Ask MetaFilter questions tagged with zero

Why did tar and nc not play nice?

flabdablet — Sat, 26 Sep 2009 17:54:13 -0800

Can anybody immediately see why nc and tar didn't work together the way I expected they would? I wanted to copy an Ubuntu installation from a laptop with one filesystem to a desktop box with two. So I booted an Ubuntu live CD on each and opened terminals; then on the laptop did



sudo su -

mount /dev/sda2 /mnt

cd /mnt

tar c . | nc -l -p 10000

and on the desktop box did



sudo su -

mkfs -t ext3 -L root /dev/sda3

mkfs -t ext3 -L home /dev/sda4

mount /dev/sda3 /mnt

mkdir /mnt/home

mount /dev/sda4 /mnt/home

cd /mnt

nc 192.168.1.3 10000 -q5 | tar xv --numeric-owner

As expected, a huge list of filenames scrolled by on the desktop box as tar extracted the files. When that all stopped, I hit ctrl-D on the desktop end to close nc's standard input; five seconds later the shell prompt returned on the laptop as well. So everything seemed to be working as expected.

After making the necessary corrections to /mnt/boot/grub/menu.lst, /mnt/etc/fstab, /mnt/etc/hosts and /mnt/etc/hostname on the desktop box, I umounted everything and rebooted it, but assorted things were badly amiss. Turns out that a random assortment of vital files had been created with zero length and zero permissions instead of being properly copied.

I have since got the machine-to-machine copy done by mounting the laptop's hard drive in a USB enclosure, plugging it into the desktop box and using cp -av so I'm not looking for ways to get the primary job done any more.

What I would like to know: before I spend more time trying to work out why the tar | nc <--> nc | tar method failed, can anybody see some documented reason why it was doomed to do so?

What does a trailing zero mean in a Dewey decimal catalog?

saguaro — Sat, 20 Dec 2008 14:30:07 -0800

Hey Librarians! Why is there a trailing zero on this Dewey number? I've asked the available meatspace librarians why Tim Wendel's book The New Face of Baseball is cataloged at 796.3570, and the best they can come up with is that it's some topical designation. (The worst so far was, "Good question, troublemaker, I'm not a cataloger.") OK, so if that's it, which topic does a trailing zero indicate? If that's not it, what's going on here? Is it extraneous? FWIW, there's one other book in this collection with the same catalog number, and I can pull up more in the google.

Looking for resources regarding sustainability.

valentinepig — Mon, 17 Dec 2007 10:36:16 -0800

Zero waste is the topic. Turned up zero hits in my AskMeFi search. What I am in need of is a web 2.1 muti-media blast to present to an audience of more than 2,000.

Our company is looking at sustainability as a major topic for the coming year. The first quarter is my chance to blow them away with resources to dazzle, amuse and convert folks to the idea of zero-waste. Or a Newtonian type of approach to zero waste.

Please do your darndest to help me find the latest, the greatest, most bulletproof and the mostest superlativest resources available that are not of a particular political persuasion and have a serious, reasonable and verifiable economic benefit slant (consumer or corporate), in addition to any tree-hugging feel good appeal.

How many times to erase hard drive

bad grammar — Mon, 08 Jan 2007 18:51:16 -0800

How many times should I zero the hard drive of a laptop I am going to sell? I have an old iBook (the display fritzed) that I am planning to sell on Ebay. I had the hard disk zeroed in a single pass. This took two and a half hours. Because the display is not working, I had to take it to a Mac repair shop and wait. Now I am wondering about security. Should I have the hard disk zeroed again, seven times, thirty-five times?

There was no financial information on the computer (Quicken, tax programs, etc.). I prefer to contemplate my dismal finances on scribbled scraps of paper. My net-surf patterns would show that I sometimes visit websites with encrypted pages for buying on-line; I have an Ebay account, etc.

I hope that nobody is interested in my journal, fanfic, or academic papers and manuscripts.

Zero

furiousxgeorge — Tue, 18 Jul 2006 13:02:57 -0800

Does absolute zero actually exist in the universe or is it just a theoretical concept? Settle an argument.

Is zero a cube?

ubernostrum — Wed, 02 Mar 2005 17:16:58 -0800

This page mentions, among other things, that "100 is the smallest square which is also the sum of 4 consecutive cubes." Obviously, this refers to the sum of 1^3 (1), 2^3 (8), 3^3 (27) and 4^3 (64). But it seems to me that the sequence can be pushed back to start with 0^3 (0), in which case you can get four consecutive cubes adding up to 36, which is a square. Is zero then not considered a cube? I've been thinking about this for far too long, and I can see it going either way. For example: zero should not be considered a cube, because the logical implication of this is that it can be divided by its cube root. But its cube root is zero, and division by zero is an undefined operation.

But at the same time, there is a number n such that n^3 = 0, which seems to me to be the very definition of a cube.

Is Zero odd or even

Phatty Lumpkin — Sat, 03 Jul 2004 21:37:00 -0800

The Number Zero: odd, even, or neither?