I'm struggling trying to debug a cron job which isn't working correctly. The cron job calls a shell script which should unrar a rar file - this works correctly when i run the script manually, but for some reason it's not working via cron. I am using the absolute file path and have verified that the path is correct. Has anyone got any ideas why this could be happening?
Well, you already said that you have used absolute paths, so the number one problem is dealt with.
Next to check are permissions. Which user is the cron job run as? Does it have all the permissions necessary?
Then, a little trick: if you have a shell script that fails and it's not run in a terminal I like to redirect the output of it to some files. Right at the start of the script, add:
exec &>/tmp/my.log
This will redirect STDOUT and STDERR to /tmp/my.log. Then it might also be a good idea to also add the line:
set -x
This will make bash print which command it's about to execute, and at what nesting level.
Happy debugging!
The first thing to check when cron jobs fail is to see if the full environment is available to the script you are trying to execute. In other words, you need to realize that a job executed via cron runs as a detached process meaning it is not associated with a login environment. Therefore whenever you try to debug a cron job that works when you execute manually, you need to be sure the same environment is available to the cronjob as is available to you when you execute it manually. This include any PATH settings, and other envvars that the script may depend on.
For me, the problem was a different shell interpreter in crontab.
Related
I have modified my rc.local script to run some python script at startup.
This python script seems to be started successfully.
As the script is running forever (intended) and I want to see what the script does, my question is:
Is there a way to access the shell that runs this script?
Yes, to see what is going on, I could log to some file, but what if that script needs to get input from the user via console?
Thanks for your help!
You will not be able to interact with the script run by rc.local. But you can see what it does by logging its output into dedicated files:
python myscript.py > /home/myhome/log/myscript.log 2> /home/myhome/log/myscript.err
where error messages go into a separate log file.
Note that your script will be executed by root, having permissions and ownership accordingly.
Here's a link to an earlier answer about this with a method to log all outputs of rc.local.
Now you can see in your log file, if the execution stops due to the script demanding input or indeed crashing, and then you can fix the script accordingly.
If you don't want to mess with rc.local for testing, you could also first run it through crontab on your or root's account (scheduled execution by user, see man crontab). This might be easier for debugging, and you can start it through rc.local once it works as you want.
I have a script abc.sh and I have scheduled it in crontab.now abc.sh is calling another script using sudo. When I am executing abc.sh manually it is working fine..but from scheduler abc.sh is running every 5 minutes but It is unable to call another script using sudo. This is strange for me..can any one help me on this please
You can take a look at /var/mail/<username> file to see if cron job is sending some error or warning message. Or maybe you have not set executable permissions for the /opt/clearcache.sh file?
This happens often when people use sudo.
The environment YOU use is not set for the privileged user. As such, your $PATH and other environment variables may not be set as you expect.
You can set this up, or change the sudo behavior... however most people simply work-around this by using full paths to files in cron.
Have a look at this post as well: Where can I set environment variables that crontab will use?
I am facing a weird issue with cron utility.
I have some script which if i run from shell works fine.
However, if run the same script using cron it results in error.
The error it says, is that it is not able to find a particular cmd.
I source my user shell file in the script that i am running.
Any possible reasons for this issue ?
Probably a PATH issue. echo $PATH in terminal, then take the result and put it on the top of the cron file like PATH=/RESULT/STUFF
Recently I created a bash script which I am supposed to run in cron.
After preparing the bash script and its normal working, I put it in Cron and found that it was failing. As as second step , I removed all the environment dependencies i.e instead of just file.txt, I specified /home/blah-blah/file.txt
I still found the script to be failing still at one step. The step was a data processing tool.
The command i executed was /bin/blah-blah/processing_tool -parameter $INDEX where $INDEX is a variable calculated within the bash script.
Third step was to add the bash profile as source at the beginning of the bash script. Voila!!!! The script started executing perfectly from cron.
My question is why is this happening even after I removed all the environment dependencies from my script. Also I have heard that sourcing a cron job to a bash profile is not recommended. If so, Is there any other way in which I can avoid doing this.
Basicly: Anything started from cron starts with a totally clean slate.
You can make no assumptions whatsoever about the content of environment variables or whichever folder is the current folder at the start of any script run from cron.
Easiest solution:
cd to the desired directory to make sure your path is in the desired location.
source /etc/profile to mak sure you get the system wide environment variables setup.
source ~myuserid/.profile to read your personal environment settings. (~/.profile won't work as that would indicate the cron user.)
Then start executing the actual script.
Of course the approach above requires the cron process to have read access to your home-dir adn it's probably doing a lot more work thatn is actually required.
Slightly more complicated: Figure out which environment variables are required by the script and anything that gets called by the script.
Explicitly export these at the beginning of the cron script.
(P.s. replace /etc/profile and ~myuserid/.profile with whatever are the corresponding files for your shell of choice.)
A cron can be thought of as a separate user. So, this "user" may not "see" or "read" the same files as you do. It is thus essential that all path names etc. be defined in the absolute.
Every script runs within its own process. So, when you run a script, you can change the $SHELL and any other variable within but it will be lost once you get out of it. My guess is that the $INDEX variable computation may have had been computed within the script successfully but its use outside of the script may have failed. Without more information about what job it was, or what you wanted to do, it is hard to tell.
There are two ways to run a cron job:
As root, you can run su -user -c < job > in root crontab.
Sourcing your profile explicitly, as you have done.
You can also set environment variables within the crontab.
As user in the user crontab, you can run it like so: "/home/blah/.profile && myScript"
That said, there HAS to be something in your environment variables (apart from file extensions) that is not present when you run the cron job. You will have to execute that script with -x flag (in bash) and then pore over the output. Using a diff between your environment variables and that of root/cron might be a pointer. Also, check if there are some utilities that are being used in your scripts whose locations are not part of the $PATH variable for cron/root.
I have tried exporting my paths and variables and crontab still will not run my script. I'm sure I am doing something wrong.
I have a shell script which runs a jar file. This is not working correctly.
After reading around I have read this is commonly due to incorrect paths due to cron running via its own shell instance and therefore does not have the same preferences setup as my profile does.
Here is what my script looks like today after several modifications:
#!/bin/bash --
. /root/.bash_profile
/usr/bin/java -jar Pharmagistics_auto.jar -o
...
those are the most important pieces of the script, the rest are straightforward shell based.
Can someone tell me what I am doing wrong?
Try specifying the full path to the jar file:
/usr/bin/java -jar /path/to/Pharmagistics_auto.jar -o
I would just tell you what you have already ruled out: Check your path and environment.
Since you have alredy done this, start debugging. Like write checkpoints into a logfile to see how far your script gets (if even started at all), check the cronjob log file for errors, check your mail (cron sends mails on errors) and so on ...
Not very specific, sorry.
"exporting my paths and variables" won't work since crontab runs in a different shell by a different user.
Also, not sure if this is a typo in how you entered the question, but I see:
usr/bin/java
...and I can't help but notice you're not specifying the fully qualified path. It's looking for a directory named "usr" in the current working directory. Oft times for crontab, the cwd is undefined, hence your reference goes nowhere.
Try specifying the full path from root, like so:
/usr/bin/java
Or, if you want to see an example of relative pathing in action, you could also try:
cd /
usr/bin/java
A few thoughts.
Remove the -- after the #!/bin/bash
Make sure to direct script output seen by cron to mail or somewhere else where you can view it (e.g. MAILTO=desiredUser)
Confirm that your script is running and not blocked by a different long-running script (e.g. on the second line, add touch /tmp/MY_SCRIPT_RAN && exit)
Debug the script using set -x and set -v once you know it's actually running
Do you define necessary paths and env vars in your personal .profile (or other script)? Have you tried sourcing that particular file (or is that what you're doing already with /root/.bash_profile?)
Another way of asking this is: are you certain that whatever necessary paths and env vars you expect are actually available?
If nothing else, have you tried echo'ing individual values or just using the "env" command in your script and then reviewing the stdout?
provide full paths to your jar file, and what user are you running the crontab in? If you set it up for a normal user, do you think that user has permission to source the root's profile?