When you stop Xampp in your linux system and you may get an error, XAMPP Stopping Apache fail apachectl returned 1.

Stopping XAMPP for Linux 1.8.3-5...
XAMPP: Stopping Apache...fail.
apachectl returned 1.
XAMPP: Stopping MySQL...ok.
XAMPP: Stopping ProFTPD...kill: usage: kill [-s sigspec | -n signum | -sigspec] pid | jobspec ... or kill -l [sigspec]
kill returned 1.

…delete the following files:

sudo rm /opt/lampp/logs/httpd.pid
sudo rm /opt/lampp/var/mysql/$(hostname).pid
sudo rm /opt/lampp/var/proftpd.pid

Note: Replace “$(hostname)” with your device name (for example: localhost or whatever)