,appserver,rhel6
   ....
   

   Psh. Group1 uptime

   Would run on both

   Psh rhel6 uptime

   would run only on host02

   Each server is listed once, not i. 10 different files.

   Later xcat switched to a db format for hosts, but was more complicated.

   Loved that nodelist.tab simplicity.

   Reply
2. Rick Maus says: October 11, 2018 at 4:45 pm

   Thanks for the article! Always looking for more options to perform similar tasks.

   When you want to interact with multiple hosts simultaneously, MobaXterm (mobaxterm.mobatek.net), is a powerful tool. You can even use your favorite text editor (vim, emacs, nano, ed) in real time.

   Each character typed is sent in parallel to all hosts and you immediately see the effect. Selectively toggling whether the input stream is sent to individual host(s) during a session allows for custom changes that only affect a desired subset of hosts.

   MobaXterm has a free home version as well as a paid professional edition. The company was highly responsive to issues reports that I provided and corrected the issues quickly.

   I have no affiliation with the company other than being a happy free edition customer.

   Reply
   • Aaron Kili says: October 12, 2018 at 12:59 pm

     @Rick

     Many thanks for sharing this seful information.

[Aug 07, 2018] Managing Multiple Linux Servers with ClusterSSH Linux.com The source for Linux information

Aug 07, 2018 | www.linux.com

Managing Multiple Linux Servers with ClusterSSH

If you're a Linux system administrator, chances are you've got more than one machine that you're responsible for on a daily basis. You may even have a bank of machines that you maintain that are similar -- a farm of Web servers, for example. If you have a need to type the same command into several machines at once, you can login to each one with SSH and do it serially, or you can save yourself a lot of time and effort and use a tool like ClusterSSH.

ClusterSSH is a Tk/Perl wrapper around standard Linux tools like XTerm and SSH. As such, it'll run on just about any POSIX-compliant OS where the libraries exist -- I've run it on Linux, Solaris, and Mac OS X. It requires the Perl libraries Tk ( perl-tk on Debian or Ubuntu) and X11::Protocol ( libx11-protocol-perl on Debian or Ubuntu), in addition to xterm and OpenSSH.

Installation

Installing ClusterSSH on a Debian or Ubuntu system is trivial -- a simple sudo apt-get install clusterssh will install it and its dependencies. It is also packaged for use with Fedora, and it is installable via the ports system on FreeBSD. There's also a MacPorts version for use with Mac OS X, if you use an Apple machine. Of course, it can also be compiled from source.

Configuration

ClusterSSH can be configured either via its global configuration file -- /etc/clusters , or via a file in the user's home directory called .csshrc . I tend to favor the user-level configuration as that lets multiple people on the same system to setup their ClusterSSH client as they choose. Configuration is straightforward in either case, as the file format is the same. ClusterSSH defines a "cluster" as a group of machines that you'd like to control via one interface. With that in mind, you enumerate your clusters at the top of the file in a "clusters" block, and then you describe each cluster in a separate section below.

For example, let's say I've got two clusters, each consisting of two machines. "Cluster1" has the machines "Test1" and "Test2" in it, and "Cluster2" has the machines "Test3" and "Test4" in it. The ~.csshrc (or /etc/clusters ) control file would look like this:

clusters = cluster1 cluster2

cluster1 = test1 test2
cluster2 = test3 test4

You can also make meta-clusters -- clusters that refer to clusters. If you wanted to make a cluster called "all" that encompassed all the machines, you could define it two ways. First, you could simply create a cluster that held all the machines, like the following:

clusters = cluster1 cluster2 all

cluster1 = test1 test2
cluster2 = test3 test4
all = test1 test2 test3 test4

However, my preferred method is to use a meta-cluster that encompasses the other clusters:

clusters = cluster1 cluster2 all

cluster1 = test1 test2
cluster2 = test3 test4
all = cluster1 cluster2

By calling out the "all" cluster as containing cluster1 and cluster2, if either of those clusters ever change, the change is automatically captured so you don't have to update the "all" definition. This will save you time and headache if your .csshrc file ever grows in size.

Using ClusterSSH

Using ClusterSSH is similar to launching SSH by itself. Simply running cssh -l <username> <clustername> will launch ClusterSSH and log you in as the desired user on that cluster. In the figure below, you can see I've logged into "cluster1" as myself. The small window labeled "CSSH [2]" is the Cluster SSH console window. Anything I type into that small window gets echoed to all the machines in the cluster -- in this case, machines "test1" and "test2". In a pinch, you can also login to machines that aren't in your .csshrc file, simply by running cssh -l <username> <machinename1> <machinename2> <machinename3> .

If I want to send something to one of the terminals, I can simply switch focus by clicking in the desired XTerm, and just type in that window like I usually would. ClusterSSH has a few menu items that really help when dealing with a mix of machines. As per the figure below, in the "Hosts" menu of the ClusterSSH console there's are several options that come in handy.

"Retile Windows" does just that if you've manually resized or moved something. "Add host(s) or Cluster(s)" is great if you want to add another set of machines or another cluster to the running ClusterSSH session. Finally, you'll see each host listed at the bottom of the "Hosts" menu. By checking or unchecking the boxes next to each hostname, you can select which hosts the ClusterSSH console will echo commands to. This is handy if you want to exclude a host or two for a one-off or particular reason. The final menu option that's nice to have is under the "Send" menu, called "Hostname". This simply echoes each machine's hostname to the command line, which can be handy if you're constructing something host-specific across your cluster.

Caveats with ClusterSSH

Like many UNIX tools, ClusterSSH has the potential to go horribly awry if you aren't very careful with its use. I've seen ClusterSSH mistakes take out an entire tier of Web servers simply by propagating a typo in an Apache configuration. Having access to multiple machines at once, possibly as a privileged user, means mistakes come at a great cost. Take care, and double-check what you're doing before you punch that Enter key.

Conclusion

ClusterSSH isn't a replacement for having a configuration management system or any of the other best practices when managing a number of machines. However, if you need to do something in a pinch outside of your usual toolset or process, or if you're doing prototype work, ClusterSSH is indispensable. It can save a lot of time when doing tasks that need to be done on more than one machine, but like any power tool, it can cause a lot of damage if used haphazardly.

[Feb 12, 2017] Linux Server Hacks, Volume Two

Notable quotes:

"... multixterm ..."

"... xterms ..."

"... multixterm ..."

"... host1 host2 ..."

Feb 12, 2017 | www.amazon.com

Execute Commands Simultaneously on Multiple Servers

Run the same command at the same time on multiple systems, simplifying administrative tasks and reducing synchronization problems .

If you have multiple servers with similar or identical configurations (such as nodes in a cluster), it's often difficult to make sure the contents and configuration of those servers are identical. It's even more difficult when you need to make configuration modifications from the command line, knowing you'll have to execute the exact same command on a large number of systems (better get coffee first). You could try writing a script to perform the task automatically, but sometimes scripting is overkill for the work to be done. Fortunately, there's another way to execute commands on multiple hosts simultaneously.

A great solution for this problem is an excellent tool called multixterm , which enables you to simultaneously open xterms to any number of systems, type your commands in a single central window and have the commands executed in each of the xterm windows you've started. Sound appealing? Type once, execute many-it sounds like a new pipelining instruction set.

multixterm is available from http://expect.nist.gov/example/multixterm.man.html , and it requires expect and tk . The most common way to run multixterm is with a command like the following:

	$ 
multixterm -xc "ssh %n"


host1 host2

This command will open ssh connections to host1 and host2 ( Figure 4-1 ). Anything typed in the area labeled "stdin window" (which is usually gray or green, depending on your color scheme) will be sent to both windows, as shown in the figure.

As you can see from the sample command, the –xc option stands for execute command, and it must be followed by the command that you want to execute on each host, enclosed in double quotation marks. If the specified command includes a wildcard such as %n , each hostname that follows the command will be substituted into the command in turn when it is executed. Thus, in our example, the commands ssh host1 and ssh host2 were both executed by multixterm , each within its own xterm window.

See Also

• man multixterm
• "Enable Quick telnet/SSH Connections from the Desktop" [Hack #41]
• "Disconnect Your Console Without Ending Your Session" [Hack #34]

[Dec 18, 2014] Execute commands simultaneously on multiple servers Using PSSH/Cluster SSH/Multixterm

[Jul 06, 2010] What is a good modern parallel SSH tool - Server Fault

Q. I have heard that pssh and clusterssh are two popular ones, but I thought I would open it to discussion here and see what the community's experiences with these tools were? What are the gotchas? Any decent hacks or use cases?

A: I have used pssh and it's easy and works quite well. It's really great for quick queries.

If you find yourself managing servers I'd suggest something more robust and in a slightly different realm (configuration management) such as Puppet or CFEngine.

There is also dsh for parallel ssh runs.

Mussh is a good alternative, it is already included in many Linux distros.

Mussh is a shell script that allows you to execute a command or script over ssh on multiple hosts with one command. When possible mussh will use ssh-agent and RSA/DSA keys to minimize the need to enter your password more than once.

The SSH Power Tool (sshpt) was designed for parallel SSH without requiring that the user setup pre-shared SSH keys. It is superior to pssh and clusterssh in that it supports executions via sudo and can also copy files and execute them afterwards (optionally, via sudo as well). By default it outputs results in CSV format but sshpt.py doubles as an importable Python module so you can use it in your own programs (I used to use it as a back-end behind a a custom-built web-based reporting tool at my former employer).

[Jul 05, 2010] parallel-ssh - Project Hosting on Google Code

Python-based. More sophisticated then cluster ssh which is Perl-based...

PSSH provides parallel versions of OpenSSH and related tools. Included are pssh, pscp, prsync, pnuke, and pslurp. The project includes psshlib which can be used within custom applications. The source code is written in Python and can be cloned from:

git clone git://aml.cs.byu.edu/pssh.git

PSSH was originally written and maintained by Brent N. Chun. Due to his busy schedule, Brent handed over maintenance to Andrew McNabb in October 2009.

Save time managing multiple systems with Parallel SSH Linux and Open Source

TechRepublic.com

OpenSSH is perhaps one of the most powerful and versatile tools available to any Linux user. It allows you to securely connect to a remote system via a shell or encrypted FTP and also allows you to copy files securely to and from remote systems.

For a user caring for multiple systems, OpenSSH is extremely useful, but being able to execute OpenSSH commands in parallel is even more so. This is where Parallel SSH, or pssh, comes in. Pssh provides parallel versions of the OpenSSH tools, meaning you can execute commands on various hosts in parallel, copy files in parallel, and so forth. Pssh is essentially a frontend to OpenSSH written in Python. It includes pssh, pscp, and prsync, as well as pslurp (the opposite of pscp in that it downloads rather than uploads) and pnuke (a frontend to the kill command).

Using pssh is extremely easy. There are no manpages, but calling the command with no arguments will bring up the help, which describes each option.

Every command uses a plaintext "hosts" file that is a simple text file containing the hosts to act upon, one per line. As an example, assume you wanted to make sure that the time on each server was identical. This could be done using the date command, but to do it with regular SSH, you would have to execute the command at the same time on each host using screen or multiple terminals. With pssh, this is one simple command:

$ pssh -h hosts -P date

hades: Wed Nov 12 10:21:11 MST 2008

hades: [1] 10:21:11 [SUCCESS] hades 22

odin: Wed Nov 12 10:21:11 MST 2008

odin: [2] 10:21:11 [SUCCESS] odin 22

$ cat hosts

hades

odin

Contrast that to using ssh directly:

$ for host in hades odin; do ssh ${host} "date"; done

Wed Nov 12 10:24:02 MST 2008

Wed Nov 12 10:24:02 MST 2008

Recommended Links

• parallel-ssh - PSSH Parallel SSH Tools - Google Project Hosting
• pssh Run Command On Multiple SSH Servers - nixCraft
• Execute commands simultaneously on multiple servers Using PSSH-Cluster SSH-Multixterm -- Ubuntu Geek
• Linux.com Execute commands simultaneously on multiple servers
• Blog O' Matty " Blog Archive " Running commands across multiple servers with clusterssh

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