I am trying to uninstall logstash, but sudo apt-get remove logstash fails because the user is being used by a process. If I try to manually delete the logstash user, I cannot because even when I kill the process, a new one immediately pops up. For example, if I check for processes using logstash:

ps -fp $(pgrep -u logstash)

I get

UID        PID  PPID  C STIME TTY          TIME CMD

logstash 17376     1 99 10:04 ?        00:00:10 /usr/bin/java -Djava.io.tmpdir=/

Then I try to kill the process and delete the user:

sudo killall -KILL -u logstash

sudo userdel logstash

But now logstash is already being used by another process:

userdel: user logstash is currently used by process 17794

How can I delete the logstash user?