We're running a Redhat server (2.6.33.3-85.fc13.x86_64) and experienced some odd behaviour with our cron setup. We're running an out-of-the-box installation of cron.
We have a task that runs daily at 2am and has done so successfully for many months. However yesterday (27/03/2011) morning 8 instances of the task were started.
Here is the relevant section of our cron log file:
...
Mar 27 02:00:01 fs1 CROND[19557]: (root) CMD (true && /home/youdev/you_server/NEW_FS1/housekeeping_scripts/copy_pdf_printer_files_to_fs2.sh)
Mar 27 02:00:01 fs1 CROND[19563]: (youdev) CMD (true && /home/youdev/you_server/NEW_FS1/backup_scripts/fetch_db_data.sh)
Mar 27 02:00:02 fs1 CROND[19597]: (youdev) CMD (true && /home/youdev/you_server/NEW_FS1/backup_scripts/fetch_db_data.sh)
Mar 27 02:00:12 fs1 CROND[19931]: (youdev) CMD (true && /home/youdev/you_server/NEW_FS1/backup_scripts/fetch_db_data.sh)
Mar 27 02:00:22 fs1 CROND[20060]: (youdev) CMD (true && /home/youdev/you_server/NEW_FS1/backup_scripts/fetch_db_data.sh)
Mar 27 02:00:32 fs1 CROND[20067]: (youdev) CMD (true && /home/youdev/you_server/NEW_FS1/backup_scripts/fetch_db_data.sh)
Mar 27 02:00:42 fs1 CROND[20077]: (youdev) CMD (true && /home/youdev/you_server/NEW_FS1/backup_scripts/fetch_db_data.sh)
Mar 27 02:00:52 fs1 CROND[20084]: (youdev) CMD (true && /home/youdev/you_server/NEW_FS1/backup_scripts/fetch_db_data.sh)
Mar 27 02:01:02 fs1 CROND[20094]: (youdev) CMD (true && /home/youdev/you_server/NEW_FS1/backup_scripts/fetch_db_data.sh)
Mar 27 02:01:02 fs1 CROND[20095]: (root) CMD (run-parts /etc/cron.hourly)
Mar 27 02:01:02 fs1 CROND[20096]: (root) CMD (true && /home/youdev/you_server/NEW_FS1/housekeeping_scripts/copy_pdf_printer_files_to_fs2.sh)
Mar 27 02:01:02 fs1 run-parts(/etc/cron.hourly)[20095]: starting 0anacron
...
Each of the fetch_db_data.sh scripts started correctly (they're just a shell script that calls a rsync - and the rsync tmp files exist as do the files that were successfully rsynced across).
This is the only job we have that starts at 02:00, yet we have a job that runs on the minute (copy_pdf_printer_files_to_fs2.sh) and this correctly ran just once at 02:00.
The only thing that we can think could have caused it is a daylight saving issue (we're in the UK so went from GMT to BST at 02:00 on the day in question) - however all the digging we've done says that cron handles daylight saving issues fine. And even then, shouldn't we have expected 0 runs (as time skipped from 00:59 to 02:00) rather than 8?
Here is the crontab entry:
MAILTO=XXX@XXX.YYY
# BACKUP LATEST DB FROM LIVE (takes approx one hour)
0 2 * * * true && /home/youdev/you_server/NEW_FS1/backup_scripts/fetch_db_data.sh
Many thanks in advance for reading this and for any help and suggestions,
Chris.
