Send An Email Alert When Your Disk Space Gets Low

The following script alerts you when your root partition is almost full:

1. Update the Server : - apt-get update
2. Install mailx client :- apt-get install bsd-mailx
3. Create a File disk.sh
4. Add the Content

#!/bin/bash

CURRENT=$(df / | grep / | awk '{ print $5}' | sed 's/%//g')

THRESHOLD=9

if [ "$CURRENT" -gt "$THRESHOLD" ] ; then

    mail -s 'Disk Space Alert' ictops@gmail.com << EOF

Your root partition remaining free space is critically low. Used: $CURRENT%

EOF

fi

                                      The script sends an email when the disk usage rises above the percentage specified by the THRESHOLD variable (9% here).

Script automatically run when it added into the Crontab file

root@ubuntu:~# crontab -e

10 15 * * * /root/disk.sh (Execute the command at 3.10 pm everyday)

Set SSH Login Email Alerts In Linux Server

                        To enable server to automatically send a notification email to predefined email address every time someone logs in as root to the host. To configure the automatic email alert notification to a default email address on each incident of root logon on the server.

1. Update the Server : - apt-get update
2. Install Optional (apt-get install mailutils)
3. Install mailx client :- apt-get install bsd-mailx

                  During the installation Its ask for selecting following features “Postfix Configuration and Package Configuration” (Leave its as Default)

4. Login as root user and go to root’s home directory by typing cd /root command.

# cd /root

5. Open .bashrc file with vi or nano editor. Please remember .bashrc is a hidden file, you won’t see it by doing ls -l command. You’ve to use -a flag to see hidden files in Linux.

        root@ubuntu:~# ls -a

.  ..  .bash_history  .bashrc  .cache  .profile  .viminfo

root@ubuntu:~# vi .bashrc

                                              Add the following whole line at the bottom of the file. Make sure to replace “ServerName” with a hostname of your Server and change “your@yourdomain.com” with a your email address.

Syntax:- echo 'ALERT - Root Shell Access (ServerName) on:' `date` `who` | mail -s

"Alert: Root Access from `who | cut -d'(' -f2 | cut -d')' -f1`" your@yourdomain.com

Eg:- echo 'ALERT - SSH Access Detected To (ubuntu) on:' `date` `who` | mail -s "Alert: Root Access from `who | cut -d"(" -f2 | cut -d")" -f1`" ictops@gmail.com

6. Execute the following for instant result.

root@ubuntu:~# source .bashrc

Schedule Tasks In Linux With CRON

Schedule Tasks In Linux With CRON

                                      There is an utility in Linux known as CRON with which you can start your jobs automatically at a desired time and schedule them to get executed periodically.

                                     Cron utility consists of two parts: The cron daemon and the cron configuration files. Cron daemon is just like any service that is started automatically whenever your system boots. Cron configuration files hold the information of what to do and when to do

1. Edit a Crontab Entry :- crontab -e
2. Select Favorite editor.If You select any other option, use the following command to open in VI editor

            export VISUAL=vi

     3. Create a new crontab file from another user

            crontab -l > name  (Created in Present Working Directory)

     4. Listing the Cron Jobs :- crontab –l

     5. To enlist the cron jobs for a particular user :- crontab –u [USER] –l

Example :- crontab –u root –l

     6. For deleting Crontab entry : - crontab -r

     7. For activating crontab entry : - crontab crontab name

Crontab syntax :-

                                           A crontab file has six fields for specifying minute, hour, day of month, month, day of week and the command to be run at that interval. See below:

• 1: Minute (0-59)
• 2: Hours (0-23)
• 3: Day (0-31)
• 4: Month (0-12 [12 == December])
• 5: Day of the week(0-7 [7 or 0 == sunday])
• /path/to/command - Script or command name to schedule

Easy to remember format:

*     *     *     *     *  command to be executed
-     -     -     -     -
|     |     |     |     |
|     |     |     |     +----- day of week (0 - 6) (Sunday=0)
|     |     |     +------- month (1 - 12)
|     |     +--------- day of month (1 - 31)
|     +----------- hour (0 - 23)
+------------- min (0 - 59)

Sample :-

1. Created a bash script for making directory

root@IPAM:/home/ictops#vi job.sh

mkdir -p /home/ictops/test1

mkdir -p /home/ictops/test1

      2. Provide Executable permission :- chmod +x /home/ictops/job.sh

      3. Add this batch file “job.sh” into crontab entry for sheduling task

        root@IPAM:/home/ictops#crontab -l > mycron   

            no crontab for root

        root@IPAM:/home/ictops#crontab -e

no crontab for root - using an empty one

root@IPAM:/home/ictops#crontab -l > mycron   

root@IPAM:/home/ictops#crontab  mycron

php.exe is not recognized as an internal or external command, operable program or batch file

                After installing wamp, i try to check the php version in user running command prompt

C:\Users\jagannathanv> php -v

“php.exe’ is not recognized as an internal or external command, operable program or batch file”

                                 But the same its working when i change the path in command prompt to “C:\wamp\bin\php\php5.4.3\”

In CMD:-

cd C:\wamp\bin\php\php5.4.3\

C:\wamp\bin\php\php5.4.3\>php -v

PHP 5.4.7 (cli) (built: Sep 12 2012 23:48:31)
Copyright (c) 1997-2012 The PHP Group
Zend Engine v2.4.0, Copyright (c) 1998-2012 Zend Technologies

Cause :- PHP is not included in your PATH.that is in Environment Variables

Solution :-

1. Take System Properties (Right click your My Computer, then Properties)
2. Advanced System Settings --> Environment Variables ---> system variables
3. Edit the PATH variable, add your PHP installation directory (C:\wamp\bin\php\php5.4.3)
4. Restart the PC

Reset A Lost Administrative Password In Ubuntu

                        By default the first user's account is an administrative account, If the user doesn't remember their password you need to reset it.For this

1.  Boot into recovery mode:-

                 Boot up the machine, and after the BIOS screen, hold down the left Shift key. You will then be prompted by a menu that looks something like this

2 . Get the Window like below

3. You should now see a root prompt, something like this:

root@ubuntu:~#

At this stage you should have a read-only file system. You have to remount it with write permissions:

root@ubuntu:~# mount -rw -o remount /

Now we can set the user's password with the passwd command.If you find the user names goto /home.

In this example I will use jagan user's username

root@ubuntu:~# passwd jagan

                                     Enter new UNIX password:
                                     Retype new UNIX password:
                                     passwd: password updated successfully
                                     root@ubuntu:~#