Introduction to the Z File System (ZFS) - Linux

An Introduction to the Z File System (ZFS) for Linux

ZFS is commonly used by data hoarders, NAS lovers, and other geeks who prefer to put their trust in a redundant storage system of their own rather than the cloud.  It’s a great file system to use for managing multiple disks of data and rivals some of the greatest RAID setups.

Photo by Kenny Louie.

What is ZFS and Why Should I Use it?

The Z file system is a free and open source logical volume manager built by Sun Microsystems for use in their Solaris operating system.  Some of its most appealing features include:

Endless scalability

Well, it’s not technically endless, but it’s a 128-bit file system that’s capable of managing zettabytes (one billion terabytes) of data.  No matter how much hard drive space you have, ZFS will be suitable for managing it.

Maximum integrity

Everything you do inside of ZFS uses a checksum to ensure file integrity.  You can rest assured that your files and their redundant copies will not encounter silent data corruption.  Also, while ZFS is busy quietly checking your data for integrity, it will do automatic repairs anytime it can.

Drive pooling

The creators of ZFS want you to think of it as being similar to the way your computer uses RAM.  When you need more memory in your computer, you put in another stick and you’re done.  Similarly with ZFS, when you need more hard drive space, you put in another hard drive and you’re done.  No need to spend time partitioning, formatting, initializing, or doing anything else to your disks – when you need a bigger storage “pool,” just add disks.

RAID

ZFS is capable of many different RAID levels, all while delivering performance that’s comparable to that of hardware RAID controllers.  This allows you to save money, make setup easier, and have access to superior RAID levels that ZFS has improved upon.

Installing ZFS

Since we’re only covering the basics in this guide, we’re not going to install ZFS as a root file system.  This section assumes that you’re using ext4 or some other file system and would like to use ZFS for some secondary hard drives.  Here are the commands for installing ZFS on some of the most popular Linux distributions.

Solaris and FreeBSD should already come with ZFS installed and ready to use.

Ubuntu:

$ sudo add-apt-repository ppa:zfs-native/stable
$ sudo apt-get update
$ sudo apt-get install ubuntu-zfs

Debian:

$ su -
# wget http://archive.zfsonlinux.org/debian/pool/main/z/zfsonlinux/zfsonlinux_2%7Ewheezy_all.deb
# dpkg -i zfsonlinux_2~wheezy_all.deb
# apt-get update
# apt-get install debian-zfs

RHEL / CentOS:

$ sudo yum localinstall --nogpgcheck http://archive.zfsonlinux.org/epel/zfs-release-1-3.el6.noarch.rpm
$ sudo yum install zfs

If you have some other distribution, check out zfsonlinux.org and click on your distribution under the “Packages” list for instructions on how to install ZFS.

As we continue with this guide, we’re going to use Ubuntu because that seems to be the #1 choice for Linux geeks.  You should still be able to follow along no matter what, as the ZFS commands won’t change across different distributions.

Installation takes quite a while, but once it’s finished, run $ sudo zfs list to make sure it’s installed correctly.  You should get an output like this:

We’re using a fresh installation of Ubuntu server right now, with only one hard drive.

Configuring ZFS

Now, let’s say we put six more hard drives into our computer.

$ sudo fdisk -l | grep Error will show us the six hard drives we just installed.  They’re currently unusable since they don’t contain any kind of partition table.

As we mentioned earlier, one of the nice things about ZFS is that we don’t need to bother with partitions (although you can if you want to).  Let’s start by taking three of our hard disks and putting them in a storage pool by running the following command:

$ sudo zpool create -f geek1 /dev/sdb /dev/sdc /dev/sdd

zpool create is the command used to create a new storage pool, -f overrides any errors that occur (such as if the disk(s) already have information on them), geek1 is the name of the storage pool, and /dev/sdb /dev/sdc /dev/sdd are the hard drives we put in the pool.

After you’ve created your pool, you should be able to see it with the df command or sudo zfs list:

As you can see, /geek1 has already been mounted and is ready to use.

If you want to see which three disks you selected for your pool, you can run sudo zpool status:

What we’ve done so far is create a 9 TB dynamic stripe pool (effectively, RAID 0).  In case you’re not familiar with what that means, imagine we created a 3 KB file on /geek1.  1 KB would automatically go to sdb, 1 KB to sdc, and 1 KB to sdd.  Then when we go to read the 3 KB file, each hard drive would present 1 KB to us, combining the speed of the three drives.  This makes writing and reading data fast, but also means we have a single point of failure.  If just one hard drive fails, we will lose our 3 KB file.

Assuming that protecting your data is more important than accessing it quickly, let’s take a look at other popular setups.  First, we’ll delete the zpool we’ve created so we can use these disks in a more redundant setup:

$ sudo zpool destroy geek1

Bam, our zpool is gone.  This time, let’s use our three disks to create a RAID-Z pool.  RAID-Z is basically an improved version of RAID 5, because it avoids the “write hole” by using copy-on-write.  RAID-Z requires a minimum of three hard drives, and is sort of a compromise between RAID 0 and RAID 1.  In a RAID-Z pool, you’ll still get the speed of block-level striping but will also have distributed parity.  If a single disk in your pool dies, simply replace that disk and ZFS will automatically rebuild the data based on parity information from the other disks.  To lose all of the information in your storage pool, two disks would have to die.  To make things even more redundant, you can use RAID 6 (RAID-Z2 in the case of ZFS) and have double parity.

To accomplish this, we can use the same zpool create command as before but specify raidzafter the name of the pool:

$ sudo zpool create -f geek1 raidz /dev/sdb /dev/sdc /dev/sdd

As you can see, df -h shows that our 9 TB pool has now been reduced to 6 TB, since 3 TB is being used to hold parity information.  With the zpool status command, we see that our pool is mostly the same as before, but is using RAID-Z now.

To show how easy it is to add more disks to our storage pool, let’s add the other three disks (another 9 TB) to our geek1 storage pool as another RAID-Z configuration:

$ sudo zpool add -f geek1 raidz /dev/sde /dev/sdf /dev/sdg

We end up with:

The Saga Continues…

We’ve barely scraped the surface of ZFS and its capabilities, but using what you’ve learned in this article you should now be able to create redundant storage pools of your data.  Check back with us for future articles about ZFS, see the man pages, and search around for the endless niche guides and Youtube videos covering ZFS functions.

Taken From: http://www.howtogeek.com/175159/an-introduction-to-the-z-file-system-zfs-for-linux/

Huawei Switches Crash Course

Serial Connection
- Connect the Roll Over cable to the console port (RS232)
 
- Open Putty / Hiperterminal

- Configure the serial connection with following parameters:
    - Bits per Second: 9600
    - Parity: None
    - Stop Bits: 1
    - Flow Control: None

Clear Configuration (if the equipment is used)

- Connect the rollover cable to the console port

- Remove the power cable

- Reconnect the power cable
 
<Quidway>

Starting......

*******************************************
*                                         *
*   Quidway S3026G BOOTROM, Version 160   *
*                                         *
*******************************************

Copyright(C) 2000-2004 by HUAWEI TECHNOLOGIES CO.,LTD.
Creation Date   : Nov 03 2004, 18:41:59
CPU Type        : MIPS
CPU Clock Speed : 150MHz
Memory Size     : 64MB

Initialize LS66LTSU.......................OK!
SDRAM selftest............................OK!
FLASH selftest............................OK!
CPLD selftest.............................OK!
Switch chip selftest......................OK!
Switch SDRAM selftest.....................OK!
PHY selftest..............................OK!
Please check port leds..............finished!

The switch Mac is: 00E0-FC72-1912

Press Ctrl-B to enter Boot Menu...  0
Password:

             BOOT  MENU

1. Download application file to flash
2. Select application file to boot
3. Display all files in flash
4. Delete file from flash
5. Modify bootrom password
0. Reboot

Enter your choice(0-5): 4

No.    File Name                           
=================================================
1 *    S3026EFGTC-PWR-VRP310-r0036-32-a.bin
2      wnm2.2.2-0004.zip
3      snmpboots
4      vrpcfg.txt
Free space: 3938304 bytes
The current application file is S3026EFGTC-PWR-VRP310-r0036-32-a.bin

Please input the file number to delete: 4

Show the Running Config
display current-configuration

Show the Startup Config
display saved-configuration

Show the Startup Config
display current-configuration

Global Configuration Mode (Privileged Mode)
system-view

Undo Config. Commands
undo xxxxxx    ! equivalent to "no" in cisco

Change Hostname
sysname Huawei

Disable Spanning Tree (does not play well with cisco)
stp disable

Show a Vlan(s)
display vlan 1    ! show a vlan
display vlan       ! show vlans

Management Interface and Default Gateway
interface vlan-interface 1        ! managment vlan
ip address 1.1.1.1 255.0.0.0    ! management ip
undo shutdown                      ! activate the interface
ip route-static 0.0.0.0 0.0.0.0 129.102.0.2    ! default gateway

display ip routing-table          ! verify the default route

System View Password
password simple 20030422    ! plain text password
or
password cipher 20030422    ! encripted password

undo password                     ! remove password

Console Password
user-interface aux 0    
authentication-mode password
user privilege level 3

By default, ping, tracert, and telnet are
at visit level (0); display and debugging are
at monitoring level (1); all the configuration
commands are at configuration level (2);
and FTP, XMODEM, TFTP and commands for file
system operations are at management level (3).

set authentication password simple <password> ! plain text password
or
set authentication password cipher <password>  ! encrypted password

display user-interface    ! validate the password authentication

Telnet/SSH Password
user-interface vty 0 4
authentication-mode password
user privilege level 3

By default, ping, tracert, and telnet are
at visit level (0); display and debugging are
at monitoring level (1); all the configuration
commands are at configuration level (2);
and FTP, XMODEM, TFTP and commands for file
system operations are at management level (3).

set authentication password simple <password> ! plain text password
or
set authentication password cipher <password> ! encrypted password

display user-interface    ! validate the password authentication

Configure a Vlan on an Acess Port (unttaged)
interface Ethernet 0/1
  port access vlan

Configure a Vlan on an Range of Acess Ports (unttaged)
vlan 20                                             ! add vlan to the vlan DB
  port Ethernet 0/1 to Ethernet 0/23   ! range of access ports to add to the vlan

 
the switch automatically does the following:
<..>
interface Ethernet0/1
  port access vlan 10    ! configure a vlan on an access port
...
interface Ethernet0/23
  port access vlan 10    ! configure a vlan on an access port
<..>

Configure a Trunk Port (tagged)

interface Ethernet 0/24
  port link-type trunk                 ! define the port as trunk
  port trunk permit vlan all          ! permit all vlans
  description *** Uplink IF ***   ! port description

Save the Running Config

save

This will save the configuration in the flash memory.
The switch configurations will be written to flash.
Are you sure?[Y/N]
Now saving current configuration to flash memory.
Please wait for a while...
Save current configuration to flash memory successfully

LABNARIO - An AWSOME page with lots of tutorials about Huawei Networking is labnario, you should really check it out:

• http://labnario.com/

Cisco to Huawei Mapping 
Base: http://lifeoflogs.blogspot.pt/2011/04/cisco-vs-huawei-essential-command.html

CISCO                                --> HUAWEI

ping                              --> ping
traceroute                     --> tracert
show                            --> display
show interfaces              --> display interface
Show ip route                 --> display routing-table
show ip interface            --> display ip interface
show version                  --> display version
show ip bgp                   --> display bgp routing-table
show clock                     --> display clock
show port                      --> display port-mapping
show flash                     --> dir flash: (on user view mode)
show logging                  --> display logbuffer
show snmp                    --> display snmp-agent statistics
show frame-relay pvc      --> display fr pvc-info
show users                    --> display users
show terminal length       --> screen-length disable
                                        undo screen-length disable
enable                          --> super
disable                          --> super 0 (number is privilege level from 0 to 3, where 3 is default and equivalent to “enable” on Cisco)
conf t                           --> system-view
exit                              --> quit
end                              --> return
show policy-map interface --> display qos policy interface
send -                           --> send (on user view mode)
show running-config         --> display current-configuration
show startup-config         --> display saved-configuration
write erase                     --> reset saved-configuration
write mem                      --> save
clear counters                --> reset (on user view mode)    
clear interface                --> reset counters interface
telnet                           --> telnet
enable secret                 --> Super pass cipher (system mode)
clock                            --> clock
no                                --> undo
debug / no debug            --> debugging / undo debugging
copy running-config         --> Save safely
terminal monitor              --> terminal monitor
terminal length                --> screen-length disable
                                         undo screen-length disable
terminal no monitor          --> undo terminal monitor
clear counters                -->    reset counters interface
clear interface                -->    reset counters interface
clear crypto                   -->    ipsec sa
                                            ike sa
clear access-list counters -->    reset acl counter all
reload                           -->    reboot
shutdown                      -->    shutdown
boot                             -->    boot bootrom
Aaa                              -->    hwtacacs scheme
tacacs-server                -->    hwtacacs scheme
snmp-server                  -->    tftp-server (in conf command)
router bgp                     -->    bgp
Router rip                      -->    rip
clear ip cef                    -->    reset ip fast-forwarding
clear ip route *              -->   reset ip routing-table statistics protocol all
Clear ip bgp                   -->    reset bgp all
Show tech                    -->    display diagnostic-information
Sh ip nat translation       -->    display nat session
Show Controller             -->    display controller
show dsl int atm 0         -->    display dsl status interface Atm 2/0
show atm pvc                -->    display atm pvc-info
debug pvc nego             -->    debug atm all
sho crypto isakmp sa      -->    display ike sa
sho crypto isakmp key     -->    display ike peer
sho crypto isakmp police  -->    display ike proposal

Fix ‘File Path Too Long’ Error – Windows

How to Fix ‘File Path Too Long’ Error While Copying, Deleting or Opening Files, Without Using Third Party Applications

This is an error you might have experienced more at work than at home. You decided to copy a file or take a backup of it to another location or drive, you browse to the source location and starts copying. But you get this error, instead.

Why does it come?

There is a pre-defined character limit beyond which you cannot name a file or folder, and it varies from one OS to another. Mostly it varies between 256 and 260 characters. This is the character limit for a file name, which excludes the file path under which it is located, like “C:\Documents and Settings\Test User\Desktop\test file.txt”. But, when you copy a file from one location, it takes into account the entire file path. So, if the file is residing under a folder which is too deep or too long, that has a length beyond the set-limit, you will get errors like the ones shown above.

How do I know that the file path length is causing the issue?

• One way you will know is definitely from the error messages similar to the ones above which clearly mentions the problem.
• Some other times, it won’t. You will simply get a message saying ‘Cannot Copy’ in the title.
• Or, some other times, the files won’t open properly. They would open and close instantly without giving any errors.
• Also when you right-click such files, the number of options available in the right-click menu would also be limited compared to other files.

All these are caused by those incredibly long file paths.

So, how can I copy the files or fix this issue?

There are a couple of ways you can fix this easily without the use of any 3rd party applications.

1. Check the folder path, and shorten some of the folder names in between thereby reducing the file path length. You don’t necessarily need to put the folder name as ‘Mission Impossible Three’ when you can still recognize it as ‘MI 3.’
2. The main thing many people miss when they save a file or folder their Desktop is that the actual path to that folder in desktop is either ‘C:\Documents and Settings\%username%\Desktop’ or ‘C:\Users\%username%\Desktop’ depending on your OS. So as you can see, its already longer than you thought it is. Go to Start — Run and type ‘cmd‘ and press OK, or click start/press windows key and type ‘Command Prompt‘. Once in the command prompt window, type the following command :

subst V: “C:\TheRidiculouslyLongFolderName

WhichYouDontNeedAtAll” ,

where

subst = substitute command

V = a drive letter of my choice, you can select your own.

C:\TheRidiculouslyLongFolderNameWhichYouDontNeedAtAll = the file path you want to shorten. Change it according to your situation.

So, basically this command would convert the entire folder path you provide in the command, into a single temporary drive letter, like V in this case, which gets created in My Computer. Now all you need to do is, go to the My Computer, and open the V drive, and copy the data from there.

Note : To remove the new drive from My Computer, go to Command Prompt again and type subst V: /d

There you have it, try this the next time you get the error, and see how it goes. If you are still confused, let me know in the comments section below.

Taken From: http://vimalsuresh.com/2013/08/08/how-to-fix-file-path-too-long-error-while-copying-deleting-or-opening-files-without-using-third-party-applications/

More Details on “subst”, can be found at:

• http://technet.microsoft.com/en-us/library/bb491006.aspx
• http://www.computerhope.com/substhlp.htm

Beginner’s Guide to IPTables (Linux Firewall)

The Beginner’s Guide to iptables, the Linux Firewall

Iptables is an extremely flexible firewall utility built for Linux operating systems. Whether you’re a novice Linux geek or a system administrator, there’s probably some way that iptables can be a great use to you. Read on as we show you how to configure the most versatile Linux firewall.

About iptables

iptables is a command-line firewall utility that uses policy chains to allow or block traffic. When a connection tries to establish itself on your system, iptables looks for a rule in its list to match it to. If it doesn’t find one, it resorts to the default action.

iptables almost always comes pre-installed on any Linux distribution. To update/install it, just retrieve the iptables package:

sudo apt-get install iptables

There are GUI alternatives to iptables like Firestarter, but iptables isn’t really that hard once you have a few commands down. You want to be extremely careful when configuring iptables rules, particularly if you’re SSH’d into a server, because one wrong command can permanently lock you out until it’s manually fixed at the physical machine.

Types of Chains

iptables uses three different chains: input, forward, and output.

Input – This chain is used to control the behavior for incoming connections. For example, if a user attempts to SSH into your PC/server, iptables will attempt to match the IP address and port to a rule in the input chain.

Forward – This chain is used for incoming connections that aren’t actually being delivered locally. Think of a router – data is always being sent to it but rarely actually destined for the router itself; the data is just forwarded to its target. Unless you’re doing some kind of routing, NATing, or something else on your system that requires forwarding, you won’t even use this chain.

There’s one sure-fire way to check whether or not your system uses/needs the forward chain.

iptables -L -v

The screenshot above is of a server that’s been running for a few weeks and has no restrictions on incoming or outgoing connections. As you can see, the input chain has processed 11GB of packets and the output chain has processed 17GB. The forward chain, on the other hand, has not needed to process a single packet. This is because the server isn’t doing any kind of forwarding or being used as a pass-through device.

Output – This chain is used for outgoing connections. For example, if you try to ping howtogeek.com, iptables will check its output chain to see what the rules are regarding ping and howtogeek.com before making a decision to allow or deny the connection attempt.

The caveat

Even though pinging an external host seems like something that would only need to traverse the output chain, keep in mind that to return the data, the input chain will be used as well. When using iptables to lock down your system, remember that a lot of protocols will require two-way communication, so both the input and output chains will need to be configured properly. SSH is a common protocol that people forget to allow on both chains.

Policy Chain Default Behavior

Before going in and configuring specific rules, you’ll want to decide what you want the default behavior of the three chains to be. In other words, what do you want iptables to do if the connection doesn’t match any existing rules?

To see what your policy chains are currently configured to do with unmatched traffic, run theiptables -L command.

As you can see, we also used the grep command to give us cleaner output. In that screenshot, our chains are currently figured to accept traffic.

More times than not, you’ll want your system to accept connections by default. Unless you’ve changed the policy chain rules previously, this setting should already be configured. Either way, here’s the command to accept connections by default:

iptables --policy INPUT ACCEPT
iptables --policy OUTPUT ACCEPT
iptables --policy FORWARD ACCEPT

By defaulting to the accept rule, you can then use iptables to deny specific IP addresses or port numbers, while continuing to accept all other connections. We’ll get to those commands in a minute.

If you would rather deny all connections and manually specify which ones you want to allow to connect, you should change the default policy of your chains to drop. Doing this would probably only be useful for servers that contain sensitive information and only ever have the same IP addresses connect to them.

iptables --policy INPUT DROP
iptables --policy OUTPUT DROP
iptables --policy FORWARD DROP

Connection-specific Responses

With your default chain policies configured, you can start adding rules to iptables so it knows what to do when it encounters a connection from or to a particular IP address or port. In this guide, we’re going to go over the three most basic and commonly used “responses”.

Accept – Allow the connection.

Drop – Drop the connection, act like it never happened. This is best if you don’t want the source to realize your system exists.

Reject – Don’t allow the connection, but send back an error. This is best if you don’t want a particular source to connect to your system, but you want them to know that your firewall blocked them.

The best way to show the difference between these three rules is to show what it looks like when a PC tries to ping a Linux machine with iptables configured for each one of these settings.

Allowing the connection:

Dropping the connection:

Rejecting the connection:

Allowing or Blocking Specific Connections

With your policy chains configured, you can now configure iptables to allow or block specific addresses, address ranges, and ports. In these examples, we’ll set the connections to DROP, but you can switch them to ACCEPT or REJECT, depending on your needs and how you configured your policy chains.

Note: In these examples, we’re going to use iptables -A to append rules to the existing chain. iptables starts at the top of its list and goes through each rule until it finds one that it matches. If you need to insert a rule above another, you can use iptables -I [chain] [number] to specify the number it should be in the list.

Connections from a single IP address

This example shows how to block all connections from the IP address 10.10.10.10.

iptables -A INPUT -s 10.10.10.10 -j DROP

Connections from a range of IP addresses

This example shows how to block all of the IP addresses in the 10.10.10.0/24 network range. You can use a netmask or standard slash notation to specify the range of IP addresses.

iptables -A INPUT -s 10.10.10.0/24 -j DROP

or

iptables -A INPUT -s 10.10.10.0/255.255.255.0 -j DROP

Connections to a specific port

This example shows how to block SSH connections from 10.10.10.10.

iptables -A INPUT -p tcp --dport ssh -s 10.10.10.10 -j DROP

You can replace “ssh” with any protocol or port number. The -p tcp part of the code tells iptables what kind of connection the protocol uses.  If you were blocking a protocol that uses UDP rather than TCP, then -p udp would be necessary instead.

This example shows how to block SSH connections from any IP address.

iptables -A INPUT -p tcp --dport ssh -j DROP

Connection States

As we mentioned earlier, a lot of protocols are going to require two-way communication. For example, if you want to allow SSH connections to your system, the input and output chains are going to need a rule added to them. But, what if you only want SSH coming into your system to be allowed? Won’t adding a rule to the output chain also allow outgoing SSH attempts?

That’s where connection states come in, which give you the capability you’d need to allow two way communication but only allow one way connections to be established. Take a look at this example, where SSH connections FROM 10.10.10.10 are permitted, but SSH connections TO 10.10.10.10 are not. However, the system is permitted to send back information over SSH as long as the session has already been established, which makes SSH communication possible between these two hosts.

iptables -A INPUT -p tcp --dport ssh -s 10.10.10.10 -m state --state NEW,ESTABLISHED -j ACCEPT

iptables -A OUTPUT -p tcp --sport 22 -d 10.10.10.10 -m state --state ESTABLISHED -j ACCEPT

Saving Changes

The changes that you make to your iptables rules will be scrapped the next time that the iptables service gets restarted unless you execute a command to save the changes.  This command can differ depending on your distribution:

Ubuntu:

sudo /sbin/iptables-save

Red Hat / CentOS:

/sbin/service iptables save

Or

/etc/init.d/iptables save

Other Commands

List the currently configured iptables rules:

iptables -L

Adding the -v option will give you packet and byte information, and adding -n will list everything numerically. In other words – hostnames, protocols, and networks are listed as numbers.

To clear all the currently configured rules, you can issue the flush command.

iptables -F

Taken From: http://www.howtogeek.com/177621/the-beginners-guide-to-iptables-the-linux-firewall/

Sainsmart 2-Channel 5V Relay - Arduino / Raspberry Pi

Introduction

The Arduino Relay module allows a wide range of microcontroller such as Arduino, Raspberry Pi, AVR ,PIC, ARM with digital outputs to control larger loads and devices like AC or DC Motors, electromagnets, solenoids, and incandescent light bulbs. This module is designed to be integrated with 2 relays that it is capable of control 2 relays.The relay shield use one QIANJI JQC-3F high-quality relay with rated load 7A/240VAC,10A/125VAC,10A/28VDC.The relay output state is individually indicated by a light-emitting diode.

Features

• Model: SRD-05VDC-SL-C
• Number of Relays: 2
• Control signal: TTL level
• Rated load: 7A/240VAC 10A/125VAC 10A/28VDC
• Contact action time: 10ms/5ms

Pin definition

• COM - Common pin: This is source pin, that starts connected to NC, and connects to NO when you apply 0v / GND (active low)
• NC (Normally Closed): in which case NC is connected with COM when INT1 is set low and disconnected when INT1 is high;
• NO (Normally Open): in which case NO is disconnected with COM1 when INT1 is set low and connected when INT1 is high.
• INT 1- Relay 1 control port: changes from the COM–>NO to the COM–>NC when you apply 0v / GND (active low)
• INT 2- Relay 2 control port: changes from the COM à NO to the COM à NC when you apply 0v / GND (active low)

Video Explaination

Usage with Arduino

Example Code

int Relay = 12;

void setup()
{
    pinMode(Relay, OUTPUT); //Set Pin12 as output
}

void loop()
{
    digitalWrite(Relay, HIGH); //Turn off relay
    delay(2000);
    digitalWrite(Relay, LOW); //Turn on relay
    delay(2000);
}

Videos

• Relay Video Explanation: http://www.youtube.com/watch?v=YJNUe65BVM0
• Using Relays and Relay Boards with the Raspberry Pi - http://www.youtube.com/watch?v=b6ZagKRnRdM

How to buy

• http://www.sainsmart.com/arduino-pro-mini.html
• http://www.banggood.com/Wholesale-5V-2-Channel-Relay-Module-Shield-For-Arduino-ARM-PIC-AVR-DSP-Electronic-10A-p-48610.html
• http://www.amazon.com/SunFounder-Channel-Shield-Arduino-Raspberry/dp/B00E0NTPP4
• http://www.ebay.com/itm/5V-10A-2-Channel-Relay-Module-Shield-for-Arduino-ARM-PIC-AVR-DSP-Electronic-/390667760836?pt=LH_DefaultDomain_0&hash=item5af59cf4c4

 

Based On:

• http://www.geeetech.com/wiki/index.php/2-Channel_Relay_module
• http://www.youtube.com/watch?v=b6ZagKRnRdM

Share a VM on VMWare Workstation (aka Server Mode)

The virtual machine sharing service is not available in VMWare Workstation 8

Posted on April 16, 2012 by Ben

I wanted to share a VM, but this error message appeared when doing so:

The virtual machine sharing service is not available.

Solution

Changing the TCP Port that VMWare Workstation uses for the Shared VMs feature did the trick!

First startup VMWare Workstartion as an admin, otherwise you don’t have sufficient permissions;

Started as administrator:

Stop the service first, by hitting the “Disable Sharing” button. Then change the port number, and start the the sharing service again. I changed it to 242;

Before sharing a VM, I changed the location where all shared VMs are located. Because I wanted VMs on a second SSD.

Share a VM by moving  a machine into the Shared VMs container in the Library;

The Share VM Wizard starts. Transfer the VM to the “Shared Virtual Machines” directory (the one I changed a minute ago);

Adding a user for remote access (this is a windows user, but it can´t be you current user)

On your local firewall you must allow the following TCP Ports:

• HTTPs: TCP port 242 (in this case)
• MKS: TCP port 902 (without this it doesn´t display the remote VM desktop)

Now connect to the machine where the VM is stored using VMware Workstation 8 on another machine. But specify the port name we just changed!

Maybe you have to add permissions on the remote VM server, but the above should solve the “The virtual machine sharing service is not available” issue.

ONE THOUGHT ON “THE VIRTUAL MACHINE SHARING SERVICE IS NOT AVAILABLE IN VMWARE WORKSTATION 8”

• https://www.youtube.com/watch?v=cjJ0aXdhv_Y – Micro Nugget
• https://www.youtube.com/watch?v=-yQax--xLjs – KB VMware

Based On: http://esense.be/33/2012/04/16/the-virtual-machine-sharing-service-is-not-available-in-vmware-workstation-8/

Multiple Remote Desktop Sessions in Windows

Enable Concurrent Desktop Sessions in Windows

By Jose Vilches on January 6, 2012

Professional and Ultimate editions of Windows come with a built in Remote Desktop (RDP) feature that allows you to access your machine remotely while away from home or the office. Unfortunately, it is limited by default to one concurrent user per session, meaning that if someone remotely connects to the computer, whoever was logged in at the moment will be automatically logged off, even if the user is physically at the computer.

This is not a technical limitation but rather a licensing one. Case in point, Remote Desktop in server editions of Windows by default supports two concurrent connections to remotely troubleshoot or administer a computer. More users can connect simultaneously, too, as long as the machine can handle it with the resources it has available and you have the required client access licenses for that particular server.

However, there are a few reasons why concurrent sessions would come in handy for power users not necessarily running a server. For example, if you have a dedicated Media Center PC running in the living room, you'll be able to remotely access all files on the machine without interrupting the person watching TV.

Or if you are sharing a computer with other users, concurrent Remote Desktop sessions will allow more than one person use that system under a different or even the same user account, without kicking each other off. By patching a file called termsrv.dll, located in %SystemRoot%System32, this is possible in all editions of Windows 7, Windows Vista and Windows XP.

Download: UniversalTermsrvPatch_20090425.zip (zip File, 66 KB, mirror #2 mirror #3)

Fortunately for us, Internet user DeepXW already did all the dirty work a while ago and posted his Universal Termsrv.dll Patchfor anyone to get their hands on. Simply download and unzip the file, then run the corresponding file as administrator (right-click the exe file and select Run as Administrator). For 32-bit systems use UniversalTermsrvPatch-x86.exe and for 64-bit versions of Windows use UniversalTermsrvPatch-x64.exe.

You should see a window like the one above where you can patch termsrv.dll to remove the Concurrent Remote Desktop sessions limit and restore the original file at any time (a backup file is located at 'windowssystem32termsrv.dll.backup'). After applying the patch, restart your system and you are ready to go.

To test it out simply leave a session open on to the PC where you applied the patch, then from another machine try and connect to the computer remotely. If all goes well both users will be logged on and active.

Taken From: http://www.techspot.com/guides/485-windows-concurrent-sessions/