Add items to crontab
Background
Skills required
You must be able to connect to your QNAP device using SSH and edit using a text editor such as vi or nano.
crontab
The crontab can be used to execute tasks (scripts) based on a recurring schedule. The crontab is used, for example, to restart the webserver during the night.
To view the content of your crontab, login to your QNAP via SSH and type:
crontab -l
You will see a (small) list of crontab entries.
Standard crontab jobs
The following table contains the standard QNAP jobs that run on schedules.
This list is by no means complete. Jobs may depend on the firmware version, start times may vary. If you find a job on your QNAP, that is missing from the table, add it. The list could help to identify unwanted jobs that regularly wake up your harddisk(s).
| Default Time |
Job |
Explanation |
|---|---|---|
| 0 4 * * * |
/sbin/hwclock -s | http://linux.die.net/man/8/hwclock |
| 0 3 * * * | /sbin/vs_refresh | vs_refresh is for share folder space usage calculation (for Network Share Management) |
| 0 3 * * 0 |
/etc/init.d/idmap.sh dump | related to SAMBA Active Directory configuration. Used if security is set to ADS. |
| 0 3 * * * |
/sbin/clean_reset_pwd | (unclear) might be the new behaviour of the network recycle bin (purging files after a certain amount of days) |
| 0-59/15 * * * * |
/etc/init.d/nss2_dusg.sh | is a job of the Surveillance Station |
| 10 15 * * * | /usr/bin/power_clean -c 2>/dev/null | ? |
| 4 3 * * 3 | /etc/init.d/backup_conf.sh | does an automatic backup of several config files in /etc/config. |
| 0 3 * * * |
/bin/rm -rf /mnt/HDA_ROOT/twonkymedia/twonkymedia.db/cache/* |
Will clear the Twonky media cache |
| 5 0 * * 1 |
/etc/init.d/antivirus.sh scan 1 |
If Antivirus is enabled, this will scan the files for viruses |
| 0 0 * * * |
/etc/init.d/antivirus.sh archive_log |
If Antivirus report jobs are enabled |
| 0 0 */1 * * |
/etc/init.d/antivirus.sh update_db |
If Antivirus is enabled, this will check clamav.net for updates |
| /etc/init.d/startup |
If a restart/powerof job is configured in power management | |
| /etc/init.d/poweroff |
If a restart/powerof job is configured in power management |
Adding entries at the command-line
Here are a couple of examples that append new entries to the crontab file:
echo "1 4 * * * /share/custom/scripts/custom1.sh" >> /etc/config/crontab echo "40 5 * * * /share/custom/scripts/custom2.sh" >> /etc/config/crontab
Modifying entries
Do NOT edit crontab the usual way!
On a desktop or server distribution, you would edit a user's crontab with:
crontab -e
However, due to the way the QNAP firmware updates crontab, it will be overwritten on the next reboot. Obviously, you want your automation to survive reboots, so edit the crontab file directly with your text editor:
vi /etc/config/crontab
or
nano /etc/config/crontab
Restart the daemon
When you're done, reload the crontab file and restart the cron daemon:
crontab /etc/config/crontab && /etc/init.d/crond.sh restart
Notes
Don't forget to make your scripts executable! Otherwise they will silently fail! You tested your script, right?
chmod +x filename.sh