Chit chat

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Have not taken time yet to fix the email server..

Was able to get my old RP1 up and running again. Somehow it had a bad image. Put Openelec on the mm card for testing.

The Easter bunny brought me an RPi-2.

Finally getting used to connecting wireless with my nexus 7 tablet with much regret.

Hopefully Libreoffice will come out with their web based version soon. Saving a place on the server for it. Like the policy of install once but us many.

Keep getting messages about updating the Pogoplug. Since going to arch linux, we have not used that service in forever.

Raspberry Pi case?

SUNP0012

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Now let us take a look a remote music controller called mpd. With mplayer we could do everything from the command line, mpw we should be able to use the gui on the remote machine. We will not need to use ssh here either.

You will want to set up your host machines with speakers as before. Then we need to add a new piece of software called mpd. It is available for a wide variety of systems including android.

$ sudo apt-get install mpd.

Server does not have to have gui installed. Copy your music files to the server if they are not already there. Then you will want so edit the config file for you file settings and etc.

$ sudo vim /etc/mpd.conf

Once you have that done, you will need to go to the client machine and install the following:

$ sudo apt-get install mpc gmpc

Then go to the gui menu for the  sound and video.   Choose the gnome-music-okayer-client. Everything is gui form there. You will need to set the servername and the port number (usually 6600). In many cases it will autodetect it for you.

Start playing music from the server.

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Remember the old concentration game from many years ago. You can make your own version. you will need thirty clear plastic envelopes. They can be make from cheap clear plastic lunch bags and clear plastic tape. Poster board can be used for making the large frames. You will also need to make some blue cards with the embossed numbers for each of the bags. Of course you will need a frame to hold the puzzle background.

Lastly you will need a puzzle to use as the background. You can use your favorite drawing program the will let you import pictures. Gimp is what we like to use  There are thousands on-line that you can use or even use your own. Such as:

The sky is the limit with your imagination. More information at: http://en.wikipedia.org/wiki/Concentration_%28game_show%29

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Just an experiment to determine the amount of days between two dates. In this case it is the days left in the current presidency.

<pre>#!/bin/bash
D=`date +%Y-%m-%d`
D1=`date +%s -d "$D"`
D2=`date +%s -d "2017-01-20"`
((diff_sec=D2-D1))
echo - | awk -v SECS=$diff_sec '{printf "Number of days : %d",SECS/(60*60*24)}'
echo " till Obama leaves office."

Result:

$ ./datediff.sh
Number of days : 656 days till Obama leaves office.
$

or semigui:

#!/bin/bash
D=`date +%Y-%m-%d`
D1=`date +%s -d "$D"`
D2=`date +%s -d "2017-01-20"`
((diff_sec=D2-D1))
a=`echo - | awk -v SECS=$diff_sec '{printf "Number of days : %d",SECS/(60*60*24)}'`
a=$a" till Obama leaves office."
zenity --info --text="$a"

Screenshot from 2015-04-11 03:54:56

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Really feel for Mr. Banzi and the fact that everyone is making their own version of the Arduino. You can get the bare  chips and make your own. You can get the boards as low as ten dollars even at a retail outlet. Had a spare ethernet board I bought from Radio shack on sale. So when I saw a compatible board for only ten dollars, I had to get it.

The main reason, I wanted this version of the board is that I have some Arduino chips that that can be plugged and played on the board versus the surface mounted versions which will not plug and play.

For those systems that need acm

$ sudo apt-get install hal
$ sudo usermod -a -G tty $USER
$ sudo usermod -a -G dialout $USER

Speaking the Arduino, they have a newer IDE. When I downloaded a recent version, I had problems. The one I downloaded today seems to work. Tested the new Arduino board and the extra ethernet board we had. Seemed to work. The page for the new software is: http://arduino.cc/en/Main/Software

One thing I like about the new ide is that if gives you a basic form to start with, which saves time. In fact you cut and paste the minimal code in the old ide software/

void setup() {
// put your setup code here, to run once:

}

void loop() {
// put your main code here, to run repeatedly:

}
Time to go back and work on the Sous vide project.

The Nexus 7 has a neat little ide also

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Primer on ipv6

Intro

One of the main benefits of Internet Protocol version 6 (IPv6) over previously used Internet Protocol version 4 (IPv4) is the large address-space that contains (addressing) information to route packets for the next generation Internet.

IPv6 supports 128-bit address space and can potentially support 2128 or 3.4W1038 unique IP addresses (as opposed to 32-bit address space of IPv4). With this large address-space scheme, IPv6 has the capability to provide unique addresses to each and every device or node attached to the Internet.

 

IPv6

Why we need IPv6 Addressing

An escalating demand for IP addresses acted as the driving force behind the development of the large address space offered by the IPv6. According to industry estimates, in the wireless domain, more than a billion mobile phones, Personal Digital Assistants (PDA), and other wireless devices will require Internet access, and each will need its own unique IP address.

The extended address length offered by IPv6 eliminates the need to use techniques such as network address translation to avoid running out of the available address space. IPv6 contains addressing and control information to route packets for the next generation Internet.

IPv6 addresse formats are divided into three classes:

1) Unicast addresses A Unicast address acts as an identifier for a single interface. An IPv6 packet sent to a Unicast address is delivered to the interface identified by that address.

2) Multicast addresses A Multicast address acts as an identifier for a group/set of interfaces that may belong to the different nodes. An IPv6 packet delivered to a Multicast address is delivered to the multiple interfaces.

3) Anycast addresses Anycast addresses act as identifiers for a set of interfaces that may belong to the different nodes. An IPv6 packet destined for an Anycast address is delivered to one of the interfaces identified by the address.

(http://en.wikipedia.org/wiki/IPv6_address#Address_formats)

IPv6 Address Notation

IPv6 addresses are denoted by eight groups of hexadecimal quartets separated by colons in between them.

Following is an example of a valid IPv6 address: 2001:cdba:0000:0000:0000:0000:3257:9652

Any four-digit group of zeroes within an IPv6 address may be reduced to a single zero or altogether omitted. Therefore, the following IPv6 addresses are similar and equally valid:

2001:cdba:0000:0000:0000:0000:3257:9652

2001:cdba:0:0:0:0:3257:9652

2001:cdba::3257:9652

The URL for the above address will be of the form:

http://%5B2001:cdba:0000:0000:0000:0000:3257:9652%5D/

Network Notation in IPv6

The IPv6 networks are denoted by Classless Inter Domain Routing (CIDR) notation. A network or subnet using the IPv6 protocol is denoted as a contiguous group of IPv6 addresses whose size must be a power of two. The initial bits of an IPv6 address (these are identical for all hosts in a network) form the network s prefix. The size of bits in a network prefix are separated with a / . For example, 2001:cdba:9abc:5678::/64 denotes the network address 2001:cdba:9abc:5678. This network comprises of addresses rearranging from 2001:cdba:9abc:5678:: up to 2001:cdba:9abc:5678:ffff:ffff:ffff:ffff. In a similar fashion, a single host may be denoted as a network with a 128-bit prefix. In this way, IPv6 allows a network to comprise of a single host and above.

Special Addresses in IPv6

::/96 The zero prefix denotes addresses that are compatible with the previously used IPv4 protocol.

::/128 An IPv6 address with all zeroes in it is referred to as an unspecified address and is used for addressing purposes within a software.

::1/128 This is called the loop back address and is used to refer to the local host. An application sending a packet to this address will get the packet back after it is looped back by the IPv6 stack. The local host address in the IPv4 was 127.0.0.1 .

2001:db8::/32 This is a documentation prefix allowed in the IPv6. All the examples of IPv6 addresses should ideally use this prefix to indicate that it is an example.

fec0::/10 This is a site-local prefix offered by IPv6. This address prefix signifies that the address is valid only within the local organization. Subsequently, the usage of this prefix has been discouraged by the RFC.

fc00::/7 This is called the Unique Local Address (ULA). These addresses are routed only within a set of cooperating sites. These were introduced in the IPv6 to replace the site-local addresses. These addresses also provide a 40-bit pseudorandom number that reduces the risk of address conflicts.

ff00::/8 This prefix is offered by IPv6 to denote the multicast addresses. Any address carrying this prefix is automatically understood to be a multicast address.

fe80::/10 This is a link-local prefix offered by IPv6. This address prefix signifies that the address is valid only in the local physical link.

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ipv4 web calculator. You can find it on the web if you look.

Screenshot from 2015-04-10 00:49:58

Screenshot from 2015-04-10 00:47:56

Screenshot from 2015-04-10 00:51:03

Screenshot from 2015-04-10 00:52:18

Some ipv6 calculators also on the web

Screenshot from 2015-04-10 00:46:42

Screenshot from 2015-04-10 00:45:14

Screenshot from 2015-04-10 00:43:53

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Another ipv6 Calcer

Screenshot from 2015-04-12 22:16:34

Screenshot from 2015-04-12 22:17:15

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If you’re a Linux system administrator, chances are you’ve got more than one machine that you’re responsible for on a daily basis. You may even have a bank of machines that you maintain that are similar — a farm of Web servers, for example. If you have a need to type the same command into several machines at once, you can login to each one with SSH and do it serially, or you can save yourself a lot of time and effort and use a tool like ClusterSSH.

ClusterSSH is a Tk/Perl wrapper around standard Linux tools like XTerm and SSH. As such, it’ll run on just about any POSIX-compliant OS where the libraries exist — I’ve run it on Linux, Solaris, and Mac OS X. It requires the Perl libraries Tk (perl-tk on Debian or Ubuntu) and X11::Protocol (libx11-protocol-perl on Debian or Ubuntu), in addition to xterm and OpenSSH.

Installation

Installing ClusterSSH on a Debian or Ubuntu system is trivial — a simple sudo apt-get install clusterssh will install it and its dependencies. It is also packaged for use with Fedora, and it is installable via the ports system on FreeBSD. There’s also a MacPorts version for use with Mac OS X, if you use an Apple machine. Of course, it can also be compiled from source.

Configuration

ClusterSSH can be configured either via its global configuration file — /etc/clusters, or via a file in the user’s home directory called .csshrc. I tend to favor the user-level configuration as that lets multiple people on the same system to setup their ClusterSSH client as they choose. Configuration is straightforward in either case, as the file format is the same. ClusterSSH defines a “cluster” as a group of machines that you’d like to control via one interface. With that in mind, you enumerate your clusters at the top of the file in a “clusters” block, and then you describe each cluster in a separate section below.

For example, let’s say I’ve got two clusters, each consisting of two machines. “Cluster1” has the machines “Server1” and “Server2” in it, and “Cluster2” has the machines “Server3” and “Server4” in it. The ~.csshrc (or /etc/clusters) control file would look like this:

clusters = cluster1 cluster2

cluster1 = server1 server2
cluster2 = server3 server4

You can also make meta-clusters — clusters that refer to clusters. If you wanted to make a cluster called “all” that encompassed all the machines, you could define it two ways. First, you could simply create a cluster that held all the machines, like the following:

clusters = cluster1 cluster2 all

cluster1 = server1 server2
cluster2 = server3 server4
all = server1 server2 server3 server4

However, my preferred method is to use a meta-cluster that encompasses the other clusters:

clusters = cluster1 cluster2 all

cluster1 =Server1 server2
cluster2 = server3 server4
all = cluster1 cluster2

Figure 1: Lauching ClusterSSH

By calling out the “all” cluster as containing cluster1 and cluster2, if either of those clusters ever change, the change is automatically captured so you don’t have to update the “all” definition. This will save you time and headache if your .csshrc file ever grows in size.

Using ClusterSSH

Using ClusterSSH is similar to launching SSH by itself. Simply running cssh -l <username> <clustername> will launch ClusterSSH and log you in as the desired user on that cluster. In the figure below, you can see I’ve logged into “cluster1” as myself. The small window labeled “CSSH [2]” is the Cluster SSH console window. Anything I type into that small window gets echoed to all the machines in the cluster — in this case, machines “server1” and “server2”. In a pinch, you can also login to machines that aren’t in your .csshrc file, simply by running cssh -l <username> <machinename1> <machinename2> <machinename3>.

If I want to send something to one of the terminals, I can simply switch focus by clicking in the desired XTerm, and just type in that window like I usually would. ClusterSSH has a few menu items that really help when dealing with a mix of machines. As per the figure below, in the “Hosts” menu of the ClusterSSH console there’s are several options that come in handy.

“Retile Windows” does just that if you’ve manually resized or moved something. “Add host(s) or Cluster(s)” is great if you want to add another set of machines or another cluster to the running ClusterSSH session. Finally, you’ll see each host listed at the bottom of the “Hosts” menu. By checking or unchecking the boxes next to each hostname, you can select which hosts the ClusterSSH console will echo commands to. This is handy if you want to exclude a host or two for a one-off or particular reason. The final menu option that’s nice to have is under the “Send” menu, called “Hostname”. This simply echoes each machine’s hostname to the command line, which can be handy if you’re constructing something host-specific across your cluster.

Caveats with ClusterSSH

Like many UNIX tools, ClusterSSH has the potential to go horribly awry if you aren’t very careful with its use. I’ve seen ClusterSSH mistakes take out an entire tier of Web servers simply by propagating a typo in an Apache configuration. Having access to multiple machines at once, possibly as a privileged user, means mistakes come at a great cost. Take care, and double-check what you’re doing before you punch that Enter key.

Conclusion

ClusterSSH isn’t a replacement for having a configuration management system or any of the other best practices when managing a number of machines. However, if you need to do something in a pinch outside of your usual toolset or process, or if you’re doing prototype work, ClusterSSH is indispensable. It can save a lot of time when doing tasks that need to be done on more than one machine, but like any power tool, it can cause a lot of damage if used haphazardly.

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Homnemade SOS

SUNP0009

Good day.

 

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