72

I have pretty simple command which is working fine standalone as a command or bash script but not when I put it in crontab

40 05 * * * bash /root/scripts/direct.sh >> /root/cron.log

which has following line

PATH=$PATH:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin
SHELL=/bin/sh PATH=/bin:/sbin:/usr/bin:/usr/sbin:/root/
# Mongo Backup
docker exec -it mongodb mongodump -d meteor -o /dump/

I tried to change the url of script to /usr/bin/scirpts/ no luck

I even tried to run script directly in cron

26 08 * * * docker exec -it mongodb mongodump -d meteor -o /dump/ >> /root/cron.log

with no luck, any help appreciated.

EDIT

I don't see any errors in /root/cron.log file either

user555
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    Does not work is not a very helpful error description. Please check your system log, also add any error messages and/or the contents of /root/cron.log to your question. – Erik Dannenberg May 07 '16 at 15:08
  • Can you please explain what file contains what code? I can't really understand what come first or even where it is written... By the way, try to write the output to your user's file (in stead of root/cron.log) it worked for me once – I-V May 21 '16 at 10:29
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    First `PATH=` is useless because you overwrite it in second line. – Cyrus May 21 '16 at 18:30
  • What exactly didn't work? Where do you expect the dump? I would expect it to be saved in a directory `/dump/` - but _inside_ the container. Maybe you added that directory as volume mount to the mongodb container? – gesellix May 23 '16 at 17:55
  • If you care enough to post a bounty, certainly you should also care enough to redirect stderr to a file and include those logs in your question. – Charles Duffy May 24 '16 at 22:23
  • ...redirecting only stdout, as you're doing presently, is generally unlikely to be useful with respect to unexpected errors. – Charles Duffy May 24 '16 at 22:24

6 Answers6

163

Your docker exec command says it needs "pseudo terminal and runs in interactive mode" (-it flags) while cron doesn't attach to any TTYs.

Try changing your docker exec command to this and see if that works?

docker exec mongodb mongodump -d meteor -o /dump/
VDR
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    One can keep the `-t` – mfit Jul 03 '18 at 10:29
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    For those using `docker-compose`, you will need to *add* the `-T` flag, which is documented as: "Disable pseudo-tty allocation. By default `docker-compose exec` allocates a TTY." – Scott Weldon Feb 09 '19 at 04:49
14

for what it's worth I had this exact same problem. Fixing your PATH, changing permissions, and making sure you are running as the appropriate docker user are all good things, but that's not enough. It's going to continue failing because you are using "docker exec -it", which tells docker to use an interactive shell. Change it to "docker exec -t" and it'll work fine. There will be no log output anywhere telling you this, however. Enjoy!

Jason Hughes
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8

cron debugging

1. /var/log or sendmail

As crond work as a daemon, without ability of failing, execution is more important than logging. Then by default, if something goes wrong, cron will send a mail to $USER@localhost reporting script output and errors.

Have a look at /var/mail or /var/spool/mail for some mails, maybe

and at /etc/aliases to see where root's mail are sents.

2. crond and $PATH

When you run a command by cron, have care that $PATH is user's default path and not root default path (ie no */sbin and other reserved path to super user tools).

For this, the simplier way is to print your default path in the environment where everything run fine:

echo $PATH

or patch your script from command line:

sed -e "2aPATH='$PATH'" -i /root/scripts/direct.sh

This will add current $PATH initializer at line 2 in your script.

Or this, will whipe from your script all other PATH=:

sed -e "s/PATH=[^ ]*\( \|$\)/\1/;2aPATH='$PATH'" -i /root/scripts/direct.sh

3. Force logging

Add at top of your script:

exec 1>/tmp/cronlog-$$.log
exec 2>/tmp/cronlog-$$.err

Try this:

sed -e '1a\\nexec 1>/tmp/cronlog-$$.log\nexec 2>/tmp/cronlog-$$.err' -i ~/scripts/direct.sh

Finalized script could look like:

#!/bin/bash

# uncomment two following lines to force log to /tmp
# exec 1>/tmp/cronlog-$$.log
# exec 2>/tmp/cronlog-$$.err

PATH='....' # copied from terminal console!

docker exec -it mongodb mongodump -d meteor -o /dump/

Executable flag

If you run your script by

40 05 * * * bash /root/scripts/direct.sh

no executable flag are required, but you must add them:

chmod +x ~/scripts/direct.sh

if you want to run:

40 05 * * * /root/scripts/direct.sh
F. Hauri - Give Up GitHub
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6

1) Make sure this task is in the root user's crontab - it's probably the case but you didn't write it explicitly

2) cron may be unable to find bash. I would remove it and call directly your script after making it executable:

chmod 755 /root/scripts/direct.sh

and then set your crontab entry as 40 05 * * * /root/scripts/direct.sh 2>&1 >> /root/cron.log

If it's still not working, then you should have some useful output in /root/cron.log

mbarthelemy
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  • thanks for the reply but both of your suggestions are not working somehow and I don't see anything in log file too. – user555 May 20 '16 at 18:06
  • @user555 well please add the output you get when you run it from the command line, to your OP. – SaintHax May 23 '16 at 20:31
1

Are you sure your script is running? Add an other command like touch /tmp/cronok before the docker exec call.

Don't forget that the crontab needs a newline at the end. Use crontab -e to edit it.

Restart the cron service and check the logs (grep -i cron /var/log/syslog).

If your OS is redhat/centos/fedora, you should try with the username (root) between the frequency and the command.

Check your mails with the mail command.

Check the crontab permissions. chmod 644 /etc/crontab.

Maybe you just don't want to reinvent the wheel.

rdupz
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1

Here's a few things I'd change-- first, capture STDERR along with STDOUT and remove the shell specification in cron-- use #! in your script instead.

40 05 * * * /root/scripts/direct.sh &>> /root/cron.log

Next, you are setting your PATH in the reverse order, and you are missing your shbang. I have no idea why you are defining SHELL as /bin/sh, when you are running bash, instead of dash. Change your script to this.

#!/usr/bin/env bash

PATH=/bin:/sbin:/usr/bin:/usr/sbin:/root
PATH=$PATH:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin
# Mongo Backup
docker exec -it mongodb mongodump -d meteor -o /dump/

See if that yields something better to work with.

SaintHax
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