I'm accessing a webserver via PHP. I want to update some info in the Apache configs, so I start a shell script that makes the changes. Then I want to stop and restart Apache.
Problem: as soon as I stop Apache, my process stops and my shell script, being a child process, is killed. Apache never restarts. This also happens with Apache restart.
Is there a way to fork an independent, non-child process for the shell script, so I can restart Apache?
Thx,
Mr B
You can use disown:
disown [-ar] [-h] [jobspec ...]
Without options, each jobspec is removed from the table of active jobs. If the `-h' option is given, the job is not removed from the table, but is marked so that SIGHUP is not sent to the job if the shell receives a SIGHUP. If jobspec is not present, and neither the `-a' nor `-r' option is supplied, the current job is used. If no jobspec is supplied, the `-a' option means to remove or mark all jobs; the `-r' option without a jobspec argument restricts operation to running jobs.
./myscript.sh &
disown
./myscript.sh will continue running even if the script that started it dies.
Take a look at nohup, may fit you needs.
let's say you have a script called test.sh
for i in $(seq 100); do
echo $i >> test.temp
sleep 1;
done
if you run nohup ./test.sh & you can kill the shell and the process stay alive.
Related
Consider a package that offers some client/server functionalities. In such
a context some regression tests (as defined with ADD_TEST(...) ) concern
the server and some others tests concern the client. Typically, I thus need
to launch a server at the beginning of ctest, then to run each individual
client test, and then to cleanly kill the server (oh well, in theory :).
For this, I use CTEST_CUSTOM_PRE_TEST which I configured to be a shell script
(I know this is not portable but, for the time being, I don't know any
better way). This typical CUSTOM_PRE_TEST is of the form:
#!/bin/bash
the_server_to_test > log &
echo Done
The problem is that ctest seems to wait for the disassociation of the
child process (in this case the server I wish to test) before proceeding with
each atomic test. This can be easily checked by configuring
CTEST_CUSTOM_PRE_TEST with the following simple script:
#!/bin/bash
sleep 30 >log &
for which ctest will wait for 30 seconds i.e. the end of the child process
before proceeding with the test suite per se. In despair, and just to
make sure, I also tried
sleep 30 < /dev/null >log 2>&1 &
and in drunken despair I even tried
nohup sleep 30 < /dev/null >log 2>&1 &
but ctest behavior seems to always be the same...
Interestingly enough when I launch those shell scripts manually from
the command line (as opposed to launching them from within ctest) I then
get my hands back on the invoking shell while the server (on in the
above examples the sleep command) keeps on running...
My questions is thus: when using CTEST_CUSTOM_PRE_TEST how can one force
ctest not to wait for child process disassociation ?
Yours,
Eric Boix.
I met a problem, it was exactly same as described here, which was asked 16 years before: https://cmake.cmake.narkive.com/JLfzLWS9/ctest-custom-pre-test-and-child-process-disassociation#post1 But no answer. I pasted it here, hope someone can help
I tested it today. both below ways will not block the pre-test stage, but ctest can show up some warnings:
[ctest] There was an error running ctest to determine available test executables
nohup sleep 30 < /dev/null >log 2>&1 &
sleep 30 <dev/null >/dev/null 2>&1 &
to avoid the warning, use to start a daemon, for python please use python-daemon, to ensure the process can exit
for example
python3 your_python_daemon.py >/dev/null 2>&1 </dev/null
Please be noted the stdin, stdout, and stderr should be provided other wise ctest still use their own one and wait it to be close, which can still block the pre-test stage
As mentioned by #KamilCuk, ctest fixture is the best facility to implement this task. be aware that when starting daemon in ctest fixture, stdin, stdout and stderr also need to be proved like above
I'm using singularity to run python in an environnement deprived of python. I'm also running a mysql instance as explained by the IOWA state university (running an instance of mysql, and closing it when done).
For clarity, I'm using a bash script to open mysql, then do what i have to do (a python script) and close mysql, and it works fine. But Python's only way to stop if an error occured is sys.exit([value]) and this not only stops the python script, but also the bash script that ran it. This makes it impossible for me to manage the errors and close the instance of mysql if the python script exits.
My question is : Is there a way for me to execute a 'singularity instance stop mysql' while being in the python sandbox. Something to tell singularity "hey, this command here must be used on the host !" ?
I keep searching but can't find anything.
I only tried to execute it with subprocess like any other command, but it returned an error message because I don't have this instance inside the python sandbox. I don't even have singularity in this sandbox.
For any clarifications, just ask me, I'm trying to be clear but I'm pretty sure it's not very clear.
Thanks a lot !
Generally speaking, it would be a big security issue if a process could be initiated from inside a container (docker or singularity) but run in the host OS's namespace.
If the bash script is exiting on the python failure, it sounds like you're using set -e or #!/bin/bash -e. This causes the script to abort if any command returns non-zero. It's commonly recommended for safer processing, but can cause problems like this at times. To bypass that for the python step you can modify your script:
# start mysql, do some stuff
set +x # disable abort on non-zero return
python my_script.py
set -x # re-enable abort on non-zero
# shut down mysql, do other stuff
I have a unique problem using jmeter SSH command.
I use this step to run spark jobs.
the problem is that one of the commands not working, to clarify it connects and not get response and just wait and wait for hours, and nothing displayed on screen.
I know how to work with the tool, and this behavior is special for this script alone.
All other script worked, I duplicate one that worked for example
sudo /run_stg.sh this command worked
sudo /run_off2-stg.sh this command not worked
if I run the job manually via jenkins it worked
if I entered to command line and use plik ssh it worked,
the problem is just Jmeter, that is waiting and waiting and I can not understand for what?
the job is about 3 minutes, and I wait for response in Jmeter for 4 hours and nothing Jmeter just waiting.
in the console log I set to trace level and nothing, absolutely no idea how to start handle this issue in Jmeter.
an anyone please assists how to make Jmeter to write what happened?
or just to know if he connect or anything
since this behavior all the test can not be performed
Most probably you are as usual misconfiguring the SSH Command sampler.
The idea is not to run the script per se, you need to delegate the script execution to the Unix Shell, for example Bash this way you will be able to combine several commands together, see the output, amend debugging level, etc.
So I would recommend setting your command to something like /bin/bash -c -x /your/script.sh
Another guess, given you use sudo it might be the case that the sudo command simply waits for the password (which JMeter never provides), if this is the case try amending your script permissions using chmod command and allowing your user its execution without root privileges.
And finally, given you're able to run your command using "plik ssh" (whatever it is) you can run it using OS Process Sampler
More information: How to Run External Commands and Programs Locally and Remotely from JMeter
Having trouble running a crontab psql backup job from a locally stored script. I added the job via crontab -e and when I used crontab -l, it shows up in the list of jobs. The script that it is supposed to run works fine, checked that, runs as it should and dumps the output on the designated s3 bucket when using ./backup.sh
This is what I set the job as:
59 23 * * 7 /Users/myusername/backup.sh
The job should run at 11:59PM every Sunday, but it doesn't. I can't figure out what the issue is (do I need to leave line breaks/spaces in between each job, or just after the very lost job in my crontab list?
Any help would be very much appreciated. Thanks.
Depending on your distribution, you might want to check logs for Cron service.
Non-exhaustive list of possible problem reasons:
Cron service is not running at all and hence is not starting any of the tasks;
Usually Cron passes your script a very limited set of environment variables, so your script might fail because of some missing environment. That will probably be reflected in cron daemon logs
What can you do
Cron service: if your distro uses systemd then try running systemctl status cron (or systemctl status crond?) to check if it is running.
Your script is started but fails: here are several things to try.
Try checking cron service logs, maybe with something like journalctl --unit cron or journalctl -f before the script should be started;
Check if there is a dead.letter file in your home directory containing output of the failed script. When Cron starts your script and the script outputs something (which is considered a problem), that output is mailed to you. If mailing is not properly configured then it usually goes to that file.
Put something like this in the beginning of your script:
(
date
id -a
set
echo
) >> /tmp/myscript.log
Then wait until cron runs your script and check if the file /tmp/myscript.log was created. Then try to run your script manually, replicating all the environment created by cron which you now know. I.e. unset all but the variables Cron leaves, and make sure id is correct.
Jenkins version: 1.574
I created a simple job which performs the following:
Using "Execute shell script on remote host using SSH" as one of the BUILD steps, I'm just calling a shell script. This shell script performs stop and start operations on Tomcat to restart an application on the target machine.
I have a valid username, password, port defined for the target SSH server in Jenkins Global settings.
I saw this behavior that when I run a Jenkins job and call the restart script (which gets the application name as parameter $1), it works fine, but as soon as "Execute shell script on remote host using SSH" step completes, I see the new process dies on the remote/target application server.
If I run the script from the target/remote server itself, everything works fine and the new process/PID remains live forever, but running the same script from Jenkins, though I don't see any errors and everything works as expected, the new process dies as soon as the above mentioned SSH step is complete and control comes back to the next BUILD step in Jenkins job OR the Jenkins job is complete.
I saw a few posts/blogs and tried setting: BUILD_ID=dontKillMe in the Jenkins job (in various places i.e. Prepare Environment variables and also using Inject Environment variables...). When the job's particular build# is complete, I can see Environment Variables for that build# does say BUILD_ID=dontKillMe as its value (instead of the default Timestamp tag value).
I tried putting nohup before calling the restart script, i.e.,
nohup restart_tomcat.sh "${app}"
I also tried:
BUILD_ID=dontKillMe nohup restart_tomcat.sh "${app}"
This doesn't give any error and creates a nohup.out file on the remote server (but I'm not worried about it as the restart_tomcat.sh script itself creates its own LOG file which I'm "cat"ing after the restart_tomcat.sh script is complete. cat'ing on the log file is performed using another "Execute shell script on remote host using SSH" build step, and it successfully shows the log file created by the restart script).
I don't know what I'm missing at this point, but as soon as the restart_tomcat.sh step is complete, the new PID/process on the remote/target server dies.
How can I fix this?
I've been through this myself.
On my first iteration, before I knew about Jenkins ProcessTreeKiller, I ended up just daemonizing Tomcat. The Apache Tomcat documentation includes a section on running as a daemon.
You can also try disabling the ProcessTreeKiller for your whole Jenkins instance, if it's relatively small (read the first link for information).
The BUILD_ID=dontKillMe should be passed to the shell, and therefore it should be in your command line, not in Jenkins global configuration or job parameters.
BUILD_ID=dontKillMe restart_tomcat.sh "${app}" should have worked without problems.
You can also try nohup restart_tomcat.sh "${app}" & with the & at the end.
My solution (it worked after trying everything else) in Ubuntu 14.04 (Trusty Tahr) (Amazon AWS - Amazon EC2), Jenkins 1.601:
Exec command: (setsid COMMAND < /dev/null > /dev/null 2>&1 &);
Exec in PTY: DISABLED
// Example COMMAND=socat TCP4-LISTEN:1337,fork TCP4:127.0.0.1:1338
I created this Transfer as my last one.
#!/bin/ksh
export BUILD_ID=dontKillMe
I added the above line to the start of my script and the issue was resolved.