A Service Has Gone Rogue. How Do I Manage It?

Once I installed a development service on port 3000 and I forgot about it. When I ran my project I couldn't start it because the port was in use. Baffled. 😕

This post forms part of a sequence of command line references that I will be writing where I forget the command or its syntax.

Although it is easily Google-able, there are usually a chain of commands that I want kept together for ease of use.

The commands I use should be universal but just in case, I am running Fedora release 28 (Twenty Eight).

Also, if you want to contribute something interesting in any of my posts, please create a pull-request or write a comment below. 😄

Getting back to my forgetfulness. I wanted to know what was using that port. I'll get to that. First let's take a look at how I interrogate the system to get a list of running services.

systemctl let's us query or send control commands to the systemd manager.systemd starts core programs, journal of system activity, the network stack, a cron-style job scheduler, user logins and other jobs. Find out more at ZDNet.

If we want to find a list of installed programs and services (units) that are enabled:

systemctl list-unit-files | grep enabled

If we want to print out all services and see if they have been loaded or not:

systemctl -l --type service --all

What service is hogging my port?

To get to the meat of the problem I interrogate the network, get a pid and kill it. I can also uninstall the service if I no longer want it to run.

netstat prints network connections, routing tables, interface statistics, masquerade connections, and multicast memberships.

When I run the below command, I can see the program name and pid

sudo netstat -tulpn | grep 3000

Another command can be run using ss which is a utility to investigate sockets.

sudo ss -lptn 'sport = :3000'

Just stop the service for now

sudo systemctl stop [servicename]
sudo systemctl disable [servicename]

Killing processes

Once I have a pid for the process I want to shut down, I can kill it. First I query the process to make doubly sure ps -aux | grep 12345

Then I can kill it sudo kill 12345. In some cases, the kill doesn't want to play along in which case I need to force it, sudo kill -9 12345.

Uninstall the service

If I am adamant that the service should not exist, I can uninstall it.

sudo systemctl stop [servicename]
sudo systemctl disable [servicename]
sudo rm /etc/systemd/system/[servicename]
sudo rm /etc/systemd/system/[servicename] #symlinks that might be related
sudo systemctl daemon-reload
sudo systemctl reset-failed

Summary

systemctl list-unit-files | grep enabled
systemctl -l --type service --all

sudo netstat -tulpn | grep 3000
sudo ss -lptn 'sport = :3000'

ps -aux | grep 12345
sudo kill 12345
sudo kill -9 12345

systemctl stop [servicename]
systemctl disable [servicename]
rm /etc/systemd/system/[servicename]
rm /etc/systemd/system/[servicename]
systemctl daemon-reload
systemctl reset-failed

References

• Linus Torvalds and others on Linux's systemd - ZDNet
• How to remove systemd services - superuser