clustersh

clustersh

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Introduction

a simple command tool, which can execute shell script in target servers, without need to install anything in these servers. More over, it can execute the script for specific Linux distribution (like ubuntu, centos etc.) in target server.

You can simply understand it as a "cluster version" of sh command on Linux.clustersh shname merely omits .sh suffix in shname, and it is able to choose whether to execute shname_centos.sh or shname_ubuntu.sh according to target server's operation system type. If there is no script for specific operation system, shname.sh will be executed.

Scenes

If you want to execute shell script together in plenty of computers (perhaps hundreds of computers) which are just installed linux operation system, clustersh is very suitable for you

"just installed linux operation system" only to emphasize clustersh needn't install any thing in target servers, it's not necessary condition.

Get Started

clustersh is very simple to use. Simply choose a Linux machine that is connected to the cluster network and follow the steps below.

Suppose our task is to install an nfs client for all machines in the cluster. There are centos machines and ubuntu machines in the cluster.

Download cluster sh

Download clustersh binary file from the download address(use wget as follows) , and then move it to the PATH of Linux:

wget https://github.com/DQinYuan/clustersh/releases/download/v0.1.0/clustersh
chmod a+x clustersh
mv clustersh /usr/local/bin

Try to execute it:

clustersh --help

Then you can see some help info.

Prepare a directory

Assume the prepared directory is ~/clustershtest:

mkdir ~/clustershtest
cd ~/clustershtest

Config ips file

Create a file named ips in the directory:

touch ips

Then config ips of all the machines in the cluster in the file, assuming that there are 5 machines , 10.10.108.23,10.10.108.71, 10.10.108.72,10.10.108.73,10.10.108.90 respectively. So we can config as follow:

10.10.108.23
10.10.108.71-73
10.10.108.90

Here we use 71-73 to target a range of ip. clustersh just surpport range ip in last segment of ip address.

default config file name is ips, but you can add --ips param when execute clustersh command to customize config file name.

Write shell script

Write two scripts in the directory, as follows:

• nfs_centos.sh, to install nfs-client in centos machine

#!/bin/sh

yum install -y  nfs-utils

• nfs_ubuntu.sh, to install nfs-client in ubuntu machine

#!/bin/sh

apt install -y nfs-common

Before starting the next step, you'd better make sure that all the shell scripts you write are tested on the corresponding operating system.

Execute clustersh

Final, you only need to execute command as follow:

clustersh nfs -U root -P xxxxxx

clustersh will look for ips in current directory, and read ip from it. Then apply username and password provided by command line(here, username is "root" and password is "xxxxxx") to log in them. ( in practice, servers in a cluster often have the same username and password, so clustersh only use a pair of username and password )

nfs is the simple name of the shell script to be executed, it will be extended to nfs_os.sh by clustersh according to target server's operation system type. If nfs_os.sh not exists, nfs.sh will be executed.

For example, clustersh log in a centos server, discovering its os is centos. Then it will look for nfs_centos.sh.If successful, clustersh will execute it, else it will execute nfs.sh.

If there is more os type in your cluster, you should name specific script as:

simplename_os.sh

(in this case, simplename is "nfs")

clustersh can recognize follow os:

You can extra provide a simplename.sh file to execute when clustersh can not recognize os type or there is no specific scripts for target os

Check output

Although shell scripts pass tests on the corresponding operating system, it is still possible to fail in some servers for some unpredictable reasons(no enough space on disks, dns config err, for example). clustersh will print if script is executed successfully on a target server in the runtime. For a few failed machines, better to log in them and manually complete your task.

From the picture above, we can see 10.10.108.41 fail to execute the shell script for some reason, you'd better log in it and manually compete it. Fortunately, this not often happen, so it will not expend too many energy.

source code for this case

Another case

Suppose I am too lazy to set up a DNS server in the cluster, so they can only identify each other's hostnames through the local hosts file. We need to update all the hosts files of the machines in the cluster. clustersh can help you easily complete the task.

Suppose there are only 4 machines in the cluster, 10.10.108.91,10.10.108.92,10.10.108.93, 10.10.108.94 respectively. (here are only four machines for the sake of convenience. In reality, there may be hundreds of machines.)

source code for this case

Steps as follows.

Create a directory

Create a work directory

mkdir unihosts
cd unihosts

Edit ips file

Edit ips file in this directory:

10.10.108.91-94

Edit uniform hosts file

The uniform hosts file in the cluster, I call it "unihosts":

touch unihosts

edit it as follows:

127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
10.10.108.91 h91
10.10.108.92 h92
10.10.108.93 h93
10.10.108.94 h94

Write shell script

The main function of the script is to overwrite /etc/hosts with unihosts.

unihosts.sh:

#!/bin/sh

\cp -f ./unihosts /etc/hosts

The script is common to all operating system, so we needn't to provide os specific scrips like last case.

Execute clustersh

clustersh unihosts -U root -P xxxxxx

The task is relatively simple, so execution is very fast even if there are hundreds of machines.

Summary

This case is to illustrate that you can use any file in the current directory and subdirectories in your shell script, because all files in the current directory and subdirectories will be sent to the target servers by clustersh.

Params introduction

You can get all available param and introduction by clustersh --help

Principle

clustersh is only a simple abstraction on ssh.It will first send all files in the working directory and its subdirectories to the target server, After which it chooses a suitable script to be executed.

clustersh will connect to machines with the same number of CPU cores at the same time.