Articles taggués ‘administration’

Track Multiple Files Simultaneously With MultiTail

08/01/2021 Comments off tail utility is one of the most useful tools an admin has — but it’s also a bit limited and dated. For watching two or more logs at once, and much more, you want MultiTail.

The tail utility is one of the most useful admin tools, but it’s limited and outdated. Bring your log-watching capabilities into the 21st century and view multiple logs at one time with MultiTail.

What’s MultiTail? It’s an ncurses utility that can display multiple files using “windows” (much like GNU Screen or Tmux) in a terminal or at the console. It also supports color highlighting, filtering and much more.

To get MultiTail, head over to the download page or see if your operating system already has packages. On Debian-based systems, you should need to look for only the multitail package. The project released an update (5.2.8) on April 14, so the most recent release probably won’t be in your upstream package repo just yet.

Once it’s installed, run multitail and hit F1. It will pop up a help menu with all of its keybindings. You’ll need to scroll down (use the down arrow key) to see all of the commands. It can be deceptive, otherwise, and it looks like you just have a few commands. Let’s look at a couple of the commands you’ll want to start with.

First, run t — this displays the stats for your instance of MultiTail. To add files, use the a command.

If you want to start multitail with a file or output of a command to access, use multitailfilename or multitail filename1 filename2 for more than one file. Use multitail -R 3 -l "command" -R 3 -l "command2" to see two commands displayed in one window.

Using the h command within MultiTail, you can set the height of each window. If you want to search through a window, use / or shift / to highlight the search string. Using I will toggle case sensitivity.

When you’ve used the search feature, you’ll get a buffer that displays in a “window” above the file. You can write this to a file using s, which will bring up a dialog that prompts for a filename to which to save.

If you get a MultiTail session configured just right you can save it for later using w from within the session. It will prompt you for a filename to which to save the script.

Basically, you can do just about anything you’d be able to do with tail and then some. It’s very interactive, and much of its commands have dialogs that will walk you through creating regular expressions or re-arranging windows and more.

The only caveat I have is that, occasionally, MultiTail is a bit crashy. Not wholly unreliable, but I have managed to crash MultiTail a few times while putting it through its paces. (I’ve never managed to crashtail…). But it’s still an invaluable tool to have around for any Linux or UNIX admin.

Joe ‘Zonker’ Brockmeier is a freelance writer and editor with more than 10 years covering IT. Formerly the openSUSE Community Manager for Novell, Brockmeier has written for Linux Magazine, Sys Admin, Linux Pro Magazine, IBM developerWorks,,, Linux Weekly News, ZDNet, and many other publications. You can reach Zonker at and follow him on Twitter.

Source: ServerWatch

Categories: Système Tags: , ,

How to set up web-based network traffic monitoring system on Linux

07/01/2021 Comments off

When you are tasked with monitoring network traffic on the local network, you can consider many different options to do it, depending on the scale/traffic of the local network, monitoring platforms/interface, types of backend database, etc.

ntopng is an open-source (GPLv3) network traffic analyzer which provides a web interface for real-time network traffic monitoring. It runs on multiple platforms including Linux and MacOS X. ntopng comes with a simple RMON-like agent with built-in web server capability, and uses Redis-backed key-value server to store time series statistics. You can install ntopng network traffic analyzer on any designated monitoring server connected to your network, and use a web browser to access real-time traffic reports available on the server.

In this tutorial, I will describe how to set up a web-based network traffic monitoring system on Linux by using ntopng.

Features of ntopng

  • Flow-level, protocol-level real-time analysis of local network traffic.
  • Domain, AS (Autonomous System), VLAN level statistics.
  • Geolocation of IP addresses.
  • Deep packet inspection (DPI) based service discovery (e.g., Google, Facebook).
  • Historical traffic analysis (e.g., hourly, daily, weekly, monthly, yearly).
  • Support for sFlow, NetFlow (v5/v9) and IPFIX through nProbe.
  • Network traffic matrix (who’s talking to who?).
  • IPv6 support.

Install ntopng on Linux

The official website offers binary packages for Ubuntu and CentOS. So if you use either platform, you can install these packages.

If you want to build the latest ntopng from its source, follow the instructions below. (Update: these instructions are valid for ntopng 1.0. For ntopng 1.1 and higher, see the updated instructions).

To build ntopng on Debian, Ubuntu or Linux Mint:

$ sudo apt-get install libpcap-dev libglib2.0-dev libgeoip-dev redis-server wget libxml2-dev
$ tar xzf ntopng-1.0.tar.gz -C ~
$ cd ~/ntopng-1.0/
$ ./configure
$ make geoip
$ make

In the above steps, “make geoip” will automatically download a free version of GeoIP databases with wget from So make sure that your system is connected to the network.

To build ntopng on Fedora:

$ sudo yum install libpcap-devel glib2-devel GeoIP-devel libxml2-devel libxml2-devel redis wget
$ tar xzf ntopng-1.0.tar.gz -C ~
$ cd ~/ntopng-1.0/
$ ./configure
$ make geoip
$ make

To install ntopng on CentOS or RHEL, first set up EPEL repository, and then follow the same instructions as in Fedora above.

Configure ntopng on Linux

After building ntopng, create a configuration directory for ntopng, and prepare default configuration files as follows. I assume that “” is the CIDR address prefix of your local network.

$ sudo mkir /etc/ntopng -p
$ sudo -e /etc/ntopng/ntopng.start
--local-networks ""
--interface 1
$ sudo -e /etc/ntopng/ntopng.conf

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How to monitor a Linux server and desktop remotely from web browser

05/01/2021 Comments off

Monitoring Linux server

When it comes to monitoring a Linux server, there are more than enough options to choose from. While there are many production-quality monitoring solutions (e.g., Nagios, Zabbix, Zenoss), boasting of fancy UI, monitoring scalability, comprehensive reporting capabilities, etc., these solutions are probably an overkill for most of us end users. If all you need is to check the basic status (e.g., CPU load, memory usage, active processes, disk usage) of a remote Linux server or desktop, consider linux-dash.

linux-dash is a web-based lightweight monitoring dashboard for Linux machines, which can display, in real-time, various system properties, such as CPU load, RAM usage, disk usage, Internet speed, network connections, RX/TX bandwidth, logged-in users, running processes etc. linux-dash does not come with any backend database for storing long-term statistics. Simply drop in linux-dash app in an existing web server (e.g., Apache, Nginx), and you are good to go. It is a quick and easy way to set up remote monitoring for personal projects.

In this tutorial, I am going to describe how to set up linux-dash in Nginx web server on Linux. Nginx is preferred over Apache web server due to its lightweight engine.

Set up linux-dash on Debian, Ubuntu or Linux Mint

First, install Nginx web server with php-fpm.

$ sudo apt-get install git nginx php5-json php5-fpm php5-curl

Configure Nginx for linux-dash app by creating /etc/nginx/conf.d/linuxdash.conf as follows. In this example, we are going to use port 8080.

$ sudo vi /etc/nginx/conf.d/linuxdash.conf
server {
 server_name $domain_name;
 listen 8080;
 root /var/www;
 index index.html index.php;
 access_log /var/log/nginx/access.log;
 error_log /var/log/nginx/error.log;
 location ~* .(?:xml|ogg|mp3|mp4|ogv|svg|svgz|eot|otf|woff|ttf|css|js|jpg|jpeg|gif|png|ico)$ {
 try_files $uri =404;
 expires max;
 access_log off;
 add_header Pragma public;
 add_header Cache-Control "public, must-revalidate, proxy-revalidate";
 location /linux-dash {
 index index.html index.php;
 # PHP-FPM via sockets
 location ~ .php(/|$) {
 fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
 fastcgi_split_path_info ^(. ?.php)(/.*)$;
 fastcgi_pass unix:/var/run/php5-fpm.sock;
 if (!-f $document_root$fastcgi_script_name) {
 return 404;
 try_files $uri $uri/ /index.php?$args;
 include fastcgi_params;

Disable the default site configuration.

$ sudo rm /etc/nginx/sites-enabled/default

Configure php-fpm by editing /etc/php5/fpm/pool.d/www.conf. Make sure to edit “user“, “group” and “listen” directives as shown below. You can keep the rest of the configuration unchanged.

$ sudo vi /etc/php5/fpm/pool.d/www.conf

. . .
user = www-data
group = www-data
listen = /var/run/php5-fpm.sock
. . .

Proceed to download and install linux-dash.

$ git clone
$ sudo cp -r linux-dash/ /var/www/
$ sudo chown -R www-data:www-data /var/www

Restart Nginx web server as well as php5-fpm to finalize installation.

$ sudo service php5-fpm restart
$ sudo service nginx restart

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How to monitor a log file on Linux with logwatch

14/12/2020 Comments off

Linux operating system and many applications create special files commonly referred to as “logs” to record their operational events. These system logs or application-specific log files are an essential tool when it comes to understanding and troubleshooting the behavior of the operating system and third-party applications. However, log files are not precisely what you would call “light” or “easy” reading, and analyzing raw log files by hand is often time-consuming and tedious. For that reason, any utility that can convert raw log files into a more user-friendly log digest is a great boon for sysadmins.

logwatch is an open-source log parser and analyzer written in Perl, which can parse and convert raw log files into a structured format, making a customizable report based on your use cases and requirements. In logwatch, the focus is on producing more easily consumable log summary, not on real-time log processing and monitoring. As such, logwatch is typically invoked as an automated cron task with desired time and frequency, or manually from the command line whenever log processing is needed. Once a log report is generated, logwatch can email the report to you, save it to a file, or display it on the screen.

A logwatch report is fully customizable in terms of verbosity and processing coverage. The log processing engine of logwatch is extensible, in a sense that if you want to enable logwatch for a new application, you can write a log processing script (in Perl) for the application’s log file, and plug it under logwatch.

One downside of logwatch is that it does not include in its report detailed timestamp information available in original log files. You will only know that a particular event was logged in a requested range of time, and you will have to access original log files to get exact timing information.

Installing Logwatch

On Debian and derivatives:

# aptitude install logwatch

On Red Hat-based distributions:

# yum install logwatch

Configuring Logwatch

During installation, the main configuration file (logwatch.conf) is placed in /etc/logwatch/conf. Configuration options defined in this file override system-wide settings defined in /usr/share/logwatch/default.conf/logwatch.conf.

If logwatch is launched from the command line without any arguments, the custom options defined in /etc/logwatch/conf/logwatch.conf will be used. However, if any command-line arguments are specified with logwatch command, those arguments in turn override any default/custom settings in /etc/logwatch/conf/logwatch.conf.

In this article, we will customize several default settings of logwatch by editing /etc/logwatch/conf/logwatch.conf file.

Detail = <Low, Med, High, or a number>

“Detail” directive controls the verbosity of a logwatch report. It can be a positive integer, or High, Med, Low, which correspond to 10, 5, and 0, respectively.

MailTo =

“MailTo” directive is used if you want to have a logwatch report emailed to you. To send a logwatch report to multiple recipients, you can specify their email addresses separated with a space. To be able to use this directive, however, you will need to configure a local mail transfer agent (MTA) such as sendmail or Postfix on the server where logwatch is running.

Range = <Yesterday|Today|All>

“Range” directive specifies the time duration of a logwatch report. Common values for this directive are Yesterday, Today or All. When “Range = All” is used, “Archive = yes” directive is also needed, so that all archived versions of a given log file (e.g., /var/log/maillog, /var/log/maillog.X, or /var/log/maillog.X.gz) are processed.

Besides such common range values, you can also use more complex range options such as the following.

  • Range = “2 hours ago for that hour”
  • Range = “-5 days”
  • Range = “between -7 days and -3 days”
  • Range = “since September 15, 2014”
  • Range = “first Friday in October”
  • Range = “2014/10/15 12:50:15 for that second”

To be able to use such free-form range examples, you need to install Date::Manip Perl module from CPAN. Refer to this post for CPAN module installation instructions.

Service = <service-name-1>
Service = <service-name-2>
. . .

“Service” option specifies one or more services to monitor using logwath. All available services are listed in /usr/share/logwatch/scripts/services, which cover essential system services (e.g., pam, secure, iptables, syslogd), as well as popular application services such as sudo, sshd, http, fail2ban, samba. If you want to add a new service to the list, you will have to write a corresponding log processing Perl script, and place it in this directory.

If this option is used to select specific services, you need to comment out the line “Service = All” in /usr/share/logwatch/default.conf/logwatch.conf.


Format = <text|html>

“Format” directive specifies the format (e.g., text or HTML) of a logwatch report.

Output = <file|mail|stdout>

“Output” directive indicates where a logwatch report should be sent. It can be saved to a file (file), emailed (mail), or shown to screen (stdout).

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Packet Analyzer: 15 TCPDUMP Command Examples

14/12/2020 Comments off

Packet Analyzer: efficient network traffic analysispacket analyzer

tcpdump command is also called as packet analyzer.

tcpdump command will work on most flavors of unix operating system. tcpdump allows us to save the packets that are captured, so that we can use it for future analysis. The saved file can be viewed by the same tcpdump command. We can also use open source software like wireshark to read the tcpdump pcap files.

In this tcpdump tutorial, let us discuss some practical examples on how to use the tcpdump command.

1. Capture packets from a particular ethernet interface using tcpdump -i

When you execute tcpdump command without any option, it will capture all the packets flowing through all the interfaces. -i option with tcpdump command, allows you to filter on a particular ethernet interface.

$ tcpdump -i eth1
14:59:26.608728 IP > . ack 540 win 16554
14:59:26.610602 IP >  4278 1/0/0 (73)
14:59:26.611262 IP >  26364  PTR? (45)

In this example, tcpdump captured all the packets flows in the interface eth1 and displays in the standard output.

Note: Editcap utility is used to select or remove specific packets from dump file and translate them into a given format.

2. Capture only N number of packets using tcpdump -c

When you execute tcpdump command it gives packets until you cancel the tcpdump command. Using -c option you can specify the number of packets to capture.

$ tcpdump -c 2 -i eth0
listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
14:38:38.184913 IP > P 1457255642:1457255758(116) ack 1561463966 win 63652
14:38:38.690919 IP > P 116:232(116) ack 1 win 63652
2 packets captured
13 packets received by filter
0 packets dropped by kernel

The above tcpdump command captured only 2 packets from interface eth0.

Note: Mergecap and TShark: Mergecap is a packet dump combining tool, which will combine multiple dumps into a single dump file. Tshark is a powerful tool to capture network packets, which can be used to analyze the network traffic. It comes with wireshark network analyzer distribution.

3. Display Captured Packets in ASCII using tcpdump -A

The following tcpdump syntax prints the packet in ASCII.

$ tcpdump -A -i eth0
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
14:34:50.913995 IP > P 1457239478:1457239594(116) ack 1561461262 win 63652
......G..7 KA....A...L.
14:34:51.423640 IP > P 116:232(116) ack 1 win 63652

Note: Ifconfig command is used to configure network interfaces

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