Question of the Week
This week’s Question of the Week comes from MaxMaxie, and is about command line usage in Linux:
I’ve found myself using the
-vflag for lots of applications less and less (especially for trivial stuff like
cp). However, when I did and I was, say, unzipping a large file, it would take longer than when I didn’t use the
-vflag. I assume this is because the terminal has to process the text and I’m filling up whatever buffer it might have. But my question is, does this make the application actually run slower or does it complete in the same amount of time and what I’m seeing is the terminal trying to catch up?
According to Matt Jenkins, it does indeed. His explanation of why is an interesting read, but the question remains: exactly how much does it slow things down? I decided to find out – read on to see just how much of a difference verbose flags can make.
This week at Super User, MaxMackie asked “How far will you get with a ‘rm -rf /’” ? Within minutes of the post, it had not only my attention, but others as well. It had 39 upvotes just eight short hours later, and answers and thoughts poured in.
I’ve often wondered how far the system will actually get if you run
rm -rf /. I doubt the OS would be able to erase itself (?)
We’ve all heard the stories – and please, don’t try this at home!
rm -rf has caused a LOT of problems with accidental usage in the past. It is a linux/unix command which erases all files recursively, and won’t stop to ask if you’re sure. Adding the extra / has it start at the root directory – meaning you’re erasing the whole system! But if we did run this on the entire system, how far would the trail of destruction go? I took it upon myself to find out. I fired up VirtualBox, and installed a new copy of Fedora 15 (XFCE). Within minutes I had a fresh install all set and ready to destroy.
A person buys a stolen prototype gadget that was found in a bar and takes pictures and video of it. After publishing them on the Internet their house is raided and their computer equipment is confiscated.
Luckily for them, they erased all of the data regarding the gadget so they’re safe, right?
Today’s Question of the Week appeared on Superuser.com courtesy of Jerry when he asked how detectives in the Casey Anthony trial had recovered keyword searches for evidence that had been manually deleted from a computer.
Every week, the Super User community nominated and votes on an interesting Question of the Week, which we write about on the blog. One nominee that interested me was:
Is there a correlation between CPU usage and heat? RAM usage? Other things? How can software affect overheating in a laptop?
This Question of the Week raises some interesting security implications. With many high-profile sites compromised recently, it’s worth taking a moment to consider the security of your passwords. Michael McGowan asked:
Suppose a user uses a secure password at site A and a different but similar secure password at site B. Maybe something like
mySecure12#PasswordAon site A and
mySecure12#PasswordBon site B (feel free to use a different definition of “similarity” if it makes sense). Suppose then that the password for site A is somehow compromised…maybe a malicious employee of site A or a security leak. Does this mean that site B’s password has effectively been compromised as well, or is there no such thing as “password similarity” in this context? Does it make any difference whether the compromise on site A was a plain-text leak or a hashed version?
Anyone active on Super User has encountered the infamous shopping requests before, and you can’t really blame them for trying: They don’t know what they need, and here’s a website about computers where people understand all the latest gadgetry, standards, and most importantly, the endless acronyms.
But we’re missing the most crucial part: We don’t understand their needs.
After spending an hour or two working with several others in the Super User chatroom to help a user make heads or tails of how to translate his needs into hardware, it became clear that for all the questions about how to understand and judge performance vs. needs for individual components of a computer, they were extremely spread out over the site, which made them as a whole hard to find, especially if you didn’t know what you were looking for.
Super User needed a new community wiki. This week, the community is collectively wondering and defining How do I know what hardware to buy to meet my needs?:
- How do I find out if a given CPU will be enough for a certain game or application that I want to run?
- How do I find out if a given graphics card is powerful enough for a certain game or application?
- What is important when looking at motherboards?
- How much memory do I need?
- How do I know how much wattage I need for a power supply?
- What size case do I need?
- What relevant standards do I need to read up on and be aware of?
- What “gotchas” do I need to be on the lookout for?
All of this information should still apply regardless of whether you are buying a pre-configured system or building your own from scratch. Configuring a system online at a retailer such as Dell, Apple, or HP still has a pretty wide range of systems and configurations, so making heads or tails of the options provided there is still necessary – you’re trading wide selection for the comfort of knowing that all the parts should work well together and letting someone else assemble and configure it.
There are a lot of things computers do that, in usage, seem very simple. Under the hood, though, there are a lot of parts that work together to enable basic behavior. One example is rebooting a computer. Reboot is conceptually very simple, it turns off and then turns back on again. In today’s Question of the Week, Seth Carnegie wondered how this actually happens:
This may be a really stupid question, but how can a computer restart itself? After it’s off, how does it tell itself to come back on again? What kind of software is it that can do this?
Questions about setting environment variables the PATH are very common here, and in most cases the answers are very similar to each other. In the future it would be nice to have a good Q/A for this. So the question is: How do I set the executable PATH and other environment variables on major operating systems? A good answer would include a simple explanation of what environment variables and especially PATH mean to the OS, as well as simple guidelines on how to set them accordingly.
Being an avid computer user for years now, the PATH is something that has crossed me quite a few times now. So when I saw this question, it was time to put my learning hat on.
One of the most well-known is called
PATHon Windows, Linux and Mac OS X. It specifies the directories in which executable programs* are located on the machine that can be started without knowing and typing the whole path to the file on the command line. (Or in Windows, the Run dialog in the Start Menu or Windows Key+R).
So now that we know what the PATH is, where are these things set? With a quick look around, I found it was easily found on Windows 7, by simply popping open the Start Menu and typing in “Environment.” The first option was Edit environment variables for your account. Click it, and here we are:
A few days ago, my area had a little storm roll in. It didn’t sound bad at first, but then I saw one big dark cloud. With a crack of thunder, I realized we were in for a thunder storm. As I sat typing away at my computer, it came to mind that there might be a power surge. Now what was I supposed to do about my computer if that happened? I took it to the friendly people at Super User, to find out:
Generally when I hear the crack of thunder, my PC goes off immediately. Today I’m working though, and wondered – how bad is it to leave it on? If the power goes out, will it kill it? I use a power strip – that protects it, right?
In minutes I had a response from Randolf Richardson, who explained that my poor little power bar just wouldn’t stand up to any power surge. As the thunder and lightning went on outside, I continued reading through the comments flooding in.
Ultimate Fish Battle Royale
I have Mac PC, in which I have created a Windows partition and have installed Windows using Boot Camp. If I log in to the Mac OS, I can read all the files from the Windows partition from Mac. If I compare the same scenario from within Windows, Windows claims to secure a user’s private files (stored in My Documents for instance) from other users with equal or less privilege. I was expecting to see the same protection from Mac as well. I was expecting an error message in Mac to show that these files are inaccessible, if I try to see or open them. Can someone explain if my perception is right or am I missing something?
While the question specifically mentions NTFS the answer applies to almost every file system that is able to be accessed by another operating system and has not had native support for that file system built in.
The same would apply to EXT2/3/4 (Linux) support on Windows, HFS (Mac) support on Linux or any combination of file systems that are standard for one system and just barely “supported” on another.