How to use parallel ssh (PSSH) for executing ssh in parallel on a number of Linux servers

Recently I come across a nice little nifty tool called pssh to run a single command on multiple Linux / UNIX / BSD servers. You can easily increase your productivy with this SSH tool.

More about pssh

pssh is a command line tool for executing ssh in parallel on some hosts. It specialties includes:

    Sending input to all of the processes
    Inputting a password to ssh
    Saving output to files
    IT/sysadmin taks automation such as patching servers
    Timing out and more

Let us see how to install and use pssh on Linux and Unix-like system.


Installation

You can install pssh as per your Linux and Unix variant. Once package installed, you can get parallel versions of the openssh tools. Included in the installation:

    Parallel ssh (pssh command)
    Parallel scp (pscp command )
    Parallel rsync (prsync command)
    Parallel nuke (pnuke command)
    Parallel slurp (pslurp command)

Install pssh on Debian/Ubuntu Linux

Type the following apt-get command/apt command to install pssh:
$ sudo apt install pssh
OR
$ sudo apt-get install pssh
Sample outputs:
Fig.01: Installing pssh on Debian/Ubuntu Linux

Install pssh on Apple MacOS X

Type the following brew command:
$ brew install pssh
Sample outputs:
Fig.02: Installing pssh on MacOS Unix

Install pssh on FreeBSD unix

Type any one of the command:
# cd /usr/ports/security/pssh/ && make install clean
OR
# pkg install pssh
Sample outputs:
Fig.03: Installing pssh on FreeBSD

Install pssh on RHEL/CentOS/Fedora Linux

First turn on EPEL repo and type the following command yum command:
$ sudo yum install pssh
Sample outputs:
Fig.04: Installing pssh on RHEL/CentOS/Red Hat Enterprise Linux

Install pssh on Fedora Linux

Type the following dnf command:
$ sudo dnf install pssh
Sample outputs:
Fig.05: Installing pssh on Fedora

Install pssh on Arch Linux

Type the following command:
$ sudo pacman -S python-pip
$ pip install pssh
How to use pssh command

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 [[email protected]]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
[email protected]
[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] [email protected]
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] [email protected]
 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] [email protected]
[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.

Conclusion

pssh is a pretty good tool for parallel SSH command execution on many servers. It quite is useful if you have 5 or 10 servers. Nevertheless, if you need to do something complicated you should look into Ansible and co.