Everyday I connect to a number of servers, and everyday I send the same command to a list of servers.
Sometimes it is Ubuntu servers, sometimes Debian servers; I needed a way to slice and dice my list of servers, and start a clustered ssh session with the resulting sliced and diced list of servers.
Enter tmux, tmux-cssh, and some custom bash scripting.
So, a little while a go I switched to Windows as my daily desktop OS.
I figured out how to tune Windows Terminal to my liking, but was missing clusterssh from my OSX days.
A friend of mine (Shane Howearth), pointed me (I think he unknowingly pointed me) to tmux.
And in turn I was pointed to tmux-cssh
Very cool that this is written by a Kiwi (New Zealander).
So, tmux-cssh allows me to cluster my ssh sessions. Now I need to figure a way to slice and dice my list of servers.
The Problem
I have some Ubuntu servers, and some Debian servers.
Some of those servers are bare metal, some are not.
Some of those servers are Hyper Visors, some are not.
Sometimes I want to connect to only Debian servers, sometimes I want to connect to only real machines (bare metal installs).
I want the ability to organise my list of servers into some kind of searchable list.
My Solution
Firstly, I don’t know whether this is the most elegant way, in fact, I’m pretty sure it’s not, and I would love to hear people’s suggestions.
Comment below !
For this to work, you must have your ssh sorted.
i.e. you must be able to do:
ssh host1Here is what I came up with:
The Data
I pictured my list of hosts as a number of rows in a table (or spreadsheet), and my “categories” as row headings.
Kind of like this:
| hostname | debian_hosts | real_hosts | hv_hosts | ubuntu_hosts | mikrotik_hosts | blank |
|---|---|---|---|---|---|---|
| host1 | y | |||||
| host2 | y | |||||
| host3 | y | |||||
| host4 | y | |||||
| host5 | y | |||||
| host6 | y | |||||
| host7 | y | |||||
| host8 | y | |||||
| host9 | y | y | ||||
| host10 | y | y | ||||
| host11 | y | y | y | |||
| host12 | y | y | ||||
| host13 | y | y | ||||
| host14 | y | |||||
| host15 | y | y | ||||
| host16 | y | |||||
| host17 | y | |||||
| host18 | y | |||||
| host19 | y |
Weirdly, I had to create a blank column at the end.
Otherwise, bash would drop the last column.
So, now bash drops the blank column.
I saved this info into a csv file (input.csv).
The data is now “predictable”. 👍
Selecting from the data
awk to the rescue:
awk -v c1=3 -F , '$c1 == "y" {print " "$1}' input.csvLet’s do a quick run down on awk:
- -v allows me to pass variables to awk.
- In this case I’m using it to name my columns.
- -F means fields are separated by the following character.
- in this case “,” as this is a csv (comma separated values) file.
- {print $1 } means, print the first column. i.e. the hostname.
Some Bash things I’ll use
So, I love bash.
I think anyone who reads this blog knows that ❗
I’m going to create an array I call “categories” using bash’s internal IFS special shell variable.
IFS=',' read -a categories <<< `head -n 1 input.csv`I’m also going to use getopt to get variables passed from the command line.
Basically, I want to use pretty short AND long variable names 😊
One interesting thing I’ll note here:
I wanted a “list” function that would list all my hosts, or list the hosts in a specific category.
My getopt options expect a passed argument.
i.e. options=$(getopt -o hdrvumal: --long help,debian,real,virtual,ubuntu,mikrotik,all,list: -- "$@")
So I wrote a wee bit in the script that checks to see if $arg2 is set, and if it’s not, then sets it, and also sets “default” values.
if [ -z "$2" ]; then
arg1=${1:-"h"}
arg2=${2:-"all"}
set -- "${arg1}" "${arg2}"
unset arg1 arg2
fiThe Script
that’s enough chatter … here’s the script 😌
I’ve stored tmux-cssh in my ~/bin/ directory, and made sure it is executable.
#!/bin/bash
DATA_SRC=input.csv
IFS=',' read -a categories <<< `head -n 1 $DATA_SRC`
ShowHelp() {
SCRIPT_NAME="$(basename "$(test -L "$0" && readlink "$0" || echo "$0")")"
echo "
$SCRIPT_NAME is a small shell script that opens a tmux window pane to a bunch of hosts.
Then runs a tmux session to simulate ClusterSSH
It can only take one argument at a time.
Usage:
$SCRIPT_NAME [single option]
Options
-h, --help Show this help screen
-d, --debian Open all Debian hosts
-r, --real Open all 'real' bare-metal hosts
-v, --virtualhost Open all hypervisors (i.e. virtual servers)
-u, --ubuntu Open all Ubuntu hosts
-m, --mikrotik Open all Mikrotik hosts
-a, --all Open all hosts (excluding Mikrotik Hosts)
-l, --list List all hosts (optionally pass a category name)
All hosts are defined in the file $DATA_SRC and are categorised as:
* Debian hosts (debian_hosts).
* Real hosts (real_hosts).
* Hyper Visor hosts (hv_hosts).
* Ubunutu hosts (ubuntu_hosts).
* and Mikrotik hosts (mikrotik_hosts).
A valid csv file with the following headers is required:
hostname,debian_hosts,real_hosts,hv_hosts,ubuntu_hosts,mikrotik_hosts,blank
Note: a blank column is required at the end
"
exit 1
}
connect_hosts() {
COLNUM=$1
if [[ $COLNUM == 1 ]]; then
# Column 6 is Mikrotik, let's connect to all NON-mikrotik hosts
ARRAY=(`awk -F , '$6 != "y" {print $1}' <(tail -n +2 $DATA_SRC)`)
else
ARRAY=(`awk -v c1=$COLNUM -F , '$c1 == "y" {print $1}' $DATA_SRC`)
fi
# echo -e ${ARRAY[@]}
clusterSSH ${ARRAY[@]}
}
clusterSSH() {
h=("$@")
~/bin/tmux-cssh ${h[@]}
}
listHosts() {
echo Categories
case "$1" in
all)
localCOUNT=1
;;
debian_hosts)
localCOUNT=2
;;
real_hosts)
localCOUNT=3
;;
hv_hosts)
localCOUNT=4
;;
ubuntu_hosts)
localCOUNT=5
;;
mikrotik_hosts)
localCOUNT=6
;;
*)
esac
localARRCOUNT=${#categories[@]}
if [ $localCOUNT -gt 1 ]; then
echo " "$1
awk -v c1=$localCOUNT -F , '$c1 == "y" {print " "$1}' $DATA_SRC
else
for cat in "${categories[@]}"; do
# Column 7 ( -lt $localARRCOUNT ) is "blank", let's show all NON-blank categories
if [[ $localCOUNT -gt 1 && $localCOUNT -lt $localARRCOUNT ]]; then
echo " "$cat
awk -v c1=$localCOUNT -F , '$c1 == "y" {print " "$1}' $DATA_SRC
fi
((localCOUNT++))
done
fi
#
# echo All Hosts:
# awk -F , '$1 != "hostname" { print " "$1 }' $DATA_SRC
#
}
if [ -z "$2" ]; then
arg1=${1:-"h"}
arg2=${2:-"all"}
set -- "${arg1}" "${arg2}"
unset arg1 arg2
fi
options=$(getopt -o hdrvumal: --long help,debian,real,virtual,ubuntu,mikrotik,all,list: -- "$@")
eval set -- "$options"
while :
do
case "$1" in
-h | --help ) ShowHelp; shift; break ;;
-d | --debian ) connect_hosts "2"; shift; break ;;
-r | --real ) connect_hosts "3"; shift; break ;;
-v | --virtual ) connect_hosts "4"; shift; break ;;
-u | --ubuntu ) connect_hosts "5"; shift; break ;;
-m | --mikrotik ) connect_hosts "6"; shift; break ;;
-a | --all ) connect_hosts "1"; shift; break ;;
-l | --list ) listHosts "$2"; shift 2; break ;;
* ) ShowHelp; shift; break;;
-- ) shift; break ;;
esac
doneConclusion
Well, it works 👍
I’m not sure this is the “best” way of achieving what I wanted? I’d love to hear what you think.
1 Comment