Nagios Monitoring - Server und Services überwachen | Blog

Nagios ist ein bewährtes Open-Source-Monitoring-System. Es überwacht Server, Netzwerkgeräte und Services und alarmiert bei Problemen. Dieser Artikel zeigt die Einrichtung von Nagios Core.

Nagios Architektur

┌─────────────────────────────────────────────────┐
│                  Nagios Core                     │
│  ┌─────────┐  ┌─────────┐  ┌─────────────────┐  │
│  │ Checks  │  │ Status  │  │ Notifications   │  │
│  │ Engine  │──│  Data   │──│ (E-Mail/SMS)    │  │
│  └────┬────┘  └─────────┘  └─────────────────┘  │
│       │                                          │
└───────┼──────────────────────────────────────────┘
        │ Check-Plugins
        ▼
┌───────────────┐  ┌───────────────┐  ┌───────────────┐
│   Server 1    │  │   Server 2    │  │   Router      │
│   (NRPE)      │  │   (NRPE)      │  │   (SNMP)      │
└───────────────┘  └───────────────┘  └───────────────┘

Installation (Ubuntu/Debian)

Abhängigkeiten installieren

apt update
apt install -y apache2 php libapache2-mod-php php-gd
apt install -y autoconf gcc make unzip libgd-dev libssl-dev
apt install -y libmcrypt-dev bc gawk dc build-essential snmp libnet-snmp-perl gettext

Nagios-Benutzer erstellen

useradd -m -s /bin/bash nagios
groupadd nagcmd
usermod -a -G nagcmd nagios
usermod -a -G nagcmd www-data

Nagios Core kompilieren

cd /tmp
wget https://github.com/NagiosEnterprises/nagioscore/releases/download/nagios-4.5.0/nagios-4.5.0.tar.gz
tar xzf nagios-4.5.0.tar.gz
cd nagios-4.5.0

./configure --with-httpd-conf=/etc/apache2/sites-enabled
make all
make install
make install-init
make install-commandmode
make install-config
make install-webconf

Nagios Plugins installieren

cd /tmp
wget https://github.com/nagios-plugins/nagios-plugins/releases/download/release-2.4.6/nagios-plugins-2.4.6.tar.gz
tar xzf nagios-plugins-2.4.6.tar.gz
cd nagios-plugins-2.4.6

./configure
make
make install

Apache konfigurieren

a2enmod rewrite cgi
htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin
systemctl restart apache2

Nagios starten

systemctl enable nagios
systemctl start nagios

Web-Interface

Öffnen Sie http://server-ip/nagios und melden Sie sich an.

Konfigurationsstruktur

/usr/local/nagios/etc/
├── nagios.cfg          # Hauptkonfiguration
├── cgi.cfg            # CGI-Konfiguration
├── resource.cfg       # Makros und Variablen
├── objects/
│   ├── commands.cfg   # Check-Befehle
│   ├── contacts.cfg   # Kontakte
│   ├── timeperiods.cfg
│   ├── templates.cfg  # Vorlagen
│   ├── localhost.cfg  # Lokaler Host
│   └── hosts/         # Eigene Host-Definitionen
└── htpasswd.users     # Web-Authentifizierung

Hosts definieren

Host-Template

# /usr/local/nagios/etc/objects/templates.cfg

define host {
    name                            linux-server
    use                             generic-host
    check_period                    24x7
    check_interval                  5
    retry_interval                  1
    max_check_attempts              10
    check_command                   check-host-alive
    notification_period             24x7
    notification_interval           30
    notification_options            d,u,r
    contact_groups                  admins
    register                        0
}

Host hinzufügen

# /usr/local/nagios/etc/objects/hosts/webserver.cfg

define host {
    use                     linux-server
    host_name               webserver1
    alias                   Web Server 1
    address                 192.168.1.10
}

define host {
    use                     linux-server
    host_name               dbserver1
    alias                   Database Server 1
    address                 192.168.1.20
}

In nagios.cfg einbinden

# /usr/local/nagios/etc/nagios.cfg

cfg_dir=/usr/local/nagios/etc/objects/hosts

Services definieren

Service-Template

# /usr/local/nagios/etc/objects/templates.cfg

define service {
    name                            generic-service
    active_checks_enabled           1
    passive_checks_enabled          1
    parallelize_check               1
    obsess_over_service             1
    check_freshness                 0
    notifications_enabled           1
    event_handler_enabled           1
    flap_detection_enabled          1
    process_perf_data               1
    retain_status_information       1
    retain_nonstatus_information    1
    is_volatile                     0
    check_period                    24x7
    max_check_attempts              3
    check_interval                  10
    retry_interval                  2
    contact_groups                  admins
    notification_options            w,u,c,r
    notification_interval           60
    notification_period             24x7
    register                        0
}

Services für einen Host

# /usr/local/nagios/etc/objects/hosts/webserver.cfg

# PING Check
define service {
    use                     generic-service
    host_name               webserver1
    service_description     PING
    check_command           check_ping!100.0,20%!500.0,60%
}

# SSH Check
define service {
    use                     generic-service
    host_name               webserver1
    service_description     SSH
    check_command           check_ssh
}

# HTTP Check
define service {
    use                     generic-service
    host_name               webserver1
    service_description     HTTP
    check_command           check_http
}

# HTTPS Check
define service {
    use                     generic-service
    host_name               webserver1
    service_description     HTTPS
    check_command           check_http!-S -p 443
}

# Disk Space (via NRPE)
define service {
    use                     generic-service
    host_name               webserver1
    service_description     Disk Space
    check_command           check_nrpe!check_disk
}

# Load (via NRPE)
define service {
    use                     generic-service
    host_name               webserver1
    service_description     CPU Load
    check_command           check_nrpe!check_load
}

Check-Befehle

Wichtige Check-Commands

# /usr/local/nagios/etc/objects/commands.cfg

# HTTP Check
define command {
    command_name    check_http
    command_line    $USER1$/check_http -H $HOSTADDRESS$ $ARG1$
}

# HTTPS mit Zertifikatsprüfung
define command {
    command_name    check_https_cert
    command_line    $USER1$/check_http -H $HOSTADDRESS$ -S -C $ARG1$
}

# MySQL
define command {
    command_name    check_mysql
    command_line    $USER1$/check_mysql -H $HOSTADDRESS$ -u $ARG1$ -p $ARG2$
}

# NRPE (Remote-Checks)
define command {
    command_name    check_nrpe
    command_line    $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
}

# TCP Port
define command {
    command_name    check_tcp
    command_line    $USER1$/check_tcp -H $HOSTADDRESS$ -p $ARG1$
}

NRPE für Remote-Checks

NRPE auf überwachtem Server installieren

# Auf dem zu überwachenden Server
apt install nagios-nrpe-server nagios-plugins

NRPE konfigurieren

# /etc/nagios/nrpe.cfg

# Erlaubte Nagios-Server
allowed_hosts=127.0.0.1,192.168.1.5

# Check-Befehle
command[check_users]=/usr/lib/nagios/plugins/check_users -w 5 -c 10
command[check_load]=/usr/lib/nagios/plugins/check_load -r -w .15,.10,.05 -c .30,.25,.20
command[check_disk]=/usr/lib/nagios/plugins/check_disk -w 20% -c 10% -p /
command[check_zombie_procs]=/usr/lib/nagios/plugins/check_procs -w 5 -c 10 -s Z
command[check_total_procs]=/usr/lib/nagios/plugins/check_procs -w 150 -c 200
command[check_mem]=/usr/lib/nagios/plugins/check_mem.sh -w 80 -c 90

NRPE starten

systemctl restart nagios-nrpe-server
systemctl enable nagios-nrpe-server

Firewall öffnen

ufw allow from 192.168.1.5 to any port 5666

Kontakte und Benachrichtigungen

Kontakt definieren

# /usr/local/nagios/etc/objects/contacts.cfg

define contact {
    contact_name                    admin
    alias                           System Administrator
    email                           admin@example.com
    service_notification_period     24x7
    host_notification_period        24x7
    service_notification_options    w,u,c,r
    host_notification_options       d,u,r
    service_notification_commands   notify-service-by-email
    host_notification_commands      notify-host-by-email
}

define contactgroup {
    contactgroup_name       admins
    alias                   System Administrators
    members                 admin
}

E-Mail-Benachrichtigung

# /usr/local/nagios/etc/objects/commands.cfg

define command {
    command_name    notify-host-by-email
    command_line    /usr/bin/printf "%b" "***** Nagios *****\n\nHost: $HOSTNAME$\nState: $HOSTSTATE$\nAddress: $HOSTADDRESS$\nInfo: $HOSTOUTPUT$\n\nDate/Time: $LONGDATETIME$\n" | /usr/bin/mail -s "** $NOTIFICATIONTYPE$ Host Alert: $HOSTNAME$ is $HOSTSTATE$ **" $CONTACTEMAIL$
}

define command {
    command_name    notify-service-by-email
    command_line    /usr/bin/printf "%b" "***** Nagios *****\n\nHost: $HOSTNAME$\nService: $SERVICEDESC$\nState: $SERVICESTATE$\nInfo: $SERVICEOUTPUT$\n\nDate/Time: $LONGDATETIME$\n" | /usr/bin/mail -s "** $NOTIFICATIONTYPE$ Service Alert: $HOSTNAME$/$SERVICEDESC$ is $SERVICESTATE$ **" $CONTACTEMAIL$
}

Host-Gruppen

# /usr/local/nagios/etc/objects/hostgroups.cfg

define hostgroup {
    hostgroup_name  linux-servers
    alias           Linux Servers
    members         webserver1,dbserver1
}

define hostgroup {
    hostgroup_name  web-servers
    alias           Web Servers
    members         webserver1
}

define hostgroup {
    hostgroup_name  database-servers
    alias           Database Servers
    members         dbserver1
}

Konfiguration prüfen

# Syntax prüfen
/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

# Nagios neu laden
systemctl reload nagios

Wichtige Check-Plugins

Lokale Checks

# Festplatte
/usr/lib/nagios/plugins/check_disk -w 20% -c 10% -p /

# Load
/usr/lib/nagios/plugins/check_load -w 5,4,3 -c 10,8,6

# Prozesse
/usr/lib/nagios/plugins/check_procs -w 250 -c 400

# Swap
/usr/lib/nagios/plugins/check_swap -w 20% -c 10%

Netzwerk-Checks

# Ping
/usr/lib/nagios/plugins/check_ping -H 192.168.1.10 -w 100,20% -c 500,60%

# HTTP
/usr/lib/nagios/plugins/check_http -H example.com

# HTTPS mit Zertifikat
/usr/lib/nagios/plugins/check_http -H example.com -S -C 30

# TCP Port
/usr/lib/nagios/plugins/check_tcp -H 192.168.1.10 -p 3306

Eigene Plugins schreiben

Plugin-Format

#!/bin/bash
# check_custom.sh

# Exit-Codes:
# 0 = OK
# 1 = WARNING
# 2 = CRITICAL
# 3 = UNKNOWN

VALUE=$(cat /proc/loadavg | cut -d' ' -f1)
WARNING=5
CRITICAL=10

if (( $(echo "$VALUE >= $CRITICAL" | bc -l) )); then
    echo "CRITICAL - Load is $VALUE"
    exit 2
elif (( $(echo "$VALUE >= $WARNING" | bc -l) )); then
    echo "WARNING - Load is $VALUE"
    exit 1
else
    echo "OK - Load is $VALUE"
    exit 0
fi

Plugin registrieren

# commands.cfg
define command {
    command_name    check_custom
    command_line    $USER1$/check_custom.sh $ARG1$ $ARG2$
}

Performance-Daten

PNP4Nagios für Graphen

apt install pnp4nagios

In nagios.cfg aktivieren

process_performance_data=1
host_perfdata_command=process-host-perfdata
service_perfdata_command=process-service-perfdata

Zusammenfassung

| Aufgabe | Befehl/Datei | |---------|--------------| | Konfig prüfen | nagios -v /usr/local/nagios/etc/nagios.cfg | | Neu laden | systemctl reload nagios | | Host hinzufügen | /etc/objects/hosts/.cfg | | Service hinzufügen | Gleiche Datei wie Host | | Manueller Check | /usr/lib/nagios/plugins/check_ | | Web-Interface | http://server/nagios |

Fazit

Nagios ist ein robustes Monitoring-System mit großer Community und vielen Plugins. Die Konfiguration ist textbasiert und damit versionierbar. Für moderne Umgebungen sind Alternativen wie Icinga2, Prometheus oder Zabbix eventuell besser geeignet, aber Nagios bleibt ein zuverlässiger Klassiker.