...making Linux just a little more fun!



[ In reference to "Laptop review: Averatec 5400 series" in LG#108 ]

Ben Okopnik [ben at linuxgazette.net]

Wed, 16 Apr 2008 20:17:53 -0400

----- Forwarded message from Edward Blaize <edwardblaize@gmail.com> -----

Date: Wed, 16 Apr 2008 17:48:06 -0500
From: Edward Blaize <edwardblaize@gmail.com>
To: editor@linuxgazette.net
Subject: 5400 series averatec & linux.
hello, this is directed towards Ben, i just read his review of how the 5400 series worked with linux, honestly most of it was over my head, i didnt really know what he was talking about with all the technical stuff. having said that, i own an averatec 5400 series laptop, and have had it for 3.5 years and i love it. i am interested in starting to use linux and have tried several distros and cant get them to work. which one would he recommend to a non technophile like me who just hates windows and is willing to learn to program if i have to, but dont really have the time. i used to program in machine language, basic, and fortran77, but was a beginner. i have long since forgotten those things a lifetime ago.im looking for a distro i can install and be relatively easy to use and will function well on this machine. i want to set up a dual boot system with windows/linux. any help would be greatly appreciated, thank you.

----- End forwarded message -----

* Ben Okopnik * Editor-in-Chief, Linux Gazette * http://LinuxGazette.NET *

[ Thread continues here (9 messages/13.61kB) ]


[ In reference to "TCP and Linux' Pluggable Congestion Control Algorithms" in LG#135 ]

René Pfeiffer [lynx at luchs.at]

Sun, 30 Mar 2008 23:37:14 +0200

I forward this request since I asked for

----- Forwarded message from René Pfeiffer <lynx@luchs.at> -----

From: René Pfeiffer <lynx@luchs.at>
Date: Sun, 30 Mar 2008 20:26:00 +0200
To: Erik van Zijst <erik.van.zijst@layerstream.com>
Subject: Re: Scalable TCP Tuning
Message-ID: <20080330182600.GC4927@nephtys.luchs.at>
In-Reply-To: <47EF3432.9090307@layerstream.com> Hello, Erik!

I'll answer to in private, but please let me know if I can send this answer also to The Answer Gang mailing list. We like to keep all feedback there, so our readers can find it.

On Mar 29, 2008 at 2333 -0700, Erik van Zijst appeared and said:

> Hi Rene,
> I read some of your Linux Gazette articles, specifically the one on TCP's 
> pluggable congestion control and maybe you can give me a little push in the 
> right direction.
> I'm in a startup doing streaming video over TCP (rather than UDP with 
> forward error correction), but TCP is giving me some latency headaches. To 
> ensure uninterrupted playback, we use a chunky client-side playback buffer, 
> but in its relentless quest for throughput-optimization, often under high 
> bandwidth and transcontinental RTT's, TCP manages to introduce enough 
> latency to underrun any buffer.
> With streaming video, keeping latency within bounds is often more important 
> than squeezing out a few percent extra throughput. I've looked at the 
> pluggable congestion control algorithms which are great, but pretty much all 
> of them focus on high throughput, rather than latency.

Yes, most of the algorithms deal with increasing throughput on fat pipes and high latency. Only the algorithms TCP Veno and Westwood deal with other scenarios (frequent packet loss on wireless links). Apart from that maybe Interactive TCP (iTCP) seems to be interesting, but this isn't available as module (yet). http://www.medianet.kent.edu/itcp/main.html

> TCP maintains the dynamic send buffer between user- and kernel-space and in 
> order to minimize context switches, Linux seems to have a tendency to making 
> these really large. On high-latency, transcontinental connections, I often 
> get 1MB+ send buffers that can easily contain over 10 seconds of video. From 
> what I see, the kernel modules mostly seem to tune only the size of the cwnd 
> within the send buffer, rather than the send buffer as a whole, but since 
> this is probably the main cause for increased latency, I'm looking for a way 
> to tune this and always keep it as small as possible. Linux already seems to 
> increase the send buffer's capacity when the cwnd increases, but never seems 
> to shrink it again.
> Would you have any tips for a Linux-based startup when it comes to 
> low-latency TCP tuning?

The only thing I noticed are the following settings in /proc.

[ ... ]

[ Thread continues here (1 message/4.14kB) ]


[ In reference to "Measuring TCP Congestion Windows" in LG#136 ]

Thu, 10 Apr 2008 10:35:37 -0700


Read your article in the Gazette.

I was curious to know if there is a way to read TCP Acks programatically ? If so how?

Would appreciate any feedback you can provide.




[ In reference to "2-Cent Tips" in LG#149 ]

Mulyadi Santosa [mulyadi.santosa at gmail.com]

Wed, 16 Apr 2008 08:58:00 +0700

Hi Rolland... :)

On Wed, Apr 16, 2008 at 2:46 AM, Rolland Sovarszki <rollandsov@gmail.com> wrote:

> Hi there
> I am new to Linux, but with a big desire to become better. I have recently
> read your article "2-cent tips: convert the collection of your mp3 files
> into ogg"
> in Linux Gazzete. I have found it very interesting, and I wanted to try it
> out for myself. Everything went fine, except the script for replacing the "
> " (blanks) with "_".
>  After a little digging, and study of sed command, I have found out that the
> problem came from this line of code:
> do mv -v "$a" $(echo $a | sed s/\/\_/g);
> So I have replaced it with:
>  do mv -v "$a" $(echo $a | sed s/" "/\_/g);

Thanks a ton! :) If you check the discussion thread in TAG following my post, there are various criticism for this tip, whether it's improvement or correction. Therefore, I highly appreciate your feedback and CC your e-mail to TAG, so everybody can get the benefit.



[ Thread continues here (4 messages/4.92kB) ]


[ In reference to "VPN Networking" in LG#149 ]

Tue, 15 Apr 2008 09:09:34 -0400

This article may give me a start, but I am looking for something a little closer to my requirements. I need to emulate a network of embedded devices, preferably by creating a pseudo-router with something that acts like those devices behind it. Every article I have seen suggests putting the target devices into virtual machines with a router VM in front. But the embedded devices I need to emulate are neither PCs nor OS based. We buy the primary device from another company, and it comes with a Rabbit 2000 and Ethernet interface. That company provides us with firmware to our specifications, which we simply write into flash memory with utilities they also provide. I need to emulate a network of 2000 of these devices to do a decent load test on our servers. This emulation needs to duplicate the behavior of the TCP/IP stack as well as initiate socket connections, data requests and transactions just as the target devices do. Some of this behavior will have to be characterized by analyzing Wireshark traces and some experimentation.

Any suggestions?

Thank you,

Bob McConnell

Principal Communications Programmer
The CBORD Group, Inc.
61 Brown Road
Ithaca NY, 14850
Phone 607 257-2410
FAX 607 257-1902
Email rvm@cbord.com
Web www.cbord.com

[ Thread continues here (2 messages/3.03kB) ]


[ In reference to "Plotting the spirograph equations with 'gnuplot'" in LG#133 ]

Ben Okopnik [ben at linuxgazette.net]

Fri, 11 Apr 2008 14:35:01 -0400

----- Forwarded message from arnoldmashava@gmail.com -----

Date: Thu, 10 Apr 2008 23:03:36 +0200
From: Arnold Mashava <arnoldmashava@gmail.com>
To: tag@lists.linuxgazette.net
Subject: Talkback:133/luana.html
Cheers for the Gnu plot article. I am an OpenSUSE LINUX user and still doing my MSc.Eng at the University of Natal, Durban, South Africa. What's the Open Source equivalent of MathType and Office 2007, Open Office.org still has a long way to go until they catch up with MS Office 2007.


----- End forwarded message -----

* Ben Okopnik * Editor-in-Chief, Linux Gazette * http://LinuxGazette.NET *

[ Thread continues here (3 messages/2.35kB) ]


[ In reference to "Migrating a Mail Server to Postfix/Cyrus/OpenLDAP" in LG#124 ]

René Pfeiffer [lynx at luchs.at]

Sun, 30 Mar 2008 20:01:01 +0200

Hello, Pawel!

On Mar 11, 2008 at 1426 +0000, Pawel Eljasz appeared and said:

> Hi Rene.
> My name is Pawel and firstly I'd like to thank you for your contribution
> into open source, for sharing knowledge.

My pleasure, thanks.

> I've read your article on as in subject of this email. Ihave to mention
> don't know much about ldap and postfix much,
> I do my best to change that state of affairs. I wonder if you could
> briefly advise, put me on right line of thought.
> This is a problem I've come across:
> when I run your script:
> ../cgate_migrate_ldap.pl --source ubuntu --target localhost --verbose 4
> Connected to source server :   ubuntu
> Connected to target server :   localhost
> account has been moved to a remote system at ./cgate_migrate_ldap.pl
> line 174, <DATA> line 228.

I just saw that there is a password hardcoded into the script. I wanted to avoid that but fortunately the old server got decommissioned after the migration. :) You have to use the matching password for access to the LDAP tree on the source server. Usually you use a privileged password on the source LDAP server for that since you want to read everything from the source tree.

> I'm not sure if I understand it correctly when in the article you say:
> "...
> We use the LDAP tree of our organisation dc=example,dc=net and create a
> subtree for all our accounts.
> Then we create another subtree for the Postfix settings... "
> Do you mean here the actual creation of the structure you mention just
> just after, creation with help of
> ldap client tools like, ldapadd, ldapmodify. And I get above error
> because I did not do it?

No, I think you got the error simply because of the hardcoded password in the script (which is hopefully wrong to access your server).

Of course apart from that you can prepare any structures in your LDAP tree with the clients tools if you like. However the cgate_migrate_ldap.pl script will overwrite existing structures, so be careful.

> In case that is not the reason for the error I get, here is some info on
> systems I work on:
> cgpro 4.1.8 on ubuntu 2.6.20-16-server and target machine is fedora 8
> with openLdap 2.3.39

Should work fine, we also migrated from a 4.1.x CommuniGate Pro server.

> Sorry if I got so straight to the point, I hope you don't find it impolite.

No, I like direct questions so I can give direct answers. :)

Best regards, René.

  )\._.,--....,'``.      Let GNU/Linux work for you while you take a nap.
 /,   _.. \   _\  (`._ ,. R. Pfeiffer <lynx at luchs.at> + http://web.luchs.at/
`._.-(,_..'--(,_..'`-.;.'  - System administration + Consulting + Teaching -
Got mail delivery problems?  http://web.luchs.at/information/blockedmail.php


[ In reference to "Automatic creation of an Impress presentation from a series of images" in LG#116 ]

Karl-Heinz Herrmann [kh1 at khherrmann.de]

Sun, 30 Mar 2008 21:34:43 +0200


since this is a question directly related to the linux-gazette I'm CC'ing the mailinglist there (TAG).

On Mon, 24 Mar 2008 14:44:43 -0400 "Jim Shupert, Jr." <jshupert@pps-inc.com> wrote:

> http://linuxgazette.net/116/herrmann.html
> I have the complete perl script.

be aware that recent versions of ::OODoc broke the script. A tiny correction will make it work again, see: http://linuxgazette.net/132/lg_talkback.html#talkback.02 http://www.khherrmann.de/Programs.shtml http://www.khherrmann.de/Code/img2ooImpress.pl

> 1 matter eludes me - i do not understand -
> Where is the info to tell the program where to find a dir of images.

the inbuilt mini-help says:

  img2ooImpress.pl ImageFileList [outputfile.odp]
  ImageFileList is a file containing all images to import

and yes, the script expects a filename containing all images, each on its own line. You can easily create a file like that by following the examples in the original linux-gazette article.

essentially, after making sure your files are sorted properly by ls something like:

ls image*.jpg > filelist

will write all jpg-images starting with "image" into the file "filelist".

running img2ooImpress.pl filelist

will then create the output odp file (default odp name, if you pass a second parameter it will be used as output file).

> i see this
> my $imgFileList=shift;how is this imagefile list made? I am expecting

no -- it simply fetches the first commandline argument into $imgFileList -- and subsequently opens that file (or fails).

> to see a path to a dir of images....I have just reread your code
> before sending this and Think I might understand now.the usage
> img2ooImpress.pl ImageFileList [outputfile.swi]the perl prog     then
> a txtfile   [ and this is optional? ]and then should the
> imageFileList be in the same dir with the perl?

No -- you can keep the perl script in ~/bin (and add ~/bin to your PATH). Also the given file-name for the file-list can contain a full path -- so no need to have it lokal in the the same directory as the perl script OR the images.

[ ... ]

[ Thread continues here (1 message/3.55kB) ]

Talkback: Discuss this article with The Answer Gang

Copyright © 2008, . Released under the Open Publication License unless otherwise noted in the body of the article. Linux Gazette is not produced, sponsored, or endorsed by its prior host, SSC, Inc.

Published in Issue 150 of Linux Gazette, May 2008