Monday, July 30, 2012

Use the Magic SysRq Key on Linux to Fix Frozen X Servers, Cleanly Reboot, and Run Other Low-Level Commands


Use the Magic SysRq Key on Linux to Fix Frozen X Servers, Cleanly Reboot, and Run Other Low-Level Commands





sysrq key
On Linux, the magic SysRq key can send commands directly to the Linux kernel. You can use it to recover from freezes or cleanly restart your system, even if nothing appears to be responding.
The magic SysRq key is implemented as part of Linux’s keyboard driver – it will work as long as the Linux kernel is still running. Only a kernel panic should disable this key combination.

Using the Magic SysRq Key

The SysRq key is located near the Scroll Lock key on your keyboard – the Sys Rq key is generally the same as your Print Screen key. The “magic” SysRq combination is Alt+SysRq.
To use this key combination, your Linux kernel must have been compiled with the CONFIG_MAGIC_SYSRQ compile option – most Linux distributions will have this enabled by default. Assuming it’s compiled into your kernel, it can be enabled or disabled on a running system by changing the value of /proc/sys/kernel/sysrq. To check if it’s enabled, run the following command:
cat /proc/sys/kernel/sysrq
If you see a “1”, the magic SysRq key is enabled.
If you see a “0”, you’ll have to enable it yourself by running the following command as root:
echo “1” > /proc/sys/kernel/sysrq

Dealing With a Frozen X Server

If your X server (the program that runs your graphical desktop) freezes, you may find yourself unable to use your system. There are a few magic SysRq commands that can help:
  • Alt + SysRq + r – Takes the keyboard out of raw mode, taking control away from the X server. After running this combination, you should be able to use the Ctrl + Alt + F1 (and other F-key) keyboard shortcuts to switch to another console and restart X.
  • Alt + SysRq + k – Kills all programs on the current virtual console, including X. You can also enable the Ctrl+Alt+Backspace keyboard shortcut in Ubuntu’s keyboard preferences to restart your X server – however, this shortcut is implemented by the X server and may not always work.

Cleanly Restarting Your System

Used in sequence, some of these actions can be used to cleanly end processes, flush data to disk, unmount all file systems, and restart your computer. To perform this process, press and hold the Alt + SysRq key combination and – while holding the Alt and SysRq keys down — type the following keys in order, pausing for several seconds in between each key:
reisub
The mnemonic “Raising Elephants ISUtterly Boring” is often used to remember this sequence. Here’s what each key does:
  • r – Puts the keyboard into raw mode, taking control of it away from the X server.
  • e – Sends the terminate signal to all processes, asking them to end gracefully.
  • i – Sends the kill signal to all processes, forcing them to end immediately.
  • s – Flushes data from your cache to disk.
  • u – Remounts all file systems read-only.
  • b – Reboots your computer.

More Commands

Here are some other actions you can perform with the magic SysRq key. To perform an action, press and hold the Alt + SysRq keys while typing the letter:
  • n – Resets the nice level (priority) of all high and realtime priority processes.
  • f – Calls oom_kill, which will kill a memory-hogging process.
  • o – Shuts off the computer.
There are other actions, but they may be more useful to developers than the average Linux geek. For more information on the magic SysRq key – and a full list of actions you can perform – consult the sysrq.txt file included with the Linux kernel.

Friday, July 27, 2012

Understanding OAuth: What Happens When You Log Into a Site with Google, Twitter, or Facebook [Explainer]

Understanding OAuth: What Happens When You Log Into a Site with Google, Twitter, or Facebook [Explainer]:
from Lifehacker 
Logging into another site with your Google, Twitter, or Facebook account isn't just convenient; it's more secure than creating a new account, or entering your Google, Twitter, or Facebook password into a third-party site. That's where OAuth comes in. Here's how it works, and how it keeps your passwords safe on third-party sites. More »

Creating a secure 802.1x wireless infrastructure using Microsoft Windows

Creating a secure 802.1x wireless infrastructure using Microsoft Windows:
from Microsoft Enterprise Networking Team 
 My name is Prachand and I am an SE on the Platforms Networking Team. My intent of this post is for it to be a quick reference guide for setting up secure wireless networking using Microsoft products. It describes how to create an infrastructure for authentication...(read more)

Android File Transfer Takes the Pain Out of the Mac/Android Combo [Mac Downloads]

Android File Transfer Takes the Pain Out of the Mac/Android Combo [Mac Downloads]:
from Lifehacker 
Mac (10.5 and later) with Android (3.0 and later): Plug an Android into a Windows or Linux machine, turn on disk mode, and your phone is basically a drive. Plug into a Mac, and you get a warning. Google's own utility fixes that. More »

Safecopy Recovers Data from Hard Drives and Other Media, Keeps Working When Other Tools Give Up [Downloads]

Safecopy Recovers Data from Hard Drives and Other Media, Keeps Working When Other Tools Give Up [Downloads]:
from Lifehacker 
Linux: Whether it's a troublesome hard drive or an old DVD that's spitting out I/O errors, Safecopy is a Linux utility that will keep plugging away, trying to recover data, until it gets to the end of the media. Most data recovery tools give up and force you to start the recovery process again once it starts running into those types of errors, but Safecopy presses on, resorting to low-level read and copy operations if it has to. More »

Thursday, July 26, 2012

UpdateFreezer ices apps in place

UpdateFreezer ices apps in place:
from BetaNews 
When managing a PC you’ll normally want software updates to be installed just as soon as they become available. But there may be occasional exceptions.
If you’re working on a slow and expensive mobile internet connection, say, or you’re going to make a really important presentation tomorrow and want to be sure your PC behaves exactly as it does today, then you may want to disable updates, just temporarily. And Update Freezer is a compact, portable and free utility which makes that very straightforward.
Just launch UpdateFreezer.cmd and you’ll immediately see the current update settings for Windows, Adobe, Google, Java, Firefox and Skype. The program also displays the various update options available in each case – “Disabled”, “Notify Only”, “Automatic”, whatever they might be – and you can change them at a click. (Which of course you could do from the individual applications anyway, but Update Freezer just simplifies the process by making several settings available from a single interface.)
And, conveniently, Update Freezer also includes a Restore All option which resets your update settings to whatever they were before you first ran the program. So when you’re happy to receive updates again, simply hit the “Restore All” button and you’ll be back to normal.
Of course while disabling updates can be convenient sometimes, you don’t have to use Update Freezer for that purpose: the program is just as handy for checking a PC’s status, or turning updates on. If you’re troubleshooting a computer and wondering what its update settings might be, say, running Update Freezer from a USB stick will quickly tell you more, and you can correct any problems with a click.
Photo Credit: Stephen Orsillo/Shutterstock

Anti-Twin hunts down duplicate files

Anti-Twin hunts down duplicate files:
from BetaNews 
Emptying your Recycle Bin and clearing away temporary files are a good first step in cleaning up your system, but there’s another type of hard drive clutter which is a little less obvious: duplicate files. These can consume a surprising amount of hard drive space, but fortunately tools like Anti-Twin make it easy to detect and delete them.
While there are plenty of duplicate file finders around, Anti-Twin scores points immediately for its lengthy list of configuration options. These don’t get in your way -- the default settings are sensibly chosen, and you can have the program checking your system within seconds – but if you have more complex requirements then Anti-Twin will do its best to fulfil them.
Take the decision of where and what you’re going to scan, for instance. This could be a single folder, maybe holding your digital photos. But you could also compare two folders. You might choose to scan all subfolders, too. And a versatile filtering option means you can tell the program to only compare files of a certain size or type, while ignoring other file types to help improve performance.
Then there’s the issue of how Anti-Twin will compare your files. It could run a simple, byte-by-byte comparison. But you might also choose to compare images by pixels, or more generally, compare files by size, or name, with or without the file extension. And whatever you choose, there’s the option to set a “percentage match”: set this to, say, 90% instead of 100 percent, and now Anti-Twin will find similar files as well as precise matches.
Once the scan is complete then you can of course choose duplicates manually, deciding what you’d like to keep, and what can safely be deleted. But if there are lots of duplicates then it might be easier to have Anti-Twin choose them automatically, and this can be done in many different ways. You might choose to scrap files based on their creation date, size, directory level, name and more, for instance, and you can even combine these criteria to produce the most accurate results.
And while deleting duplicates can be a risky business -- don’t do it unless you’ve a full system backup to hand -- Anti-Twin does do its best to minimise the chance of disaster. If you specify a path including your Program Files or Windows folders then you’ll be warned; and by default the program will ignore many executable file types (EXE, DLL, DRV and more).
The program does have a few issues, in particular with performance: scanning and comparison speeds aren’t the best. It’s still perfectly usable, though, and the sheer weight of its configuration options mean Anti-Twin deserves a very high ranking on your duplicate file finder shortlist.
Photo Credit: megainarmy/Shutterstock

A New, Automated Approach to Achieving Application Compatibility in Windows 7 Migrations

From Quest Software

A New, Automated Approach to Achieving Application Compatibility in Windows 7 Migrations

April 2014 marks the end of Windows XP support. As a result, Windows 7 migrations are picking up steam.  But as many IT organizations inevitably discover during migration to a new operating system, a number of hurdles could make the move to Windows 7 far from a slam-dunk proposition. Heading the list of technical issues is application compatibility, particularly for the large number of legacy and homegrown applications in use on the average network.

Fortunately, new solutions are emerging to overcome these challenges. These tools are specifically designed to more easily and efficiently test for and fix application compatibility issues, helping to smooth the migration to Windows 7. This white paper will discuss this automated process and how it will save organizations an incredible amount of time while reducing costs and risks. 

©2012 Quest Software, Inc.

Get Email when New Aerial Images are available for your Google Maps

Get Email Alerts when New Aerial Images are available for your Area:
from Digital Inspiration Technology Blog 
google satellite images
If you are inside Google Earth or switch to the Satellite View in Google Maps, you can see aerial images of your home and most other places of our planet.
These images are updated every few years (or months depending on the area) and Google, in the long term, is very likely to switch to high-resolution imagery for most countries and regions. Now that Apple has joined the Maps business, providing high-quality imagery will be an even higher priority item for Google.

Email Alerts for Google Maps & Earth

If you would like to know when Google Maps (and Google Earth) is updated with new satellite and aerial images of your area, or any other point of interest, they have built a new alert system called Follow Your World that should keep you in the loop.
To get started, sign-in using your Google Account and mark one or more areas of interest. You can do so by either clicking the points in Google Maps or enter the latitude and longitude manually.
That’s it. Google will monitor these locations and will send you email alerts as soon as updated satellite and aerial imagery data is available for these areas in Google Maps and Google Earth.
Also see: Find Dates When Google Maps Images were Taken [via Google Blog]
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Digital Inspiration @labnolThis story, Get Email Alerts when New Aerial Images are available for your Area, was originally published at Digital Inspiration on 12/06/2012 under Google Earth, Google Maps, Internet.

Monday, July 23, 2012

Roll your own battery backup system

Roll your own battery backup system:
from Hack a Day 

[Chris] and [Dom] wanted to build their own battery backup system on the cheap. They were very creative in sourcing the parts, and ended up putting together a battery-backed CCTV system for about eighty bucks.
Since short power outages are fairly common in the area this battery backup makes sense. We’ve seen some pretty gnarly whole-house systems but this is more of a novelty. That’s a good thing, because the hacking duo decided to reuse batteries which were headed for the scrap yard. They’re connected to a trickle charger which makes sure that they’re continually topped off when mains power is energized. But when there’s a blackout a relay switches an outlet box over to the inverter (also a used part).
The system is outlined in the entertaining video after the break. You’ll see they guys show off the completed build, followed by a walk through of the circuit they designed and how it functions.



Filed under: home hacks

Make Your Own DIY Battery Backup System from Recycled Batteries [DIY]

Make Your Own DIY Battery Backup System from Recycled Batteries [DIY]:
from Lifehacker 
If you've ever had the misfortune of losing power right in the middle of a big project you know the headache that can come with that. Over on Instructables, ooda55 guides you through the process of building your own battery backup system so you never lose a minute of work. More »