Monitoring services and starting them on boot
From wikipedia
Systemd is a software suite that provides fundamental building blocks for a Linux operating system. It includes the systemd “System and Service Manager”, an init system used to bootstrap user space and manage user processes. systemd aims to unify service configuration and behavior across Linux distributions.
Before going gaga over systemd checkout arguments against it as well. But personally I find it easy to manage. Since I am not well versed in Linux it helps me make less blunders and miss out on doing some things because of lazyness and unfamiliarity. I use a command called systemctl. Check if it is supported in your Linux Distro or not.
# which systemctl/bin/systemctl
Handy Commands
Start an application
sudo systemctl start application#Examplesudo systemctl start nginx
Stop an application
sudo systemctl stop application#Examplesudo systemctl stop nginx
Restart an application
sudo systemctl restart application#Examplesudo systemctl restart nginx
Reload an application
sudo systemctl reload application#Examplesudo systemctl reload nginx
Check status
sudo systemctl status application#Examplesudo systemctl status nginx
Example output of status
● nginx.service - A high performance web server and a reverse proxy server
Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)
Active: active (running) since Wed 2019-01-30 11:29:16 IST; 1 weeks 0 days ago
Docs: man:nginx(8)
Main PID: 909 (nginx)
Tasks: 2 (limit: 1152)
CGroup: /system.slice/nginx.service
├─909 nginx: master process /usr/sbin/nginx -g daemon on; master_process on;
└─911 nginx: worker process
Jan 30 11:29:15 ubuntu-s-1vcpu-1gb-blr1-01-monitoring systemd[1]: Starting A high performance web server and a reverse proxy server...
Jan 30 11:29:16 ubuntu-s-1vcpu-1gb-blr1-01-monitoring systemd[1]: nginx.service: Failed to parse PID from file /run/nginx.pid: Invalid argument
Jan 30 11:29:16 ubuntu-s-1vcpu-1gb-blr1-01-monitoring systemd[1]: Started A high performance web server and a reverse proxy server.
Check if active
If you are using a monitoring service like zabbix and need to check if a service is active you can use
# systemctl is-active nginx
active
Ready for Restart
Inspite of all the precautions we take there will be scenarios where things fail. As debugging might take more time and can put your application or service out of action, we might be forced to restart our server. Making sure that everything works on a restart is hence very critical.
List all loaded units
systemctl list-units -all | grep loaded | awk '{print $1;}'
List all enabled units
systemctl list-unit-files| grep enabled | awk '{print $1;}' > enabled.txt
Most of the times we need to make sure that all the services we use are in the start up script.
List all loaded services
systemctl list-units -all | grep service | grep loaded | awk '{print $1;}'
List all enabled services
systemctl list-unit-files | grep service | grep enabled | awk '{print $1;}' > enabled.txt
To find the list of services which are loaded but not enabled we can do the following.
systemctl list-units -all | grep service | grep loaded | awk '{print $1;}' > loaded.txtsystemctl list-unit-files | grep service | grep enabled | awk '{print $1;}' > enabled.txtdiff -y loaded.txt enabled.txt#If you want a quick glance of missing ones you can also usediff -y loaded.txt enabled.txt | grep '<'
I know this is not fool proof but it can give you quick glance of missing services.
Docker, Ansible et al
Making sure that your server works as expected even after restarts lets you sleep with ease at night.
We are considering moving our workflow to Docker and Ansible. That will take some time. Until then we will do with a general setup, hacks like these and a monitoring tool like Zabbix. Hope it helps you.
If you liked this article and would like to read similar articles, don’t forget to clap.
Click and drag to clap more than once. 50 is the limit.
You can read the others articles from the series.
Understanding promises in JavaScript_I have had a kind of “love and hate” relationship with JavaScript. But nevertheless JavaScript was always intriguing…_hackernoon.com
Understanding async-await in Javascript — Gokul N K — Medium_Async and Await are extensions of promises. So if you are not clear about the basics of promises please get comfortable…_hackernoon.com
Should I use Promises or Async-Await_I recently read a medium post where the author claimed that using async-await is better than using promises. While this…_hackernoon.com
If you are interested in cryptocurrencies checkout
10 things to know/do before investing in cryptocurrencies_“Never Invest In Something You Don’t Understand”_hackernoon.com
Beginner’s Guide to “Investing in Cryptocurrencies”_It has been more than an year since I started investing in cryptocurrencies. Following Warren Buffet’s advice of “Never…_hackernoon.com
Why comparing cryptocurrency prices is wrong_Price is an important indicator. But it can also be misleading in many cases._blog.goodaudience.com