linux guide

Using the ‘at’ utility. The at facilty is designed to run jobs at specific times. Submitted jobs are spooled to /var/spool/at directory.
The daemon name is atd. Access Control Files:
/etc/at.allow - Contains list of users who are granted to submit ‘at’ jobs.
/etc/at.deny - Contains list of users who have ‘No’ permission to submit ‘at’ jobs.
Let us see how can we use the ‘at’ facility. For Example, we need to copy the contents of /home directory in compressed form to /tmp/backup directory.
To do this, we can run the following commands –
at 12:00
cd /home
mkdir /tmp/home
mkdir /tmp/backup
cp –Rf * /tmp/home
cd /tmp/home
tar czvf backup.tar.gz *
cp backup.tar.gz /tmp/backup
+d
We can also run a single command to make this happen – this command will do the same task above.
echo “cd /home; mkdir /tmp/home; mkdir /tmp/backup; cp –Rf * /tmp/home; cd
/tmp/home; tar czvf backup.tar.gz *; cp backup.tar.gz /tmp/backup” | at 12:00
Example for specifying times for at jobs:
at now The job will run immediately
at now + 2 minutes The job will run 2 minutes from the current time.
at next hour The job will run after 1 hour from the current time.
at next month The job will run after 1 month from the current time.
at next year The job will run after 1 year from the current time.
at next fri The job will run on next Friday
at 16:00 today The job will run today at 16 hours.
at 16:00 tomorrow The job will run tomorrow at 16 hours
at 16:00 May 31 2004 The job will run on May 31s t , 2004 at 16 hours
I think, the most efficient way to use the at facility with –f option.
• f option can be used to use contents of a file to executed as ‘at’ command.
For Example, if we use the following command –
at –f /home/newback now + 10 hours
The system will see the contents of the /home/newback file and use them as ‘at’ command

Labels: at command, backup, command, corn, job, Linux, SCHEDULING, TASKS, unix