Blogs

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xx Not Blog - Linux tutorials and articles
March 15, 2013, 07:05:34 pm by rocketnine
I'm working on my Linux skills.  Right now I'm focusing on server applications as well as common sysadmin tasks.

Visit Not Blog
xx Apple Charlatans
September 03, 2012, 11:37:31 pm by cirrus
http://cirrusminor.info/2012/09/03/apple-charlatans/

My Blog
xx Who cares about IPv6?
January 05, 2011, 01:03:50 am by Smither
My interest in IPv6 was first peaked a few months ago when someone on the local computer society chat room was ranting and joking about how no one's ready for IPv6. I think found this article on the society website, which made me make a note to have a look at IPv6 when I had some time.

https://sucs.org/Knowledge/Articles/Internet%20Protocol%20version%206

But then yesterday I found this, and thought I'd share.

http://www.youtube.com/v/zIUgH2wVt_0?fs=1&hl=en_GB

I'm about to go try that IPv6 tunnel thing right now.
xx The fallacy of bandwidth limits on hosting and internet connections
July 08, 2010, 09:17:56 pm by kirrus
- reposted from my main blog -

Currently, according to mainstream media, bandwidth is defined as the quantity of data you download or upload to the internet over a month. So, for example, your ISP will tell you the maximum bandwidth limit is 100GB. Or whatever.

That, however, is not it’s true definition. It’s true definition is:
a data transmission rate; the maximum amount of information (bits/second) that can be transmitted along a channel.[1]

This is the secret thing about bandwidth. ISPs don’t care about how much you upload to the web over a given period. We care about how fast you upload it.

When you pay for a high-level connection to the internet, that you use to connect houses to, or web-serving computers, you do not pay in quantity over time. You pay in speed. So, for example, 1 gigabit per second. If you go over that speed, longer than a allowed ‘burst’ period, you pay an overage charge, always assuming that your network is even capable of going over that speed.

Think of bandwidth like gas going through a pipe. (Terrible, terrible analogy, I know. But it’s the easiest way to explain.) That gas can only flow so fast, and only so much can be fit in the pipe at any one time. We don’t particularly care if you use 100GB by taking a trickle out of the system at any one time. We do care if you take a torrent.

Realistically though, customers never notice bandwidth. They’re too busy playing with computer-resource hungry things, like wordpress, to even be able to consume all of their allocated bandwidth. Only very, very rarely do we actually start thinking about bandwidth rather than computing resources. Normally, it’s podcasts. Static file. Almost no server-resources required to send it out onto the internet. But it eats bandwidth. Most are ~50-80Megabytes per episode. You get enough people downloading that simultaneously, and we’re going to start noticing…

As long as the current trend continues, i.e. the more computing power we have available to provide you with your shiny websites, the more the people creating the shiny websites waste computing power, the mainstream will never notice this secret.

More often than not, the reason we ask people to upgrade off our shared servers, is not because they’ve reached any arbitrary bandwidth limit, although we may use this as a guide to identify them. It’s because they’re using too much CPU time.

   1. http://wordnetweb.princeton.edu/perl/webwn?s=bandwidth
xx My second ever bash script
June 25, 2010, 01:37:03 pm by Sophia
It's very studenty :p
Code: [Select]
#!/bin/bash
# This is my second ever script. It is to decide whether or not to have a drink. It asks the
# user a series of questions to determine if it is safe for them to drink and if it is safe
# flips a coin to make a final choice.
clear
echo "Welcome to Should I Have a Drink 1.0"
echo

# first I will ask if the user is already drunk
echo "are you drunk?"
select choice in yes yesh no quit;
do
case $choice in
'yes')
  echo "do you feel sick?"
  select sick in yes no;
  do
  case $sick in
  'yes')
      echo "you are too drunk, do not have a drink!"
      exit
  ;;
  'no')
      echo "are you an alcoholic?"
      select alcoholic in yes no;
      do
      case $alcoholic in
      'yes')
          echo "go to an AA meeting!"
          exit
      ;;
      'no')
        echo "flipping coin"
          coin=$(( 1+(`od -An -N2 -i /dev/random` )%(10-0+1) ))
        if [ "$coin" -gt "5" ]; then
                                                        echo "have a drink! ^_^"
                                                        exit
                                                 else
                                                        echo "don't have a drink"
                                                        exit
                                                 fi
       ;;
       esac
       done
;;
      esac
                 done
        ;;       
'yesh')
echo "Go to bed!"
exit
;;
'no')
echo "do you feel sick?"
    select sick in yes no;
    do
case $sick in
  'no')
      echo "flipping coin"
      coin=$(( 1+(`od -An -N2 -i /dev/random` )%(10-0+1) ))
if [ "$coin" -gt "5" ]; then
echo "have a drink! ^_^"
exit
else
echo "don't have a drink"
exit
fi
;;
  'yes')
      echo "are you hungover?"
      select hung in yes no;
      do
    case $hung in
      'yes')
        echo "are you an alcoholic?"
        select alcoholic in yes no;
        do
        case $alcoholic in
        'yes')
            echo "go to an AA meeting!"
          exit
        ;;
        'no')
        echo "hair of the dog: have a drink"
          exit
;;
        esac
done
    ;;
    'no')
      echo "curl up in bed and watch films, drinking will just make you sicker!"
exit
;;
    esac
done
        ;;
esac
done
;;
'quit')
  echo "Bye Bye"
  exit
        ;;
        esac
done
exit
xx Funny FTP-client crash
June 25, 2010, 08:39:41 am by shtromm
Normally I thought that the ftp-clients are rock-stable. Not so with Debian's Lenny for ADM64 system:

Code: [Select]
swen@Augustus:~$ ftp ftp.sht-services.co.uk
Connected to ftp.sht-services.co.uk.
220-Matrix FTP server ready.
220-This is a private system - No anonymous login
220-IPv6 connections are also welcome on this server.
220 Please note: files for your website must be stored under the htdocs directory.
Name (ftp.sht-services.co.uk:swen): xxx
331 User xxx OK. Password required
Password:
230 OK. Current directory is /
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> !ls -l
*** glibc detected *** ftp: corrupted double-linked list: 0x0000000000637e80 ***
======= Backtrace: =========
/lib/libc.so.6[0x7fb5c91ff9a8]
/lib/libc.so.6[0x7fb5c91ffc70]
/lib/libc.so.6[0x7fb5c9202326]
/lib/libc.so.6(__libc_malloc+0x98)[0x7fb5c9203ad8]
/lib/libc.so.6(_obstack_begin+0x61)[0x7fb5c9206371]
ftp[0x40cc21]
/lib/libc.so.6(__libc_start_main+0xe6)[0x7fb5c91aa1a6]
ftp(fclose+0x189)[0x4025b9]
======= Memory map: ========
00400000-00412000 r-xp 00000000 08:01 1673998                            /usr/bin/netkit-ftp
00611000-00613000 rw-p 00011000 08:01 1673998                            /usr/bin/netkit-ftp
00613000-00642000 rw-p 00613000 00:00 0                                  [heap]
7fb5c3de9000-7fb5c3dff000 r-xp 00000000 08:01 1201875                    /lib/libgcc_s.so.1
7fb5c3dff000-7fb5c3fff000 ---p 00016000 08:01 1201875                    /lib/libgcc_s.so.1
7fb5c3fff000-7fb5c4000000 rw-p 00016000 08:01 1201875                    /lib/libgcc_s.so.1
7fb5c4000000-7fb5c4021000 rw-p 7fb5c4000000 00:00 0
7fb5c4021000-7fb5c8000000 ---p 7fb5c4021000 00:00 0
7fb5c8136000-7fb5c8146000 r-xp 00000000 08:01 1202227                    /lib/libresolv-2.7.so
7fb5c8146000-7fb5c8346000 ---p 00010000 08:01 1202227                    /lib/libresolv-2.7.so
7fb5c8346000-7fb5c8348000 rw-p 00010000 08:01 1202227                    /lib/libresolv-2.7.so
7fb5c8348000-7fb5c834a000 rw-p 7fb5c8348000 00:00 0
7fb5c834a000-7fb5c834e000 r-xp 00000000 08:01 1202198                    /lib/libnss_dns-2.7.so
7fb5c834e000-7fb5c854d000 ---p 00004000 08:01 1202198                    /lib/libnss_dns-2.7.so
7fb5c854d000-7fb5c854f000 rw-p 00003000 08:01 1202198                    /lib/libnss_dns-2.7.so
7fb5c854f000-7fb5c8551000 r-xp 00000000 08:01 1203104                    /lib/libnss_mdns4_minimal.so.2
7fb5c8551000-7fb5c8750000 ---p 00002000 08:01 1203104                    /lib/libnss_mdns4_minimal.so.2
7fb5c8750000-7fb5c8751000 rw-p 00001000 08:01 1203104                    /lib/libnss_mdns4_minimal.so.2
7fb5c8751000-7fb5c875a000 r-xp 00000000 08:01 1202229                    /lib/libnss_nis-2.7.so
7fb5c875a000-7fb5c895a000 ---p 00009000 08:01 1202229                    /lib/libnss_nis-2.7.so
7fb5c895a000-7fb5c895c000 rw-p 00009000 08:01 1202229                    /lib/libnss_nis-2.7.so
7fb5c895c000-7fb5c8971000 r-xp 00000000 08:01 1202206                    /lib/libnsl-2.7.so
7fb5c8971000-7fb5c8b70000 ---p 00015000 08:01 1202206                    /lib/libnsl-2.7.so
7fb5c8b70000-7fb5c8b72000 rw-p 00014000 08:01 1202206                    /lib/libnsl-2.7.so
7fb5c8b72000-7fb5c8b74000 rw-p 7fb5c8b72000 00:00 0
7fb5c8b74000-7fb5c8b7b000 r-xp 00000000 08:01 1202207                    /lib/libnss_compat-2.7.so
7fb5c8b7b000-7fb5c8d7a000 ---p 00007000 08:01 1202207                    /lib/libnss_compat-2.7.so
7fb5c8d7a000-7fb5c8d7c000 rw-p 00006000 08:01 1202207                    /lib/libnss_compat-2.7.so
7fb5c8d7c000-7fb5c8d86000 r-xp 00000000 08:01 1202233                    /lib/libnss_files-2.7.so
7fb5c8d86000-7fb5c8f86000 ---p 0000a000 08:01 1202233                    /lib/libnss_files-2.7.so
7fb5c8f86000-7fb5c8f88000 rw-p 0000a000 08:01 1202233                    /lib/libnss_files-2.7.so
7fb5c8f88000-7fb5c8f8a000 r-xp 00000000 08:01 1202208                    /lib/libdl-2.7.so
7fb5c8f8a000-7fb5c918a000 ---p 00002000 08:01 1202208                    /lib/libdl-2.7.so
7fb5c918a000-7fb5c918c000 rw-p 00002000 08:01 1202208                    /lib/libdl-2.7.so
7fb5c918c000-7fb5c92d6000 r-xp 00000000 08:01 1202225                    /lib/libc-2.7.so
7fb5c92d6000-7fb5c94d5000 ---p 0014a000 08:01 1202225                    /lib/libc-2.7.so
7fb5c94d5000-7fb5c94d8000 r--p 00149000 08:01 1202225                    /lib/libc-2.7.so
7fb5c94d8000-7fb5c94da000 rw-p 0014c000 08:01 1202225                    /lib/libc-2.7.so
7fb5c94da000-7fb5c94df000 rw-p 7fb5c94da000 00:00 0
7fb5c94df000-7fb5c951a000 r-xp 00000000 08:01 1201917                    /lib/libncurses.so.5.7
7fb5c951a000-7fb5c9719000 ---p 0003b000 08:01 1201917                    /lib/libncurses.so.5.7
7fb5c9719000-7fb5c971e000 rw-p 0003a000 08:01 1201917                    /lib/libncurses.so.5.7
7fb5c971e000-7fb5c9756000 r-xp 00000000 08:01 1202010                    /lib/libreadline.so.5.2
7fb5c9756000-7fb5c9955000 ---p 00038000 08:01 1202010                    /lib/libreadline.so.5.2
7fb5c9955000-7fb5c995d000 rw-p 00037000 08:01 1202010                    /lib/libreadline.so.5.2
7fb5c995d000-7fb5c995e000 rw-p 7fb5c995d000 00:00 0
7fb5c995e000-7fb5c997a000 r-xp 00000000 08:01 1202232                    /lib/ld-2.7.so
7fb5c9a14000-7fb5c9b4e000 r--p 00000000 08:01 1684842                    /usr/lib/locale/locale-archive
7fb5c9b4e000-7fb5c9b51000 rw-p 7fb5c9b4e000 00:00 0
7fb5c9b6b000-7fb5c9b72000 r--s 00000000 08:01 883020                     /usr/lib/gconv/gconv-modules.cache
7fb5c9b72000-7fb5c9b79000 rw-p 7fb5c9b72000 00:00 0
7fb5c9b79000-7fb5c9b7b000 rw-p 0001b000 08:01 1202232                    /lib/ld-2.7.so
7ffffffe9000-7fffffffe000 rw-p 7ffffffea000 00:00 0                      [stack]
7fffffffe000-7ffffffff000 r-xp 7fffffffe000 00:00 0                      [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]
Aborted

Funny - isn't it?

More interesting is that Debian has fix it for the i386-architecture ( http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=508378 ), but not for AMD64. I think i shall tell.
xx Desktop file sharing for people ...
May 30, 2010, 02:54:22 pm by Mad Penguin
Do you remember the good old days when you could set up drive shares between your Windows PC's and share files between machines? I do, and indeed more recently there's been all the fun of making SAMBA work between Windows and Linux so Linux PC's can also share those same files. Although not that difficult, generally it's a PITA and ultimately you just know that one day either a Windows Update or Linux distro update is going to upset the apple cart and you'll be configuring it all over again.

Still, good way to keep your skills up, eh?!

Anyway, for today's generation of "you know where you can stick your Windows box" where all you need is to share files between multiple Linux boxes, there are again a plethora of methods and invariably people will quote NFS without thinking too much. (or of course SAMBA) There are however alternatives, in particular I'm talking about SSHFS, which historically may have come across as a little obscure, but in combination with recent Gnome desktops is THE way to share files at a desktop level.

So how do we do that then?

Ok, well let's assume you have SSH running on all your boxes, typically this is what you're going to have running for the purposes of remote administration. If it's not running it's usually very easy to install - on Ubuntu or Mint for example you can do it through the GUI or from the command line;

Code: [Select]
apt-get install openssh-server

Once you have this running on a box, all you need is a username / password on the box, and everything is set up! (good eh?!)

So, to connect to a local machine on your network, in my example I'm going to use a machine with IP address 10.90.0.102 and because I never hit the wrong key, I'm going to use the root user.  ;)

Start Here :- First go to Places, and select Connect to Server, this should bring up a form that will ask you for details of where you want to connect to. See the image to the left do see the form filled in with the example details as outlined above.

What you should see then (you may have to wait a couple of seconds depending on your connection and the speed of your machines) is a file browser showing you the files available on the target machine.

What can I do with this?

You can drag and drop files between the target machine and your machine, and you can open files on this remote filesystem directly using any standard Gnome application.

Why is this really cool?

o It's works over local area networks AND over the Internet
o It's encrypted, so it's effectively a secure / VPN link
o Use the book mark option to effectively make the link persistent between reboots
o The only configuration required is listed above!

So if you need high performance file sharing and you have time on your hands, you will need to look at things like NFS, Samba (and dare I say 'gluster'). However, if you're looking for a more moderate / desktop experience without all the in depth tek, when these terms are mentioned, cover your ears and run away! These services are great, but technically complex and complete overkill!
xx Yeah, but Windows has "Terminal Server" !
May 23, 2010, 12:50:46 pm by Mad Penguin
Comparing all the things that Windows does to all the things that Linux does is often a bit of a misnomer. The fundamental issue here is that all core Windows components are produced by one company, hence it's possible to define it's features and capabilities to quite a high degree of accuracy. When looking at a Linux distribution on the other hand, not only are there many variations on "Linux", but also the core components of Linux come from many different sources and it's often difficult to obtain a definitive list of their features and how good they are. There are also many other non-core components that some people would deem essential, that others simply haven't come across.

One long running Windows 'feature' is 'Terminal Server', the ability to log into your computer from a remote location and run a full graphical connection over a network link. There have been many predecessors to Terminal Server over the years (for example "PCAnywhere") but at the end of the day, M$ have integrated a pretty competent protocol (RDP) into the heart of all their systems and when all's said and done, it does a pretty good job.

For historical reasons (and/or reasons unbeknown to me) the Linux community seem to have adopted VNC as it's core protocol, and indeed you will find that this is built into the Gnome desktop in an attempt to provide similar desktop sharing capabilities. Not to put too fine a point on it, compared to RDP on Windows, VNC is (IMHO) utter rubbish. 15 Years ago it would have been really ground breaking, but today, given the alternatives .. Why on earth .. ?!

When I say alternatives, I am of course talking about NX , which is effectively the Linux alternative to RDP and after having used both for many years, I don't think there is any question that NX is way out in front. (i.e. the Linux solution is much better than the Windows solution!) I know people out there will say "but it's not open source!", and once upon a time they may've been right, but not recently.

NoMachine.org do indeed sell a commercial version of the NX server and client (which is cheaper than Terminal Server), however they also provide a COMPLETELY FREE 2-user version of the software (which is slightly better licensing than the free Terminal Server you get with Windows XP!) AND the source code for NX "IS" Open Source, so you can go build it yourself.

So here's the question, why don't developers flush VNC down the toilet and take the source code to NX and build it into distro's by default? Not a desperately difficult concept, not one that would be particularly difficult to implement.

Note that although the NX Server is for Linux only, there are both Linux and Windows versions of the client, so it also makes for a really easy to introduce Windows users to a Linux desktop!
thumbup What do you mean "it's better than Firefox?!"
May 15, 2010, 11:58:19 pm by Mad Penguin
I've always been a fan of web browsers that aren't "Internet Explorer", all the way back to my first - NCSA Mosiac. Every browser has it's pro's and con's and with each new release, typically things keep getting better and faster - but at the end of the day, a browser is just a browser and there's not that much to choose from, right?

Well .. maybe, maybe not.

I first tried out Google Chrome about 6 months ago .. and I've not looked back. Whereas I'll load Firefox on occasion to access old bookmarks etc, or test a website for compatibility, Chrome is just SO much better than Firefox it really is a little embarrassing.

Not to put too fine a point on it, firstly it's MUCH faster than any other browser, Firefox included. Secondly as each tab is an independent process, even if you manage to hang a tab, it's just the tab you need to kill and not the entire browser. It just "feels" way more competent than Firefox and if you're using anything that's Javascript / AJAX based, Chrome will typically give you a ~x2 performance boost. (or more if you normally use something else such as Opera)

If you don't have it already, and want to take a look then click here.

smiley A Domain by any other Name ...
May 15, 2010, 01:01:29 pm by Mad Penguin
Content aside, websites are all about who visits them. If nobody visits a site then it doesn't matter how good the site is, how valuable the content is or how much effort goes into maintaining it, the value of the site in any context is zero.
 
SEO (Search Engine Optimisation) is a little bit of a black art, whereas the linux.co.uk domain name is well ranked and is classed as a Google PR5, the sub-domain we are using for the forums, although indexed by Google, is not recognised as a site in it's own right and seems not to be acquiring it's own Page Rank. The content on the forums is way more current and changing daily while the content on the main site is old and static .. go figure (!)

So, I've set up a new domain name for the Forums and while this does not replace the existing domain name the new one will work in parallel and I will see if I can persuade Google to use the new URL and if so, how long it takes them to decide the site is worth ranking.

Hence I'm please to announce, our new URL is http://linuxforums.org.uk

You can check out our visitor stats at http://linuxforums.org.uk/index.php?action=stats.
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