Issues running cron in Docker on different hosts
Im trying to get a docker container running to mange my cronjobs
im running a very simple cron as a test in a docker container using centOS 6.5 base
* * * * * /bin/echo "it works!" >> test.log
it works fine if the container is running on CoreOS host, however if I run the container on a ubuntu 13.10 host the cron is not executed. (I though the host did not effect what was running in the container)
both hosts are running docker 0.8
am I missing something obvious, or it this a bug?
thanks
Answer
short answer
add this line to your dockerfile
RUN sed -i '/session required pam_loginuid.so/c\#session required pam_loginuid.so' /etc/pam.d/crond
the long answer
from what I understand issue is related to differences in the kernal between CoreOS & Unbutu. this in-turn causes a pam security issue.
to figure it our first needed to turn on logging for cron (since we are in docker normal startup is not executed). run
service rsyslog start
service crond restart
the cron log had this error (located here /var/log/cron)
FAILED to open PAM security session (Cannot make/remove an entry for the specified session)
so then I took a look at the security log, and it had this error (located here /var/log/secure)
pam_loginuid(crond:session): set_loginuid failed
some more googling and found I needed to modify my pam cond config (found here /etc/pam.d/crond) edit this file and comment out the following line
#session required pam_loginuid.so
restart crond and all should be good