Monday, 22 June 2009

Symbolic Links in ProFTPd

A symbolic link (also referred to as a "symlink") is a file whose contents contain the name of the file to which the symbolic link points. For example:
  lrwxrwxrwx   1 root     root           11 Mar  2  2000 rmt -> /sbin/rmt

The file rmt contains the nine characters /sbin/rmt. The reason symbolic links fail when chroot(2) is used to change the position of the root (/)of the filesystem is that, once / is moved, the pointed-to file path changes. If, for example, if chroot(2) is used to change the filesystem root to /ftp, then the symlink above would be actually be pointing to /ftp/sbin/rmt. Chances that that link, if chroot(2) is used, now points to a path that does not exist. Symbolic links that point to nonexistent files are known as dangling symbolic links. Note that symbolic links to files underneath the new root, such as symlinks to a file in the same directory:
  > pwd
  /var/ftp
  > ls -l
  -rw-r--r--   1 root     root            0 Jan 16 11:50 tmpfile
  lrwxrwxrwx   1 root     root            7 Jan 16 11:50 tmplink -> tmpfile

will be unaffected; only paths that point outside/above the new root will be affected.

so clearly this will not work in a ProFTPd default directory

The trick is to use re-mount the directory you want listed again

To have an exact duplicate of the /var/ftp/incoming directory available in /home/bob/incoming and /home/dave/incoming, use one of these commands:

  • Linux (as of the 2.4.0 kernel):
      mount --bind /var/ftp/incoming /home/bob/incoming
      mount --bind /var/ftp/incoming /home/dave/incoming

    or, alternatively:
      mount -o bind /var/ftp/incoming /home/bob/incoming
      mount -o bind /var/ftp/incoming /home/dave/incoming



On Kubuntu 9.x with kernel 2.6.28-11-generic the command was:
sudo mount --bind /media/disk/Sorted\ MP3/ /home/sharedftp/download/Music/

This mounted the Sorted MP3 directory under the FTPServer DefaultRoot directory.

In order to have these tricks persist, to survive a system reboot, the /etc/fstab file may need to have these mounts added

fstab

to mount a folder locally to another folder using --bind, ie. mount --bind /path1/ /path2/
/path1 /path2 bind defaults,bind 0 0

To mount a folder with spaces in fstab use "\040"

/media/disk/Sorted\040MP3/ /home/sharedftp/download/Music/ bind defaults,bind 0 0
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Sunday, 7 June 2009

Satellite Positioning

Hardware Components

LNB

There is great post by ShaneW at

http://techies.co.za/phpBB2/viewtopic.php?t=5368&start=0&postdays=0&postorder=asc&highlight=






Hi guys. I was asked to explain to a few colleagues how an LNB works so I wrote up a bit of an explanation, thought it might help a few people on here aswell.
Please let me know if you have any comments/questions/changes.

LNB stands for Low Noise Block Down converter. Its main function is to convert a Block(Group) of High frequency signals to a lower frequency block, amplify it and give it to the decoder/receiver.
Satellites transmit and receive signals in the 3GHz – 5GHZ (Cband) and 10GHZ- 13GHz (KU Band) range, bear in mind that 5 GHZ=5 000 MHz = 5 000 000 KHz = 5 000 000 000 Hz (cycles per second). When signals are in this range, a coax cable is not a very conductor and you would lose most of your signal. This is where an LNB comes in, it converts the high frequency signal, coming from the satellite, to a lower more manageable frequency. These frequencies are in the 950 MHz to 2150 MHz range (L Band) and this is referred to as IF (intermediate frequency). Some High-end satellite earth stations use a LNA (Low Noise Amplifier) which doesn’t perform the Down-conversion, the high frequency signals are transported on a line, but it is expensive as you would need a waveguide(hollow tube with the correct dimensions for that frequency.)
Most satellite decoders are designed to receive L – Band signals, this is why we can use a satellite decoder to receive either C-Band or KU-Band, because they are both in the same frequency range (L-Band), after being down-converted by the LNB.
The First circuit in the LNB is a filter circuit, which removes all the unwanted signals, including any ‘out of band’ noise, it then passes the wanted frequencies to an amplifier which amplifies the small signal from the satellite. It then goes to the mixer circuit. How an LNB down-converts to a lower frequency is by the process of mixing. It uses a LO (Local oscillator), which is just a circuit that gives a specific frequency out, this signal has no Data or program content on it, it is just a ‘pure’ carrier. This LO signal, is then added to the signal that is coming from the satellite.
When you add 2 signals together you get a few results:
When we mix the LO FREQ with the SAT FREQ we would typically get the frequencies LO+SAT, LO-SAT, SAT-LO, LOxSAT, LO and SAT. Out of all of these signals that are produced we only want 1 of them, so the wanted freq would be filtered out and sent down the coax cable to our Decoder, sometimes we use the LO-SAT and sometimes the SAT-LO, just depending on what will get us to L-B and.
Here is an example:
Hope Channel on C-Band is transmitted at 4070 MHZ and the Local oscillator of a C-Band LNB is 5150 MHz, when these 2 signals are mixed inside the LNB, there are a few results but the one we want in the L-Band range ( LO – SAT ) 5150Mhz – 4070 MHz = 1080 MHz is filtered out and given out the decoder.
Most Decoders do this calculation for you so that you only have to insert the Satellite frequency into the decoder, provided that the LO frequency programmed into the decoder is correct. This does sometimes become a problem, in SA for instance we use KU-Band LNBs with a High LO of 10.7 GHz and most of the rest of the world uses 10.6 GHz, so most imported decoders are set to 10.6 GHz LO as standard. This is How it would work:
Say for instance we had a channel on 12 GHz, we would program this frequency into our decoder. So the decoder does its calculation 12 GHz-10.6 GHz(SAT-LO) = 1.4 GHz so it will look at 1.4 GHz ( 1400 MHz) for the signal. BUT our LNB is actually a South African type and its LO freq is 10.7 GHz. So what is happening in the LNB is 12 GHz – 10.7 GHz (SAT-LO) = 1.3 GHz. The signal is there, but it is not where the decoder assumes it to be and will give us a ‘no signal’ error. This is why it is important to give the correct LNB LO frequency details to your decoder.
A LNB also requires some power to turn it on and power its circuits. This is given by the decoder along the coax cable. So, going up to the dish we have the DC supply voltage and coming down we have the RF signal.
To save space on the satellite and allow more channels to be added, they use 2 polarities, Horizontal and Vertical. Circular polarization can also be used but I won’t attempt to explain this as I don’t fully understand how they do it yet. Polarization is basically the way the antenna is mounted, either parallel to the ground (Horizontal – Most TV antennas) or Perpendicular to the ground (Vertical – Like your car’s FM aerial). When a receive Aerial/Antenna is placed in the opposite polarity to the transmitter, a large amount of signal (If not all) is not received, so therefore they can put channels on horizontal and vertical on the satellite, without them interfering too much. This is what you are adjusting when you turn the ‘skew’ of your LNB.
Inside your LNB, you have 2 small aerials that sit inside, at 90 degrees to each other. The one will be Vertical and the other Horizontal, and they are initialized by either a 13V (Vertical) or 18/19V (Horizontal) DC supply coming from your decoder. Your decoder automatically switches between Vertical and Horizontal, depending on the polarization of the required channel.
On KU Band to get more channels onto the satellite, they expand the bandwidth and add more channels/transponders. They now introduce 2 LO’s into the LNB, A Low and a High, the high LO is initialized by a 22kHz tone on the cable. The Frequency of the Low Band would typically be 10.7 GHz – 11.7 GHz and the High Band 11.7 GHz – 12.85 GHz, produced by a LO of 9.75 GHz or 10.7 GHz respectively.
There are 4 states that an LNB could be in, provided that it as a dual band unit: Horizontal - High Band, Horizontal – Low Band, Vertical - High Band and Vertical - Low Band.


Dish Pointing

How to align a dish yourself:

Yes it is most definitely possible to do a self install, without any fancy test gear, just get the basics right!
You simply need a good sense of direction, a compass, a school protractor and a builders level, and some spanners that fits the nuts!. Of course you can always buy one of those caravaners kits because there is a simple pointing device in there, and then follow those directions! and a lot of patience is needed!

Make sure the pole mount that you screw to the wall is Vertical in all directions, as this make the pointing exercise much easier.
Mount the antenna on the pole

SKEW angle setting:

(a) Set the ELEVATION angle (up and down) in such a way as to make sure the LNB is Horizontal to the ground (the part point into the antenna).Temporarily lock the antenna in that position just so that it does not move on you.

(b) Now looking into the antenna, adjust the LNB skew angle, down from the Horizontal, rotation clockwise, to approximately the 16H00 position.

(c) Use a simple school protractor, set 0 degree to horizontal, and then turn the LNB clockwise to angle calculated.

(d) lock the LNB in place tight enough so that it does not move on you, and mark the position. If you get this right now then later skew angle adjustments may not be needed at all!.

SET the ELEVATION:

(a) to the calculated value, use the scale on the side of the antenna bracket, as this scale should already compensate for the offset angle.

(b) the pole mount is vertical, this angle will be almost perfectly correct

With the above two set you have now eliminated two of the 3 variables and only azimuth is now needed to be set!

SET the AZIMUTH:

(a) connect up the the cables, switch on the PVR, choose Mnet 101.

(b) IF this is a new PVR, then I suggest that you connect it up at home. let it scan and activate the card BEFORE you leave for your holiday home.

(c) Use the compass to find the basic direction, point the LNB arm of the antenna in that direction. Mark the position on the flange so that at least you know where that direction is.

(d) Now rotate the antenna SLOWLY in one direction until you get a signal, ( that is if you did not have a single immediately). Move until the antenna is obviously completely off position.

(e) if no signal move in opposite direction, till you get a signal, set on maximum ( should be more than 80%), and mark the position.

(f) Now deliberately move off this point in one direction till the signal drops to "zero", mark the position.

(g) Move in opposite direction till you go through maximum and drop off again to "zero", Mark that position.

(h) Set the azimuth half way between to two marks, and that should be close to the original maximum position.

(i) tighten bolts so that antenna will not move but beware of over tightening!

PEAK the elevation

(a) Now do the same as you did azimuth wise, vertically.

(b) MARK the position, loosen the clamps slightly, enough to allow antenna to just move, Move antenna UP till signal drops off to "zero", mark.

(c) Go DOWN till you get zero and mark. Divide by two and that should be where you set it originally!

(d) tighten elevation clamps

Peak the skew angle as previously described, tighten clamps enough to hold BUT beware of over tightening

[gmap]
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South Africa Satellite Information

General known satellites in South Africa

[gmap]

For a full list go to: http://www.lyngsat.com/tracker/europe.html
So both these satellites Sesat and W4 share the 36° East orbital position. The W series provide increased power and broader coverage with respect to the previous generation EUTELSAT II satellites.

Eutelsat W4

Sesat W4image

Eutelsat SESAT

imageimage 

Intelsat 7

image

Intelsat coverage map

So from the above coverage maps it is clear that the SESAT satellite is suppose to give a better reception in some parts of South Africa. The channels that is present on a satellite can be tracked by various websites, Lyngsat have up to date satellite frequency charts

http://www.lyngsat.com/sesat.html

http://www.lyngsat.com/intel7.html

http://www.lyngsat.com/intel10.html

http://www.lyngsat.com/intel68.html

http://en.kingofsat.net/tv-68.5E.php

 

Multichoice South Africa on Intelsat 7 at 68.5°E

These charts can be by viewed via Frequencies, Packages or Satellites, and as such MC South Africa is a “Package” that is available on the above mentioned satellites and is presented as follows on their website at http://www.lyngsat.com/packages/mcsafrica.html

 

Freq.
Tp		   Channel Name   Enc. system SID VPID APID Beam
10970 V
tp A7		                
SR 30000
FEC 5/6		 image KykNet image Irdeto 2 251 5005 6007 Af South Africa
                 
                 

Colour codes used on the package charts:
clear
encrypted
HD/clear
HD/encrypted
interactive

and this data can be used to configure / setup your decoder to receive the channels, obviously to receive packages like MC South Africa (MultiChoice South Africa) you need a decoder capable of decoding the “Enc. system” encryption e.g. Irdeto 2. So MultiChoice have a range of decoders available for purchase that use smartcard technology to decode the encrypted channels. This bring me to the following section of this article namely Free to Air channels (This is channels available on the satellites you don’t have to pay to see or is without encryption)

Free to Air Channels

Free To Air satellite is a term used to describe satellite signals which you can legally receive without a subscription.

Free To Air satellite programming is not encrypted.

A satellite free to air installation can be accomplished by most people that have the patience to follow instructions and a moderate electronic knowledge. If this is not for you, it will be far easier for you to contact a local satellite installer in your area to assist you. This tutorial assumes you wish to receive a single fixed satellite and not using a dish mover or rotor.
For most broadcasts in South Africa, a dish size of 90cm is sufficient. Larger dish sizes may be required for more northern or out of footprint locations.
In order to receive all channels, reception of both PAS7 & PAS10 at 68,5 degrees East on a 90cm satellite dish is required. If you cannot access all the channels listed, your dish is either not aligned properly and/or you're using a too small dish.

Channels available

Television

The following are some of the channels you'll pick up once entering the settings below:
Mindset Learning, Mindset Health, Botswana TV, Vivid Mosiac, God TV Africa, Hope Channel Africa, ITV, Astro and various commercial channels.

Radio

Radio2000, SAFM, Ikwekwezi FM, 5FM, RSG, Lesedi FM, Lotus FM, Metro FM, Good Hope FM, YFM, Classic FM, DW Radio, Radio Pulpit/Kansel, Impact Radio, Radio Pretoria, Trans World Radio, Channel Africa.

Settings for the FTA Setup

Before setting up your decoder, please ensure that your decoder software is upgraded to the latest version.
To perform a software upgrade:

Press the MENU button.

Select "ADVANCED OPTIONS" and press OK.

Select "DSD UPGRADE" and press OK.

The decoder should start to upgrade the software now. If you are not sure about the version of your decoder software, you can contact Multichoice or your local DSTV technician/supplier and they will be able to help you.

Also ensure the LNB High frequency is set to 10700

Step 2:

Press menu

Select "Advanced Options"

Select "Dish Installation"

Enter the pin "9949"

Select "Network Configuration"

Select "Network 2 Setup" NB: Leave "Network 1 Setup (Home)" unchanged!!

Set Signal Setup to "Enabled" by selecting it, and moving left or right

Set Frequency to "11170"

Set Symbol Rate to "26652

Set Polarization to "Vertical"

Set FEC to "5/6"

Select "Accept these settings"

Step 3:

Select "Network 3 Setup"

Set Signal Setup to "Enabled"

Set Frequency to "11625"

Set Symbol Rate to "15000

Set Polarization to "Vertical"

Set FEC to "3/4"

Select "Accept these settings"

Step 4:

Select "Network 4 Setup"

Set Signal Setup to "Enabled"

Set Frequency to "11674"

Set Symbol Rate to "26652

Set Polarization to "Vertical"

Set FEC to "5/6"

Select "Accept these settings"

Step 5:

Select "Network 5 Setup"

Set Signal Setup to "Enabled"

Set Frequency to "12522"

Set Symbol Rate to "26657

Set Polarization to "Horizontal"

Set FEC to "1/2"

Select "Accept these settings"

Step 6:

Select "Network 6 Setup"

Set Signal Setup to "Enabled"

Set Frequency to "12562"

Set Symbol Rate to "26657

Set Polarization to "Horizontal"

Set FEC to "1/2"

Select "Accept these settings"

Step 7:

Select "Network 7 Setup"

Set Signal Setup to "Enabled"

Set Frequency to "12682"

Set Symbol Rate to "26657

Set Polarization to "Horizontal"

Set FEC to "1/2"

Select "Accept these settings"

Step 8:

Select "Network 8 Setup"

Set Signal Setup to "Enabled"

Set Frequency to "12722"

Set Symbol Rate to "26657

Set Polarization to "Vertical"

Set FEC to "1/2"

Select "Accept these settings"

Step 9:

Exit once to go back to the "Dish Installation" menu

Select "Scan All Networks"

Your decoder will go into scanning mode and might take a while to scan all 9 networks. Do not interrupt the process even if it seams to take longer than you expected!

Once completed, your picture will return as normal

To access you public channels, press the "TV button" on your remote control.
The "Bouquet Options" menu will appear.
Select "Public PAS7/10"
Pressing any of the arrow buttons on your remote, will open the screen with all the available Free to Air channels.
Simply select the channel you wish to view and press ok to tune.
To access the radio channels, simply select the "music note" on your remote (while still on Public PAS7/10 bouquet) and select which channel you would like to listen.

Tested Free-to-Air settings

Freq

use NIT

Pol

SR

FEC

Description

11170

Yes

Vertical

26652

5/6

Sentech Vivid bouquet

11625

Yes

Vertical

15000

3/4

BTV

11674

Yes

Vertical

26652

5/6

vivid

12522

Yes

Horizontal

26657

1/2

  

12562

Yes

Horizontal

26657

1/2

View Africa Network

12577

Yes

Vertical

3378

3/4

ManaSat

12682

Yes

Horizontal

26657

1/2

Novacom

12722

Yes

Vertical

26657

1/2

  

12722

Yes

Horizontal

26657

2/3

FTV

 

Radio stations that was added:

 

Logo

Channel Name

Satellite

Beam

Video/Audio

clip_image001[4]

1 Africa

clip_image002[282]

Intelsat 10

Africa & Europe

DVB

clip_image003[4]

5 FM

clip_image002[283]

Intelsat 7

South Africa

DVB

Ackermans Stores

Intelsat 7

South Africa

DVB

CDC Radio Channel

Intelsat 7

South Africa

DVB

clip_image004[30]

Channel Africa

clip_image002[284]

Intelsat 10

Africa & Europe

DVB

clip_image005[6]

Channel Islam International

clip_image002[285]

AfriStar 1

East

DVB

clip_image006[62]

Classic FM

clip_image002[286]

Intelsat 7

South Africa

DVB

Clicks Stores

Intelsat 7

South Africa

DVB

clip_image007[4]

CNA Live

Intelsat 7

South Africa

DVB

CVC Africa

Intelsat 10

Africa & Europe

DVB

Divine Radio

Intelsat 10

Africa & Europe

DVB

Fusion FM

Intelsat 7

South Africa

DVB

Good Hope FM

clip_image002[287]

Intelsat 7

South Africa

DVB

clip_image008[4]

Ikwekwezi FM

clip_image002[288]

Intelsat 7

South Africa

DVB

clip_image009[4]

Impact Radio

clip_image002[289]

Intelsat 7

South Africa

DVB

clip_image010[4]

Jet FM Pula

Intelsat 7

South Africa

DVB

clip_image010[5]

Jet FM Rand

Intelsat 7

South Africa

DVB

clip_image011[4]

Legit FM

Intelsat 7

South Africa

DVB

clip_image012

Lesedi FM

clip_image002[290]

Intelsat 7

South Africa

DVB

clip_image013[4]

Ligwalagwala FM

clip_image002[291]

Intelsat 7

South Africa

DVB

clip_image014

Lotus FM

clip_image002[292]

Intelsat 7

South Africa

DVB

clip_image015[6]

Metro FM

clip_image002[293]

Intelsat 7

South Africa

DVB

clip_image016

Motsweding FM

clip_image002[294]

Intelsat 7

South Africa

DVB

clip_image017[4]

Munghana Lonene FM

clip_image002[295]

Intelsat 7

South Africa

DVB

Nandos Heatwave Radio

Intelsat 7

South Africa

DVB

Pep Stores

Intelsat 7

South Africa

DVB

Pep Stores 2

Intelsat 7

South Africa

DVB

clip_image018

Phalaphala FM

clip_image002[296]

Intelsat 7

South Africa

DVB

Pick'n Pay

Intelsat 7

South Africa

DVB

clip_image019[4]

Radio 2000

clip_image002[297]

Intelsat 7

South Africa

DVB

Radio Cidade

Intelsat 902

SW zone

PAL

Radio Diskom

Intelsat 7

South Africa

DVB

clip_image020[4]

Radio Pretoria

clip_image002[298]

Intelsat 10

Africa & Europe

DVB

clip_image021[4]

Radio Pulpit

clip_image002[299]

Intelsat 7

South Africa

DVB

Red Cap Radio Mr Price Home

Intelsat 7

South Africa

DVB

Red Cap Radio Mr Price Weekend

Intelsat 7

South Africa

DVB

clip_image022[4]

RSG

clip_image002[300]

Intelsat 7

South Africa

DVB

clip_image023[8]

SAFM

clip_image002[301]

Intelsat 7

South Africa

DVB

Satellite Islam

Intelsat 7

South Africa

DVB

clip_image024[4]

Thobela FM

clip_image002[302]

Intelsat 7

South Africa

DVB

clip_image025[4]

Ukhozi FM

clip_image002[303]

Intelsat 7

South Africa

DVB

clip_image026[4]

Umhlobo Wenene FM

clip_image002[304]

Intelsat 7

South Africa

DVB

clip_image027[4]

YFM

clip_image002[305]

Intelsat 7

South Africa

DVB
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