Posts Tagged ‘bandwidth’

Monitoring network traffic tools to debug network issues in console interactively on Linux

Thursday, December 14th, 2023



In my last article Debugging and routing network issues on Linux (common approaches), I've given some step by step methology on how to debug a network routing or unreachability issues between network hosts. As the article was mostly targetting a command line tools that can help debugging the network without much interactivity. I've decided to blog of a few other tools that might help the system administrator to debug network issues by using few a bit more interactive tools. Throughout the years of managing multitude of Linux based laptops and servers, as well as being involved in security testing and penetration in the past, these tools has always played an important role and are worthy to be well known and used by any self respecting sys admin or network security expert that has to deal with Linux and *Unix operating systems.

1. Debugging what is going on on a network level interactively with iptraf-ng

Historically iptraf and today's iptraf is also a great tool one can use to further aid the arsenal debug a network issue or Protocol problem, failure of packets or network interaction issues SYN -> ACK etc. proto interactions and check for Flag states and packets flow.

To use iptraf-ng which is a ncurses based tool just install it and launch it and select the interface you would like to debug trafic on.

To install On Debians distros

# apt install iptraf-ng –yes

# iptraf-ng




2. Use hackers old tool sniffit to monitor current ongoing traffic and read plain text messages

Those older who remember the rise of Linux to the masses, should remember sniffit was a great tool to snoop for traffic on the network.

root@pcfreak:~# apt-cache show sniffit|grep -i description -A 10 -B10
Package: sniffit
Version: 0.5-1
Installed-Size: 139
Maintainer: Joao Eriberto Mota Filho <>
Architecture: amd64
Depends: libc6 (>= 2.14), libncurses6 (>= 6), libpcap0.8 (>= 0.9.8), libtinfo6 (>= 6)
Description-en: packet sniffer and monitoring tool
 Sniffit is a packet sniffer for TCP/UDP/ICMP packets over IPv4. It is able
 to give you a very detailed technical info on these packets, as SEQ, ACK,
 TTL, Window, etc. The packet contents also can be viewed, in different
 formats (hex or plain text, etc.).
 Sniffit is based in libpcap and is useful when learning about computer
 networks and their security.
Description-md5: 973beeeaadf4c31bef683350f1346ee9
Tag: interface::text-mode, mail::notification, role::program, scope::utility,
 uitoolkit::ncurses, use::monitor, use::scanning, works-with::mail,
Section: net
Priority: optional
Filename: pool/main/s/sniffit/sniffit_0.5-1_amd64.deb
Size: 61796
MD5sum: ea4cc0bc73f9e94d5a3c1ceeaa485ee1
SHA256: 7ec76b62ab508ec55c2ef0ecea952b7d1c55120b37b28fb8bc7c86645a43c485


Sniffit is not installed by default on deb distros, so to give it a try install it

# apt install sniffit –yes
# sniffit


3. Use bmon to monitor bandwidth and any potential traffic losses and check qdisc pfifo
Linux network stack queues


root@pcfreak:~# apt-cache show bmon |grep -i description
Description-en: portable bandwidth monitor and rate estimator
Description-md5: 3288eb0a673978e478042369c7927d3f
root@pcfreak:~# apt-cache show bmon |grep -i description -A 10 -B10
Package: bmon
Version: 1:4.0-7
Installed-Size: 146
Maintainer: Patrick Matthäi <>
Architecture: amd64
Depends: libc6 (>= 2.17), libconfuse2 (>= 3.2.1~), libncursesw6 (>= 6), libnl-3-200 (>= 3.2.7), libnl-route-3-200 (>= 3.2.7), libtinfo6 (>= 6)
Description-en: portable bandwidth monitor and rate estimator
 bmon is a commandline bandwidth monitor which supports various output
 methods including an interactive curses interface, lightweight HTML output but
 also simple ASCII output.
 Statistics may be distributed over a network using multicast or unicast and
 collected at some point to generate a summary of statistics for a set of
Description-md5: 3288eb0a673978e478042369c7927d3f
Tag: implemented-in::c, interface::text-mode, network::scanner,
 role::program, scope::utility, uitoolkit::ncurses, use::monitor,
Section: net
Priority: optional
Filename: pool/main/b/bmon/bmon_4.0-7_amd64.deb
Size: 47348
MD5sum: c210f8317eafa22d9e3a8fb8316e0901
SHA256: 21730fc62241aee827f523dd33c458f4a5a7d4a8cf0a6e9266a3e00122d80645


root@pcfreak:~# apt install bmon –yes

root@pcfreak:~# bmon


4. Use nethogs net diagnosis text interactive tool

NetHogs is a small 'net top' tool. 
Instead of breaking the traffic down per protocol or per subnet, like most tools do, it groups bandwidth by process.

root@pcfreak:~# apt-cache show nethogs|grep -i description -A10 -B10
Package: nethogs
Source: nethogs (0.8.5-2)
Version: 0.8.5-2+b1
Installed-Size: 79
Maintainer: Paulo Roberto Alves de Oliveira (aka kretcheu) <>
Architecture: amd64
Depends: libc6 (>= 2.15), libgcc1 (>= 1:3.0), libncurses6 (>= 6), libpcap0.8 (>= 0.9.8), libstdc++6 (>= 5.2), libtinfo6 (>= 6)
Description-en: Net top tool grouping bandwidth per process
 NetHogs is a small 'net top' tool. Instead of breaking the traffic down per
 protocol or per subnet, like most tools do, it groups bandwidth by process.
 NetHogs does not rely on a special kernel module to be loaded.
Description-md5: 04c153c901ad7ca75e53e2ae32565ccd
Tag: admin::monitoring, implemented-in::c++, role::program,
 uitoolkit::ncurses, use::monitor, works-with::network-traffic
Section: net
Priority: optional
Filename: pool/main/n/nethogs/nethogs_0.8.5-2+b1_amd64.deb
Size: 30936
MD5sum: 500047d154a1fcde5f6eacaee45148e7
SHA256: 8bc69509f6a8c689bf53925ff35a5df78cf8ad76fff176add4f1530e66eba9dc

root@pcfreak:~# apt install nethogs –yes

# nethogs


5;.Use iftop –  to display network interface usage


root@pcfreak:~# apt-cache show iftop |grep -i description -A10 -B10
Package: iftop
Version: 1.0~pre4-7
Installed-Size: 97
Maintainer: Markus Koschany <>
Architecture: amd64
Depends: libc6 (>= 2.29), libncurses6 (>= 6), libpcap0.8 (>= 0.9.8), libtinfo6 (>= 6)
Description-en: displays bandwidth usage information on an network interface
 iftop does for network usage what top(1) does for CPU usage. It listens to
 network traffic on a named interface and displays a table of current bandwidth
 usage by pairs of hosts. Handy for answering the question "Why is my Internet
 link so slow?".
Description-md5: f7e93593aba6acc7b5a331b49f97466f
Tag: admin::monitoring, implemented-in::c, interface::text-mode,
 role::program, scope::utility, uitoolkit::ncurses, use::monitor,
Section: net
Priority: optional
Filename: pool/main/i/iftop/iftop_1.0~pre4-7_amd64.deb
Size: 42044
MD5sum: c9bb9c591b70753880e455f8dc416e0a
SHA256: 0366a4e54f3c65b2bbed6739ae70216b0017e2b7421b416d7c1888e1f1cb98b7



root@pcfreak:~# apt install –yes iftop


6. Ettercap (tool) to active and passive dissect network protocols for in depth network and host analysis

root@pcfreak:/var/www/images# apt-cache show ettercap-common|grep -i description -A10 -B10
Package: ettercap-common
Source: ettercap
Version: 1:
Installed-Size: 2518
Maintainer: Debian Security Tools <>
Architecture: amd64
Depends: ethtool, geoip-database, libbsd0 (>= 0.0), libc6 (>= 2.14), libcurl4 (>= 7.16.2), libgeoip1 (>= 1.6.12), libluajit-5.1-2 (>= 2.0.4+dfsg), libnet1 (>= 1.1.6), libpcap0.8 (>= 0.9.8), libpcre3, libssl1.1 (>= 1.1.1), zlib1g (>= 1:1.1.4)
Recommends: ettercap-graphical | ettercap-text-only
Description-en: Multipurpose sniffer/interceptor/logger for switched LAN
 Ettercap supports active and passive dissection of many protocols
 (even encrypted ones) and includes many feature for network and host
 Data injection in an established connection and filtering (substitute
 or drop a packet) on the fly is also possible, keeping the connection
 Many sniffing modes are implemented, for a powerful and complete
 sniffing suite. It is possible to sniff in four modes: IP Based, MAC Based,
 ARP Based (full-duplex) and PublicARP Based (half-duplex).
 Ettercap also has the ability to detect a switched LAN, and to use OS
 fingerprints (active or passive) to find the geometry of the LAN.
 This package contains the Common support files, configuration files,
 plugins, and documentation.  You must also install either
 ettercap-graphical or ettercap-text-only for the actual GUI-enabled
 or text-only ettercap executable, respectively.
Description-md5: f1d894b138f387661d0f40a8940fb185
Tag: interface::text-mode, network::scanner, role::app-data, role::program,
 uitoolkit::ncurses, use::scanning
Section: net
Priority: optional
Filename: pool/main/e/ettercap/ettercap-common_0.8.3.1-3_amd64.deb
Size: 734972
MD5sum: 403d87841f8cdd278abf20bce83cb95e
SHA256: 500aee2f07e0fae82489321097aee8a97f9f1970f6e4f8978140550db87e4ba9

root@pcfreak:/ # apt install ettercap-text-only –yes

root@pcfreak:/ # ettercap -C



7. iperf and netperf to measure connecitivity speed on Network LAN and between Linux server hosts

iperf and netperf are two very handy tools to measure the speed of a network and various aspects of the bandwidth. It is mostly useful when designing network infrastructure or building networks from scratch.

If you never used netperf in the past here is a description from man netperf

       netperf – a network performance benchmark

       netperf [global options] — [test specific options]

       Netperf  is  a benchmark that can be used to measure various aspects of
       networking performance.  Currently, its focus is on bulk data  transfer
       and  request/response  performance  using  either  TCP  or UDP, and the
       Berkeley Sockets interface. In addition, tests for DLPI, and  Unix  Do‐
       main Sockets, tests for IPv6 may be conditionally compiled-in.


root@freak:~# netperf
MIGRATED TCP STREAM TEST from ( port 0 AF_INET to localhost () port 0 AF_INET : demo
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

 87380  65536  65536    10.00    17669.96


Testing UDP network throughput using NetPerf

Change the test name from TCP_STREAM to UDP_STREAM. Let’s use 1024 (1MB) as the message size to be sent by the client.
If you receive the following error send_data: data send error: Network is unreachable (errno 101) netperf: send_omni:

send_data failed: Network is unreachable, add option -R 1 to remove the iptable rule that prohibits NetPerf UDP flow.

$ netperf -H -t UDP_STREAM -l 300 — -R 1 -m 1024
MIGRATED UDP STREAM TEST from ( port 0 AF_INET to () port 0 AF_INET
Socket Message Elapsed Messages
Size Size Time Okay Errors Throughput
bytes bytes secs # # 10^6bits/sec

212992 1024 300.00 9193386 0 251.04
212992 300.00 9131380 249.35

UDP Throughput in a WAN

$ netperf -H HOST -t UDP_STREAM -l 300 — -R 1 -m 1024
MIGRATED UDP STREAM TEST from (null) ( port 0 AF_INET to (null) () port 0 AF_INET : histogram : spin interval
Socket Message Elapsed Messages
Size Size Time Okay Errors Throughput
bytes bytes secs # # 10^6bits/sec

9216 1024 300.01 35627791 0 972.83
212992 300.01 253099 6.91



Testing TCP throughput using iPerf

Here is a short description of iperf

       iperf – perform network throughput tests

       iperf -s [options]

       iperf -c server [options]

       iperf -u -s [options]

       iperf -u -c server [options]

       iperf  2  is  a tool for performing network throughput and latency mea‐
       surements. It can test using either TCP or UDP protocols.  It  supports
       both  unidirectional  and  bidirectional traffic. Multiple simultaneous
       traffic streams are also supported. Metrics are displayed to help  iso‐
       late the causes which impact performance. Setting the enhanced (-e) op‐
       tion provides all available metrics.

       The user must establish both a both a server (to discard traffic) and a
       client (to generate traffic) for a test to occur. The client and server
       typically are on different hosts or computers but need not be.


Run iPerf3 as server on the server:

$ iperf3 –server –interval 30
Server listening on 5201


Test TCP Throughput in Local LAN


$ iperf3 –client –time 300 –interval 30
Connecting to host, port 5201
[ 4] local port 44728 connected to port 5201
[ ID] Interval Transfer Bandwidth Retr Cwnd
[ 4] 0.00-30.00 sec 1.70 GBytes 488 Mbits/sec 138 533 KBytes
[ 4] 30.00-60.00 sec 260 MBytes 72.6 Mbits/sec 19 489 KBytes
[ 4] 60.00-90.00 sec 227 MBytes 63.5 Mbits/sec 15 542 KBytes
[ 4] 90.00-120.00 sec 227 MBytes 63.3 Mbits/sec 13 559 KBytes
[ 4] 120.00-150.00 sec 228 MBytes 63.7 Mbits/sec 16 463 KBytes
[ 4] 150.00-180.00 sec 227 MBytes 63.4 Mbits/sec 13 524 KBytes
[ 4] 180.00-210.00 sec 227 MBytes 63.5 Mbits/sec 14 559 KBytes
[ 4] 210.00-240.00 sec 227 MBytes 63.5 Mbits/sec 14 437 KBytes
[ 4] 240.00-270.00 sec 228 MBytes 63.7 Mbits/sec 14 516 KBytes
[ 4] 270.00-300.00 sec 227 MBytes 63.5 Mbits/sec 14 524 KBytes
– – – – – – – – – – – – – – – – – – – – – – – – –
[ ID] Interval Transfer Bandwidth Retr
[ 4] 0.00-300.00 sec 3.73 GBytes 107 Mbits/sec 270 sender
[ 4] 0.00-300.00 sec 3.73 GBytes 107 Mbits/sec receiver

Test TCP Throughput in a WAN Network

$ iperf3 –client HOST –time 300 –interval 30
Connecting to host HOST, port 5201
[ 5] local port 56756 connected to HOST port 5201
[ ID] Interval Transfer Bitrate
[ 5] 0.00-30.00 sec 21.2 MBytes 5.93 Mbits/sec
[ 5] 30.00-60.00 sec 27.0 MBytes 7.55 Mbits/sec
[ 5] 60.00-90.00 sec 28.6 MBytes 7.99 Mbits/sec
[ 5] 90.00-120.00 sec 28.7 MBytes 8.02 Mbits/sec
[ 5] 120.00-150.00 sec 28.5 MBytes 7.97 Mbits/sec
[ 5] 150.00-180.00 sec 28.6 MBytes 7.99 Mbits/sec
[ 5] 180.00-210.00 sec 28.4 MBytes 7.94 Mbits/sec
[ 5] 210.00-240.00 sec 28.5 MBytes 7.97 Mbits/sec
[ 5] 240.00-270.00 sec 28.6 MBytes 8.00 Mbits/sec
[ 5] 270.00-300.00 sec 27.9 MBytes 7.81 Mbits/sec
– – – – – – – – – – – – – – – – – – – – – – – – –
[ ID] Interval Transfer Bitrate
[ 5] 0.00-300.00 sec 276 MBytes 7.72 Mbits/sec sender
[ 5] 0.00-300.00 sec 276 MBytes 7.71 Mbits/sec receiver


$ iperf3 –client –interval 30 -u -b 100MB
Accepted connection from, port 39444
[ 5] local port 5201 connected to port 36436
[ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams
[ 5] 0.00-30.00 sec 354 MBytes 98.9 Mbits/sec 0.052 ms 330/41774 (0.79%)
[ 5] 30.00-60.00 sec 355 MBytes 99.2 Mbits/sec 0.047 ms 355/41903 (0.85%)
[ 5] 60.00-90.00 sec 354 MBytes 98.9 Mbits/sec 0.048 ms 446/41905 (1.1%)
[ 5] 90.00-120.00 sec 355 MBytes 99.4 Mbits/sec 0.045 ms 261/41902 (0.62%)
[ 5] 120.00-150.00 sec 354 MBytes 99.1 Mbits/sec 0.048 ms 401/41908 (0.96%)
[ 5] 150.00-180.00 sec 353 MBytes 98.7 Mbits/sec 0.047 ms 530/41902 (1.3%)
[ 5] 180.00-210.00 sec 353 MBytes 98.8 Mbits/sec 0.059 ms 496/41904 (1.2%)
[ 5] 210.00-240.00 sec 354 MBytes 99.0 Mbits/sec 0.052 ms 407/41904 (0.97%)
[ 5] 240.00-270.00 sec 351 MBytes 98.3 Mbits/sec 0.059 ms 725/41903 (1.7%)
[ 5] 270.00-300.00 sec 354 MBytes 99.1 Mbits/sec 0.043 ms 393/41908 (0.94%)
– – – – – – – – – – – – – – – – – – – – – – – – –
[ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams
[ 5] 0.00-300.04 sec 3.45 GBytes 98.94 Mbits/sec 0.043 ms 4344/418913 (1%)

UDP Throughput in a WAN

$ iperf3 –client HOST –time 300 -u -b 7.7MB
Accepted connection from, port 60634
[ 5] local port 5201 connected to port 52586
[ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams
[ 5] 0.00-30.00 sec 27.4 MBytes 7.67 Mbits/sec 0.438 ms 64/19902 (0.32%)
[ 5] 30.00-60.00 sec 27.5 MBytes 7.69 Mbits/sec 0.446 ms 35/19940 (0.18%)
[ 5] 60.00-90.00 sec 27.5 MBytes 7.68 Mbits/sec 0.384 ms 39/19925 (0.2%)
[ 5] 90.00-120.00 sec 27.5 MBytes 7.68 Mbits/sec 0.528 ms 70/19950 (0.35%)
[ 5] 120.00-150.00 sec 27.4 MBytes 7.67 Mbits/sec 0.460 ms 51/19924 (0.26%)
[ 5] 150.00-180.00 sec 27.5 MBytes 7.69 Mbits/sec 0.485 ms 37/19948 (0.19%)
[ 5] 180.00-210.00 sec 27.5 MBytes 7.68 Mbits/sec 0.572 ms 49/19941 (0.25%)
[ 5] 210.00-240.00 sec 26.8 MBytes 7.50 Mbits/sec 0.800 ms 443/19856 (2.2%)
[ 5] 240.00-270.00 sec 27.4 MBytes 7.66 Mbits/sec 0.570 ms 172/20009 (0.86%)
[ 5] 270.00-300.00 sec 25.3 MBytes 7.07 Mbits/sec 0.423 ms 1562/19867 (7.9%)
– – – – – – – – – – – – – – – – – – – – – – – – –
[ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams
[ 5] 0.00-300.00 sec 272 MBytes 7.60 Mbits/sec 0.423 ms 2522/199284 (1.3%)
[SUM] 0.0-300.2 sec 31 datagrams received out-of-order

Sum it up what learned

Debugging network issues and snooping on a Local LAN (DMZ) network on a server or home LAN is useful  to debug for various network issues and more importantly track and know abou tsecurity threads such as plain text passowd communication via insecure protocols a failure of proper communication between Linux network nodes at times, or simply to get a better idea on what kind of network is your new purchased dedicated server living in .It can help you also strenghten your security and close up any possible security holes, or even help you start thinking like a security intruder (cracker / hacker) would do. In this article we went through few of my favourite tools I use for many years quite often. These tools are just part of the tons of useful *Unix free tools available to do a network debug. Tools mentioned up are worthy to install on every server you have to administratrate or even your home desktop PCs, these are iptraf, sniffit, iftop, bmon, nethogs, nmon, ettercap, iperf and netperf.
 If you have some other useful tools used on Linux sys admin tasks please share, I'll be glad to know it and put them in my arsenal of used tools.

Enjoy ! 🙂

Check server Internet connectivity Speedtest from Linux terminal CLI

Friday, August 7th, 2020


If you are a system administrator of a dedicated server and you have no access to Xserver Graphical GNOME / KDE etc. environment and you wonder how you can track the bandwidth connectivity speed of remote system to the internet and you happen to have a modern Linux distribution, here is few ways to do a speedtest.

1. Use speedtest-cli command line tool to test connectivity


speedtest-cli is a tiny tool written in python, to use it hence you need to have python installed on the server.
It is available both for Redhat Linux distros and Debians / Ubuntus etc. in the list of standard installable packages.

a) Install speedtest-cli on Fedora / CentOS / RHEL

On CentOS / RHEL / Scientific Linux lower than ver 8:



$ sudo yum install python

On CentOS 8 / RHEL 8 user type the following command to install Python 3 or 2:



$sudo yum install python3
$ sudo yum install python2




On Fedora Linux version 22+



$ sudo dnf install python
$ sudo dnf install pytho3


Once python is at place download or in case if link is not reachable download mirrored version of on here



$ wget -O speedtest-cli
$ chmod +x speedtest-cli


Then it is time to run script speedtest-screenshot-linux-terminal-console-cli-cmd
To test enabled Bandwidth on the server



$ python speedtest-cli

b) Install speedtest-cli on Debian

On Latest Debian 10 Buster speedtest is available out of the box in regular .deb repositories, so fetch it with apt


# apt install –yes speedtest-cli


You can give now speedtest-cli a try with –bytes arguments to get speed values in bytes instead of bits or if you want to generate an image with test results in picture just like it will appear if you use inside a gui browser, use the –share option





2. Getting connectivity results of all defined speedtest test City Locations

Speedtest has a list of servers through which a Upload and Download speed is tested, to run speedtest-cli to test with each and every server and get a better picture on what kind of connectivity to expect from your server towards the closest region capital cities, fetch speedtest-servers.php list and use a small shell loop below is how:






root@pcfreak:~#  wget
–2020-08-07 16:31:34–
Преобразувам (…,,, …
Connecting to (||:80… успешно свързване.
HTTP изпратено искане, чакам отговор… 301 Moved Permanently
Адрес: [следва]
–2020-08-07 16:31:34–
Connecting to (||:443… успешно свързване.
HTTP изпратено искане, чакам отговор… 307 Temporary Redirect
Адрес: [следва]
–2020-08-07 16:31:35–
Преобразувам (…
Connecting to (||:443… успешно свързване.
HTTP изпратено искане, чакам отговор… 200 OK
Дължина: 211695 (207K) [text/xml]
Saving to: ‘speedtest-servers.php’
speedtest-servers.php                  100%[==========================================================================>] 206,73K  –.-KB/s    in 0,1s
2020-08-07 16:31:35 (1,75 MB/s) – ‘speedtest-servers.php’ saved [211695/211695]

Once file is there with below loop we extract all file defined servers id="" 's 

root@pcfreak:~# for i in $(cat speedtest-servers.php | egrep -Eo 'id="[0-9]{4}"' |sed -e 's#id="##' -e 's#"##g'); do speedtest-cli  –server $i; done
Retrieving configuration…
Testing from Vivacom (…
Retrieving server list…
Retrieving information for the selected server…
Hosted by Telecoms Ltd. (Varna) [38.88 km]: 25.947 ms
Testing download speed……………………………………………………………………..
Download: 57.71 Mbit/s
Testing upload speed…………………………………………………………………………………………
Upload: 93.85 Mbit/s
Retrieving configuration…
Testing from Vivacom (…
Retrieving server list…
Retrieving information for the selected server…
Hosted by GMB Computers (Constanta) [94.03 km]: 80.247 ms
Testing download speed……………………………………………………………………..
Download: 35.86 Mbit/s
Testing upload speed…………………………………………………………………………………………
Upload: 80.15 Mbit/s
Retrieving configuration…
Testing from Vivacom (…




For better readability you might want to add the ouput to a file or even put it to run periodically on a cron if you have some suspcion that your server Internet dedicated lines dies out to some general locations sometimes.

3. Testing UPlink speed with Download some big file from source location

In the past a classical way to test the bandwidth connectivity of your Internet Service Provider was to fetch some big file, Linux guys should remember it was almost a standard to roll a download of Linux kernel source .tar file with some test browser as elinks / lynx / w3c.
speedtest-screenshot-kernel-org-shot1 speedtest-screenshot-kernel-org-shot2
or if those are not at hand test connectivity on remote free shell servers whatever file downloader as wget or curl was used.
Analogical method is still possible, for example to use wget to get an idea about bandwidtch connectivity, let it roll below 500 mb from to /dev/null few times:


$ wget –output-document=/dev/null

$ wget –output-document=/dev/null

$ wget –output-document=/dev/null


# wget -O /dev/null –progress=dot:mega ; date
–2020-08-07 13:56:49–
Resolving (…
Connecting to (||:80… connected.
HTTP request sent, awaiting response… 200 OK
Length: 10485760 (10M) [application/octet-stream]
Saving to: ‘/dev/null’

     0K …….. …….. …….. …….. …….. …….. 30%  142M 0s
  3072K …….. …….. …….. …….. …….. …….. 60%  179M 0s
  6144K …….. …….. …….. …….. …….. …….. 90%  204M 0s
  9216K …….. ……..                                    100%  197M=0.06s

2020-08-07 13:56:50 (173 MB/s) – ‘/dev/null’ saved [10485760/10485760]

Fri 07 Aug 2020 01:56:50 PM UTC

To be sure you have a real picture on remote machine Internet speed it is always a good idea to run download of random big files on a certain locations that are well known to have a very stable Internet bandwidth to the Internet backbone routers.

4. Using Simple shell script to test Internet speed

Fetch and use


wget && chmod u+x && bash



5. Using iperf to test connectivity between two servers 


iperf is another good tool worthy to mention that can be used to test the speed between client and server.

To use iperf install it with apt and do on the server machine to which bandwidth will be tested:


# iperf -s 


On the client machine do:


# iperf -c 


where is the IP of the server where iperf was spawned to listen.

6. Using Netflix fast to determine Internet connection speed on host


fast is a service provided by Netflix. Its web interface is located at and it has a command-line interface available through npm (npm is a package manager for nodejs) so if you don't have it you will have to install it first with:

# apt install –yes npm


Note that if you run on Debian this will install you some 249 new nodejs packages which you might not want to have on the system, so this is useful only for machines that has already use of nodejs.


$ fast


     82 Mbps ↓

The command returns your Internet download speed. To get your upload speed, use the -u flag:


$ fast -u


   ⠧ 80 Mbps ↓ / 8.2 Mbps ↑


7. Use speedometer / iftop to measure incoming and outgoing traffic on interface

If you're measuring connectivity on a live production server system, then you might consider that the measurement output might not be exactly correct especially if you're measuring the Uplink / Downlink on a Heavy loaded webserver / Mail Server / Samba or DNS server.
If this is the case a very useful tools to consider to extract the already taken traffic used on your Incoming and Outgoing ( TX / RX ) Network interfaces
are speedometer and iftop, they're present and installable depending on the OS via yum / apt or the respective package manager.


To install on Debian server:




# apt install –yes iftop speedometer


The most basic use to check the live received traffic in a nice Ncurses like text graphic is with: 





# speedometer -r 


To generate real time ASCII art graph on RX / TX traffic do:



# speedometer -r eth0 -t eth0






# iftop -P -i eth0









How to make a mirror of website on GNU / Linux with wget / Few tips on wget site mirroring

Wednesday, February 22nd, 2012


Everyone who used Linux is probably familiar with wget or has used this handy download console tools at least thousand of times. Not so many Desktop GNU / Linux users like Ubuntu and Fedora Linux users had tried using wget to do something more than single files download.
Actually wget is not so popular as it used to be in earlier linux days. I've noticed the tendency for newer Linux users to prefer using curl (I don't know why).

With all said I'm sure there is plenty of Linux users curious on how a website mirror can be made through wget.
This article will briefly suggest few ways to do website mirroring on linux / bsd as wget is both available on those two free operating systems.

1. Most Simple exact mirror copy of website

The most basic use of wget's mirror capabilities is by using wget's -mirror argument:

# wget -m

Creating a mirror like this is not a very good practice, as the links of the mirrored pages will still link to external URLs. In other words link URL will not pointing to your local copy and therefore if you're not connected to the internet and try to browse random links of the webpage you will end up with many links which are not opening because you don't have internet connection.

2. Mirroring with rewritting links to point to localhost and in between download page delay

Making mirror with wget can put an heavy load on the remote server as it fetches the files as quick as the bandwidth allows it. On heavy servers rapid downloads with wget can significantly reduce the download server responce time. Even on a some high-loaded servers it can cause the server to hang completely.
Hence mirroring pages with wget without explicity setting delay in between each page download, could be considered by remote server as a kind of DoS – (denial of service) attack. Even some site administrators have already set firewall rules or web server modules configured like Apache mod_security which filter requests to IPs which are doing too frequent HTTP GET /POST requests to the web server.
To make wget delay with a 10 seconds download between mirrored pages use:

# wget -mk -w 10 -np --random-wait

The -mk stands for -m/-mirror and -k / shortcut argument for –convert-links (make links point locally), –random-wait tells wget to make random waits between o and 10 seconds between each page download request.

3. Mirror / retrieve website sub directory ignoring robots.txt "mirror restrictions"

Some websites has a robots.txt which restricts content download with clients like wget, curl or even prohibits, crawlers to download their website pages completely.

/robots.txt restrictions are not a problem as wget has an option to disable robots.txt checking when downloading.
Getting around the robots.txt restrictions with wget is possible through -e robots=off option.
For instance if you want to make a local mirror copy of the whole sub-directory with all links and do it with a delay of 10 seconds between each consequential page request without reading at all the robots.txt allow/forbid rules:

# wget -mk -w 10 -np -e robots=off --random-wait

4. Mirror website which is prohibiting Download managers like flashget, getright, go!zilla etc.

Sometimes when try to use wget to make a mirror copy of an entire site domain subdirectory or the root site domain, you get an error similar to:

Sorry, but the download manager you are using to view this site is not supported.
We do not support use of such download managers as flashget, go!zilla, or getright

This message is produced by the site dynamic generation language PHP / ASP / JSP etc. used, as the website code is written to check on the browser UserAgent sent.
wget's default sent UserAgent to the remote webserver is:

As this is not a common desktop browser useragent many webmasters configure their websites to only accept well known established desktop browser useragents sent by client browsers.
Here are few typical user agents which identify a desktop browser:

  • Mozilla/5.0 (Windows NT 6.1; rv:6.0) Gecko/20110814 Firefox/6.0
  • Mozilla/5.0 (X11; Linux i686; rv:6.0) Gecko/20100101 Firefox/6.0
  • Mozilla/6.0 (Macintosh; I; Intel Mac OS X 11_7_9; de-LI; rv:1.9b4) Gecko/2012010317 Firefox/10.0a4
  • Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:2.2a1pre) Gecko/20110324 Firefox/4.2a1pre

etc. etc.

If you're trying to mirror a website which has implied some kind of useragent restriction based on some "valid" useragent, wget has the -U option enabling you to fake the useragent.

If you get the Sorry but the download manager you are using to view this site is not supported , fake / change wget's UserAgent with cmd:

# wget -mk -w 10 -np -e robots=off \
--referer="" \--user-agent="Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv: Gecko/20070725 Firefox/" \--header="Accept:text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5" \--header="Accept-Language: en-us,en;q=0.5" \--header="Accept-Encoding: gzip,deflate" \--header="Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7" \--header="Keep-Alive: 300"

For the sake of some wget anonimity – to make wget permanently hide its user agent and pretend like a Mozilla Firefox running on MS Windows XP use .wgetrc like this in home directory.

5. Make a complete mirror of a website under a domain name

To retrieve complete working copy of a site with wget a good way is like so:

# wget -rkpNl5 -w 10 --random-wait

Where the arguments meaning is:
-r – Retrieve recursively
-k – Convert the links in documents to make them suitable for local viewing
-p – Download everything (inline images, sounds and referenced stylesheets etc.)
-N – Turn on time-stamping
-l5 – Specify recursion maximum depth level of 5

6. Make a dynamic pages static site mirror, by converting CGI, ASP, PHP etc. to HTML for offline browsing

It is often websites pages are ending in a .php / .asp / .cgi … extensions. An example of what I mean is for instance the URL You see the url page is tutorial.php once mirrored with wget the local copy will also end up in .php and therefore will not be suitable for local browsing as .php extension is not understood how to interpret by the local browser.
Therefore to copy website with a non-html extension and make it offline browsable in HTML there is the –html-extension option e.g.:

# wget -mk -w 10 -np -e robots=off \
--random-wait \

A good practice in mirror making is to set a download limit rate. Setting such rate is both good for UP and DOWN side (the local host where downloading and remote server). download-limit is also useful when mirroring websites consisting of many enormous files (documental movies, some music etc.).
To set a download limit to add –limit-rate= option. Passing by to wget –limit-rate=200K would limit download speed to 200KB.

Other useful thing to assure wget has made an accurate mirror is wget logging. To use it pass -o ./my_mirror.log to wget.

How to enable output compression (gzipfile content compression) in nginx webserver

Friday, April 8th, 2011

I have recently installed and configured a Debian Linux server with nginx
. Since then I’ve been testing around different ways to optimize the nginx performance.

In my nginx quest, one of the most crucial settings which dramatically improved the end client performance was enabling the so called output compression which in Apache based servers is also known as content gzip compression .
In Apache webservers the content gzip compression is provided by a server module called mod_deflate .

The output compression nginx settings saves a lot of bandwidth and though it adds up a bit more load to the server, the plain text files like html, xml, js and css’s download time reduces drasticly as they’re streamed to the browser in gzip compressed format.
This little improvement in download speed also does impact the overall end user browser experience and therefore improves the browsing speed experience with websites.

If you have already had experience nginx you already know it is a bit fastidious and you have to be very careful with it’s configuration, however thanksfully enabling the gzip compression was actually rather easier than I thought.

Here is what I added in my nginx config to enable output compression:

## Compression
gzip on;
gzip_buffers 16 8k;
gzip_comp_level 9;
gzip_http_version 1.1;
gzip_min_length 0;
gzip_vary on;

Important note here is that need to add this code in the nginx configuration block starting with:

http {
## Compression
gzip on;
gzip_buffers 16 8k;
gzip_comp_level 9;
gzip_http_version 1.1;
gzip_min_length 0;
gzip_vary on;

In order to load the gzip output compression as a next step you need to restart the nginx server, either by it’s init script if you use one or by killing the old nginx server instances and starting up the nginx server binary again:
I personally use an init script, so restarting nginx for me is done via the cmd:

debian:~# /etc/init.d/nginx restart
Restarting nginx: nginx.

Now to test if the output gzip compression is enabled for nginx, you can simply use telnet

hipo@linux:~$ telnet 80
Escape character is '^]'.

After the Escape character is set ‘^]’ appears on your screen type in the blank space:


and press enter twice.
The output which should follow should look like:

HTTP/1.1 200 OK
Server: nginx
Date: Fri, 08 Apr 2011 12:04:43 GMT
Content-Type: text/html
Content-Length: 13
Last-Modified: Tue, 22 Mar 2011 15:04:26 GMT
Connection: close
Vary: Accept-Encoding
Expires: Fri, 15 Apr 2011 12:04:43 GMT
Cache-Control: max-age=604800
Accept-Ranges: bytes

The whole transaction with telnet command issued and the nginx webserver output should look like so:

hipo@linux:~$ telnet 80
Connected to
.Escape character is '^]'.

HTTP/1.1 200 OK
Server: nginx
Date: Fri, 08 Apr 2011 12:04:43 GMT
Content-Type: text/html
Content-Length: 13
Last-Modified: Tue, 22 Mar 2011 15:04:26 GMT
Connection: close
Vary: Accept-Encoding
Expires: Fri, 15 Apr 2011 12:04:43 GMT
Cache-Control: max-age=604800
Accept-Ranges: bytes

The important message in the returned output which confirms your nginx output compression is properly configured is:

Vary: Accept-Encoding

If this message is returned by your nginx server, this means your nginx now will distribute it’s content to it’s clients in compressed format and apart from the browsing boost a lot of server and client bandwitdth will be saved.

Using rsync to copy / synchronize files or backups between Linux / BSD / Unix servers

Monday, November 21st, 2011

Rsync and Rsync over ssh logo picture

Many of us have already taken advantage of the powerful Rsync proggie, however I'm quite sure there are still people who never used rsync to transfer files between servers.. That's why I came with this small post to possibly introduce rsync to my blog readers.
Why Rsync and not Scp or SFTP? Well Rsync is designed from the start for large files transfer and optimized to do the file copying job really efficient. Some tests with scp against rsync will clearly show rsync's superiority.
Rsync is also handy to contiue copying of half copied files or backups and thus in many cases saves bandwidth and machine hdd i/o operations.

The most simple way to use rsync is:

server:~# rsync -avz -e ssh remoteuser@remotehost:/remote/directory /local/directory/

Where remoteuser@remotehost — is the the username and hostname of remote server to copy files to.
/remote/directory — is the directory where the rsync copied files should be stored
/local/directory — is the local directory from which files will be copied to remote directory

If not a preliminary passwordless ssh key (RSA / DSA) authentication is configured on remote server, the above command will prompt for a password otherwise the rsync will start doing the transfer.

If one needs to have a RSA or DSA (public / private key) passwordless SSH key authentication , a RSA key first should be generated and copied over to the remote server, like so:

server:~# ssh-keygen -t dsa
server:~# ssh-copy-id -i ~/.ssh/ root@remotehost

That's all folks, enjoy rsyncing 😉