Linux Basic Commands

Basic commands

 

SYNTAX

crontab [-u user] file

crontab [-u user] [-l | -r | -e] [-i] [-s]

 

List all crontabs:

# crontab -l

$ crontab -u root -l

 

Edit crontab

# crontab -e     //edits crontab for user root

 

Removing all crontabs for specific user

# crontab -r       //for root user

$ crontab -u root -r

 

Import crontab from file

$ crontab -u root /etc/crontab

 

Notice:

Commands crontab -e and crontab <file> creates new file. For example /var/spool/cron/root .

 

Crontab job example

SHELL=/bin/bash
PATH=/sbin:/bin:/usr/sbin:/usr/bin
MAILTO=root
HOME=/

# For details see man 4 crontabs

# Example of job definition:
# .---------------- minute (0 - 59)
# |  .------------- hour (0 - 23)
# |  |  .---------- day of month (1 - 31)
# |  |  |  .------- month (1 - 12) OR jan,feb,mar,apr ...
# |  |  |  |  .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat
# |  |  |  |  |
# *  *  *  *  * user-name command to be executed

# Campaigns sender, runs each minute.
* * * * * /usr/bin/php -q /homemiko/info_mikosoft/mej/public_html/apps/console/console.php send-campaigns >/dev/null 2>&1

# Transactional email sender, runs once at 2 minutes.
*/2 * * * * /usr/bin/php -q /homemiko/info_mikosoft/mej/public_html/apps/console/console.php send-transactional-emails >/dev/null 2>&1

# Bounce handler, runs once at 10 minutes.
*/10 * * * * /usr/bin/php -q /homemiko/info_mikosoft/mej/public_html/apps/console/console.php bounce-handler >/dev/null 2>&1

# Feedback loop handler, runs once at 20 minutes.
*/20 * * * * /usr/bin/php -q /homemiko/info_mikosoft/mej/public_html/apps/console/console.php feedback-loop-handler >/dev/null 2>&1

# Delivery/Bounce processor, runs once at 3 minutes.
*/3 * * * * /usr/bin/php -q /homemiko/info_mikosoft/mej/public_html/apps/console/console.php process-delivery-and-bounce-log >/dev/null 2>&1

# Daily cleaner, runs once a day.
0 0 * * * /usr/bin/php -q /homemiko/info_mikosoft/mej/public_html/apps/console/console.php daily >/dev/null 2>&1

 

 

 

 Controlling cron service

Centos 6.6 ------>         # service crond start | restart | stop | status

Ubuntu 12.04 -------->      # service cron start | restart | stop | status