Unix Cron & WordPress

Creëer voor elke WordPress-site een cron job for user www-data.

Dit is het commando dat WP Rocket ca. elke 10 minuten uitgevoerd wil hebben via Cron:

wget -q -O - https://example.com/wp-cron.php?doing_wp_cron >/dev/null 2>&1

Oftewel: Een bepaalde file uit de betreffende installatie wordt aangeroepen, en de output gaat naar /dev/null.

Syntaxis

Timefields:

Minute   Hour   Day of month   Month   Day of week        Opmerkingen
0-59     0-23   1-31           1-12    0-6 (0 = Sunday)   Mogelijke waardes
------   ----   ------------   -----   ----------------   -----------
0          16           1,15       *                  *   Do something on day 1 & 15 at 16:00
*/10        *              *       *                  *   Do something every 10 minutes

crontab - Voorbeelden

$ crontab -l
no crontab for jeroen

$ crontab -l -u www-data
must be privileged to use -u

$ sudo crontab -l -u www-data
no crontab for www-data

$ sudo crontab -e -u www-data
no crontab for www-data - using an empty one

Select an editor.  To change later, run 'select-editor'.
  1. /bin/nano        <---- easiest
  2. /usr/bin/vim.basic
  3. /usr/bin/vim.tiny
  4. /bin/ed

Choose 1-4 [1]: 2

... interactieve bijwerken cronfile...

crontab: installing new crontab

$ sudo crontab -l -u www-data

# Edit this file to introduce tasks to be run by cron.
# 
# Each task to run has to be defined through a single line
# indicating with different fields when the task will be run
# and what command to run for the task
# 
# To define the time you can provide concrete values for
# minute (m), hour (h), day of month (dom), month (mon),
# and day of week (dow) or use '*' in these fields (for 'any').
# 
# Notice that tasks will be started based on the cron's system
# daemon's notion of time and timezones.
# 
# Output of the crontab jobs (including errors) is sent through
# email to the user the crontab file belongs to (unless redirected).
# 
# For example, you can run a backup of all your user accounts
# at 5 a.m every week with:
# 0 5 * * 1 tar -zcf /var/backups/home.tgz /home/
# 
# For more information see the manual pages of crontab(5) and cron(8)
# 
# m h  dom mon dow   command

*/10 * * * * wget -q -O - https://example/wp-cron.php?doing_wp_cron >/dev/null 2>&1

Log

Om te zien of het ook echt werkt:

sudo grep CRON /var/log/syslog

of

sudo grep www-data /var/log/syslog

Zie ook

• WP Rocket (WordPress-plugin)

Bronnen

• https://docs.wp-rocket.me/article/1279-cron-and-wp-rocket
• https://stackoverflow.com/questions/46442933/create-cronjob-ubuntu-for-user-www-data-using-bash#46443063
• https://docs.oracle.com/cd/E19455-01/805-7229/sysrescron-62861/index.html
• https://crontab.guru/every-10-minutes
• https://www.cyberciti.biz/faq/crontab-every-10-min/