I wrote a python script to work with a message queue and the script was launched by crontab. I removed from crontab but the root user of my linux system keeps launching it every 9 minutes.
I've rebooted system and restarted cron but this script keeps getting executed.
Any idea how to keep it from happening?
If you start a cron, service does not stop even if you delete the file in which you have specified the cron.
This link should help:
https://askubuntu.com/questions/313033/how-can-i-see-stop-current-running-crontab-tasks
Also, you can also kill your cron by looking its PId, using: ps -e | grep cron-name, then kill -9 PId
Related
Let's say I have a silly script:
while true;do
touch ~/test_file
sleep 3
done
And I start the script into the background and leave the terminal:
chmod u+x silly_script.sh
./silly_script.sh &
exit
Is there a way for me to identify and stop that script now? The way I see it is, that every command is started in it's own process and I might be able to catch and kill one command like the 'sleep 3' but not the execution of the entire script, am I mistaken? I expected a process to appear with the scripts name, but it does not. If I start the script with 'source silly_script.sh' I can't find a process by the name of 'source'. Do I need to identify the instance of bash, that is executing the script? How would I do that?
EDIT: There have been a few creative solutions, but so far they require the PID of the script execution to be stored right away, or the bash session to not be left with ^D or exit. I understand, that this way of running scripts should maybe be avoided, but I find it hard to believe, that any low privilege user could, even by accident, start an annoying script into the background, that is for instance filling the drive with garbage files or repeatedly starting new instances of some software and even the admin has no other option, than to restart the server, because a simple script can hide it's identifier without even trying.
With the help of the fine people here I was able to derive the answer I needed:
It is true, that the script runs every command in it's own process, so for instance killing the sleep 3 command won't do anything to the script being run, but through a command like the sleep 3 you can find the bash instance running the script, by looking for the parent process:
So after doing the above, you can run ps axf to show all processes in a tree form. You will then find this section:
18660 ? S 0:00 /bin/bash
18696 ? S 0:00 \_ sleep 3
Now you have found the bash instance, that is running the script and can stop it: kill 18660
(Of course your PID will be different from mine)
The jobs command will show you all running background jobs.
You can kill background jobs by id using kill, e.g.:
$ sleep 9999 &
[1] 58730
$ jobs
[1]+ Running sleep 9999 &
$ kill %1
[1]+ Terminated sleep 9999
$ jobs
$
58730 is the PID of the backgrounded task, and 1 is the task id of it. In this case kill 58730 and kill %1` would have the same effect.
See the JOB CONTROL section of man bash for more info.
When you exit, the backgrounded job will get a kill signal and die (assuming that's how it handles the signal - in your simple example it is), unless you disown it first.
That kill will propogate to the sleep process, which may well ignore it and continue sleeping. If this is the case you'll still see it in ps -e output, but with a parent pid of 1 indicating its original parent no longer exists.
You can use ps -o ppid= <pid> to find the parent of a process, or pstree -ap to visualise the job hierarchy and find the parent visually.
I use SSH to connect to Linux, maybe run a Linux script multiple times, and use nohup to suspend these processes, and then close the SSH connection. After the next SSH connection to Linux, how can I distinguish between different scripts and get different PIDs?
This Linux script will always print content on the screen. I use Python's paramiko library, SSH to Linux, run the script and use nohup to suspend the process and redirect the output to the file. This process may be multiple times. How to distinguish the starting process, find its PID and kill it. It is best not to modify the Linux script because the script is not written by me.
I use the script name to find the process number, get a lot of PIDs, I can't distinguish them.
You could parse the output of ps -eo pid,lstart,cmd which shows the process id, start time and path, e.g.:
PID STARTED CMD
1 Mon Jun 19 21:31:08 2017 /sbin/init
2 Mon Jun 19 21:31:08 2017 [kthreadd]
3 Mon Jun 19 21:31:08 2017 [ksoftirqd/0]
== Edit ==
Be aware that if the remote is macOS the ps command does not recognize the cmd keyword, use comm or command instead, e.g.: ps -eo pid,lstart,comm
Use ps command to check running process.
For checking only shell scripts , You an do something like this:-
ps -eaf |grep .sh
This will give you all the information about running shell scripts only, easily you can distinguish b/w running scripts.
In place of ".sh" you can give file name also, than you will get information only about that running file.
maybe change the command you run to do something like:
nohup command.sh &
echo "$! `date`" >> runlog.txt
wait
i.e. run the command in the background, append its PID to a log (you might want to include more identifying information here or use a format that's more easily machine readable), then wait for it to finish
another variant would be to run tmux (GNU screen) on the server and run commands in an existing session:
tmux new-window command
which would also let you "reconnect" to running scripts later to check output / terminate
On a Raspberry Pi 2 with Raspbian, I discovered that I can use crontab -e and then add a line like #reboot sudo /root/.nvm/v0.10.26/bin/node /root/tweetmonkey-raspi & to the table to start a node process on boot.
I can't figure out how to quickly kill that process. I don't see it in ps -e. What process is that running under?
Cron jobs are started by cron or crond, which will spawn sh to run your command. However, your command forked to run in the background, and then finished executing, so the node process is reparented to the root process, init.
Hi everyone,
I've got a few scripts running with crontab and I know they are actually running thanks to a log file.
The thing is, each time I type ps -ef | grep .sh (because my scripts are .sh files) i have no results.
I read that crontab was using its own environment to execute his scripts and so I was wondering if ps command was able to detect them.
I'm a newbie to Linux environment, so I'm sorry if my question might seem obvious. Thanks
If you run ps while your script is running, then ps will report that process.
crond is the cron process, and it belongs to root. When crond notices that it's time for your process to run, it will fork a process, change that process's user to your ID, then exec() your script.
This process will appear in ps, if ps is run while it's active, but if the process is short-lived, you only have a short window of opportunity to glimpse it..
I made a python script running on background:
nohup python app.py &
then close the terminal, a few days later, I want to see this job, so I run
jobs
there list no jobs, but I'm sure the script app.py is still running.
jobs will only give you a list of process running under the session group of the bash shell. nohup processes run in their own session group. There are a number of simple commands you can run to check if your nohup'd process is still running, the simplest being lsof | grep nohup (this command may take a few seconds to run)