Articles taggués ‘monitoring’

20 Linux System Monitoring Tools Every SysAdmin Should Know

17/11/2018 Aucun commentaire

monitoring toolsNeed to monitor Linux server performance? Try these built-in command and a few add-on tools. Most Linux distributions are equipped with tons of monitoring. These tools provide metrics which can be used to get information about system activities. You can use these tools to find the possible causes of a performance problem. The commands discussed below are some of the most basic commands when it comes to system analysis and debugging server issues such as:

  1. Finding out bottlenecks.
  2. Disk (storage) bottlenecks.
  3. CPU and memory bottlenecks.
  4. Network bottlenecks.

#1: top – Process Activity Command

The top program provides a dynamic real-time view of a running system i.e. actual process activity. By default, it displays the most CPU-intensive tasks running on the server and updates the list every five seconds.

top-output-269x300Commonly Used Hot Keys

The top command provides several useful hot keys:

Hot Key Usage
t Displays summary information off and on.
m Displays memory information off and on.
A Sorts the display by top consumers of various system resources. Useful for quick identification of performance-hungry tasks on a system.
f Enters an interactive configuration screen for top. Helpful for setting up top for a specific task.
o Enables you to interactively select the ordering within top.
r Issues renice command.
k Issues kill command.
z Turn on or off color/mono

Lire la suite…

MySQL – Monitorer le port 3306

30/10/2018 Comments off

Pour faire le monitoring du port 3306 sous Linux il suffit d’utiliser la commande :

tcpdump  -i eth0 -nN -vvv -xX  -s 1500  port 3306

s représente la longueur du paquet.

Supervision de postfix via mailgraph avec le plugin via Nagios/Centreon

26/10/2018 Comments off

Source:  l’admin sous GNU/Linux – blog libreCentreon_graph_mailstat_home


Voici une procédure permettant de contrôler l’activité d’un serveur de messagerie postfix via Nagios / Centreon.

Pour cela nous allons utiliser le plugins avec une petite adaptation du script afin de le rendre compatible avec la génération de graphe sous Centreon.

Le plugin va récupérer depuis des données depuis mailgraph qui permet de générer des graphes via RRDTool

Tout d’abord, il faut installer Mailgraph sur l’hôte à superviser, ici une Debian.

Installation de Mailgraph

aptitude install mailgraph

Si l’installation ne vous a pas poser les questions propres au paramétrage, lancer :

dpkg-reconfigure mailgraph

Voici les questions et réponse à fournir :

Mailgraph doit-il être lancé au démarrage ? OUI

Fichier de journalisation à utiliser par mailgraph : /var/log/mail.log (à adapter)

Faut-il compter les courriels entrants comme des courriels sortants ? NON (J’utilise Amavis, donc j’ai choisi cette option, encore une fois à adapter.

Lire la suite…

Find all active IP addresses in a network

11/10/2018 Comments off

Today I found myself reconfiguring a wireless access point I hadn’t used in a very long time. I no longer have the manual (so I could reset it to factory defaults) nor do I remember what the obscure IP address I configured it with was. Luckily I do know what network it’s setup for ( 192.168.1.x ) but I don’t want to have to try to connect to all 254 IP addresses ( through as that would take quite some time.

So what I’m going to do is use Nmap a swiss army knife for network operators and system admins. What we’re going to do is use Nmap to scan the entire network and tell us which IP addresses are active. This will allow us to drastically reduce the number of IP addresses we have to try.

There are Nmap versions for all three major OS’s *nix, OS X and Windows. I’ll be showing you the syntax for the *nix/OS X version.

nmap -sP

replace with whatever network it is you’re trying to scan.
The /24 is the netmask of the network in CDIR notation. If you need a cheat sheet you can find one here

Once you press return (or enter) Nmap will start to work pinging each and every IP address on your network and noting which ones respond and which don’t. (Note that if your device has a firewall that discards ping requests it will appear to be down to this scan)

You’ll quickly get an output similar to the following

Starting Nmap 4.50 ( ) at 2008-08-19 10:15 PDT
HOST appears to be up.
MAC Address: 0:0F:1F:4C:0B:E6 (WW Pcba Test)
Nmap finished: 256 IP addresses (3 hosts up) scanned in 5.711 seconds

Monitor Network Connections in Mac OS X for Free with Private Eye

04/10/2018 Comments off

Source: OSXdaily

Private Eye is a free real-time network monitor app for Mac OS X that is extremely easy to use. Upon launching the app, you’ll start to see all open network connections by application and process, and you can then filter connections by app, monitor all open connections, or watch only incoming or outgoing transfer.


Connections are reported by application, the time of the connection, and arguably the most useful, the IP address that is being connected to by the app, making it easy to see socket and routing data, letting you know exactly what app is communicating with what server or IP address, for both local and broader internet networks. If you have any interest in networking, privacy, security, or you just want to keep an eye on what apps are connecting to the internet and to where, you should download this app, but it’s also an amazingly useful tool for troubleshooting network problems and figuring out what is using the network.


Download and install Private Eye by putting it into your /Applications/ folder, then open PrivateEye to get started. The list of open network connections is easy to read, you’ll see a time stamp of the connection, the application name, and where the connection is going to by IP (or coming from, as determined by the arrow pointing left for in, or right for out).


Using the left side menu you can quickly break down connections to see them all, only show incoming transfers, outgoing connections, or display connections by specific application only. Apps are easy to identify in this list, as are daemons running in the background (like PubSubAgent), and command line processes belonging to the user are also visible (ssh, for example).

This is a simple yet powerful tool without the complexity or the learning curves related to compiling and using the command line tools lsof, watch, open_ports, or wireshark, and is therefore highly recommended for anyone who is interested in seeing this kind of information, whether it’s out of general curiosity, or to help troubleshoot and diagnose specific network activities.