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Cron scheduling question
Posted: Thu Aug 03, 2017 8:26 pm
by ngauruhoe
Hi, I'm trying to follow the example in the doc here:
http://zoneminder.readthedocs.io/en/lat ... on-example. But not much luck so far. This is what I tried and the result:
1) Added to root crontab (sudo -s and using crontab -e):
0 22 * * 0-6 root /usr/bin/zmpkg.pl Test
cron.log shows:
CRON[3562]: (root) CMD (root /usr/bin/zmpkg.pl Test)
ZM console shows no difference, i.e. not the Test run state
2) Added to ZM (user skywalker) crontab:
0 22 * * 0-6 skywalker /usr/bin/zmpkg.pl Test
cron.log shows:
CRON[3735]: (skywalker) CMD (skywalker /usr/bin/zmpkg.pl Test)
ZM console shows no difference, i.e. not the Test run state
3) I also tried the 2nd one but with 'sudo' in front of the /usr/bin/......... No difference, no state change
Btw, Ubuntu is 15.10 and zmpkg.pl is in /usr/bin (and not in /usr/local/bin).
What can I try next? Appreciate your help!
Mike
ps. ZM run state Test exists of course.......If anyone would wonder
Re: Cron scheduling question
Posted: Thu Aug 03, 2017 10:21 pm
by bbunge
My recommendation is to install Webmin if you are not a Linux command line guru. Webmin puts many tasks, including cron, into a web gui which is easy!
Re: Cron scheduling question
Posted: Fri Aug 04, 2017 10:11 am
by ngauruhoe
I may, but I'dd like to learn and understand what it is that I am doing incorrectly. Any clue's?
Thank you.
Re: Cron scheduling question
Posted: Thu Aug 24, 2017 7:47 pm
by ngauruhoe
Also got this figured out at last. I initially followed the syntax of the cron entries already in root's crontab. The six'th field of every entry in there was the uid ('root'). So, that's what I used as well in the entries I added. But in the cronlog the resulting commands seem to start with the uid. After removing it, everything works fine. Run states are nicely changed at the specified times. See below.
Code: Select all
# m h dom mon dow user command
17 * * * * root cd / && run-parts --report /etc/cron.hourly
25 6 * * * root test -x /usr/sbin/anacron || ( cd / && run-parts --repo$
47 6 * * 7 root test -x /usr/sbin/anacron || ( cd / && run-parts --repo$
52 6 1 * * root test -x /usr/sbin/anacron || ( cd / && run-parts --repo$
0 8 * * 1-5 /usr/bin/zmpkg.pl Weekday_Daytime
0 20 * * 1-5 /usr/bin/zmpkg.pl Weekday_Nighttime
0 8 * * 6 /usr/bin/zmpkg.pl Weekend
# 36 22 * * 0-6 /usr/bin/zmpkg.pl Test
#
I have no clue why my entries do not work with a uid and the original entries do work with it. If anyone knows......I still like to learn......
Re: Cron scheduling question
Posted: Fri Aug 25, 2017 5:51 pm
by mikb
On my Slackware systems, no crontab entries have a user field.
Try "man crontab" on your system and read what it says about the fields -- I've just skimmed mine and see nothing about handing off to other users, the crontab file called "root" runs the rooty things, a crontab file called "myuser" would run them as "myuser" etc. -- they are not lumped into one file. Maybe yours are?
Maybe you have a more advanced version of cron?
Or maybe you have a script/binary called "root" which runs the following arguments as root for some reason? A bit like "sudo something"
Try "which root" or "whereis root" to see if it coughs up a clever helper script -- I don't have one!
Re: Cron scheduling question
Posted: Fri Aug 25, 2017 6:19 pm
by Baylink
Crons are one of the most widely disparate -- and least well documented -- facilities amongst *nix distros.
I think the one that takes the username as a column is the 'Vixie' cron, written by Paul Vixie, late of DEC. Usually, the /etc/crontab takes the username, and the ones in /var/spool/cron/crontabs/$USERNAME don't... but what I've *never* seen is one where a single crontab has both types.
Re: Cron scheduling question
Posted: Sat Aug 26, 2017 5:49 pm
by mikb
Slackware: "Our crontab format is roughly similar to that used by vixiecron. "
So the "roughly similar" is probably where all this diverges.
I don't have an /etc/crontab (although there are /etc/cron.d - empty, and /etc/cron.[hourly/daily/monthly/weekly] which just contain scripts to directly execute, not a "crontab" fornatted file in sight.
Re: Cron scheduling question
Posted: Mon Aug 28, 2017 8:05 pm
by ngauruhoe
Thanks for the answers. The 'whereis root' etc. didn't show much.
Directly editing (nano /etc/crontab) or becoming root and editing through crontab -e results in editing the same, system-wide, crontab. The answer is in the header where it explains how the system-wide is different from a user crontab.
It still doesn't explain though why my entries, without the user, do work. Hard to see how a positional field may be skipped. Perhaps the logic is smart enough to figure out that something with a '/' cannot be a user name and subsequently defaults to root because it is the system-wide crontab.
Code: Select all
# /etc/crontab: system-wide crontab
# Unlike any other crontab you don't have to run the `crontab'
# command to install the new version when you edit this file
# and files in /etc/cron.d. [b]These files also have username fields,
# that none of the other crontabs do.[/b]
SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
# m h dom mon dow [b]user[/b] command
17 * * * * root cd / && run-parts --report /etc/cron.hourly
25 6 * * * root test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.daily )
47 6 * * 7 root test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.weekly )
52 6 1 * * root test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.monthly )
0 8 * * 1-5 /usr/bin/zmpkg.pl Weekday_Daytime
0 20 * * 1-5 /usr/bin/zmpkg.pl Weekday_Nighttime
0 8 * * 6 /usr/bin/zmpkg.pl Weekend
# 36 22 * * 0-6 /usr/bin/zmpkg.pl Test
#