Monit

Manual

check host example address example.org
        if failed port 22 protocol ssh then alert
        if failed host cloud.example.org port 80 protocol http then alert

/etc/monit/conf-available/samba

# Monit SMB Server Monitoring
check process Samba with pidfile "/var/run/samba/smbd.pid"
    start program = "/etc/init.d/smbd start"
    stop program  = "/etc/init.d/smbd stop"
    if failed host 127.0.0.1 port 139 type tcp for 2 cycles then restart
    if 2 restarts within 3 cycles then unmonitor

/etc/monit/conf-available/nfs

# Monit NFS Server Monitoring
check process NFS with pidfile /var/run/rpc.statd.pid
  	start program = "/etc/init.d/nfs-kernel-server start"
  	stop program  = "/etc/init.d/nfs-kernel-server stop"
  	if failed host 127.0.0.1 port 2049 type tcp for 2 cycles then restart
  	if 2 restarts within 3 cycles then unmonitor

/opt/scripts/btrfsck_data.sh

#!/bin/bash
/bin/btrfs device stats /mnt/data | grep -vE ' 0$'

/etc/monit/conf-available/btrfsck

check program btrfsck_data with path /opt/scripts/btrfsck_data.sh
        if status != 1 then alert