Monit est un logiciel permettant de surveiller des services locaux : il s'assure qu'ils fonctionnent et, au besoin, les redémarre.
Très adaptable, il fonctionne aussi bien avec des services locaux (apache, postfix, ...) qu'avec des daemons (cron, rsyslog, ...).
Il peut également nous alerter par mail pour chaque action qu'il entreprend (détection d'un service qui ne répond plus, redémarrage, changement de PID, ...).
Enfin, il supervise également la consommation de ressources de certains services et les relance en cas de forte consommation.
Cerise sur le gâteau, il dispose d'une interface web permettant de l'administrer.

Installation et configuration de Monit

Installation

Monit est disponible dans les dépôts Debian et Ubuntu. Pour l'installer, un simple

apt-get install monit

suffit

Configuration

Il faut ensuite éditer le fichier /etc/default/monit pour autoriser son démarrage en mettant startup=1.
Pour paramétrer le comportement de Monit, il faut passer par l'édition du fichier /etc/monit/conf.d/monitrc.

#lancement en tant que daemon pour 60s

set daemon  60

#détermination de l'emplacement des logs (ici dans syslog)

set logfile syslog facility log_daemon

#indication du serveur SMTP pour l'envoi des mails

set mailserver smtp.toto.fr

#définition de l'expéditeur des mails

set mail-format { from: toto@toto.fr }

#l'adresse mail du destinataire des mails

set alert tata@toto.fr

#activation du serveur HTTP embarqué permettant d'administrer avec une interface web Monit

set httpd port 2812 and

#définition du couple login/mot de passe pour l'interface web

     allow utilisateur:motdepasse

Définition des services et daemons à surveiller

Il ne reste plus alors qu'à indiquer à Monit les services ou daemons qu'il va superviser. Des exemples sont fournis sur le site officiel de Monit.

Il faut créer pour chaque service un fichier dans /etc/monit/conf.d.

cron

check process cron with pidfile /var/run/crond.pid

   group system

   start program = "/etc/init.d/cron start"

   stop  program = "/etc/init.d/cron stop"

   if 5 restarts within 5 cycles then timeout

RSyslog

check process rsyslogd with pidfile /var/run/rsyslogd.pid

   start program = "/etc/init.d/rsyslog start"

   stop program = "/etc/init.d/rsyslog stop"

   if 5 restarts within 5 cycles then timeout

Mdadm

 check process mdadm with pidfile /var/run/mdadm/monitor.pid

   start program = "/etc/init.d/mdadm start"

   stop  program = "/etc/init.d/mdadm stop"

   if 5 restarts within 5 cycles then timeout

PSAD

 check process psad with pidfile /var/run/psad/psad.pid

   start program = "/etc/init.d/psad start"

   stop  program = "/etc/init.d/psad stop"

   if 5 restarts within 5 cycles then timeout

Clamav

 check process clamd with pidfile /var/run/clamav/clamd.pid

   group clamav

   start program = "/etc/init.d/clamav-daemon start"

   stop  program = "/etc/init.d/clamav-daemon stop"

   if failed unixsocket /var/run/clamav/clamd.ctl then restart

   if 5 restarts within 5 cycles then timeout

Freshclam

 check process freshclam with pidfile /var/run/clamav/freshclam.pid

   group clamav

   start program = "/etc/init.d/clamav-freshclam start"

   stop  program = "/etc/init.d/clamav-freshclam stop"

   if 5 restarts within 5 cycles then timeout

NTP

 check process ntpd with pidfile /var/run/ntpd.pid

   start program = "/etc/init.d/ntp start"

   stop  program = "/etc/init.d/ntp stop"

   if failed host 127.0.0.1 port 123 type udp then alert

   if 5 restarts within 5 cycles then timeout

Chrony

 check process chronyd with pidfile /var/run/chronyd.pid

   start program = "/etc/init.d/chrony start"

   stop  program = "/etc/init.d/chrony stop"

   if failed host 127.0.0.1 port 123 type udp then alert

   if 5 restarts within 5 cycles then timeout

SSH

 check process sshd with pidfile /var/run/sshd.pid

   start program  "/etc/init.d/ssh start"

   stop program  "/etc/init.d/ssh stop"

   if failed host adresseip port 22 then restart

   if 5 restarts within 5 cycles then timeout

Postfix

check process postfix with pidfile /var/spool/postfix/pid/master.pid

   group mail

   start program = "/etc/init.d/postfix start"

   stop  program = "/etc/init.d/postfix stop"

   if failed host localhost port 25 protocol smtp then restart

   if 5 restarts within 5 cycles then timeout

Dovecot

check process dovecot with pidfile /var/run/dovecot/master.pid

   group dovecot

   start program = "/etc/init.d/dovecot start"

   stop  program = "/etc/init.d/dovecot stop"

   if failed host adresseip port 143 protocol imap then restart

   if failed host adresseip port 993 type tcpssl sslauto protocol imap then restart

   if 5 restarts within 5 cycles then timeout

MailScanner

 check process MailScanner with pidfile /var/run/MailScanner/MailScanner.pid

   group mail

   start program = "/etc/init.d/mailscanner start"

   stop  program = "/etc/init.d/mailscanner stop"

   if 5 restarts within 5 cycles then timeout

   if cpu usage > 99% for 5 cycles then alert

   if mem usage > 99% for 5 cycles then alert

OpenDKIM

check process opendkim with pidfile /var/run/opendkim/opendkim.pid

   group opendkim

   start program = "/etc/init.d/opendkim start"

   stop  program = "/etc/init.d/opendkim stop"

   if failed host localhost port 12345 type tcp then restart

   if 5 restarts within 5 cycles then timeout

Postgrey

check process postgrey with pidfile /var/run/postgrey.pid

   group postgrey

   start program = "/etc/init.d/postgrey start"

   stop  program = "/etc/init.d/postgrey stop"

   if failed host 127.0.0.1 port 10023 type tcp then restart

   if 5 restarts within 5 cycles then timeout

SpamAssassin

 check process spamd with pidfile /var/run/spamd.pid

   group mail

   start program = "/etc/init.d/spamassassin start"

   stop  program = "/etc/init.d/spamassassin stop"

   if 5 restarts within 5 cycles then timeout

   if cpu usage > 99% for 5 cycles then alert

   if mem usage > 99% for 5 cycles then alert

vsFTPd

 check process vsftpd with pidfile /var/run/vsftpd/vsftpd.pid

   start program = "/etc/init.d/vsftpd start"

   stop program  = "/etc/init.d/vsftpd stop"

   if failed port 21 protocol ftp then restart

   if 5 restarts within 5 cycles then timeout

Apache 2

check process apache2 with pidfile /var/run/apache2.pid

   group www-data

   start program = "/etc/init.d/apache2 start"

   stop program  = "/etc/init.d/apache2 stop"

   if failed host toto.fr port 80 protocol http

      and request "/index.php" then restart

   if cpu is greater than 60% for 2 cycles then alert

   if cpu > 80% for 5 cycles then restart

   if totalmem > 500 MB for 5 cycles then restart

   if children > 250 then restart

   if loadavg(5min) greater than 10 for 8 cycles then stop

   if 3 restarts within 5 cycles then timeout

Memcached

check process memcached with pidfile /var/run/memcached.pid

   group memcached

   start program = "/etc/init.d/memcached start"

   stop  program = "/etc/init.d/memcached stop"

   if failed host localhost port 11211 type tcp then restart

   if 5 restarts within 5 cycles then timeout

MySQL

check process mysql with pidfile /var/run/mysqld/mysqld.pid

   group mysql

   start program = "/etc/init.d/mysql start"

   stop program = "/etc/init.d/mysql stop"

   if failed host localhost port 3306 then restart

   if 5 restarts within 5 cycles then timeout

MaraDNS

check process maradns with pidfile /var/run/maradns.etc_maradns_mararc.pid

start program = "/etc/init.d/maradns start"

 stop program = "/etc/init.d/maradns stop"

 if failed host adresseip port 53 type udp protocol dns then restart

 if 5 restarts within 5 cycles then timeout

Munin

check process munin with pidfile /var/run/munin/munin-node.pid

   group munin

   start program = "/etc/init.d/munin-node start"

   stop program = "/etc/init.d/munin-node stop"

   if failed host adresseip port 4949 then restart

   if 5 restarts within 5 cycles then timeout

Mumble

check process murmurd with pidfile /var/run/mumble-server/mumble-server.pid

   group mumble-server

   start program = "/etc/init.d/mumble-server start"

   stop  program = "/etc/init.d/mumble-server stop"

   if failed host adresseip port 64738 type tcp then restart

   if failed host adresseip port 64738 type udp then restart

   if 5 restarts within 5 cycles then timeout

Urban Terror

check process UrbanTerror with pidfile /var/run/urbanterror/urbanterror.pid

   group utuser

   start program = "/etc/init.d/urbanterror start"

   stop  program = "/etc/init.d/urbanterror stop"

   if failed host adresseip port 27960 type udp then restart

   if 5 restarts within 5 cycles then timeout

Bloc-notes

Monit : supervision de services