Terminal Terminator

There are tons of tools to get you moving via the terminal, you have the nifty Yakuake, which drops from the top of you screen like blind shade.

However what if moment calls that you be able to execute commands in a sync with several servers?  Terminator to the rescue.  Terminator is an excellent tool for firing-up several connections in one instance and be able to cascade your executed commands to all the rest those you connected.

To install it all you need is just do a simply apt-get for Debian based systems, for RedHat versions you have to install the EPEL repos to download and install the package.  

Site Reputation Checkers

There are times that you will be baffled by reports from users telling you that your site is a staging for Malware, Bots and Viruses.  If you believe you are free from these known vulnerabilities, take the time to step-back and check the links provided below.  It will pretty give you a summary of things hidden away from your eyes.

1. http://safeweb.norton.com
2. http://www.trustedsource.org
3. http://www.alken.nl/web-security-check.htm
4. http://www.unmaskparasites.com/security-report/
5. http://www.avg.com.au/resources/web-page-scanner

The Fiber Optic Association - Tech Topics

The Truth about Fiber Optic and Copper Wires 

---

Copper or Fiber? What's the real story? (Here is a specific look at fiber vs copper in LANs)
Every time we read another article about copper and fiber cabling that was written by someone who was either ignorant or prejudiced - or both - it is full of pure, unadulterated garbage. What is the real comparison of fiber and copper? Let's take a more careful look.
Point of view: Well, everybody has a point of view. We're the professional society of fiber optics, aren't we? But we have an interest in both technologies and know they are complementary in many ways, so if we're prejudiced, it's toward making sure everybody uses lots of both of them, but gets trained so they install either properly!
And as part of the point of view, we are focusing on premises cabling for communications, although we'll look at some other applications like outside plant telephones.

Start With Phones
First of all, telephone wire is over a century old. The actual way a phone works is that old too!
The telephone wire used for POTS (plain old telephone service, like in your home or a small office) goes to a switch, where the analog voice signal is digitized and most probably sent off on a fiber optic cable. It it isn't now, it will be soon.

The copper phone wire has very limited bandwidth. It was designed to provide 3,000 Hz bandwidth, perfectly adequate for a voice signal. The modem has to play some pretty sophisticated games to get higher bit rates over the limited bandwidth of the POTS line. Two digital systems work on this old cable style: ISDN and xDSL. ISDN is a low bit rate digital signal that never caught on - since analog modems are just as fast and a lot cheaper and easier to set up. xDSL or digital subscriber loop is faster - as high as 1.5 Mb/s - but only if you are close to the phone switch - less than about 15,000 feet.
So the phone system is mostly fiber optics beyond the short subscriber link. Fiber links offer over 1,000 times as much bandwidth over distances over 100 times further. Specifically, you can have:

	Distance	Bandwidth	Voice Channels
Copper	2.5 km	1.5 Mb/s	24
Fiber	200 KM	2.5+ Gb/s	32,000 +

That tremendously higher capacity comes at a price. But even if it costs 1000 times as much for two fibers (one to transmit and receive), it is still 1/100th the cost of copper per voice channel. And it has other advantages, like a fiber optic cable being a fraction of the size and weight of a copper cable, a big point in underground conduits in crowded cities!
Depending on the application, fiber costs are typically 1-5% as much as copper in the backbone.

In the subscriber loop, where one connection only is used, the economics are quite different. A drop to the home is less than $100, while a fiber to the home would cost over $1000 and require an onsite way to power the transceivers. So fiber to the home is a non-player, except in rural areas where the line is long and would require a repeater. Then the longer distance capability of fiber makes it cheaper to run fiber than have copper with repeaters and providing power to the repeater.

CATV?
What about the coax cable used for CATV? Well, it has lots of bandwidth (100 MHz to 1000 MHz depending on how old the installation is), but it even cheaper than telephone wire to install. CATV systems are using this coax for everything, (television signals, Internet connections, and even telephones) but it too is quickly converted to fiber, which provides the backbone connectivity due to lower loss (and subsequently longer runs betweem repeaters) and much greater reliability. Both those features translate into cost savings, of course. And the fiber backbones are bi-directional to allow for all the new services being offered.
In both telephone and CATV systems, fiber and copper coexist, with each being used where the economics dictate.

The Real Controversy:
When most people talk about copper vs. fiber, they are talking about LANs or premises cabling. Here there is a lot of controversy, a lot of "positioning" and a lot of misinformation.
The wire we use for LANs is a lot younger than fiber optics. Fiber use is over 20 years old, but computer networks on unshielded-twisted-pair cable (UTP) have only been around about 15 years. In that time, UTP has gone through at least 5 generations, each time to keep up with the increasing bandwidth requirements of LANs. Today, it's hardly the "telephone wire" that some people think it is.

In that time, LANs have grown in capacity via: 

LAN	Bandwidth
Ethernet	10 Mb/s
FDDI	100 Mb/s
Fast Ethernet	100 Mb/s
ATM	55, 155 Mb/s
Gigabit Ethernet	1,000 Mb/s (1 gigabit/s)
10 Gigabit Ethernet	10 Gb/s

The copper cabling manufacturers should be praised for their technical efforts to expand the capacity of UTP cabling. And the hardware manufacturers deserve a pat on the back too! They have been able to keep up with networks by some really sophisticated product development (including the electronics that perform the miracles of getting signals on and off the cabling.)

But all their efforts have produced a product that is not easily installed if one needs the maximum performance offered. Recently, a number of magazine articles and even a representative of AMP was quoted as saying that as much as 80-90% of all Cat 5 cabling was improperly installed and would not provide the rated performance. Contractors have told us that 40% of their Cat 6 installations pass certification tests.

The performance of the Cat 5 cable is dependent on close control of the physical characteristics of the cable and the materials used in the insulation. Untwist the wires too much at a connection or remove too much jacket and the cable may fail crosstalk testing. Pull it too hard (only 25 pounds tension allowed!) or kink it and loss the performance you paid for.
Even if top performance is not necessary, getting all 8 of the wires connected correctly requires a lot of care. 1-5% of all connections will not be correct first time around, according to the installers I have talked with. And did we mention the problem of electromagnetic interference (EMI) from motors, flourescent light ballasts, etc.?

But most networks only run at Ethernet at 10 Mb/s to the desktop. Even if you use 10/100 Ethernet cards, they will fall back to 10 Mb/s if the cabling won't support the faster speeds. And I'm told quite a few networks do. It's hard to tell unless you have a sophisticated network management system.

So what about fiber ? Fiber is not that easy to install either. Pulling the cable is easy - in fact it can be pulled at 8 times the pulling tension of Cat 5 and the typical cables used include strength members and stiffeners that make it hard to kink and damage. Fiber, by the way, is a lot stronger than steel - remember they don't reinforce fiber glass boats, airplanes, or even tires now with steel - they use glass fiber or aramid fibers, the strength members used in fiber optic cable.

Terminating fiber optic cable is not as simple as copper. While manufacturers have developed crimp-on connectors, they are expensive, high loss and have not been very reliable. Fiber optic connectors need adhesives for reliability and low cost. And most installation involves stripping fibers, injecting adhesives and polishing the ends. No IDC (insulation displacement connectors) here. Any good installer can learn how to terminate fiber in less than 2 hours.
Fiber does not have infinite bandwidth either! At least not the multimode fiber used in most premises networks. It's a lot higher than copper, but as you approach gigabit speeds, you are limiting the distances available for links to 500 meters or so.

Singlemode fiber, as used in telco and CATV networks, practically has infinite bandwidth. But it uses higher cost components and can be pricey for shorter links. It's not necessary for today's networks but may be for the next generation. (You've heard they are working on 10 GB Ethernet, haven't you?)

How about cost? Isn't that the bottom line for copper vs. fiber? Well, fiber prices continue to fall while copper prices (and the more sophisticated hardware needed to support high bandwidth transmission) rise. The cable plant is a wash - comparing Cat 5 and multimode fiber - both are about the same price by the time you consider everything (including fiber testers at $995 and copper testers at $4,000-6,000 and going up for Cat 6, 7 etc.)

It's the electronics that make the difference. A 10/100 Ethernet card for Cat 5 is $10-100, while a 10/100 fiber card (the new 100BASE-SX style) is $100-200 or so. And double the difference because you have to have electronics at each end of the link. Media converters from copper to fiber sell for as little as $100 and solve the problem of getting a fiber connection where a copper one now exists.

The additional cost of fiber is usually offset by the additional cost imposed by copper hubs (with the limited distance of copper - 90m - you need local telecom closets) and the cost of conditioned, uninterruptable power supplies (UPS), data-quality grounds and HVAC for every closet! These costs made one job estimate only $9 per desktop more with fiber - yet the customer still chose copper! Here's another viewpoint.

So why are 99% of all desktops connected with copper? The comfort factor. Installers and customers are both more comfortable with that old familiar copper wire (even if what they install has little in common with their simplistic perception!) and they like the fact that they save $100 or so on every desktop with copper.

The majority of backbones in large companies are fiber. They want the bandwidth and reliability of fiber, and the networking equipment vendors recommend fiber for the backbone. They expect to upgrade to higher bandwidth in the future, and only fiber offers upgradeability.

So what do we think you should do?
If you are a typical user, Cat 5e to the desk is fine. You probably use Fast Ethernet and might use Gigabit Ethernet in the future, and that's what Cat 5e is designed for. However, I suggest you make sure it is installed properly - or you are wasting your money.
Power users should go fiber to the desk today, running a cable with 2 multimode 62.5/125 fibers of the new high bandwidth 50/125 laser-optimized type (>500 MH-km at 850 and 1300 nm) for future 10 GBE applications. Will you need 10 GBE at the desk? Not unless you are a heavy graphics user, like CAD or prepress? Not designing airliners or cars on the desktop? Go back to Cat 5e.

What about Cat 5E or Cat 6?
Right now, Cat 6 is in limbo - no network calls for it and it needs a boost in performance for 10GbE. You get more performance, but no network is yet designed to operate on it. If you want a higher performance UTP cabling system - buy a complete solution from one vendor, require documentation on performance, and hope it has a purpose someday!

Can't I future-proof my network?
At the desktop -no. Flatly, no. You have no guarantee that anything you install for cabling today, Category "whatever" copper or multimode fiber, will be useful in another few years. That's why manufacturers offer 15-25 year warranties - they know you will not be using that cabling more than another few years! A lifetime warranty is the only one that makes sense, since its lifetime is very short! Maybe you could install multimode and singlemode fiber, but you would be the first!
In the backbone, maybe, if you install a large fiber count optical fiber cable with lots of spare singlemode fibers, you probably have a good chance of supporting your network for ten or twenty years. The backbone is easier to deal with since it changes a lot less than the desktop connection.

Silly Move Dept.
For some reason, the LAN migrated away from coax cable to UTP. Granted old "thicknet" Ethernet was a pain to deal with and expensive, but RG-58 ("thinnet" or "cheapernet") was cheap and reliable. GBE would run like a charm over CATV RG-6, and it's cheaper than everything but string!
Oh well, nobody said it was gonna make sense!

reference:  

http://www.thefoa.org/tech/fo-or-cu.htm

Using mod_rewrite to redirect web pages

There are plenty of tutorials to get this done but in its simpliest form redirecting an entire page to a different url all all together allows for greater internal security.  This can be done by using htaccess file to create a re-write rule.  A good example of code would look like this:

================================

   RewriteEngine on

   RewriteCond %{HTTP_HOST} ^x\.x\.x\.x$
   RewriteRule ^(.*)$ https://x.x.x.x/myapp/$1 [L,R=301]

   RewriteRule    ^$ app/webroot/    [L]
   RewriteRule    (.*) app/webroot/$1 [L]

======================================

Where "x" is the IP address separated by the dotted "." notation

Cheers!!!

Bash Internals a Researchers Eye View

Bash info, scripting examples, regex parameter substitution, interactive shell, and morekeywords:bash,shell,commmand,parameter,file,name,path,regular,expression,glob,login,mingetty,tty,console,terminal,screen,prompt,sudo,stdout,permission,permissionsdescription:Shell trivia and scripting examples including file name and path substitutions, as well as how to detect a live human logging in, and how to fix the session title and titlebar.Table of contents-----------------IntroductionLink to list of hintsDisabling xon xoff and detecting interactive loginRegular expressions and globbingChecking return status (return value) of programsCan't write a fileFixing the session titleUsing dd and gmime-uuencode to create passwordsA little rant about examplesIntroduction------------Shell programming and expecially shell variables are weird things. Therules are bizarre to those of use schooled in normal programminglanguages such as C, Perl, or Java. I'm not a shell programmer, butafter much painful, irritating, frustrating trial and error, (andhours of Google searches) I've managed to glean a few really usefulfacts. This document assumes that you are facile with the Linux shellbash, and that you are comfortable with shell commands and withviewing files, and comfortable viewing (and searching) man pages.By the way, it appears that the man page for bash is missing most ofthe available content. Heaven only knows why. For instance the manpage says "Expressions are composed of the primaries described aboveunder CONDITIONAL EXPRESSIONS." There is no heading "CONDITIONALEXPRESSIONS" in the man page.I couldn't find the list of CONDITIONAL EXPRESSIONS via the "infobash" command either. However, hope is not lost. Fedora (and probablymost distros of Linux) have full docs on the hard drive. Mine are at:file:///usr/share/doc/bash-3.1/bash.htmlSimply use your web browser to read the docs off your hard drive. ForFedora these docs are mostly in HTML format. They also appear to becomplete.You can always search Google, and many web sites will have the fulldocs.If you are frustrated with the shell, I feel your pain. Except for themost trivial operations, I use Perl for all sysadmin scriptingtasks. (I don't want to start a religious war here: if you like shellprogramming I'm happy for you. However, most of us will be moreproductive in Perl.) Perl makes sense and has many examples andencyclopedic documentation. For those times where Perl does't makesense (which I will readily admit occur on a regular basis), checkGoogle or "man perltoc" for the Perl docs table of contents.For examples of shell scripts, check out the scripts in /etc/init.d. Link to list of hints---------------------This information is implied by the bash man page (which is lackingexamples). There are also home nice hints at:http://linuxgazette.net/issue18/bash.htmlDisabling xon xoff and detecting interactive login--------------------------------------------------As of KDE4 (2008 and 2009) the terminal application konsole isbroken. It no longer accepts -ls. See my work around below.Reading between the lines, the -ls may have been added by one of thekonsole developers, and then removed by another developer (who Ipresume did not understand the implications).http://www.linuxquestions.org/questions/slackware-14/kde-konsole-gone-after-installing-kde4-608652/The work around is simple enough, and I hope you haven't wasted anhour looking for the solution.1) Run konsole2) Settings menu -> Edit Current Profile... -> General tab -> Command:3) Change to /bin/bash --loginThis changes a KDE config file Shell (probably some where such as/home/mst3k/.kde/share/apps/konsole/Shell.profile) that konsole usesat startup. By invoking bash as --login, shopt login_shell will be"on".Now your .bashrc or whatever will be able to distinguish when a humanis logged in, and when a script is running. The reason for this wouldbe to disable xon/xoff flow control for the human.From the bash prompt, "konsole -e /bin/bash --login" seems to work,but gives an interesting KDE error:[zeus ~]$ konsole -e /bin/bash --loginkonsole(659): Attempt to use QAction "change-profile" with KXMLGUIFactory![zeus ~]$ Undecodable sequence: \001b(hex)[?1034hAlso "/bin/bash -i" does *not* create an interactive session. I'mguessing this is due to shopt login_shell being somehow inherited bychild processes.Note: This information has subtle inaccuracies in the distinctionbetween "interactive shells" and "login shells". I hope to clarifythis soon. The Bash documentation says there is a difference, but doesnot get around to giving the reason(s) for the distinction.This example shows the solution two problems: how to disable the veryirritating software flow control xon and xoff mapped to keys control-x(C-x) and control-s (C-s). I'm an emacs user, and in emacs I use thosekeys constantly. Bash is set up for emacs command line editing, so allmy emacs reactions get used on the command line too, but co-minglingemacs with the semi-emacs keystroke support in bash can lead toissues. The big one was accidentally stopping i/o by hitting the xoffkey. This key hasn't been needed since they days of dedicated CRTterminals (without scroll back buffers). Heaven only knows why it isstill the bash default. I don't even use flow control on a runlevel 3non-graphical console session.Using shopt -q login_shell seems to be the modern and reliable way todetect interactive shell sessions. When the session is interactive,disable start and stop which are xon and xoff. ******Note: -ls only applies to older versions of konsole. See above.******There is a potential problem with this. The default state of terminal(console) applications such as KDE's konsole is *not* as a loginshell. This seems like a bug. To cure this obscure issue launchKonsole as:konsole -lsChange how Konsole is run in you start menu. Right click your startbutton (Fedora button, KDE button, whatever you call it). Select "MenuEditor". Click on one or more of the Terminal (konsole) entries, andadd " -ls" at the end of the "Command".******Note: -ls only applies to older versions of konsole. See above.******You can see the output of shopt in human readable form by leaving offthe -q option (-q for quiet):shopt login_shellor shopt# The newer (?) method of detecting an interactive shell.# This works with Fedora Core 6, and probably most modern versions of# Linux. Disable xon xoff, and alias rm to rm -iif shopt -q login_shell ; then      stty stop undef      stty start undef     alias rm='rm -i'fiBelow is another technique for testing to see if a login is aninteractive session. For reasons not quite clear, Apple's OSX has a problem setting and resetting the session name. It works under Linux,but not with OSX, and I can't figure out why Linux worksseamlessly. In any case, I created a weak workaround for OSX.The character strings being echoed are "escape sequences" for theterminal program. This seems to be more or less the same betweenxterm, "linux" (a terrible name for a tty since this is also the trueand real name of the operating system/kernel(?)), vt100, and mabe even"ansi" (another terrible name for a tty).# This works for OSX and should be fine for Linux too.# if [ ! -z "$(echo $- | grep i)" ]# Similar to the line above, but tests for 1 match instead of a# non-zero length return string. The shell variable $- contains the# values of the "set" command (which is different in Bash than in# csh(?) or some other shells). Do this:echo $-The result in my shell is "himBH". The "i" undocumented, but meansthat the shell is "interactive". The bash man page describes the otheroptions under the "set" section (try searching the man page for setwith multiple spaces in front "    set " or better yet forget man anduse browse the docs with Firefox from /usr/share/doc/ )Bash's "if" command with [ ] checks the boolean result. The shoptmethod is checking the command return value. Therefore using "echo"piped to "grep" you must check against equivalence to 1.I don't know why the command has to be surrounded by double quotes,parentheses, and preceded by $. if [ "$(echo $- | grep -c i)" == 1 ]then    stty stop undef    stty start undef    alias rm='rm -i'    # Don't echo except for a tty. Non-ttys (like scp) will break if    # you echo text to them.    # hostname -s    # id -nu    # echo -e -n  is bash specific (as opposed to a feature of /bin/echo)    # http://www.mit.edu/afs/sipb/project/outland/doc/rxvt/html/refer.html#XTerm    # 0 window title and icon name(?)    # 1 icon name    # 2 window title    # 30 type-of(?), usually Shell    #echo -ne "\033]1;one\007"    #echo -ne "\033]2;two\007"    echo -ne "\033]0;`id -nu`@`hostname -s`\007"fi# The following older code worked for a while, or at least in some cases.# This checks to see if the session has a prompt string of non-zero# length.# http://www.faqs.org/docs/bashman/bashref_68.html# Perhaps it stopped working when I made a small modification to my prompt.# In any case, it is less robust than the method above.# For interactive shells disable xon and xoff, and alias rm to rm -i# Use the a modern test.if [ ! -z "$PS1" ]then    stty stop undef    stty start undef    alias rm='rm -i'fiThis older method didn't work when scp'ing into the machine.I got the following result when using scp into the machine:[mst3k@zeus ~]$ scp tmp.txt hera.example.com:stty: standard input: Invalid argumentstty: standard input: Invalid argumenttmp.txt                                                       100% 1919     1.9KB/s   00:00[mst3k@zeus ~]$ scp x_next.txt hera.example.com:Regular expressions and globbing--------------------------------Globbing is use of * as a wildcard to glob file name listtogether. Use of wildcards is not a regular expression.These following examples should also work inside bash scripts. These may or maynot be compatible with sh. These are "interesting" regex or globbingexamples. I say "interesting" because they don't seem to follow thepath of "true" regular expressions used by Perl.[mst3k@zeus ~]$ echo ${HOME/\/home\//}mst3k[mst3k@zeus ~]$ echo ${HOME##home}/home/mst3k[mst3k@zeus ~]$ echo ${HOME##/home}/mst3k[mst3k@zeus ~]$ echo ${HOME##/home/}mst3k[mst3k@zeus ~]$ echo ${HOME##*}[mst3k@zeus ~]$ echo ${HOME##*/}mst3k[mst3k@zeus ~]$Checking return status (return value) of programs-------------------------------------------------Linux and unix-like systems are not inclined to tell you the returnstatus of commands you run at the shell prompt. Use this little oneline shell if statement to check true/false return values.[zeus ~]$ if  shopt -q login_shell; then echo "yes"; fi;yes[zeus ~]$ if !  shopt -q login_shell; then echo "yes"; fi;[zeus ~]$   Here is a better example, and includes a Perl script with differentexit values.Create a Perl script try.pl just like my try.pl that I've cat'edbelow. Here is a session transcript that should be clear. Yes, thePerl script is 6 lines. Yes, I strongly prefer my curly braces onseparate lines.[zeus ~]$ cat try.pl#!/usr/bin/perlif ($ARGV[0]){    exit(0);}exit(1);[zeus ~]$ if ./try.pl stuff ; then echo "yes"; else echo "no"; fi;yes[zeus ~]$ if ./try.pl ; then echo "yes"; else echo "no"; fi;no[zeus ~]$Can't write a file------------------There are cases (especially with Apache and CGI scripts) where you (atthe shell command line) or one or your scripts is unable to write to afile due to permissions. This will be true even when you sudo thewriting command. The short answer is: the shell permissions controlfile writing, not the permissions of the command. We will use anexample of a user www (think: apache) trying to write to a file ownedby mst3k. In reality mst3k wrote the script but due to variousconfiguration issues, the CGI scripts are running as www.Here is the solution (more explanation below). Add a tee command toyour sudoers file:www  ALL=(ALL) NOPASSWD:  /usr/bin/teeOr perhaps the more secure version:www  ALL=(ALL) NOPASSWD:  /usr/bin/tee -a /var/log/text.txtUse this command in your script:/bin/echo "i like pie" | sudo /usr/bin/tee -a /var/log/test.txt >/dev/nullFor instance you have a CGI script written in Perl, and www is insudoers for /bin/echo and the following does *not* work. I'll use aPerl script, but it is probably true even at the bash prompt. Note:adding /bin/echo to your sudoers doesn't solve the problem. You mightsolve the problem by using another shell and su'ing or sudo'ing thenew shell.#!/usr/bin/perl`/bin/echo "i like pie" | sudo /usr/bin/tee -a /var/log/test.txt > /dev/null`;my $id = `/usr/bin/id`;print "Content-type: text/html\n\nScript runs as:$id\n";exit(0);Keep in mind when trying to diagnose this problem that your script hasto run. The debugging processs has steps such as:1) Does the command work at the bash command line for the owner of the   directory/file?2) Does the command work at the bash command line for non-owners in sudoers?3) Did the CGI script run? CGI scripts can silently fail. There won't   be any http output, but you'll get no errors in your web browser   (unless you've got CGI::Carp enabled). There will be messages in   the Apache logs. Apache won't run scripts with group-write or   other-write privs, directories with group-write or other-write   privs, or that aren't owned by the directory owner   (/home/mst3k/public_html has to be owned by mst3k) and won't run   scripts that have no AddHandler or if ExecCGI is not enabled. There   are details about this elsewhere in these readme and mini howto   documents, but your .htaccess should include:Options +ExecCGIAddHandler cgi-script .plFixing the session title------------------------Most xterm software will put a session title in the windowtitlebar. The bash shell has an environment variable PROMPT_COMMANDthat is run every time the prompt is printed. This env var is missingon Apple Mac OSX, but you can easily add it to your .bashrc on anysystem.Briefly, the format is:export PROMPT_COMMAND='echo -ne "\033]0;title; echo -ne "\007"'Usually, we want this to be the userid, hostname, and current directory (pwdis "print working directory").export PROMPT_COMMAND='echo -ne "\033]0;${USER}@${HOSTNAME%%.*}:${PWD/#$HOME/~}"; echo -ne "\007"'Put the line above into your .bashrc file. You can test this two ways:1) "source" .bashrc by typing ". .bashrc"2) enter the export command at the bash promptThis is how the prompt changes correctly when you log off a host. Thismight also be called fixing the prompt, fixing the titlebar, titlebar, session name, xterm session name, konsole session name, changesession name, change title bar, change session when logging off,logoff session change, terminal session name change, titlebar tweaks,escape sequence to change titlebar, vt100 sequence, vt102 sequences. Related information is:shell variables, environment variables, env,set, bash, .bashrc, bashrc, .bash_profile.Not related to this (at least not directly related) is.bash_logout. There is no magic at logout that "resets" the prompt ortitle bar. Each shell knows what its prompt and title bar should be,and the prompt and titlebar commands are run every time bash printsthe prompt. However you *must* have the shell variable PROMPT_COMMANDset and this is one of many fundamental features that OSX fails to set.Note that the env command doesn't show PROMPT_COMMAND. This is becausePROMPT_COMMAND is a variable. You can only see PROMPT_COMMAND's valuewith the "set" command or with "echo $PROMPT_COMMAND". In fact, if you really want to know all about your environment (in thegeneral sense of the word) you need two commands, and I like to havethe env vars sorted (set automatically sorts):env | sortsetWhen I export PROMPT_COMMAND is it both an env var and a set var. I'mmissing the distinction between the two kinds of variables. Using dd and gmime-uuencode to create passwords-----------------------------------------------Use /dev/urandom instead of /dev/random. Urandom gives better data andworks better with dd.if=file  is read from file instead of rading from stdinibs=n  is read n bytes at a timecount=n   is copy n input blocksGetting the random input is easy, however, it is binary. We need toconvert to normal printing characters to produce a random stringuseful as a password. Encoding as uuencode or base64 handles thisproblem. dd if=/dev/urandom ibs=6 count=1 | base64dd if=/dev/urandom ibs=6 count=1 | gmime-uuencode -m -A little rant about examples----------------------------Authors of documentation, need to include a large number of examples.If you love your operating system then please include examples. Theoperating system with the most documentation examples will win thewar.

Building Subversion from Bleeding Edge Repos (CentOS/RHE)

There are times that you wanted to get the latest stable release software packages available, but is not readily found via the repos of your distribution of choice.  RHE and CentOS are know for its notoriety of  using very old and stable packages, albeit to say -- they carry older stocks.  RHE Engineers pride themselves for being well known in compiling source to RPM packages with security in mind.

Now, if you are the type of sysadmin/developer who wants to try out "bleeding edge" technologies you can always turn to downloading the source packages and doing the necessary leg-work to get what you wanted.   One such package that technical people can't live without is subversion.  Subversion technology allows for greater versioning control and code audit trail.  If you use RHE / CentOS you may want to look into these repos for some new features that may interest you.

http://pkgs.repoforge.org/subversion/

http://subversion.apache.org/download/

Cheers!!!

Permanent Redirection to HTTPS

Redirection of HTTP to HTTPS (80 - 443) is a nasty business and some of the items seen from the Internet would not really give you the exact procedure on how to do it. In this post I am going to give-away my "secret recipe" to totally do just that.   So without further introduction lets go down the details:

Requirement is that you have your mod_rewrite module loaded by apache so I won't show you how to that here since its already elementary.

Look at this piece of code and its one of those tadah moments!

==========================================================

#########################################
#### XXX: BEGIN EDIT FOR MOD_REWRITE ####
#### This is intended to force HTTPS ####
#### for all inbound HTTP requests ####


####
# This module (mod_rewrite) simply tells Apache2 that all connections to
# port 80 need to go to port 443 – SSL – No exceptions
####



    LoadModule rewrite_module modules/mod_rewrite.so


   RewriteEngine on


####
# The line below sets the rewrite condition for mod_rewrite.so.
# That is, if the server port does not equal 443, then this condition is true
####


ReWriteCond %{SERVER_PORT} !^443$


####
# The line below is the rule, it states that if above condition is true,
# and the request can be any url, then redirect everything to https:// plus
# the original url that was requested.
####


RewriteRule ^/(.*) https://%{HTTP_HOST}/$1 [NC,R,L]



#### XXX: END EDIT FOR MOD_REWRITE ####
#######################################

I guess the rest of the story resides in your ability to learn this promptly. Cheers!!!

ip_conntrack: table full, dropping packet

There are times when you need to increase a key value to your system to get tcp traffic as expected.

For this this type of problem:

Mar 4 22:21:05 viking1 kernel: printk: 4883 messages suppressed.
Mar 4 22:21:05 viking1 kernel: ip_conntrack: table full, dropping packet.
Mar 4 22:21:10 viking1 kernel: printk: 4654 messages suppressed.
Mar 4 22:21:10 viking1 kernel: ip_conntrack: table full, dropping packet.
Mar 4 22:21:15 viking1 kernel: printk: 3943 messages suppressed.
Mar 4 22:21:15 viking1 kernel: ip_conntrack: table full, dropping packet.
Mar 4 22:21:20 viking1 kernel: printk: 3392 messages suppressed.

------------------
CentOS 5 Solution:
------------------

Increase your ip_conntrack_max value from the default of

cat /proc/sys/net/ipv4/ip_conntrack_max
65536

to:

cat /proc/sys/net/ipv4/ip_conntrack_max
1131072

Issue the command:

echo 1131072 > /proc/sys/net/ipv4/ip_conntrack_max


To check the number of current sessions open for this host:

wc -l /proc/net/ip_conntrack

------------------
CentOS 6 Solution:
------------------

To print current limit type:

# sysctl net.nf_conntrack_max

Output:

65536

To increase this limit to e.g. 100000, type:

# sysctl -w net.nf_conntrack_max = 100000

To make this settings permanent add the following line to /etc/sysctl.conf file:

net.nf_conntrack_max = 100000

The following will tell you how many sessions are open right now:

# wc -l /proc/net/nf_conntrack


Done! Cheers!!!

Remote Linux Desktop Sharing: NoMachine

I have used tools in the past that allows me remotely manage shared linux desktop sessions with NoMachine.

For 64bit machines: http://www.nomachine.com/download-package.php?Prod_Id=3592

You will have to install three (3) components: a) nxclient; b) nxnode; c) nxserver

Cheers!!!

RAID status check for CentOS/RH/Fedora

For those who want a quick/elegant way of checking the software RAID status of your disk in RH/CentOS/Fedora use this command. "mdadm"

e.g.

mdadm --detail /dev

(the /dev, pertains to the device block that currently holds your RAID)

Cheers!!!

ERROR: /var/cache/apt/archives/gstreamer0.10-plugins-bad_0.10.22-3_amd64.deb: trying to overwrite '/usr/lib/gstreamer-0.10/libgstxvid.so', which is also in package gstreamer0.10-plugins-really-bad 0.10.22-0.1

There is a critical bug with the new LinuxMint Debian edition of 11. During an initial apt-get upgrade if you get this error:

/var/cache/apt/archives/gstreamer0.10-plugins-bad_0.10.22-3_amd64.deb: trying to overwrite '/usr/lib/gstreamer-0.10/libgstxvid.so', which is also in package gstreamer0.10-plugins-really-bad 0.10.22-0.1

To get around this issue the resolution would be to install all gstreamer plugins.

apt-get install gstreamer0.10-plugins

Once this has been installed retry the upgrade process, it should successfully install.

Cheers!!!

Postfix "+" configuration How To

For you to get a wildcard domain to start working under postfix you need to add this critical piece of information via your "main.cf"

recipient_delimiter = +

Add the email you want for this to work. Add an Alias entry to acting as a catch basin for the email account. Afterwards reload postfix.

Done.

IPv6 Quick check your system

Here is a one liner quick check to Ipv6 your system.

At the command prompt:

[ -f /proc/net/if_inet6 ] && echo 'IPv6 ready system!' || echo 'No IPv6 support found! Re-Compile the kernel!!'


Neat. :)

ip_conntrack problem: error: "net.ipv4.ip_conntrack_max" is an unknown key

To fix this issue do the following:

1. modprobe ip_conntrack
2. lsmod |grep conn -- if you see entries it means modules have been loaded correctly
3. sysctl -w -- to write the changes you made under /etc/sysctl.conf
4. sysctl -p -- to view the changes and see if it was actually loaded.

Command to check CronJobs

There are times that you need to immediately check if there are run-away cron entries hidden somewhere. This terminal command will save you time doing just that.


for user in $(cut -f1 -d: /etc/passwd); do crontab -u $user -l; done

Now, if for example you need to issue this remotely you can do it like this:


ssh someusername@some_remote_host sudo for user in $(cut -f1 -d: /etc/passwd); do crontab -u $user -l; done

Enjoy!

Error writing message: File too large

A postfix error that occurs when a user's mailbox is full.
Regularly caused by cronjob output, particularly when there are systematic errors in the cron job that lead to long and frequent email reports.

mailbox_size_limit and virtual_mailbox_limit may be relevant.
You can use
postconf | egrep '(mailbox_size_limit|virtual_mailbox_limit)'
...to see what size they are currently set at, which is probably 50MB.

Set this to a higher limit (in your .cf files), or even to 0 to remove limits.

Fix issue with "@" on a Perl Script

There are times that you encounter problems executing PERL scripts which failed for example this one:


Possible unintended interpolation of @23mxxxx in string at
/usr/local/scripts/mysqltunerv.pl line 212 (#1)
(W ambiguous) You said something like `@foo' in a double-quoted string
but there was no array @foo in scope at the time. If you wanted a
literal @foo, then write it as \@foo; otherwise find out what happened
to the array you apparently lost track of.

Name "main::23mxxxx" used only once: possible typo at
/usr/local/scripts/mysqltunerv.pl line 212 (#2)
(W once) Typographical errors often show up as unique variable names.
If you had a good reason for having a unique name, then just mention it
again somehow to suppress the message. The our declaration is
provided for this purpose.

NOTE: This warning detects symbols that have been used only once so $c, @c,
%c, *c, &c, sub c{}, c(), and c (the filehandle or format) are considered
the same; if a program uses $c only once but also uses any of the others it
will not trigger this warning.

SOLUTION:

Escape the character before "@" with "\" this should fix it.

Advice to employees on the proper use of the System Administrator's valuable time

(In following examples, we will substitute the name "Ted" as the System Administrator)

* Make sure to save all your MP3 files on your network drive. No sense in wasting valuable space on your local drive! Plus, Ted loves browsing through 100+ GB of music files while he backs up the servers.
* Play with all the wires you can find. If you can't find enough, open something up to expose them. After you have finished, and nothing works anymore, put it all back together and call Ted. Deny that you touched anything and that it was working perfectly only five minutes ago. Ted just loves a good mystery. For added effect you can keep looking over his shoulder and ask what each wire is for.
* Never write down error messages. Just click OK, or restart your computer. Ted likes to guess what the error message was.
* When talking about your computer, use terms like "Thingy" and "Big Connector."
* If you get an EXE file in an email attachment, open it immediately. Ted likes to make sure the anti-virus software is working properly.
* When Ted says he coming right over, log out and go for coffee. It's no problem for him to remember your password.
* When you call Ted to have your computer moved, be sure to leave it buried under a year-old pile of postcards, baby pictures, stuffed animals, dried flowers, unpaid bills, bowling trophies and Popsicle sticks. Ted doesn't have a life, and he finds it deeply moving to catch a glimpse of yours.
* When Ted sends you an email marked as "Highly Important" or "Action Required", delete it at once. He's probably just testing some new-fangled email software.
* When Ted's eating lunch at his desk or in the lunchroom, walk right in, grab a few of his fries, then spill your guts and expect him to respond immediately. Ted lives to serve, and he's always ready to think about fixing computers, especially yours.
* When Ted's at the water cooler or outside taking a breath of fresh air, find him and ask him a computer question. The only reason he takes breaks at all is to ferret out all those employees who don't have email or a telephone.
* Send urgent email ALL IN UPPERCASE. The mail server picks it up and flags it as a rush delivery.
* When the photocopier doesn't work, call Ted. There's electronics in it, so it should be right up his alley.
* When you're getting a NO DIAL TONE message at your home computer, call Ted. He enjoys fixing telephone problems from remote locations. Especially on weekends.
* When something goes wrong with your home PC, dump it on Ted's chair the next morning with no name, no phone number, and no description of the problem. Ted just loves a good mystery.
* When you have Ted on the phone walking you through changing a setting on your PC, read the newspaper. Ted doesn't actually mean for you to DO anything. He just loves to hear himself talk.
* When your company offers training on an upcoming OS upgrade, don't bother to sign up. Ted will be there to hold your hand when the time comes.
* When the printer won't print, re-send the job 20 times in rapid succession. That should do the trick.
* When the printer still won't print after 20 tries, send the job to all the printers in the office. One of them is bound to work.
* Don't use online help. Online help is for wimps.
* Don't read the operator's manual. Manuals are for wussies.
* If you're taking night classes in computer science, feel free to demonstrate your fledgling expertise by updating the network drivers for you and all your co-workers. Ted will be grateful for the overtime when he has to stay until 2:30am fixing all of them.
* When Ted's fixing your computer at a quarter past one, eat your Whopper with cheese in his face. He functions better when he's slightly dizzy from hunger.
* When Ted asks you whether you've installed any new software on your computer, LIE. It's no one else's business what you've got on your computer.
* If the mouse cable keeps knocking down the framed picture of your dog, lift the monitor and stuff the cable under it. Those skinny Mouse cables were designed to have 55 lbs. of computer monitor crushing them.
* If the space bar on your keyboard doesn't work, blame Ted for not upgrading it sooner. Hell, it's not your fault there's a half pound of pizza crust crumbs, nail clippings, and big sticky drops of Mountain Dew under the keys.
* When you get the message saying "Are you sure?", click the "Yes" button as fast as you can. Hell, if you weren't sure, you wouldn't be doing it, would you?
* Feel perfectly free to say things like "I don't know nothing about that boneheaded computer crap." It never bothers Ted to hear his area of professional expertise referred to as boneheaded crap.
* Don't even think of breaking large print jobs down into smaller chunks. God forbid somebody else should sneak a one-page job in between your 500-page Word document.
* When you send that 500-page document to the printer, don't bother to check if the printer has enough paper. That's Ted's job.
* When Ted calls you 30 minutes later and tells you that the printer printed 24 pages of your 500-page document before it ran out of paper, and there are now nine other jobs in the queue behind yours, ask him why he didn't bother to add more paper.
* When you receive a 130 MB movie file, send it to everyone as a high-priority mail attachment. Ted's provided plenty of disk space and processor capacity on the new mail server for just those kinds of important things.
* When you bump into Ted in the grocery store on a Sunday afternoon, ask him computer questions. He works 24/7, and is always thinking about computers, even when he's at super-market buying toilet paper and doggie treats.
* If your son is a student in computer science, have him come in on the weekends and do his projects on your office computer. Ted will be there for you when your son's illegal copy of Visual Basic 6.0 makes the Access database keel over and die.
* When you bring Ted your own "no-name" brand PC to repair for free at the office, tell him how urgently he needs to fix it so you can get back to playing EverQuest. He'll get on it right away, because everyone knows he doesn't do anything all day except surf the Internet.
* Don't ever thank Ted. He loves fixing everything AND getting paid for it!

Now this is assuming that you are like Ted! But I am not Ted and most of the stuff here are fun anyways! :P

ATTRIBUTION: http://sysadminday.com/time.html

EPEL Repositories for your CentOS

To enable EPEL (Extra Packages for Enterprise Linux) for CentOS 5 x86 or x64, log in to SSH on your server and execute the following command (dependent on your OS – unsure of what version of CentOS you are running?):

CentOS 6.x 32-bit (x86/i386):

rpm -Uvh http://download.fedora.redhat.com/pub/epel/6/i386/epel-release-6-5.noarch.rpm

CentOS 6.x 64-bit (x64):

rpm -Uvh http://download.fedora.redhat.com/pub/epel/6/x86_64/epel-release-6-5.noarch.rpm

CentOS 5.x 32-bit (x86/i386):

rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/i386/epel-release-5-4.noarch.rpm

CentOS 5.x 64-bit (x64):

rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/x86_64/epel-release-5-4.noarch.rpm



Disable EPEL Repo:

If you want to disable the EPEL repo on your server, set “enabled=0″ in “/etc/yum.repos.d/epel.repo”:

vim /etc/yum.repos.d/epel.repo

Transfer Files from Linux to a Samsung Tab 10.1v

There are instances that Samsung won't mount automatically there is a couple of fixes out there but this one works fine with my setup. I am using a Mint Linux

Works on 32bit and 64bit Linux. Just a quick guide on how to configure Linux for file transfers using MTP. The instructions and config is intended for Ubuntu Natty 32bit and 64bit, though the same process will work on other platforms – the only real difference being the package manager commands and possibly the config file locations.

The attached files are for the Galaxy Tab 10.1v but should work for the 10.1g / 10.1 as well. See the end of the post to learn how to modify this config to work for other devices.

How to configure for gMTP and other Media Sync tools

1) Install aptitude

sudo apt-get install aptitude

2) Install mtp-tools and mtpfs

sudo aptitude install mtpfs mtp-tools

3) Download this file: 98-gtab.zip for 32bit Linux or 98-gtab.rules-AMD64.zip for 64bit Linux to your desktop.

4) Extract the 98-gtab.rules file to your desktop

5) Copy the rules file to /etc/udev/rules.d/

sudo cp ~/Desktop/98-gtab.rules /etc/udev/rules.d

6) Reboot

7) Connect your Tab

8) Run the following command to confirm it is working:

ls /dev | grep gtab

This command should return “gtab” if successful. If not, follow the “Modifying” guide below.

9) Download / install gMTP

sudo apt-get install gmtp

10) Open gMTP and select “connect” from the menu



Setting up for Automount (Optional, but recommended)

Before follow these instructions, you must have completed Steps 1-8 above.

1) Edit your fstab file to add your gtab:

sudo gedit /etc/fstab

2) Add this to the end of the file:

#gtab

mtpfs /media/gtab fuse user,noauto,allow_other 0 0

3) Save and exit

4) Open fuse.conf for editing:

sudo gedit /etc/fuse.conf

5) Find the following line and remove the #

#user_allow_other

6) Save and exit

7) Open and edit the groups file:

sudo gedit /etc/group

8) Find the details for the group ‘fuse’ and append your username to the end of the line eg.

fuse:x:104:

9) Save and exit

10) Create the folder to mount your Tab:

sudo mkdir /media/gtab

11) Take ownership of the folder:

sudo chown :users /media/gtab

12) Reboot

13) Plug in your Tab.

14) Click on the Places menu and click gtab.

15) You’re in business!



Modifying for other devices

If the above doesn’t work immediately on the 10.1g / 10.1 (I have only tested on the 10.1v), you can easily edit the rules file to support your device.

1) Install lsusb

sudo apt-get install lsusb

2) Run lsusb

lsusb

3) Check the output of this command to find your device. The 10.1v is shown like this:

Bus 001 Device 010: ID 04e8:6860 Samsung Electronics Co., Ltd

4) Make a note of the Vendor and Product IDs. In the example above, the vendor ID is 04e8 and device ID is 6860 (note 04e8:6860 in the output).

5) Open the rules file for editing (if it’s not already in /etc/udev/rules.d, copy it there now)

sudo gedit /etc/udev/rules.d/98-gtab.rules

6) Find this line

ATTRS{idVendor}==”04e8″, ATTRS{idProduct}==”6860″, MODE=”0666″ SYMLINK+=”gtab”

7) Replace the Vendor ID (04e8) and Product ID (6860) with the ones that you got from step 3 above.

8) Save and exit

9) Reboot

10) Follow step 7 onward in the first guide above



32bit RULES FILE:

ACTION!=”add”, GOTO=”gtab_rules_end”
SUBSYSTEM!=”usb|usb_device”, GOTO=”gtab_usb_end”

ATTRS{idVendor}==”04e8″, ATTRS{idProduct}==”6860″, MODE=”0666″ SYMLINK+=”gtab”

LABEL=”gtab_usb_end”

LABEL=”gtab_rules_end”

64bit RULES FILE:

ACTION!=”add”, GOTO=”gtab_rules_end”
SUBSYSTEM!=”usb|usb_device”, GOTO=”gtab_usb_end”

ATTRS{idVendor}==”04e8″, ATTRS{idProduct}==”6860″, MODE=”0777″ SYMLINK+=”gtab”

LABEL=”gtab_usb_end”

LABEL=”gtab_rules_end”