Hi

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CRONTAB USAGE : For Using "crontab" utility to Edit Cron Files
using Vi as the Editor, perform the below mentioned Steps.

# EDITOR=vi; export EDITOR;
# crontab -e <username>

U will get a Vi Editor Screen for editing the mentioned User's Cron File. { Only use this way to edit any Cron File, as directly editing the Cron files might corrupt the File }

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CRONTAB TROUBLESHOOTING : If Ur Cronjob is not getting executed correctly, Then check for the below mentioned....

1. Check for the Permissions of the Cron File and Syntax of its contents.

# ls -l /var/spool/cron/crontabs/
total 4
-r-------- 1 root other 310 Mar 31 12:50 backup_user
-r-------- 1 root root 424 Feb 21 21:41 root

2. Check the UserName Entries present in the below mentioned Files.

/etc/cron.d/cron.allow
/etc/cron.d/cron.deny

3. Check whether Daemon for Cron is running or not.

# ps -ef |grep cron |grep -v grep
root 183 1 0 Mar 28 ? 0:03 /usr/sbin/cron

4. If the Daemon is not running, Restart the Daemon as mentioned below

# /etc/init.d/cron stop
# /etc/init.d/cron start

5. If U are executing any customised Shell Scripts using Cron,
then U have to check whether proper Execute Permissions are
provided for that Cron User.

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If U still face any problem, Kindly get back with Proper Error Messages updated in the /var/adm/messages File.