Aeronetworks sro - Airborne Linux

Casting About Video multicast routing usually 'Just Works'.  Occasionally it doesn't work at all, or the video streams for a few minutes only and then one is left scratching one's head... To find out what is wrong, one has to know how to analyze a playback streaming problem when it happens. Here is something to read on streaming, multicasting and the Internet Group Management Protocol (IGMP): http://www.tldp.org/HOWTO/text/Multicast-HOWTO   Multicast Version Sometimes is is necessary to use a specific version of IGMP to get things to work. One can force the IGMP version in the /proc/sys/net/ipv4/conf/eth0/force_igmp_version to 0 (auto), 2 or 3. Multicast Routing The multicast address subnet is the 224.x.y.z address range.  For routing to work at all, you need a multicast route, set with a command like this: # route add -net 224.0.0.0 netmask 240.0.0.0 dev eth0 That is if your ethernet port is eth0.  Mine is enp0s26u1u1 at the moment - I...

How to stick a signature graphic into a PDF file, without having to print it first: A word of warning first Don't stick your signature into a MS Word document, since anyone with 2 brain cells can alter it. Also don't use your usual signature - Make a special scrawl for office use. Print the file to PDF with Foxit Reader If the file isn't in PDF format already, open your MS Office document with MS Word on Windows. Print to a file and select PDF format. If you cannot print to a PDF, install Foxit Reader: https://www.foxitsoftware.com/products/pdf-reader/ Make a signature graphic with transparent background using Gimp Make a signature graphic with transparent background: Take a pen, scrawl on a piece of paper. Scan it. Use a real computer - Linux, BSD or Mac: apt install gimp xournal pdfshuffler Open the scan file with Gimp Crop it Select the white background with the eye dropper Click Layer, Transparency, Colour to Alpha Click File, Export, signa...

These days, when people think of a file server, they assume that it must support Windows CIFS (a.k.a. SMB or Samba).  A few grizzled sysadmins know that NFS would be much, much simpler to set up and almost nobody would consider using FTP. Well, that is too bad, since for many situations, anonymous FTP is best and it works purrfectly on my little OpenBSD netbook. FTP is a very simple protocol, it only talks when it has to and is completely quiet otherwise.  It has none of the chattyness and incessant 'CACA' packets of CIFS.  It is extremely easy to set up and has native support in all operating systems.  Even Windows can do anonymous FTP transparently and can map a FTP server to a drive letter, thus enabling any program to connect to the server directly. Some will speak up and say that FTP is insecure.  Well, yes, but so is NFS and CIFS.  The difference is that FTP doesn't even pretend to be secure.    The joke is that nowadays, since script...

Recently, I got fed-up with the bloated Linux distributions and wanted to try something that is secure, small and efficient and downloaded OpenBSD 6.0 from Theo De Raadt's server in Calgary.  Since Calgary is actually my old home town - why not? OpenBSD tries to be the most simple and secure UNIX system out of the box.  It is very much server oriented, but it can do anything and many architectures are supported just for fun. For example, Arm RPi and Beaglebone, Intel 32 and 64 bit and several more.  So OpenBSD is a good choice whether you want to build a server farm, a network router, or a robot. I have an old little Lenovo S10e netbook that I threatened to toss away numerous times, but it doesn't want to break.  As I feel guilty about tossing something that works perfectly well in a bin, once in a while when I run short of resources, I end up using it again.  Last year, it was pressed into service as a Linux Mirror server to install a bunch of emb...

I have a love/hate relationship with the Linux NetworkManager daemon.  It usually works and keeps your laptop PC network connections going smoothly when you move around, but it gets in the way when one does network tests and system integration using a laptop PC. Each time you plug a cable in, or turn an embedded system off/on, NetworkManager restarts the connection and you can then lose your static IP address setting, which gets tiring really quickly in a lab setup. Usually, I completely disable NetworkManager and assign a static IP address to my machine on a laboratory bench with a script in /usr/local/bin called static : #! /bin/bash echo Configure network for PDLU access # Disable the Network Manager systemctl disable NetworkManager.service systemctl stop NetworkManager.service # Set static IP address ifconfig em1 192.168.111.1 netmask 255.255.255.0 up # Set multi casting route route add -net 224.0.0.0 netmask 240.0.0.0 dev em1 # Open up the firewall iptables -F # Show ...

The power of marketing, advertising and glossy brochures subtly warp people's minds to wherever advertising Dollars go.  This affects Free and Open embedded operating system software as well.   Users visit a software company web site that showcases a new software feature and they don't realize that the " new feature" is 30 years old and exists in numerous other systems also .  Some people do not understand that there is a large corpus of almost identical operating systems known as UNIX-like or POSIX compatible operating systems and that they can use any one of them and port their software between them, without shedding too many tears. Embedded OS selection criteria should therefore not concentrate on perceived feature differences, but rather on availability:  Copyrights, Patents, Licensing and Export Permits . This is especially important in small countries which are subject to the political whims of the big five, who can make you wait indefini...

Electronic signatures are commonly used in the more advanced enterprises to sign documents - PDF files mostly.  Unfortunately, the implementation is broken and it doesn't work.  The broken implementation reduces it to snake oil. A typical IT system is set up and managed by one or two overworked computer geeks who clicked through a setup wizard to configure a key server on the company LAN.  The public and private keys are distributed on the company workstations and laptop PCs by Active Directory and GPG and once it looks like it is working and some users can sign a document, the whole universe shakes, angels and birds sing, flowers fall down from heaven and all is well... or is it? I wanted to be able to sign documents on my engineering laptop PC which runs Linux, not just my office PC, which runs Windows (and which usually has some problem or another).  So I asked IT for a copy of my Private key.  After a few months, they emailed me my Public key.  ...