sudo apt update
sudo apt install monit
sudo systemctl start monit
sudo systemctl enable monit
sudo systemctl status monit

/lib/systemd/system/monit.service erstellen:

# This file is systemd template for monit service. To
# register monit with systemd, place the monit.service file
# to the /lib/systemd/system/ directory and then start it
# using systemctl (see below).
#
# Enable monit to start on boot: 
#         systemctl enable monit.service
#
# Start monit immediately: 
#         systemctl start monit.service
#
# Stop monit:
#         systemctl stop monit.service
#
# Status:
#         systemctl status monit.service

[Unit]
Description=Pro-active monitoring utility for unix systems
After=network-online.target
Documentation=man:monit(1) https://mmonit.com/wiki/Monit/HowTo 

[Service]
Type=simple
KillMode=process
ExecStart=/usr/local/bin/monit -I
ExecStop=/usr/local/bin/monit quit
ExecReload=/usr/local/bin/monit reload
Restart = on-abnormal
StandardOutput=null

[Install]
WantedBy=multi-user.target

Monit aktivieren und starten:

sudo systemctl enable monit.service
sudo systemctl start monit.service
sudo systemctl status monit.service

/etc/monit/conf-enabled/monit.conf erstellen:

set httpd port 2812 and
    use address localhost  # only accept connection from localhost (drop if you use M/Monit)
    allow localhost        # allow localhost to connect to the server and
    allow admin:monit      # require user 'admin' with password 'monit'

sudo monit reload
sudo monit status

monit

Usage: monit [options]+ [command]
Options are as follows:
 -c file       Use this control file
 -d n          Run as a daemon once per n seconds
 -g name       Set group name for monit commands
 -l logfile    Print log information to this file
 -p pidfile    Use this lock file in daemon mode
 -s statefile  Set the file monit should write state information to
 -I            Do not run in background (needed when run from init)
 --id          Print Monit's unique ID
 --resetid     Reset Monit's unique ID. Use with caution
 -B            Batch command line mode (do not output tables or colors)
 -t            Run syntax check for the control file
 -v            Verbose mode, work noisy (diagnostic output)
 -vv           Very verbose mode, same as -v plus log stacktrace on error
 -H [filename] Print SHA1 and MD5 hashes of the file or of stdin if the
               filename is omitted; monit will exit afterwards
 -V            Print version number and patchlevel
 -h            Print this text
Optional commands are as follows:
 start all             - Start all services
 start <name>          - Only start the named service
 stop all              - Stop all services
 stop <name>           - Stop the named service
 restart all           - Stop and start all services
 restart <name>        - Only restart the named service
 monitor all           - Enable monitoring of all services
 monitor <name>        - Only enable monitoring of the named service
 unmonitor all         - Disable monitoring of all services
 unmonitor <name>      - Only disable monitoring of the named service
 reload                - Reinitialize monit
 status [name]         - Print full status information for service(s)
 summary [name]        - Print short status information for service(s)
 report [up|down|..]   - Report state of services. See manual for options
 quit                  - Kill the monit daemon process
 validate              - Check all services and start if not running
 procmatch <pattern>   - Test process matching pattern