10 Commandments !! U like it for sure!!

This is a guest post by Praveen

10 COMMANDMENTS !! U LIKE IT FOR SURE !!


=>1 People are illogical, unreasonable, and self-centered. Love them anyway.

=>2 If you do good, people will accuse you of selfish, ulterior motives. Do good anyway.

=>3 If you are successful, you will win false friends and true enemies. Succeed anyway.

=>4 The good you do today, will be forgotten tomorrow. Do good anyway.

=>5 Honesty and frankness make you vulnerable. Be honest and frank anyway.

=>6 The smallest men and women with the smallest minds can shoot down the biggest men and women with the biggest ideas. Think big anyway.

=>7 People favor underdogs, but follow only top dogs. Fight for a few underdogs anyway.

=>8 What you spend years building may be destroyed overnight. Build anyway.

=>9 People really need help, but may attack you if you do help them. Help people anyway.

=>10 Give the world the best you have and you’ll get kicked in the teeth. Give the world the best you have anyway.

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Crontab issues

For basic crontab configurations please click here

Issue1:How to deny a user not to use his/her crontab to schedule his jobs

there is seperate contab file for dening for user open and file and specify users name in that file

#vi /etc/cron.deny

Issue2:Display cron jobs for all users

When migrating from one system to another it is good to know if there are cron jobs from other users on the system, here is how to display all of them:

1. for i in `cat /etc/passwd | cut -f 1 -d ':'`; do crontab -u $i -l; done;

or

for user in $(cut -f1 -d: /etc/passwd); do crontab -u $user -l; done

will loop over each user name listing out their crontab. The crontabs are owned by the respective users so you won't be able to see another user's crontab w/o being them or root.

ISSUE3:Using crontab as alaram? I want a song played on every weekday at 5AM and i dont want it in weekends

here is the solution you requred mplayer or vlc player to do this which will support CLI execution.

mplayer /music.mp3 & /dev/null&

00 05 * * 1-5 mplayer /music.mp3 & /dev/null&

ISSUE4:I have written a shell script that works from console but does not work via crontab.

This type of issues will occure in four situations

1. when there is some env variable issue

2. when crontab service it self not running in your system

check wether crontab service is running or not

#pgrep cron

3. When there is some issue with cron job contents(like check for spaces and empty lines remove all of them) 

if you didnt find any cron process running please start the crontab service as below

#service crond restart

4. when you are executing script or command please specify the full path to that command

ISSUE5:I am running a script , working very fine on cmd prompt. The problem is that when I open do crontab -e its giving some weired values like below 

baafh-99.03#
baafh-99.03# crontab -e
1063

?

?

?

?

?

how to resolve this issue?

This type of issue will come when the default editor is not set to VI to do this just execute the below commands

EDITOR=vi;
export EDITOR

Some important files and command for crontab

/var/cron/log file is used for logging some crontab messages, so very much useful for debugging crontab issue

/etc/crontab is the main configuration file for crontab where you can see crontab settings and all crontab hourly,monthly etc folders in this file

/etc/cron.hourly

/etc/cron.dialy

/etc/cron.weekly

/etc/cron.monthly these folders are used for keeping scripts in this folders so that on that perticular day/time the script will execute.

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