I have an issue with later versions of ES, so have to use 7.10.2 currently.
This means that the previous method I used to install ES as a service, i.e. apt-get, doesn't work You can't choose an older version this way: it currently installs 7.16.3.
So I followed the procedure on this page for 7.10: everything worked: I was able to run ES as an app and also as a "daemon". Clearly I could simply put the "daemon" startup line in a script which runs on boot.
But what's the optimum way of turning this "daemon arrangement" into a service which you can control with systemctl, and which starts automatically when the machine boots?
PS I don't want to get involved with Docker. I'm sure that's a useful thing but I'm convinced there is a simpler way of doing it, using available Linux sys tools.
I found a workaround... this doesn't in fact create a service of the "systemd" type which can be controlled by systemctl. There seem to be one or two problems which make this non-trivial.
1) You can't start ES as root! I assume (not sure) that most services are being run by root. Anyway this was something I couldn't find a solution to.
2) I am not sure whether a shell script file called by a service is allowed to end... or should continue endlessly: initially I thought this would be sufficient. This is a shell script (run_es_daemon.sh) which does indeed start up ES (as a daemon process) when run by manually in a terminal. There is no issue to do with the fact that the script ends and you then close the terminal: the daemon process continues to run:
#!/bin/bash
# start ES as a daemon...
cd /home/mike/Elasticsearch/elasticsearch-7.10.2
./bin/elasticsearch -d -p pid
... but it never worked using a xxx.service file in /etc/systemd/system/ (maybe because of 1) above). So I also tried adding these lines under the above ones:
while true
do
echo "bubbles"
sleep 60
done
... didn't work either.
In the end I found a simple workaround solution was to start up the daemon process by using crontab:
#reboot /home/mike/sysadmin/run_es_daemon.sh
... but I'd still like to know how to set it up as a true service, which starts at boot...
Related
NOTE: I am running Red Hat 6.7
I have a service that is configured with the Linux init system to start a process as a service when the machine boots. This was done by doing this one-time configuration from the command line:
ln -snf /home/me/bin/my_service /etc/init.d/my_service
chkconfig --add my_service
chkconfig --level 235 my_service on
When the OS reboots, the service starts as expected.
I ALSO need the service to be restarted if the service (my_service) crashes. From what I've read, all I need to do is add an entry to /etc/inittab that looks like this:
mysvc:235:respawn:/home/me/bin/my_service_starter
Where my_service_starter looks like:
#!/bin/bash
/home/me/bin/my_service start
My understanding is that when the init system detects that my_service is not running, it will attempt to restart it by running "my_service_starter".
However this does not seem to be working.
I need to understand how to tell the Linux init system to restart my service when the service crashes.
Given an entry like:
mysvc:235:respawn:/home/me/bin/my_service_starter
Then inittab will:
call /home/me/bin/my_service_starter
which will call /home/me/bin/my_service start
...and then exit, so init will thing your service has failed
so init will call /home/me/bin/my_service_starter again
...and so forth, which will result in init deciding that your script is respawning too fast, after which it will ignore it completely.
A process started by inittab is not expected to exit. If you really want to use inittab to maintain your service, you could remove /etc/init.d/my_service, and then in /etc/inittab you would have something like:
mysvc:235:respawn:/home/me/bin/my_service
And you would need to ensure that my_service runs in the foreground (some programs automatically daemonize by default, although these will often have some sort of --run-in-foreground flag).
If you upgrade to CentOS 7 or something else with systemd, this all becomes easier.
You can also investigate "third-party" process supervisors like "supervisord" or "runit" that you could use for process monitoring/restarting on CentOS 6.
Update
As mangotang points out, and I forgot, RHEL 6 actually shipped with upstart, even though it used almost exclusively SysV-style init scripts. So a better solution would be to create an upstart service instead. There are some reasonable getting-started docs here.
On RHEL 6.X, at top of the /etc/inittab file it says:
# inittab is only used by upstart for the default runlevel.
#
# ADDING OTHER CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM
RHEL 6.X uses Upstart instead of the System V init system. See the man pages for initctl(8) and initctl(5), or ask Google about Upstart.
I try to execute a java application at startup in a yocto based linux device. I added a script at /etc/init.d/etic and made it executable. If I call at the shell /etc/init.d/etic start or /etc/init.d/etic stop the application is started an stopped as expected. Then I called on the shell update-rc.d etic defaults and the symlinks were created. According to what I found on the web, this should be enough, but somehow the application is not started. What did I miss? How could I check what is going wrong or is there any minimal example which should work which I can try to extend?
Well, often such issues are due to a different environment when executing the start script by hand, as compared to when it's being run from the init system. For instance, your .profile and .bashrc won't have been sourced, when running from the init system.
You can use eg logger to easily log things from your init-script, and this rather easily find out what goes wrong.
I created a cronjob with sudo crontab -u USERNAME -e and tried to start my node.js app after each reboot.
It had worked well at another server.
But this time, I installed the Node.js via nvm
Then tried to run the same cronjob lines, but every time after reboot it failed. I tried to figure out all the related folders and tried again to run as different lines. When I check with forever list, server shows that no process is running.
#reboot /home/USERNAME/.npm/forever start -c /home/USERNAME/.nvm/current/bin/node /home/USERNAME/APPNAME/app
#reboot /home/USERNAME/.npm/forever start /home/USERNAME/APPNAME/app
#reboot /usr/local/bin/forever start -c /home/USERNAME/.nvm/current/bin/node /home/USERNAME/APPNAME/app
I think that the reason is somehow related with nvm. But I am not sure of that. I don't want to do anything unnecessary unless I am fully sure about it.
Edited July 26, 2015
Though I have used the npm's forever module to deploy nodejs production apps, I really do not see the need to use it on linux based servers as there are so many system level alternatives available.
One of them is upstart. It will help you run your scripts as system level services. Amazon Web Services also use upstart in their Elastic Beanstalk nodejs tiers to keep nodejs apps running forever.
If you really just need to get down to it, here is a link to run your nodejs app as an upstart service.
However, it is not limited to deploying nodejs apps only and if you learn upstart, you will be able to do a lot of things with it. Here is a link for that as well.
If your original approach was preferable (as it was in my case) you can fix your scheduled cron job by explicitly passing the path to node like this: (found in this answer)
#reboot /root/.nvm/versions/node/v7.1.0/bin/node /root/.nvm/versions/node/v7.1.0/bin/forever start /var/www/server.json
Apparently NVM works in magic by setting up some system paths which aren't setup at the moment the cron jobs run.
I have written up a simple bash script that will copy the newest image from my ip camera into a directory, rename the file and delete the old file. The script loops every 10 seconds.
I want to have this script start running in the background and run continuously all the time that the server is up.
I understand the part about adding a & to the end of the command will cause it to run in the background.
Is init.d the best place to execute this?
I am running ubuntu server.
This sort of thing is normally done by service scripts, which you would find under /etc/init.d. Depending on the version, that might be a "System V init script", or one of the systemd scripts.
A simple service script of the sort you are asking about would start automatically (based on comments in the script's header that tell what run-levels it would use), create a file under /var/run telling what process-id the script uses (to allow killing it), and run the copying in a loop, calling sleep 10 to space the timing as indicated.
A typical service script should implement "start", "stop", "restart" and "status". Not all do, but there is rarely a good reason to not do this.
On my (Debian) system, there is a README file in the directory which is a good introduction to the topic. There are several tutorials available for the topic. Here are a few:
Linux: How to write a System V init script to start, stop, and restart my own application or service
Writing a Linux Startup Script
Manage System Startup and Boot Processes on Linux with Upstart
I wrote a simple JAVA application which runs as a service. When my application is up and running, I maintain the PID in a file which will be used while stopping the application.
Issue:
When I restart the OS the stop script is not called (not sure how to make this happen) and the old PID is left as it is in the PID file. Now, after reboot (which start my app) when I stop the app using stop script now my stop script will try to clean up all the PID listed in the file. Most of the time, I will get "No such process". But there are chance the same PID might have been used for some other process
Question:
How I can make sure my stop script will be invoked when I shutdown ore reboot the OS? I am looking a solution for RHEL environment.
I think your are looking for a init script. (startup/shutdown services at different run levels)
This is a good reference
http://blog.rimuhosting.com/2009/09/30/one-java-init-script/
this has a good refernce to Linux init.d scripts
http://coreymaynard.com/blog/creating-a-custom-initd-script-on-fedora/
Hope it helps
If you are looking for scripts that run after reboot, I guess you can write the script in /etc/rc.local and then you can start your service.
This script will run after all your init scripts have run while your machine starts. Using this you can delete the old PID file.