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Fix QMAIL mail server – “warning: dropping connection, unable to SSL accept:protocol error” and why error occurs

Friday, August 24th, 2012

Every time I had to modify something in productive QMAIL server install, I end up with some kind unexplainable problems which create huge issues for clients. For one more time I end up with errors after minor “innocent” modifications of a working for more than year time QMAIL ….

After last changes I made to combined qmail install of Thibs, QmailRocks in Daemontools qmail start up files:

/var/qmail/supervise/qmail-smtpd/run /var/qmail/supervise/qmail-smtpdssl/run

In both files I set variable:

SSL=0 to SSL=1:

After making the change I restarted qmail tested sending emails and all looked well. Therefore I thought all works as usual, e.g. e-mail are properly sent and respectively received to the mail server….

So far so good until just today, when I received urgent phone call in which my employer reported about severe problems with receiving emails.
Trying to send from Gmail or Yahoo to our mail server were unable to be received with some delivery failure errors …
First I was a bit sceptical, hoping that maybe the errors reporting are not caused by the mail server but after giving a try to send email to the mail server in question the reported problem prooved true.
As always when errors with QMail, I checked what the logs says about the problem just to find in /var/log/qmail-smtpd/current log following err:

@4000000050374a0e1a5dc374 sslserver: warning: dropping connection, unable to SSL accept:protocol error

I’ve dig over almost all primary forums, threads and blog posts online but nowhere I couldn’t find anymeaningful as explanation to the error, so was forced to look for solution myself.
Obviously, there was error with SSL, so my first thought was to check if all is fine with permissions of servercert.pem and clientcert.pem. The permissions of two files were as follows:

ls -al /var/qmail/control/clientcert.pem -rw-r----- 1 root qmail 2136 2011-10-10 13:23 /var/qmail/control/clientcert.pem ls -al /var/qmail/control/servercert.pem -rw-r--r-- 1 qmaild qmail 2311 2011-10-12 13:21 /var/qmail/control/servercert.pem

At first glimpse I was suspicious concerning permissions of /var/qmail/control/clientcert.pem but after checking on other Qmail servers which worked just fine I was sure the problem did not root in clientcert.pem permissions.

As you can guess another failure point I suspected was the previous day change of SSL=0 to SSL=1 in /var/qmail/supervise/qmail-smtpd/run and /var/qmail/supervise/qmail-smtpdssl/run. On that account, I immediately reversed back the yesterday setting of SSL=0 and then restart QMAIL.

The usual QMAIL to restart qmail is via qmailctl, but since so often qmailctl does not reload qmail current settings I had to also refresh current working qmail binaries via both stopping qmail with qmailctl stop and through /etc/inittab by commenting out in it line dealing with daemontools svscanboot:

Hence I first stopped all running qmail processes via init script:

# /usr/bin/qmailctl stop

Then commented line:

SV:123456:respawn:/usr/bin/svscanboot

to:

#SV:123456:respawn:/usr/bin/svscanboot

Onwards did reload of initab with command:

# /sbin/init q

Right onwards I uncommented the commented line:

#SV:123456:respawn:/usr/bin/svscanboot

to:

SV:123456:respawn:/usr/bin/svscanboot

And load up daemontools (svscanboot) via inittab issuing:

# /sbin/init q

Finally I had to start QMAIL processes:

# qmailctl restart ...

Change of SSL svscanboot daemontools service script SSL=0 to SSL=1 however created other problems for clients cause any present clients which used crypted connections to SMTP server viaSSL encryption rendered unable to send mails anymore with error messages like:

Cannot establish SSL with SMTP server xx.xxx.xxx.xxx:465, SSL_connect error 336031996.

To work around this issue I had to once again start SSL (set SSL=1) in /var/qmail/supervise/qmail-smtpssl/run and leave SSL switched off for /var/qmail/supervise/qmail-smtp/run.

Even doing this changes for about 20 minutes though I restarted QMAIL multiple times, qmail continued having issues with mails received with the shitty:

@4000000050374a0e1a5dc374 sslserver: warning: dropping connection, unable to SSL accept:protocol error

After multiple restarts “magically” the stupid server figured out it should load my changed setting in qmail-smtpdssl/run (before it finally worked I probably had to restart 20 times using qmailctl stop; qmailctl start ….

I’ve figured out as a good practice to put delay between qmailctl stop and qmailctl start cmds so in restarts I used a little 3 secs sleep in between like so:

# qmailctl stop; killall -9 multilog; sleep 3; qmailctl start

Also killing multilog (killall -9 multilog) is good practice cause often nevertheless restarts server logging is not refreshed …

Something else that might be important is the AUTH settings in qmail-smtpd/run and qmail-smtpdssl/run in thisfinally working qmail they are:

AUTH=1 REQUIRE_AUTH=0 ALLOW_INSECURE_AUTH=0

Hope this post helps someone to solve same crazy error …
Cheers

Tags: connection, dropping, Qmail, server, unable, Warning
Posted in Qmail, System Administration | 4 Comments »

Negative impact of Cell Phones (GSM) use on individual and society

Monday, June 25th, 2012

We all live in an age, where cell-phone communication has become a standard part of our daily lives. As with everything new adopted in basic human life. GSM tool inclusion in our life had a severe impact on both individuals and in summary to whole society groups and nations.

The benefits out of having an instant “channel” for communication to anyone else in the world are indoubtfully numerous. However as present tosicety is learned to mostly thing in one direction, most people didn’t have a clear understanding on the negative impact of this little communicators on our mind body and soul.

1.; Negative impact of mobile phones on body level

Whenever we talk over the phone especially when picking up incoming calls or initiating out-going ones, the GSM device has to connect to the closest network cell “dial up” and wait for initialization of remote or local connection. The levels of radiation waves during the two mobiles connects up is higher. Therefore if one moves the phone near his ear listening for the status of call the amount of radiation that enters our brains is slightly higher. The extra-radiation whether mobiles are connecting is also few times more whether our phone is ringning, hence it is unhealthy to put the phone near our ear before we press the Answer Call button.

2.;; Negative effect of continuous mobile phones use on human brain

Knowing about the increased radiation on connection initialization thanksfully one can protect himself by simply not putting the mobile headset near ear on call initialization. Though this “problem” can be partially solved, next comes the health brain damage (tumours) which according to some researches are higher among people who do frequentlong phone call conversations. In long phone calls the brain is exposed for a longer time to the flowing waves making the peer to peer call possible. According to some medical researches, a long and frequent phone calls could be a reason not only for brain cancers but also other misfunctions or damages in normal brain cells functioning.

3.;;; The bad impact of Cell Phones on nervous system

Another health issue which the daily phone use and the constant exposure to mobile network cells radio frequency radiation affects generally our nervous system.

Unexpected phone calls early in morning or late at night are a cause for increased bodily stress and even the fear sometimes for an incoming phone call are a cause for many types of neurological disorders diagnosed by psychiatrists.
Even when we sleep at night the mobile phone periodically connects to the nearest mobile cell generating some almost undetectable “waves contamination”. This constant waves air flow caused by the mobile network cells positioned all around cities is not usual thing for our bodies. This also has some influence on our nervous system as the nervous sysm tends to be a bit more alert because of the waves constantly passing the body. The natural reaction of our bodies nerves is to try to balance itself. As nervous system of different people is not equal some people’s nervous system is more prone to having difficulties to balance the disbalance created by the increased number of mobile air waves.
The result of this to many people is in increased sleeplessnes and hardships to get asleep (according to research taken place in American Academy of Sleep Medicine.).

4.;;;; Lost of social and ethical behaviour in people

There is lately observed a huge shift from a face to face communication to peer to peer (p2p) on the phone. The cellphones breeds a culture of socially group detached people (the communication over phone is rarely a conference) but rather consists of communication between two persons (peer to peer). The p2p communication is not only a primary mean of communication of people exposed to heavy phone use. p2p Communication is a primary communication in Skype, Google Talk and mostly all modern available communication medias and softwares.

As more and more people spend nowdays more time on the mobile than in real communication, this makes them introverted and isolated and increases the inability to deal with real human f2f interaction. In other words continuous phone use re-trains us to communicate with others via the mobile. Besides that according to numerous researches about 40 to 50% of visual communication whether a phone call is used is lost (this also makes negotiation or expressing over phone harder and at least twice longer than in real communication).

The influence of the decreased social abilities cause of the phone use has also an impact on ethical behaviour of people too. The increased lost of communication abilities makes even daily real communication vague and lacking accepted social norms and ethical values. Next to that comes the huge problem of over-simplification of communication. As the line communication over the phone loose half of the communication as well as sometimes there are quality of voice over the network interferences. People are doing their best to simplify the communication adopting short command like like phrases and talking in a slang.

5.;;;;; Addiction to mobile phone use

The use of mobile phone often has a short beep sounds, whether you work on the keyboard receive a phone call or look for some mobile functionality staring at the screen. We’re wearing the mobile everywhere with us so often we do check the mobile screen quite un-consciously (by addiction). Checking the mobile screen to see what time is it has become almost an instinct and an automated learned behaviour.

The continous use of mobile phones makes many people mobile addicts. There are huge amount of people I’ve observed who speaks everyday for few hours (whether everytime they feel lonely they call someone in order not to feel lonely). The mobile phone addiction in youngsters is slighly higher than in adults. Probably the most mobile dependent addicts are kids who were given a mobile to use since there very early years.
Anyways there are tons of adults nowdays who cannot even think to be able to live without mobile and even cannot understand: how can anyone think that life could be possible without a cell phone. This kind of thinking is a direct trait showing an addiction and dependency on the phone such people have.

Tags: age, amount, amount of radiation, Auto, body, body and soul, brain, brain damage, brains, Button, cause, communicators, connection, conversations, dial, Draft, everything, GSM, human brain, impact, inclusion, incoming calls, individual, individual and society, local connection, mind body and soul, mobile headset, Mobile phones, negative impact, phone, phone call, phone communication, reason, researches, soul, status, summary, time, tool, tosicety, tumours, waves
Posted in System Administration | 3 Comments »

Enabling talkd (Console Chat) between logged in users on FreeBSD and other BSDs

Sunday, June 10th, 2012

Talk between two useres on FreeBSD 7.2 screenshot, console peer to peer interactive talk program UNIX, Linux, BSD

Those who are in familiar with older UNIXes, UNIX BSD derivatives and GNU Linux should certainly remember the times, when we hackers used to talk to each other using talk service.

Those who don't know what talk command is it is a simple console / ssh utility to talk to another logged in users.

Talk is very similar to write and mesg one liner messasing utilities available for *nixes, the difference is it is intendted to provide interactive chat between the two logged in users. People who came to know UNIX or free software in older times most likely don't know talk, however I still remember how precious this tool was for communication back in the day.

I believe still it can be useful so I dediced to install ot on one FreeBSD host.

In order to have the talk service running on BSD it is necessery to have /usr/libexec/ntalkd installed on the system this however is installed by default with standard BSD OS installs, so no need for any external ports install to run it.

talk doesn't have it's own init script to start is not written to run as it own service but in order to run it is is necessery to enable it via inetd

Enabling it is done by;;;

1 — Editting /etc/inetd.conf

Inside the conf the line::

#ntalk dgram udp wait tty:tty /usr/libexec/ntalkd ntalkd

should be uncommented e.g, become ;;;

ntalk dgram udp wait tty:tty /usr/libexec/ntalkd ntalkd

2 — Restart inetd

freebsd# /etc/rc.d/inetd restart Stopping inetd. Starting inetd.

talk is planned to be used for peer to peer conversations over SSH so in a way it is the GRANDFATHER 🙂 of IRC, ICQ and Skype;;;

Here is an example on how talk is used ,, Let's say there are three logged in users

pcfreak# w 12:39PM up 3 days, 16:25, 3 users, load averages: 1.12, 0.91, 0.71 USER TTY FROM LOGIN@ IDLE WHAT testuser p0 192.168.0.7 10:50AM - bash hipo p3 192.168.0.8 12:23PM - w root p4 :ttyp2:S.0 12:24PM - vim /usr/local/www/dat

I'm logged in with my username hipo and I would like to talk to testuser ;;;;

pcfreak% tty /dev/ttyp3

You see I'm logged in on /dev/ttyp3 (this is the specific naming on BSDs) on Linux equivalent is /dev/tty3So to talk the other user testuser;;;;;-

$ talk testuser ttyp0 [No connection yet] [Waiting for your party to respond]

The testuser logged in via SSH will then get a message ||;

Message from Talk_Daemon@pcfreak at 12:44 on 2012/06/10 ... talk: connection requested by hipo@localhost talk: respond with: talk hipo@localhost

To enter a talk session then the logged in testuser has to type:

$ talk hipo@localhost

Tags: Auto, BSD, bsd os, BSDs, Chat, connection, conversations, derivatives, dgram, doesn, Draft, editting, external ports, free software, gnu linux, hackers, hipo, host, init, init script, irc icq, Linux, load averages, localhost, mesg, necessery, need, ntalkd, p3, pcfreak, Restart, Skype, software, ssh, testuser, tool, unix, unix bsd, wait
Posted in FreeBSD | No Comments »

Selecting Best Wireless channel / Choosing Best Wi-FI channel for Wireless Routers or (How to improve Wireless Network performance)

Monday, February 22nd, 2010

Wireless AP
Below are some valuable advices on Wireless Access Point initial install and configuration to better off your Wireless connection.It’s worthy to note that the 2.4 GHz

Wi-Fi signal range is divided into a number of smaller bands or “channels,” similar to television channels. I decided to run my wireless on channel 12 since this there was no other wireless routers operating on that frequency, though most routers are preconfigured to spread it’s signal on channel 6.

There is a difference in channels available for setup for 802.11b and 802.11g wireless networks in the United States and the European Union. In the USA the wireless channels available are from (1 to 11) whether in the EU it’s in the range of (1-13). Each of the Wireless channels run on a different frequency.

The lower the number of the channel is the lowest the radiating frequence band on which data is transmitted .Subsequently, increasing the channel increases the frequency slightly. Therefore the higher the channel you select on your AP the lesser the overlap with other devices running on the same channel and thus the lesser the possibility to overlap and interference.
It’s quite likely that you experience problems, if you use the default wireless channel which is 6.
If that’s the case it’s recommended to use either channel 1 or channel 11. In case of interference, i.e. overlap with other wireless networks, cellphones etc., there are 2 possible ways to approach the situation. In case of smaller interference, any change in channel on which there is no wireless device running could fix it up. The second way is to choose a wireless channel for your router in between 1,6 or 11 in (The USA) or 1,7,13 in Europe.
Up to 3 networks can run on the same space with minimum interference, therefore it would be a wise idea to check the list of wireless routers in your and check if there are others running on the same frequency.
As I mentioned in the beginning of the post I initially started running my wireless on channel 12, however after I discovered it is recommended to run your wireless router either on channel 1 7 or 13 in Europe I switched my D-Link DI-524 wireless router to transmit it’s signal on Channel 13.

I should testify that after changing the wireless channel, there was quite an improvement in my wireless connection.For instance before I change to Channel 13 (when my wireless internet was still streamed on channel 12) my wireless had constantly issues with disconnects because of low wireless signal.

Back then My wireless located physically in like 35 meters away set in another room, I can see my wireless router hardly connected on like 35%, changing to channel 13 enhanced my connection to the current 60% wireless router availability.

It’s also an interesting fact that Opened Wireless networks had better network thoroughput, so if you’re living in a house with a neighbors a bit distant from your place then you might consider it as a good idea to completely wipe out Wireless Router security encryption and abandon the use of WEP or WPA network encryption.

In case if all of the above is not working for you, you might consider take a close look at your Wireless Wireless LAN pc card and see if there are no any kind of bumps there. Another really interesting fact to know is that many people here in Bulgaria tend to configure there Wireless Access Points on channels either 1,6 or 11 which is quite inadequate considering that we’re in the EU and we should use a wireless channel between 1, 7 or 13 as prescribed for EU citizens.

Another thing not to forget is to place your wireless in a good way and prevent it from interferences with other computer equipment. For example keep the router at least few meters away from PC equipment, printers, scanners, cellphones, microwaves. Also try to put your wireless router on some kind of central place in your home, if you want to have the wireless signal all around your place.

At my place I have a microwave in the Kitchen which is sometimes an obstacle for the Wireless signal to flow properly to my notebook, fortunately this kind of interference happens rare (only when the Microwove is used to warm-up food etc.).Upgrading 802.11b wireless card / router to a better one as 802.11g is a wise idea too. 802.11g are said to be like 5 times faster than 802.11b.

You can expect 802.11b wireless network to transfer maximum between 2-5 Mbp/s whether 802.11g is claimed to transfer at approximately (12 to 23 Mbp/s). If even though the above prescriptions there is no wireless signal at some remote place at your home, you might consider adding a wireless repeater or change the AP router antenna.

By default wireless Routers are designed to be omni-directional (in other terms they broadcast the wireless signal all around the place. Thus is quite unhandy if you intend to use your Wireless net only in certain room or location at your place. If that’s the case for you, you might consider upgrading to a hi-gain antenna that will focus the wireless signal to an exact direction. Let me close this article with a small diagram taken from the net which illustrates a good router placement that will enable you to have a wwireless connection all over your place.

improve wireless router placement diagram

Tags: advices, band, bit, card, change, channel 1, channel 11, channel 12, channel 6, Choosing, connection, default, DI, difference, encryption, equipment, european union, fi channel, frequence, house, instance, minimum interference, network performance, number, place, Point, possibility, quot, router, routers, signal range, television channels, Union, wireless access point, wireless channels, wireless networks, wireless routers, wise idea
Posted in Everyday Life, System Administration | 4 Comments »

Viewing JPEG,GIF and PNG in ASCII with cacaview on GNU / Linux – Review on caca-utils text mode graphics utilities

Thursday, May 17th, 2012

Stitch 80x45 libcaca mascot cacaview viewing JPG, PNG, GIF images as ASCII on Linux libcaca

Probably, many don't know that it is possible to view normal graphical pictures (JPG, PNG, GIF, BMP) etc. in plain console tty.

Being able to view pictures in ASCII is something really nice especially for console geeks like me.
The images produced sometimes are a bit unreadable, if compared to the original graphics, but anyways most of the pictures looks pretty decent 🙂

Viewing in console / terminal images on GNU / Linux is possible thanks to a library called libcaca, caca labs libcaca project official website here.
Below is a shot description of libcaca:
hipo@noah:~$ apt-cache show libcaca0|grep 'Description' -A 4 Description: colour ASCII art library libcaca is the Colour AsCii Art library. It provides high level functions for colour text drawing, simple primitives for line, polygon and ellipse drawing, as well as powerful image to text conversion routines.

In Debian, Ubuntu and other deb Linux distros viewing GUI images with no need for Xserver or any kind of window manager in plain ASCII is possible with cacaview.

cacaview is part of a package called caca-utils. caca-utils is providing few other great utilities for ASCII freaks 🙂 along with cacaview console ascii viewer prog.
The package> is available for Debian distributins since many years, so even on a very old Debians like Debian – (Potato, Woody, Sarge) the package is available in default free package repositories ready to install via apt

To install apt-get it as usual:

noah:~# apt-get --yes install caca-utils

Here is a list of the binaries the package provides:

hipo@noah:~$ dpkg -L caca-utils|grep -i /usr/bin/ /usr/bin/cacaserver /usr/bin/cacaplay /usr/bin/cacafire /usr/bin/cacademo /usr/bin/cacaview /usr/bin/img2txt

1. cacaserver a tiny program allowing network streaming of applications written in caca

Belkow is a chop, from man cacaserver

cacaserver reads libcaca animation files in its standard input and
serves them as ANSI art on network port 51914. These animations can be
created by any libcaca program by setting the CACA_DRIVER environment
variable to raw and piping the program's standard output to cacaserver.

Clients can then connect to port 51914 using telnet or netcat to see
the output.

The example section of the manual points 1 example use of cacaserver to stream the console output from cacademo.
cacademo binary is a short presentation ASCII DEMO in the spirit of the old school assembly demos (demoscene) .
To run it to bind on port 51914 one has to type in bash shell:
hipo@noah:~$ CACA_DRIVER=raw cacademo | cacaserver initialised network, listening on port 51914

Then to check out how the demo looks, open telnet connection to the cacaserver host; In my case the cacaserver is binded and streamed over IP 192.168.0.2:

hipo@debian:~$ telnet 192.168.0.2 51914

Immediately you got the demo shining; Below are two screenshots of the demo played after succesful telnet connection:

Cacaserver - caca for the network screenshot Matrix cacademo

cacademo running over telnet network connection – Matrix

cacaserver running on Debian GNU / Linux drug addict like spots streamed via telnet

Blur spots cacademo shot of cacademo streamed via network

You see the demo looks quite awesome 🙂

2. Running cacafire to stream over network

Another possible example use of cacaserver is in conjunction with cacafire libcaca test application:

noah:~# CACA_DRIVER=raw cacafire | cacaserver initialised network, listening on port 51914 cacafire is a short application written to render ASCII via libcaca and is just displaying a screen with ASCII (moving) burning fire.
It is quite spectacular if you, ask an unexpecting friend to connect to your host to 51914 🙂

Cacafire Screenshot Debian GNU / Linux cacaserver streaming ASCII demo via network port 51914

Besides that bored sys admins, could run cacafire in console to hypnotize themselves watching dumb the burning fire screen for few hoursor just use it as a screensaver 😉

3. cacaview a program to display a graphic images in console using ASCII art

cacaview takes just one argument – the picture to be displayed.

Below is a screenshot of cacaview ran from my gnome-terminal displaying a ASCII text version of the MySQL server logo

hipo@noah:~$ cd /disk/pictures hipo@noah:/disk/pictures$ cacaview mysql_logo.png

Whether cacaview is invoked in GUI, the libcaca X support is used, so the text image is visualized in new window with graphics, if however it is invoked in plain let's say tty1 libcaca displays the graphics pictures drawing it with only text characters.

Here is also a screenshot, I've made while viewing a GIF website logo in ASCII in plain tty console:

hipo@noah:~$ cacaview /disk/pictures/logo.gif

The logo is in cyrillic, so for latin speaking people some of the characters in the two words seen will be unreadable 🙂

cacaview even supports viewing, the next and previous picture in line, like in any modern graphics image viewer program.
To view a bunch of graphic pictures in ASCII with cacaview pass it *.*:

hipo@noah:~$ cacaview /disk/pictures/*.*

For simplicity the common unix * is also supported, so I find it quicker to do:

hipo@noah:~$ cacaview /disk/pictures/*

Showing pictures forward and backward (Previous / Next) picture is done with n and p kbd keys, whether;
n - next; p - previous

cacaview doesn't crash or stop but skip unknown file formats – if for instance encounters filenames which are not images; lets say you have *.rar archive files along with other pictures.

The complete list of keys cacaview supports are:
br />

KEYS
? show the help screen

n, p switch to next image, previous image

Left, Right, Up, Down or h, l, k, j
scroll the image around

+, – zoom in and out

z reset the zoom level to normal

f switch fullscreen mode (hide/show menu and status bars)

d toggle the dithering mode (no dithering, 4×4 ordered dithering, 8×8 ordered dithering and random dithering)

q exit the program

4. Converting graphics images to ASCII art like (plain text pictures)

The tool that does "the trick" is img2txt. img2txt has a bit more options while compared to the rest of the aforementioned tools.The following list of arguments are recognized:

the size (font, height)
brightness
contrast
gamma and dither
format type of out the output pic

Anyways I found that the basic just in / out arguments passed are enough to produce pretty good results:

hipo@noah:~$ img2txt hipo_avatar.gif >hipo_avatar_pic.txt

The original hipo_avatar.gif file looks like so:

hipo avatar gif picture before img2txt convertion to text

After above img2txt command is run and hipo_avatar_pic.txt to see the colorful output ASCII art img2txt produces, cat it:

hipo@noah:~$ cat hipo_avatar_pic.txt

The image result if screenshot looks quite beautiful and even, can be considered or used as an ART effect image (filter) 🙂

The picture colors are plain ANSI color, so in order to display properly the picture with colors on another computers or Operating System you will need at least basic support for ANSI colors.

Plenty of output file formats are supported by img2txt

Here is the complete list of supported output formats:

ansi : coloured ANSI
caca : internal libcaca format
utf8 : UTF8 with CR
utf8 : UTF8 with CRLF (MS Windows)
html : HTML with CSS and DIV support
html3 : Pure HTML3 with tables
irc : IRC with ctrl-k codes
bbfr : BBCode (French)
ps : Postscript
svg : Scalable Vector Graphics
tga : Targa Image

libcaca is available for FreeBSD too, but the caca-utils is not available as a port yet, though probably the deb or rpm packages can easily be ported to BSD.

Well that's all, Enjoy.

Tags: animation files, art, ascii art library, Auto, caca, colour, colour text, connection, conversion routines, demo, description, Disk, dpkg, Draft, ellipse, gnu linux, graphics utilities, gui images, hipo, host, JPG, level, level functions, libcaca, linux distros, nbsp, noah, original graphics, package, plain ascii, png, polygon, primitives, screen, screenshot, shot, shot description, show, something, support, terminal, text, text conversion, text mode, tiny program, xserver
Posted in Everyday Life, Linux, System Administration, Various | 1 Comment »

Why I never liked Mandrake Linux / Mankdrake Linux has took its name from an 1930s comics Mandrake the Magician

Wednesday, May 9th, 2012

I never liked Mandrake Linux, since day 1 I saw it.
Historically Mandrake Linux was one of the best Linux distributions available for free download in the "Linux scene" some 10 to 12 years ago.

Mandrake was simple gui oriented and trendy. It also one the Linux distribution with the most simplified installer program and generally a lot of GUI software for easy configuration and use by the end user.

Though it's outside nice look, still for me it was like an "intuition" that Mandrake is not so good as it appeared.

Now many years later I found by chance that Mandrake has been sued to change their Operating System name with another, due to a law suit requit by the copyright holders of Mandrake The Magician comics. "Mandrake the Magician" used to be a very popular before the Second World war in the 1930's.

Mandrake the Magician Comics Magazine from 1930's Cover, Mandrake the Black Magic Magician

It obviously not a co-incidence that the Mandrake names was after this comics and not the mandrake herb plants available in Europe, Africa and Asia. This is clear in Mandrake Linux distro earlier mascot, you see below:

Later on they changed Mandrake's logo to loose the connection with Mandrake The Magician and used another new crafted logo:

Mandrake GNU Linux newer logo
Its quite stunning nowdays magician obsession, has so heavily infiltrated our lives that even something like a Free Softwre Linux distribution might have some kind of reference to magician and occult stuff (I saw this from the position of being Christian) …

Later due to the name copyright infringement Mandrake Linux was renamed first to Mandragora Linux.
Instead of putting some nice name non related to occultism or magic stuff the French commercian company behind Mandrake rename it to another non-Christian name Mandragora.
Interestingly the newer name Mandragora as one can read in wikipedia means:

Mandragora (demon), in occultism

Well apparently, someone from the head developers of this Linux distribution has a severe obsession with magic and occultism.

Later MandrakeSoft (The French Company behind Mandrake Linux) renamed finally the distribution to Mandriva under the influence of the merger of Mandrake with the Brazillian company Connectiva this put also an over to the legal dispute copyright infringement dispute with Hearst Corporation (owning the rights of Mandrake the Magician).

Having in mind all fact on current Mandriva "dark names history", I think it is better we Christians avoid it …

Tags: Auto, best linux distributions, chance, comics, commercian, connection, Copyright, copyright infringement, demon, dispute, distribution, download, Draft, europe africa, Free, free softwre, GUI, HEAD, herb plants, intuition, law suit, Linux, linux distribution, linux distro, linux scene, Magician, Mandragora, Mankdrake, nbsp, non, obsession, operating system, quot, requit, second world war, software, someone, something, wel, Wikipedia
Posted in Everyday Life, Various | 3 Comments »

How to check the IP address of Skype (user / Contacts) on GNU / Linux with netstat and whois

Thursday, May 3rd, 2012

netstat check skype contact IP info with netstat Linux xterm Debian Linux

Before I explain how netstat and whois commands can be used to check information about a remote skype user – e.g. (skype msg is send or receved) in Skype. I will say in a a few words ( abstract level ), how skype P2P protocol is designed.
Many hard core hackers, certainly know how skype operates, so if this is the case just skip the boring few lines of explanation on how skype proto works.

In short skype transfers its message data as most people know in Peer-to-Peer "mode" (P2P) – p2p is unique with this that it doesn't require a a server to transfer data from one peer to another. Most classical use of p2p networks in the free software realm are the bittorrents.

Skype way of connecting to peer client to other peer client is done via a so called "transport points". To make a P-to-P connection skype wents through a number of middle point destinations. This transport points (peers) are actually other users logged in Skype and the data between point A and point B is transferred via this other logged users in encrypted form. If a skype messages has to be transferred from Peer A (point A) to Peer B (Point B) or (the other way around), the data flows in a way similar to:

A -> D -> F -> B

or

B -> F -> D -> A

(where D and F are simply other people running skype on their PCs).
The communication from a person A to person B chat in Skype hence, always passes by at least few other IP addresses which are owned by some skype users who happen to be located in the middle geographically between the real geographic location of A (the skype peer sender) and B (The skype peer receiver)..

The exact way skypes communicate is way more complex, this basics however should be enough to grasp the basic skype proto concept for most ppl …

In order to find the IP address to a certain skype contact – one needs to check all ESTABLISHED connections of type skype protocol with netsat within the kernel network stack (connection) queue.

netstat displays few IPs, when skype proto established connections are grepped:

noah:~# netstat -tupan|grep -i skype | grep -i established| grep -v '0.0.0.0' tcp 0 0 192.168.2.134:59677 212.72.192.8:58401 ESTABLISHED 3606/skype tcp 0 0 192.168.2.134:49096 213.199.179.161:40029 ESTABLISHED 3606/skype tcp 0 0 192.168.2.134:57896 87.120.255.10:57063 ESTABLISHED 3606/skype

Now, as few IPs are displayed, one needs to find out which exactly from the list of the ESTABLISHED IPs is the the Skype Contact from whom are received or to whom are sent the messages in question.

The blue colored IP address:port is the local IP address of my host running the Skype client. The red one is the IP address of the remote skype host (Skype Name) to which messages are transferred (in the the exact time the netstat command was ran.

The easiest way to find exactly which, from all the listed IP is the IP address of the remote person is to send multiple messages in a low time interval (let's say 10 secs / 10 messages to the remote Skype contact).

It is a hard task to write 10 msgs for 10 seconds and run 10 times a netstat in separate terminal (simultaneously). Therefore it is a good practice instead of trying your reflex, to run a tiny loop to delay 1 sec its execution and run the prior netstat cmd.

To do so open a new terminal window and type:

noah:~# for i in $(seq 1 10); do \ sleep 1; echo '-------'; \ netstat -tupan|grep -i skype | grep -i established| grep -v '0.0.0.0'; \ done ------- tcp 0 0 192.168.2.134:55119 87.126.71.94:26309 ESTABLISHED 3606/skype ------- tcp 0 0 192.168.2.134:49096 213.199.179.161:40029 ESTABLISHED 3606/skype tcp 0 0 192.168.2.134:55119 87.126.71.94:26309 ESTABLISHED 3606/skype ------- tcp 0 0 192.168.2.134:49096 213.199.179.161:40029 ESTABLISHED 3606/skype tcp 0 0 192.168.2.134:55119 87.126.71.94:26309 ESTABLISHED 3606/skype ...

You see on the first netstat (sequence) exec, there is only 1 IP address to which a skype connection is established, once I sent some new messages to my remote skype friend, another IP immediatelly appeared. This other IP is actually the IP of the person to whom, I'm sending the "probe" skype messages.
Hence, its most likely the skype chat at hand is with a person who has an IP address of the newly appeared 213.199.179.161

Later to get exact information on who owns 213.199.179.161 and administrative contact info as well as address of the ISP or person owning the IP, do a RIPE whois

noah:~# whois 213.199.179.161 % This is the RIPE Database query service. % The objects are in RPSL format. % % The RIPE Database is subject to Terms and Conditions. % See http://www.ripe.net/db/support/db-terms-conditions.pdf

% Note: this output has been filtered. % To receive output for a database update, use the "-B" flag. % Information related to '87.126.0.0 - 87.126.127.255' inetnum: 87.126.0.0 - 87.126.127.255 netname: BTC-BROADBAND-NET-2 descr: BTC Broadband Service country: BG admin-c: LG700-RIPE tech-c: LG700-RIPE tech-c: SS4127-RIPE status: ASSIGNED PA mnt-by: BT95-ADM mnt-domains: BT95-ADM mnt-lower: BT95-ADM source: RIPE # Filteredperson: Lyubomir Georgiev .....

Note that this method of finding out the remote Skype Name IP to whom a skype chat is running is not always precise.

If for instance you tend to chat to many people simultaneously in skype, finding the exact IPs of each of the multiple Skype contacts will be a very hard not to say impossible task.
Often also by using netstat to capture a Skype Name you're in chat with, there might be plenty of "false positive" IPs..
For instance, Skype might show a remote Skype contact IP correct but still this might not be the IP from which the remote skype user is chatting, as the remote skype side might not have a unique assigned internet IP address but might use his NET connection over a NAT or DMZ.

The remote skype user might be hard or impossible to track also if skype client is run over skype tor proxy for the sake of anonymity
Though it can't be taken as granted that the IP address obtained would be 100% correct with the netstat + whois method, in most cases it is enough to give (at least approximate) info on a Country and City origin of the person you're skyping with.

Tags: Auto, client, connection, Draft, ESTABLISHED, explanation, few words, form, free software, geographic location, gnu linux, hackers, hard core, host, information, ip address, ip addresses, ips, level, Linux, location, message data, middle, netstat, noah, p2p, p2p networks, p2p protocol, peers, person, ppl, proto, Protocol, receiver, RIPEtech-c, sender, Skype, terminal, time, to, tupan, type, whois commands
Posted in Computer Security, Skype on Linux, System Administration | No Comments »

The Satanic roots of Metal and Rock Music genre – Two parts Christian movie exposing connection between Satanism and Metal music

Tuesday, May 1st, 2012

Some long time ago a bit before I repent and believed in Jesus Christ as my Lord and Saviour, I've done quite an extensive research on the trustability of the Holy Bible and mostly the Church and Christian writtings. In that times, as an ex-metal head I had a profound interest if there is really a connection between Modern Hard Rock and Heavy Metal Music?

My research back then was quite thoroughful and I found plenty of proofs clearly showing a clear connection between most of the hard rock and heavy / death metal bands to satanism. I used to listen this anti-christian music for about 8 years repeatedly believing the message is not really bad, even though subconsciously I knew something is not right with the music.

It was quite shocking to me to find that one of my favourite hard rock / psychedelic bands Led Zeppelin, The Beatles, The Doors, Rolling Stones etc. e, had a clear connection with Alester Crawley (a new age occultist magician and a forefather of modern satanism …).

Crawley was a completely insane person proclaiming himself under the alias "The Beast". This psycho travelled all around America, cursing people and cities and teaching people to worship evil. In other words the guy was a complete modern day anti-christ. I found in youtube few short 20 minute, movies exposing the relation between the new age ecumenistic beliefs and Crawley. Along with the musicians spoken about and their exposure to be a bible and God deniers, the movie explains why the message of this popular figures is anti-Christian in essence. This short few movies explains how this terrible guy Crawley become an inspirator of many of the today world popular played rock bands in most of the radio stations …

Satanism – The Root of Rock Music (part 1)

Satanism – The Root of Rock Music (part 2)

Another interesting documentary exposing some of the major pop and rock culture and musicians connection with satanism and the occult is They Sold Their Souls to the devil. The movie is again a short research on popular musicians, who openly say in their interviews they sold their souls for fame to the devil. . Many of the star musicians featured in this videos, even say openly they're possessed by evil spirits.

They Sold Their Souls to the devil part 1 of 3

They Sold Their Souls to the devil part 2 of 3

They Sold Their Souls to the devil part 3 of 3

They Sold Thir Souls to the devil part 4 of 4

Some people might think this is a joke non-serious, some crazy christian propaganda, but if you watch it without bias and analyze it nomatter if Christian or atheist you will see most of the things said in the video reflect the reality. Actually it's very sad reality, today's world has rapidly headed towards non-christianity, occult and satanism. Believe it or not, the elite in the world, we see daily on TV or hear on the Radio and read for as heroes in the newspapers has a strong connection with magicians, occult and fake spirituality. Many of them think loving evil is fun and okay but in fact it is a big lie we're said. As I've red someone says, once a lie is repeated many times it appears to sound like truth….
Anyways we should know Evil is evil and no good can come of worshipping the evil our ancestors and forefathers knew that pretty well and they used to teach us in a spirit to obey good and walk after good and not evil. Modern pop-rock culture teach us something else it teach us to go after the ways of dis-obeying satan took … Pitily our dying generation forgot that evil seeking will bring just evil and now systematically many governments and medias are working seriously for destroying the Christian moral and pureness hence by that we seek to destroy ourselves hurrying towards our own destruction….

Lets hope God will be merceful and turn more people to him and unveil them the truth we read in the Holy Bible. I have hope more and more people will realize that we have to be living in a moderate and saintly way and not like the rock and pop stars shown in those videos. We should pray for each other and love each other and keep an eye on our children to let them not go the bad ways of witchcraft, unholiness and sinfulness the modern pop – rock culture push us to.

Tags: age, Alester, anti, Auto, beast, christian character, connection, Crawley, death, death metal bands, deniers, Doors, Draft, Evil, extensive research, favourite, few movies, forefather, genre, HEAD, heavy metal music, holy bible, insane person, inspirator, interest, jesus christ, led zeppelin, musicians connection, nbsp, person, pop, profound interest, quot, radio stations, right, rock, rock bands, rock culture, rock music genre, rock psychedelic, satanism, saviour, something, thir, time, writtings, youtube, Zeppelin
Posted in Christianity | 6 Comments »

Finally TeamViewer 7 release for GNU / Linux is available

Thursday, March 29th, 2012

After a long time of inavailability, finally TeamViewer 7 for GNU / Linux is out!

Here is the short TeamViewer 7 Linux release note :

In our TeamViewer download area you will now find TeamViewer 7 for Linux.
The final version includes a selection of new features for Linux, e. g. an integrated screenshot feature and the possibility of saving individual connection settings per computer.
You can now establish cross platform connections with other computers running version 7 and hold online meetings and presentations with up to 25 participants.

We wish you best continued success with TeamViewer!

Well, guys it was about time, even later than that… Until now I've so many times experienced troubles with Windows machines which I had to administrate remotely and they only had a TeamViewer 7 installed (a real, real pain in the ass).

The issue comes cause TeamViewer 6 is incompatible with 7 and just until very recently only TV 6 for Linux was available, so trying to access a 7 install directly from Linux was impossible.
Hence to access TeamViewer 7 Windows install, I had to use either a fresh Windows copy with TeamViewer 7 installed or a Virtual Machine like (Qemu, VirtualBox) with Windows version installed in it.
Often back then, when I had to fix remotely a Windows machine behind a firewall, I had to instruct the machine owners to replace the TeamViewer 7 with TeamViewer 6 in order to be able to easily access the remote host from my Debian Linux.

I still remember, it was quite a stuggle to find a link to a Windows .exe install file for TeamViewer 6.

Now thanksfully, TeamViewer guys are starting to make it easier for the user who would for some reason want to stick to older TV version.
I've noticed on TeamViewer's website there is already a new TeamViewer download page offering for download all the old teamviewer version – 1.x, 2.x, 3.x, 4.x, 5.x, 6.x

One example, where old teamviewer release is useful is if you want to run teamviewer on older hardware or old OS (MS Windows 98 or old Linux distro).

I've made a mirror of teamviewer 6 for Debian / Ubuntu amd 32 and 64 bit versions along with all the OS available TeamViewer version 6 and 7, for the sake of preserving it if one day link to old versions of Teamviewer disappear from their website.

Here are the TeamViewer mirrored files:

Below you see a screenshot of teamviewer 7 running on my Debian Squeeze 🙂

TeamViewer 7 Debian GNU / Linux released, my desktop screenshot

It is great teamviewer produced a Linux working application, however if you run it you realize just like the previous releases TeamViewer is not natively supposed (compiled) to run on GNU / Linux OS but uses wine (windows emulator) to launch through…
Instead of porting the application to be natively for the Linux distros once again with this new release, teamviewer developers just "hacked" it to run on top of windows emulation. Though this is working its performance, is probably a bit degraded and it depends on having install on the Linux host a bunch of useless packages which wine depends on.
Besides that even if it "works" on Linux , TeamViewer has still non-free software essense. I still use it because unfortunately, I don't know of a better remote access program capable to connect to servers behind NAT / machines located behind a tight firewalled routers.
If only (I knew of?) a TeamViewer free software / open source equivalent …
I will be glad to hear if someone know a (free software / open source) TeamViewer like program able to access remote hosts with no a real (public inet) IP address?P.S.: By similar TV program I don't mean VNC, UltraVNC and this kind of other VNC derivative programs but mean close TeamViewer alternative.

Tags: Auto, connection, connection settings, copy, cross platform, debian linux, download, download area, Draft, exa, feature, firewall, gnu linux, host, inavailability, new features, online meetings, page, pain in the ass, platform, possibility, qemu, reason, screenshot, software, stuggle, TeamViewer, time, tv 6, tv version, Ubuntu, Virtual, virtual machine, VirtualBox, windows copy, windows machine, windows machines, windows version, wine, xOne
Posted in Linux and FreeBSD Desktop, News, System Administration | No Comments »

FreeBSD Jumbo Frames network configuration short how to

Wednesday, March 14th, 2012

Recently I wrote a post on how to enable Jumbo Frames on GNU / Linux , therefore I thought it will be useful to write how Jumbo Frames network boost can be achieved on FreeBSD too.

I will skip the details of what is Jumbo Frames, as in the previous article I have thoroughfully explained. Just in short to remind you what is Jumbo Frames and why you might need it? – it is a way to increase network MTU transfer frames from the MTU 1500 to MTU of 9000 bytes

It is interesting to mention that according to specifications, the maximum Jumbo Frames MTU possible for assignment are of MTU=16128
Just like on Linux to be able to take advantage of the bigger Jumbo Frames increase in network thoroughput, you need to have a gigabyt NIC card/s on the router / server.

1. Increasing MTU to 9000 to enable Jumbo Frames "manually"

Just like on Linux, the network tool to use is ifconfig. For those who don't know ifconfig on Linux is part of the net-tools package and rewritten from scratch especially for GNU / Linux OS, whether BSD's ifconfig is based on source code taken from 4.2BSD UNIX

As you know, network interface naming on FreeBSD is different, as there is no strict naming like on Linux (eth0, eth1, eth2), rather the interfaces are named after the name of the NIC card vendor for instance (Intel(R) PRO/1000 NIC is em0), RealTek is rl0 etc.

To set Jumbro Frames Maximum Transmission Units of 9000 on FreeBSD host with a Realtek and Intel gigabyt ethernet cards use: freebsd# /sbin/ifconfig em0 192.168.1.2 mtu 9000 freebsd# /sbin/ifconfig rl0 192.168.2.2 mtu 9000

!! Be very cautious here, as if you're connected to the system remotely over ssh you might loose connection to it because of broken routing.

To prevent routing loss problems, if you're executing the above two commands remotely, you better run them in GNU screen session:

freebsd# screen freebsd# /sbin/ifconfig em0 192.168.1.2 mtu 9000; /sbin/ifconfig rl0 192.168.1.2 mtu 9000; \ /etc/rc.d/netif restart; /etc/rc.d/routed restart

2. Check MTU settings are set to 9000

If everything is fine the commands will return empty output, to check further the MTU is properly set to 9000 issue:

freebsd# /sbin/ifconfig -a|grep -i em0em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 9000freebsd# /sbin/ifconfig -a|grep -i rl0 rl0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 9000

3. Reset routing for default gateway

If you have some kind of routing assigned for em0 and rl0, network interfaces they will be affected by the MTU change and the routing will be gone. To reset the routing to the previously properly assigned routing, you have to restart the BSD init script taking care for assigning routing on system boot time:

freebsd# /etc/rc.d/routing restart default 192.168.1.1 done add net default: gateway 192.168.1.1 Additional routing options: IP gateway=YES.

4. Change MTU settings for NIC card with route command

There is also a way to assign higher MTU without "breaking" the working routing, e.g. avoiding network downtime with bsd route command:

freebsd# grep -i defaultrouter /etc/rc.conf defaultrouter="192.168.1.1" freebsd# /sbin/route change 192.168.1.1 -mtu 9000 change host 192.168.1.1

5. Finding the new MTU NIC settings on the FreeBSD host

freebsd# /sbin/route -n get 192.168.1.1 route to: 192.168.1.1 destination: 192.168.1.1 interface: em0 flags: <UP,HOST,DONE,LLINFO,WASCLONED> recvpipe sendpipe ssthresh rtt,msec rttvar hopcount mtu expire 0 0 0 0 0 0 9000 1009

6. Set Jumbo Frames to load automatically on system load

To make the increased MTU to 9000 for Jumbo Frames support permanent on a FreeBSD system the /etc/rc.conf file is used:

The variable for em0 and rl0 NICs are ifconfig_em0 and ifconfig_rl0.
The lines to place in /etc/rc.conf should be similar to:

ifconfig_em0="inet 192.168.1.1 netmask 255.255.255.0 media 1000baseTX mediaopt half-duplex mtu 9000" ifconfig_em0="inet 192.168.1.1 netmask 255.255.255.0 media 1000baseTX mediaopt half-duplex mtu 9000"

Change in the above lines the gateway address 192.168.1.1 and the netmask 255.255.255.0 to yours corresponding gw and netmask.
Also in the above example you see the half-duplex ifconfig option is set insetad of full-duplex in order to prevent some duplex mismatches. A full-duplex could be used instead, if you're completely sure on the other side of the host is configured to support full-duplex connections. Otherwise if you try to set full-duplex with other side set to half-duplex or auto-duplex a duplex mismatch will occur. If this happens insetad of taking the advantage of the Increase Jumbo Frames MTU the network connection could become slower than originally with standard ethernet MTU of 1500. One other bad side if you end up with duplex-mismatch could be a high number of loss packets and degraded thoroughout …

7. Setting Jumbo Frames for interfaces assigning dynamic IP via DHCP

If you need to assign an MTU of 9000 for a gigabyt network interfaces, which are receiving its TCP/IP network configuration over DHCP server.
First, tell em0 and rl0 network interfaces to dynamically assign IP addresses via DHCP proto by adding in /etc/rc.conf:

ifconfig_em0="DHCP" ifconfig_rl0="DHCP"

Secondly make two files /etc/start_if.em0 and /etc/start_if.rl0 and include in each file:

ifconfig em0 media 1000baseTX mediaopt full-duplex mtu 9000 ifconfig rl0 media 1000baseTX mediaopt full-duplex mtu 9000

Copy / paste in root console:

echo 'ifconfig em0 media 1000baseTX mediaopt full-duplex mtu 9000' >> /etc/start_if.em0 echo 'ifconfig rl0 media 1000baseTX mediaopt full-duplex mtu 9000' >> /etc/start_if.rl0

Finally, to load the new MTU for both interfaces, reload the IPs with the increased MTUs:

freebsd# /etc/rc.d/routing restart default 192.168.1.1 done add net default: gateway 192.168.1.1

8. Testing if Jumbo Frames is working correctly

To test if an MTU packs are transferred correctly through the network you can use ping or tcpdumpa.) Testing Jumbo Frames enabled packet transfers with tcpdump

freebsd# tcpdump -vvn | grep -i 'length 9000'

You should get output like:

16:40:07.432370 IP (tos 0x0, ttl 50, id 63903, offset 0, flags [DF], proto TCP (6), length 9000) 192.168.1.2.80 > 192.168.1.1.60213: . 85825:87285(1460) ack 668 win 14343 16:40:07.432588 IP (tos 0x0, ttl 50, id 63904, offset 0, flags [DF], proto TCP (6), length 9000) 192.168.1.2.80 > 192.168.1.1.60213: . 87285:88745(1460) ack 668 win 14343 16:40:07.433091 IP (tos 0x0, ttl 50, id 63905, offset 0, flags [DF], proto TCP (6), length 9000) 192.168.1.2.80 > 192.168.1.1.60213: . 23153:24613(1460) ack 668 win 14343 16:40:07.568388 IP (tos 0x0, ttl 50, id 63907, offset 0, flags [DF], proto TCP (6), length 9000) 192.168.1.2.80 > 192.168.1.1.60213: . 88745:90205(1460) ack 668 win 14343 16:40:07.568636 IP (tos 0x0, ttl 50, id 63908, offset 0, flags [DF], proto TCP (6), length 9000) 192.168.1.2.80 > 192.168.1.1.60213: . 90205:91665(1460) ack 668 win 14343 16:40:07.569012 IP (tos 0x0, ttl 50, id 63909, offset 0, flags [DF], proto TCP (6), length 9000) 192.168.1.2.80 > 192.168.1.1.60213: . 91665:93125(1460) ack 668 win 14343 16:40:07.569888 IP (tos 0x0, ttl 50, id 63910, offset 0, flags [DF], proto TCP (6), length 9000) 192.168.1.2.80 > 192.168.1.1.60213: . 93125:94585(1460) ack 668 win 14343

b.) Testing if Jumbo Frames are enabled with ping

– Testing Jumbo Frames with ping command on Linux

linux:~# ping 192.168.1.1 -M do -s 8972 PING 192.168.1.1 (192.168.1.1) 8972(9000) bytes of data. 9000 bytes from 192.168.1.1: icmp_req=1 ttl=52 time=43.7 ms 9000 bytes from 192.168.1.1: icmp_req=2 ttl=52 time=43.3 ms 9000 bytes from 192.168.1.1: icmp_req=3 ttl=52 time=43.5 ms 9000 bytes from 192.168.1.1: icmp_req=4 ttl=52 time=44.6 ms --- 192.168.0.1 ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 3003ms rtt min/avg/max/mdev = 2.397/2.841/4.066/0.708 ms

If you get insetad an an output like:

From 192.168.1.2 icmp_seq=1 Frag needed and DF set (mtu = 1500) From 192.168.1.2 icmp_seq=1 Frag needed and DF set (mtu = 1500) From 192.168.1.2 icmp_seq=1 Frag needed and DF set (mtu = 1500) From 192.168.1.2 icmp_seq=1 Frag needed and DF set (mtu = 1500)

--- 192.168.1.1 ping statistics --- 0 packets transmitted, 0 received, +4 errors

This means a packets with maximum MTU of 1500 could be transmitted and hence something is not okay with the Jumbo Frames config.
Another helpful command in debugging MTU and showing which host in a hop queue support jumbo frames is Linux's traceroute

To debug a path between host and target, you can use:

linux:~# traceroute --mtu www.google.com ...

If you want to test the Jumbo Frames configuration from a Windows host use ms-windows ping command like so:

C:\>ping 192.168.1.2 -f -l 8972 Pinging 192.168.1.2 with 8972 bytes of data: Reply from 192.168.1.2: bytes=8972 time=2ms TTL=255 Reply from 192.168.1.2: bytes=8972 time=2ms TTL=255 Reply from 192.168.1.2: bytes=8972 time=2ms TTL=255 Reply from 192.168.1.2: bytes=8972 time=2ms TTL=255 Ping statistics for 192.168.1.2: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 2ms, Maximum = 2ms, Average = 2ms

Here -l 8972 value is actually equal to 9000. 8972 = 9000 – 20 (20 byte IP header) – 8 (ICMP header)

Tags: article, Auto, baseTX, boost, BSD, card, card vendor, change, code, Configuration, connection, Draft, eth, ethernet cards, Frames, freebsd, gateway, gigabyt, GNU, gnu screen, host, Jumbo, jumbo frames, Linux, linux os, maximum transmission, mediaopt, MTU, Netmask, network, network configuration, network interface, network tool, nic card, package, post, quot, Realtek, router server, scratch, screen, screen session, source code, ssh, tool, transmission units, way
Posted in FreeBSD, System Administration | 1 Comment »

☩ Walking in Light with Christ – Faith, Computing, Diary

Posts Tagged ‘connection’

Negative impact of Cell Phones (GSM) use on individual and society

Selecting Best Wireless channel / Choosing Best Wi-FI channel for Wireless Routers or (How to improve Wireless Network performance)

The Satanic roots of Metal and Rock Music genre – Two parts Christian movie exposing connection between Satanism and Metal music

Finally TeamViewer 7 release for GNU / Linux is available

Daily Bible quote

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