I'm currently running a python script as a systemd service. Is there any way to "switch" into the service and take control of the script? The script has a menu but runs calculations in the background in another thread. Most likely not, so is there a way to run a python script 24/7, start on boot, restart on crash etc (just like systemd service) but be able to take control of it after I connect to the server via SSH, so I can manipulate the app?
One solution you could try would be to edit the systemd configuration to launch the process in screen or tmux, then attach that when logging in via SSH.
For instance, in the systemd unit, you might have:
[Service]
Type=single
ExecStart=tmux new "command"
Using Type=single will treat the tmux command as the main process, which would be killed if you stop it with systemctl stop systemprocess
The ExecStart=tmux new "command" creates a new tmux session with the command inside of it.
You can then attach to it using tmux attach as the same user the systemd unit is running as (I believe this is root by default).
Related
I have a demo project in AWS and then I created an AMI for it so that I can use it for auto-scaling. now I am looking for something that I can put in user text in my launch configuration which will let me start the server without going to ssh. I am trying out below, let me know where is my mistake.
#!/bin/bash
cd demo
node server.js
when I launch a new instance with my AMI and just do cd through SSH it works absolutely fine, however, I want to start the server with going to SSH.
These are common one can face when running node application without process manager on a remote server.
Let suppose the above script but what if a node application encounter error? so the application will be stopped, so better to use process manager which will take care of such thing and you will not need to do ssh.
You can use pm2. Which also have slack integration another interesting feature that will help to monitor the process.
You can also set Setup startup script.
Restarting PM2 with the processes you manage on server boot/reboot is
critical. To solve this, just run this command to generate an active
startup script:
run these command in the AMI, and pm2 will take care of the process on all instances.
pm2 startup
#And to freeze a process list for automatic respawn:
pm2 save
I have packaged a Debian file of our software. Now there is a .sh script that needs to be started to run the program/software. This .sh script actually runs a Django server and few more services.
To actually start this application, we need to run the .desktop file in the menu. This .desktop file in the menu is associated with the .sh script mentioned above. This prompts the terminal and asks for the password. Once the password is given, this will start the services and the terminal stays active.
To close this service completely, we need to kill the process by finding the PID of the process and killing it from the terminal. But now I want to kill this process when I close the terminal.
How can I do that?
If you are trying to create a service (some program that runs in the background), you should create use your system's mechanism for this.
The traditional one, would be a scrip in /etc/init.d/, a more modern approach is to use systemd.
E.g. a file /etc/systemd/system/myservice.system
[Unit]
Description=My Service
[Service]
Type=simple
# you could run the service as a special user
#User=specialuser
WorkingDirectory=/var/lib/myservice/
# execute this before starting the actual script
#ExecStartPre=/usr/lib/myservice/bin/prestart.sh
ExecStart=/usr/bin/myservice
Restart=on-failure
[Install]
WantedBy=multi-user.target
You can then start/stop the service (as root) using:
systemctl start myservice
resp.
systemctl stop myservice
You can have dependency chains of services, so starting myservice will automatically start myhelper1 and myhelper2.
Checkout the manpage systemd.unit.5
When the controlling terminal is closed, the foreground process group should receive a SIGHUP signal. If your target process is already expected to be in the foreground, then it may be that it is catching or ignoring SIGHUP (the default behavior for a process receiving that signal is to terminate).
I wish to know how can I schedule a custom script to run whenever I restart a service.
My use case is that I have to run several commands whenever I restart my Tomcat Service. I want to know if there is a way I can write a script and schedule it to run whenever I restart the Tomcat service.
I have setup the tomcat script as a systemd service. I am using Cent OS 7 x64.
I have been able to achieve this by creating another service and incorporating the Tomcat service's start stop in the new service. The new service acts as a wrapper service which first starts tomcat and then executes the commands that we need to run as soon as tomcat starts.
Then while stopping, it stops tomcat and runs clean up commands.
EDIT: I found another way of doing this on unix & linux stackexchange.
Simply create an new systemd .service file in /etc which includes and overrides part of the one in /lib. For example, create /etc/systemd/system/tomcat.service to contain
.include /lib/systemd/system/tomcat.service
[Service]
ExecStartPre=/home/meuh/myscripttorun some pre args here
ExecStartPost=/home/meuh/myscripttorun some post args here
Any ExecStartPre lines will be executed before the ExecStart line, and similarly any ExecStartPost will run after tomcat has started.
Can we hook to similar start,stop etc events. Do we have to write them as shell scripts? I know of mono port of .NET.
You are looking for something called an 'init script'. These are scripts that allow you to start or stop a service with a single command, like so:
service httpd restart
service httpd stop
service httpd start
Some Linux distributions do not include the service command, in which case you access init scripts directly by their location, /etc/init.d, like so.
/etc/init.d/mysqld restart
You can program your init script to accept whatever parameters you want (start, stop, restart, etc). Some basic tutorials on writing init scripts to get you started can be found at the following web pages:
http://www.cyberciti.biz/tips/linux-write-sys-v-init-script-to-start-stop-service.html
http://www.linuxquestions.org/questions/programming-9/how-to-write-init-script-376302/
Many times an init script is unnecessary, and you can just go with the simpler option of executing your program in the background and killing it manually. Running an executable on Linux in the background can be done like so:
./some_prog arg1 arg2 &
And killing it is done like this:
kill `pgrep some_prog`
If you are fairly new to Linux, that latter option might be a much easier way to go until you get a handle on init scripts and the general Linux service ecosystem.
For example - i have process id which i want to restart. What command i should use to restart this process application ? I didn't find something about it(
Thanks!
You can find very similar question at Restart process script linux.
Linux doesn't have general command for restart, normally you should kill your process and start it over. However, if your process has been started as a service, i.e. it's contained in /etc/init.d/ directory, then you can do the following:
/etc/init.d/SERVICE_NAME restart
or
service SERVICE_NAME restart