If you want to quickly check the number of the active connections on your server you can run this command:

netstat -anp | grep :80 | grep ESTABLISHED | wc -l

Don’t forget the semi-colon.
This will work also for all other ports for example SSH on the default 22, or HTTPS on 443.

And this one will list the number of the active connections per IP sorted

netstat -ntu | grep :80 | grep -v LISTEN | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -rn 

#!/bin/sh
# script to check server for extremely high load and restart Apache/Nginx/Varnish/MySQL if the cond$
check=`cat /proc/loadavg | sed 's/\./ /' | awk '{print $1}'`
# define max load avarage when script is triggered
max_load='9'
# log file
high_load_log='/var/log/server_high_load_restart.log';
#
if [ $check -gt "$max_load" ]; then
service nginx restart
sleep 5;
service php5-fpm restart
sleep 5;
service varnish restart
echo "$(date) : Server Restart due to excessive load | $check |" >> $high_load_$
fi

This script uses rsync and ssh keys over ssh to backup remote server with anacron, it should work with cron too, but it haven’t been tested.

#!/bin/sh
#Script for VPS back ups

#This is for the desktop notification on Ubuntu
notify-send -i drive-multidisk Rsync "VPS Backup Started"

#This is for the reallusion VPS
rsync -e "ssh -i /home/user/.ssh/id_rsa.2 -p 104" -rtv --delete root@domain.com:/home /mnt/DATA-L/backups
rsync -e "ssh -i /home/user/.ssh/id_rsa.2 -p 104" -rtv --delete root@domain.com:/etc /mnt/DATA-L/backups
rsync -e "ssh -i /home/user/.ssh/id_rsa.2 -p 104" -rtv --delete root@domain.com:/var/log /mnt/DATA-L/backups
rsync -e "ssh -i /home/user/.ssh/id_rsa.2 -p 104" -rtv --delete root@domain.com:/var/mail /mnt/DATA-L/backups
rsync -e "ssh -i /home/user/.ssh/id_rsa.2 -p 104" -rtv --delete root@domain.com:/var/backups /mnt/DATA-L/backups

#This is for the desktop notification on Ubuntu
notify-send -i drive-multidisk Rsync "VPS Backup Finished"

This script can check the sytem load with cronjob and send email or even SMS if the load is too high. Anyway I preffer using monit. Tested with ubuntu.

#!/bin/bash
#Load Monitor - sends email when the sytem load reach 5.00, and sms when reach 9.
#first {print$10} check for the last 5 min load, replace with 9 to check for 1 min and 11 for 15 min.

LOAD=`uptime | tr ' ' ' ' | awk '{print$10}' | tr '.' ' ' | awk '{print$1}'`

if [ $LOAD -ge "2" ];
then
    echo "High Load: $LOAD" | mail -s "Load Alert" your@email.com
fi

if [ $LOAD -ge "5" ];
then
    echo "High Load: $LOAD" | mail -s "Load Alert" yourphonenumber@sms.mtel.net
fi

Script to backup the web dorectory and mysql databases. Tested on ubuntu with cronjob every week.

#!/bin/bash
#=======================================================================================================================
# VPS Backup Script by Ivan Denkov
#=======================================================================================================================
DATE=$(date +"%Y-%m-%d")
MYSQLDUMP="$(which mysqldump)"
TAR="$(which tar)"
PASS="MySQLPSWD"
DIR="/home/backups"
DBS=`mysql -u root -h localhost -p$PASS -e"show databases"`
UPTIME=`uptime`
FREEHD=`df -h`

#This will remove files older than 35 days
find $DIR/* -mtime +35 -exec rm -rf {} \;

$TAR -cvf $DIR/Backup-$DATE.tar /var/www
for DATABASE in $DBS
do
if [ $DATABASE != "Database" ]; then
FILENAME=$DATABASE
$MYSQLDUMP -u root -h localhost -p$PASS $DATABASE > $DIR/$FILENAME.sql
$TAR -rvf $DIR/Backup-$DATE.tar $DIR/$FILENAME.sql
fi
done

#Remove dumped .sql in the folder
rm -rf $DIR/*.sql

sleep 40

#send me e-mail when done
echo "Email Body - Back Up completed at date $DATE, or maybe not!? Let see the statistic \n\n $UPTIME \n\n  $FREEHD" | mail -s "Email Subject - Back UP $DATE" your@email.com

For Debian based distros run the following command as root :

update-rc.d servicename defaults

For CentOS and RedHat run the following command as root :

chkconfig servicename on

As a  Linux administrator you may need to force logout and kill a specific user, or an active user in pts/0 pts/1 pts/3 etc. Also this tutorial will work in most linux distros.
First of all display the out put of “w” command.

[root@server ~#]w
18:08:30 up 3:54, 3 users, load average: 0.05, 0.02, 0.00
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
root pts/0 192.168.10.100 14:15 0.00s 0.05s 0.01s w
james pts/1 192.168.10.100 18:07 50.00s 0.02s 0.02s -bash
james pts/2 10.10.20.23 18:07 39.00s 0.02s 0.02s -bash

Here the user “james” is logged in from two different machines. And you need to force logout and kill the user “james” logged in from ip: 192.168.10.100 (pts/1)

use the below command

[root@server ~#]skill -KILL -v pts/1

This command will force logout and kill the user in pts/1. and the same user logged in pts/2 will not be logged out.

If need to kill a users all the connected sessions at once

[root@server ~#]skill -KILL -u james

(this will kill both pts/1 and pts/2 cessions)

To STOP/PAUSE a user’s activities

[root@server ~#]skill -STOP -u james

To RESUME a stopped user

[root@server ~#]skill -CONT -u james

Edit

There is some bug in recent Debian(7) and distros based on them like Ubuntu, which will make the command

skill -KILL -v pts/1

do nothing

What you can do in such case is to get the PID of the terminal you want to kill with

 skill -i -t pts/1

it will return something like

pts/1    root     27933 bash               ?

Just kill it –

kill 27933