[Klug-general] Cron job

[Alan @ COMM-TECH]

Jeremy Hooks wrote:
> 2009/4/9 Nathan Friend <nathan.friend at gmail.com>:
>   
>> Afternoon All,
>> I've writen a simple script to dump a database and would like it to run as a
>> cron job.  How should I set the script permisisons?
>>     
>
> Presuming the cron job is being run by root you will probably want to
> make sure the script is owned by root:
> chown root.root /usr/local/script/dbbackup.sh
>
> Then you can set the permissions with so that only root has
> permissions to read/write/execute it:
> chmod 700 /usr/local/script/dbbackup.sh
> or
> chmod u=rwx /usr/local/script/dbbackup.sh
>
>   
>> dbbackup.sh contains:
>>
>> NOW=$(date +"%d-%b-%y"_"%l:%M")
>> FILENAME="moodle_db_backup_$NOW.sql"
>> mysqldump -uuser -ppassword databasename > /dbbck/$FILENAME
>>     
>
> Don't forget, ofcourse if you want the script to actually run you need
> a shebang too, e.g.:
> #!/usr/bin/bash
>
> The date format you are using will likely cause you problems as it
> will give you something like "09-Apr-09_ 8:30", a filename with a
> space in it.  With either a %I (12 hour, with leading zero) or %H (24
> hour, with leading zero) rather than %l (12 hour, leading space).
> Something else that is important to remember when writing cron scripts
> is that you can't always be certain that the path variable isn't
> necessarily the same as you would have when running running the script
> from an interactive shell.  So I would recommend changing 'mysqldump'
> to '/fullpath/mysqldump'.
>
>
>   
>> The cron entry is
>>
>> 30 20 * * * /usr/local/script/dbbackup.sh
>>
>> I can run the script from for command line OK with the expected output.
>> However wathcing /var/log/messages I see the cron job run but no output
>> file...
>>     
>
> One final thing, if your script running but you aren't getting the
> results you expect, it may be worth checking the output of the
> command.  Normally the output from cron scripts is emailed to the user
> using the local mail system.  You can check this by using (say) mutt
> or 'vi /var/spool/mail/root'.
>
> I think that is everything, but I don't use cron often, so I could
> have forgotten something.
>
> Regards.
>
> Jeremy
>
>   
Cron is so reliable you tend to just set it and forget it, until you 
find the backup hasn't been working for 6 months because the destination 
was unreachable, or the mysql password changed or someting..

I find it useful therefore to interrogate the exit code of  mysqldump so 
you could also have the script mail you if someting went wrong, so right 
after the mysqldump command use:

EXITSTATUS=$?
if [ "$EXITSTATUS" != "0" ] then
   == send email notifying a problem with the backup==
fi

[googling..]  here's a nice little revelation on bash exit code [arrays!]:

http://www.briandowney.net/blog/2008/05/05/bash-pipeline-exit-codes/

Alan
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