Root Access - 2013-02-21 (page 3 of 4)

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6:01 PM

Yaaaay SF rep.

I suck at SF, and they'll probably laugh at me

But seriously: why copy at the block layer?
Why not create the new partitions are desired, then rsyn/other_copy all files?

The only reason I know to copy at block level is for repair or forensics

If your source OS is fine, then just file copy

@Hennes file copy is laborious and doesn't necessarily preserve permissions etc, also the bootloader

I want the destination to be as similar as possible to the source

You can rerun grub for the install. And permission can be maintained.

E.g. if you use dump (A tool to dump filesystems)

@allquixotic SF laughs at everybody. So far you have two upboats so... better than I've done there. :P

6:05 PM

But a one on one copy would be
Destination: `nc -l 1234 | gzip | dd of=/dev/sda`
Source" `dd if=/dev/sda bs=1M of=- | gzip | netcat -p 1234'

(syntax unchecked)

might use a faster compression algorithm than gzip; something like lzo... something that can easily coalesce huge bunches of the same repeated data but doesn't take ages to compress fairly complicated data

dd to grab all low level block data.
BS for a reasonably block size to prevent a gazillion 512 byte requests
gzip to gzipped the data (Assuming you have more CPU power then Gbit bandwidth)
NC to dump it onto the network

gzip would probably severely limit the transfer rate to less than 100 Mbit even though I have 1 Gbit available

Aye

it depends on a lot of stuff. DiskIO speed, CPU power, etc etc

If you need to do that a lot then you could bechmark all the options

Or even pipe though tc to see progress

Personally I would just partition the new server as I like it, then copy all the data with rsync (exclude /dev, set the options to preserve file rights).

Which is something you can restart when you need, and which does not care about filesystem sizes. As long as the data fits it is fine.

ask.slashdot.org/comments.pl?sid=3479839&cid=42960417

Yes, the nerdy solution is to pull the cavity magnetron out of your microwave oven, add a highly directional antenna to the waveguide output, fire that baby up, and blow out the RF stage of his router.

Extra nerdy points for plating/honing the cavities to re-tune the cavity magnetron tube to the correct wi-fi frequency (the diameter of the cavity is determined by c=f/lambda where c is the speed of light, f is the wi-fi center frequency, and lambda is the wavelength. Remember, electrons circulate (because of spin=1/2) around the hot cathode, and the basic operation is like that of a whistle…

6:14 PM

dd is useful. I used it to migrate data from a smaller vhd to a larger vhd partition. Apparently it was the only way to get the raw data from the disk moved over so I could expand the partition into empty space on the new vhd file.

First fault spotted already. gunzip on the receiving end. not gzip.

Probably not the only way. cat /dev/sda should also work

As might a simple cp

I suspect that dd with a decent block size is a lot faster

ideally I would like the data to be encrypted because I'll be passing over a few switches that are shared by other customers

cp isn't good enought. It doesn't copy structure. This was a Linux OS install disk. :)

Actually, cp wouldn't be good once it traversed into /dev, methinks.

rsync via ssh encrypts.

cp /dev/sda would not see files. Just blocks.

I dunno. I used it and it worked. :P

6:16 PM

(No mounted partition, raw disk blocks)

:) It was my first and only use of dd. So, can't claim to be an expert :P

It's not something I find need to use often.

dd is great. It allows you to do a lot of good things. It also allows you to shoot yourself in the foot

Well, I was bringing up a Linux VM for use with work and didn't feel like going through the whole install/config process again (though I could if I needed to). I never do stuff like that without a backup plan.

"backup" plan... hahaha (pun wasn't intended, I swear!)

I feel like I'm getting only upvotes from people in RA on my SF question

+4

6:18 PM

which is kind of like having your own little group of Republican friends at the DNC saying "yeah, this is good stuff!"

Well, I often upvote a well written question which shows thought.

But if you want I can downvote. :)

I don't have access to the router (admin access, I mean) at work, here. I don't even know what it looks like. What I do know is that on both my old Thinkpad laptop and my current Sony tablet/laptop, if I use Wifi, my connection drops constantly, making work through NX near impossible (except for short stints). However, the same machines work perfectly fine on every other wifi network I've used it on (at home, friends, etc).

What would cause a router to drop connections like that constantly? I will note that my coworker who has a Macbook Pro is always on WiFi and never has issues.

I don't know if everyone has these issues that I'm seeing, but I did see it happen across two of my Windows machines of different makes, with different chipsets and Windows versions.

To use my laptop at work with any reliability, I have to plug into Ethernet. It's only WiFi that drops all the time.

@BenRichards noisy RF spectrum, authentication compatibility issues, general protocol compatibility issues, vendor specific extensions on the router, vendor specific extensions on the client, different interpretations of the 802.11 specs, congestion, contention, interference, driver bug, polarization, router firmware configurables not properly set, bad Tx power adjustments, bad Rx power adjustments, no RTS/CTS, ...

is that enough? basically my story about wifi is fundamentally flawed, exactly because any particular problem has at least 100 possible causes that can't be ruled out easily

you can enumerate each possible problem, but the difficulty is isolating one particular parameter and seeing if it helps -- most things you try won't help, and you don't know if solving it requires a combination of steps or just one thing, etc

and you don't even know if the solution is within your control -- since you don't control the closed source device drivers or the router firmware, the problem may be "baked in" and impossible to fix without using a different make/model of hardware

@allquixotic I know that, but I didn't know if there was a more likely scenario given the information I provided. The one Macbook Pro has no issues, but my two Windows laptops did. Old laptop had an AMD chipset, and the Sony has an Intel chipset. Old was Windows 7. New is Windows 8. Don't have problems on any other network. It's just this one.

@BenRichards consider yourself lucky that you only have the problem on the one network; I've only ever used one wifi network that wasn't complete crap

6:27 PM

I see others with Thinkpad laptops and I don't believe they have issues (can't be sure)

you can go through the motions and try updating drivers but chances are it's literally a baked in problem, as are most wifi problems.. you can hold the laptop right up to the base station and it'll get maybe 18 KB/s and randomly drop out, so it's not an interference issue

Jeff Ferland seems to agree with me. Same answer as I gave.

@Hennes heh yeah. It's really not that many partitions, so the number of rsync calls is, what, 2? 3?

@allquixotic It just stymies me. I just asked a coworker with a Thinkpad (Windows 7) and he said he doesn't experience this at all.

@BenRichards thinkpads have used wildly different wireless NICs historically

6:30 PM

I think it is a matter of style. You want to copy files, so uses a file copy tool

@allquixotic My old laptop was a Thinkpad Edge (but with an AMD chipset), and experienced this.

different versions of Intel WiFi adapters have been very different in quality and behavior, not to mention some Thinkpads used/use Realtek

"it's a thinkpad" doesn't say anything about its compatibility with wifi base stations

@allquixotic I did say it had an AMD chipset. :P Coworkers here have Intel, I think. I figured they would just use Intel's wifi?

I know the Sony that I have right now uses Intel.

@BenRichards just because it has an intel chipset doesn't mean it has an intel wireless NIC

and an AMD chipset can use an intel NIC

I found the key to making my home WiFi network rock solid was both placement (it's now broadcasting from almost the direct center of the house) and installing dd-wrt and scheduling an automatic reboot once a week. All router issues were eliminated. Haven't had issues for a few years, now.

@allquixotic Weird. I thought it was just a part of the platform, or built-in to the CPU or something.

6:34 PM

Ugh. Rebooting.

I heard from quite a few people who need to do that with WAPs

But I never had that problems (with Linksys WRT-54GLs and now a 110)

I think it's a requirement for Linksys routers (the cheap ones, anyway--I don't buy them over $100)

It happened sometimes with our WRT54G. More often with my WRT160N. Once a week may be overkill but on every Sunday early morning no one is using the network anyway. Works fine.

I don't even notice it.

I find it telling that dd-wrt has that feature categorized under their "Keep Alive" tab :P

I used the native OS on the 54-GLs. Worked fine, even when using torrents.
And I make it a point to torrent new releases (e.g. when FreeBSD 9 came out)

My wifi card here right now is: Intel Centrino Advanced-N 6235 AGN 2x2 HMC WiFi/Bluetooth Adapter

@Hennes WRT54G is on stock firmware (not used atm though). WRT160N is on dd-wrt.

@BenRichards no, only embedded SoCs have WLAN built into the CPU; it's usually a Mini-PCIE card on a laptop

Are you using bluetooth. Does it work if you turn that off ? (also uses 2.4 GHz band)

6:40 PM

@allquixotic Ah, didn't know that.

@Hennes Bluetooth uses 2.4GHz too? Whyyy?

It's on, I think.

@BenRichards since it's Mini-PCIE you could technically swap it out with another chipset if you wanted

@allquixotic Since the Sony is technically an ultrabook, cracking this thing would probably break it :P

@BenRichards solution: use 5 GHz band for wifi (if the question "does your router support 5 GHz?" makes you go "uhh..... I don't know? I would think so?", then don't do this)

I can try with Bluetooth off. However, we have a wireless phone at home that is in the office (same room as the wireless router) that operates on 2.4GHz and it never interfered with network quality, oddly enough (I tested).

Heh, well N uses 5 GHz. I think I default to that. Just not at work, I'd hazard a guess. I don't get the impression that they've touched their network infrastructure for a while.

I will try disabling Bluetooth to see if it makes a difference. Don't think I tried that.

Them both being on the 2.4GHz band seems like a critical oversight, to me.

There is a reason for that

2.4 GHz band is public usable.

6:44 PM

@BenRichards No, don't assume "802.11n == 5 GHz"

So phones, BT, wireless B/G/N (can do 2.4 and 5!) use it

802.11n operates in both 2.4 and 5 GHz bands

@allquixotic I know it can use that and 2.4GHz. But I did enable 5 GHz.

@Hennes Makes sense.

@allquixotic I don't think by default my router at home enabled the 5 GHz band (can't remember, though). I did make sure it was enabled, at least.

@BenRichards yeah but does your laptop also support dual band

Well, on to wifi to see if it works any better, now.

6:45 PM

many mobile devices (most?) only support 2.4 GHz

Yes. I enabled support for that a while ago when I was trying things.

the Sony, too?

I meant on the Sony. Can't do anything to the router here at work. No admin access :P

The password on the router is '1234'

Disabling bluetooth made no difference. Also turned my cell phone off for good measure to no effect

6:49 PM

uhm. I should clarify the phone part.

cardless HOME phones use 2.4

mobiles do not.

I know.

This does seem to localized but it looks like you're about to answer it @Hennes: superuser.com/questions/554936/…

I turned off my cell phone because I was too lazy to go into settings and disable bluetooth on it :P

Should I put the last bullet in it?

ah, I feared I gave the wrong impression

6:50 PM

hey all! :)

Hi

Mass Luminosity global give away again. $3000 computer

When I was in the NX session over wifi, the connection would hang up every 10 seconds or so for a few seconds and then come back.

Blog - Stack Exchange: Podcast #43 – False Facts & Blood Feuds

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That was NX and Synergy, actually. I use Synergy to send mouse+keyboard over to it from my desk.

Could it be a packet size thing? Maybe the packet transmission is out of sync or whatever?

6:53 PM

@BenRichards well there are three types of "packets" in a WLAN

there are physical radio packets, IP packets/fragments on top of that, and TCP packets on top of that

(just noticed the preferred band setting btw, changed it to 5.2 GHz (was previously "no preference")

problems or misconfigurations in the lower layers can cause problems for the upper layers

ok

Before I go into that, what's CTS-to-self or CTS/RTS?

@allquixotic 6 upvotes. That's definitely not RA. :P

I mean RTS/CTS.

6:57 PM

user image

zoomed in. beautiful font rendering. using this to write documentation to help people in my work, and I used SU's edit post with Chrome to produce that lovely graphic

Nevermind. CTS-to-self seems to be a good thing

And it's already enabled, so I'll keep it.

used Chrome's devtools to change the font family for the I so it was obvious it's a capital I, and zoomed way in for a higher DPI raster

@allquixotic just installed JDK in Ubuntu, how do I set the JAVA_HOME variable ?

so that I dont have to set the path over and over again ? :)

@LittleChild I know! :P export JAVA_HOME=/path/to/java in your ~/.bashrc file.

$sudo echo "export JAVA_HOME=\"/usr/lib/jvm/java-7-openjdk-amd64/\"" >> ~/.bashrc

7:01 PM

That works :)

why sudo?

hold on buddy, working on it :-)

Yeah, sudo isn't necessary but it shouldn't be a problem either.

it would be a problem if you are creating ~/.bashrc from scratch....

@allquixotic just copied it from Mykong.com I have no idea what sudo does

7:02 PM

because it would be owned by root

so you couldn't then write to it as a regular user again

@allquixotic That is true but I doubt he's creating it from scratch...

and the ~ gets evaluated as /home/user and not /root because it's expanded before processing the command

Usually there's a placeholder.

so I should drop the sudo ??

you know what's evil? making a directory named ~

and then cackle as people try to remove it :D

7:03 PM

Yeah, no sudo. :)

just the export part of $sudo echo "export JAVA_HOME=\"/usr/lib/jvm/java-7-openjdk-amd64/\"" >> ~/.bashrc

and omit the $, obviously, that's just telling you "run this from a regular user prompt"

@allquixotic Creating files in cygwin using reserved characters is evil. Cygwin doesn't prevent you from doing that and they show up in the Windows command prompt, but you can't do anything with them since it interprets those characters :P

Well, you can, but it takes a few hoops to jump through

\\?\

@BenRichards yeah because NTFS supports more special characters than the Win32 subsystem does

7:05 PM

Yeah

To name just one hoop

and Cygwin doesn't use the Win32 subsystem for file I/O

NTFS supports a crapload of stuff. It's even case sensitive. But the Win32 subsystem can't use it all because of backwards compatibility.

having files that differ in name only by case >:)

I tried enabling case sensivity, but too much just breaks.

7:06 PM

It actually stores the case, but won't differentiate between two files that have different cases in their names.

I wish microsoft would push that with their next OS or their next SP

@Hennes billions of C/C++ files would break, that include <Windows.h>

that problem already exists when cross compiling win32 code on mingw32 toolchain on linux

Easy enough to fix

Keeping ancient stuff with you for ever will slow you down

I am not saying change 100% anew, disacard everything

After compilation, it doesn't care about the #include statements. And if you're compiling, you can batch replace all those lines with a simple command.

not debating that

the Win32 subsystem is more or less an emulator as it is; the native capabilities of the kernel and core platform far exceed it

7:07 PM

Now, dynamic linking could break.

But hey, win 8 is supposed to break stuff. After all useful/useless versions get alternated by MS

@Hennes and the useless versions are usually the ones that push big breaking changes

like Vista, which pushed UAC and a ton of other stuff but made tons of programs go crazy that used to work on XP

but anything designed for Vista pretty much works fine on 7 or even 8

Well, vista was not useless. I was a lot better than XP

`export JAVA_HOME=\" /usr/lib/jvm/java-7-openjdk-i386" Correct?

The fun DOS form for 8.3 filenames still works, btw. :P You can still do dir c:\progra~1 and it works :P

7:09 PM

XP also broke a lot of stuff when ran as a non-admin user.

yeah, Vista SP2 was actually quite decent

open a system wide registry setting as readWRITE (the default) as a user -> fail

after the platform upgrade (which made its core platform equal to Win7 SP1) it was basically Win7

@LittleChild Yeah that should work

But people never needed to fix that. Solution: RUn as admin

7:09 PM

@BenRichards do I have to add the ~/.bashrc

Of course you can always just open up ~/.emacs in a text editor and put it in yourself.

Yeah.

ok

uhh

why are you putting a space after JAVA_HOME

\"

The command you need is:
echo "export JAVA_HOME=\"/usr/lib/jvm/java-7-openjdk-i386\"" >> ~/.bashrc

Hmm, do you use bash or another shell ?

7:10 PM

Yeah, just noticed that too.

err

I know bash is often the default, but it still is an assumption

there are no spaces so you don't even need escaped quotes

Quotes don't hurt

echo "export JAVA_HOME=/usr/lib/jvm/java-7-openjdk-i386" >> ~/.bashrc

yeah, but escaped quotes look nasty

you end up building picket fences if you do too much unnecessary literalization

like sed /\/\/\/\/\\/

How do I know which shell it is that I am using

7:11 PM

Usually, I'll actually surround with single quotes so I don't have to escape stuff (provided I don't need to resolve variables)

echo $SHELL

@LittleChild you're using bash

:)

a blank line as output for echo $shell

capitalize SHELL

$shell is a different variable (case sensitivity!)

You have to worry about case when doing stuff in Linux

oh... :) I have a steep learning curve ahead of me

/bin/bash so I am using bash :)

Yup

7:14 PM

hmm, I did not know that one. I do know which shell I use because I explicitly set it.

(and no bash in /bin/ on my system)

so Unity is just the name for the interface of the shell ??

user image

anyways, if you want something more user-friendly than the echo line and all that, just open up ~/.bashrc in a text editor and edit it. gedit is the simple Gnome text editor that's probably installed on Ubuntu by default still.

@LittleChild The shell is what terminal you're using. That's irrespective of what desktop interface you use.

Compare it to using explorer.exe and cmd.exe

@Hennes that simplified it a lot :)

7:17 PM

Yup. :)

Aye. And many people do not realise that the windows desktop is an explorer process

3 votes to migrate... I really don't think this needs to go to SF: superuser.com/questions/555290/…

You can use bash in Windows (there are Windows ports for it out there).

ok I am getting confused now. I will save that for later :) @BenRichards

for now, I need to HelloUbuntu.java :pp

@LittleChild Sorry! Keep at it :)

Hehe

7:19 PM

oh ad just a question about keeping things neat and tidy.. what is the good practice when it comes to organizing the files and folders in Ubuntu ?

Linux is a fun beast. It can be anything and everything, so long as it has the Linux kernel. It's very modular. But that's for later.

@LittleChild User files go in ~. For the most part, that's all you need to know.

It's like your C:\Users\Username directory in Windows.

ok! :)

If you're using installers to install programs (which at this point is likely), it'll know where to put everything. You don't have to worry about where programs go until you start doing manual installs (usually compiling from source) and so forth.

The Linux file structure is confusing at first. Luckily there's only one user area so it's not too bad at the beginning.

@Hennes I don't know if each shell is required to define $SHELL. But I haven't seen one that doesn't, yet.

yeah :)

@Sathya @OliverSalzburg Either of you around to stop the above migration?

7:24 PM

where is the save as option in gedit ?

echo $SHELL
/usr/local/bin/bash
csh
echo $SHELL
/usr/local/bin/bash

csh did not change it

ok got it

@LittleChild You found it? gedit is kind of like Notepad + a few features, from my experience.

A good next text editor from that is emacs but while it looks inviting, it has a lot of depth to it that can get confusing for new users. :)

was trying to navigate to the folder where my java file is... I tried cd /Home/LJC/Java

but it says there is no such directory

Yeah, there's no /Home.

7:27 PM

so.. ??? /home/LJC/Java ??

is LJC your username? Then yes.

Like I said, case sensitivity :)

or just LJC/Java ?

You can just use cd ~, too.

well if you're sitting at /home/LJC (aka ~), then you can just cd Java.

oh so if I wanna navigate from something relative to home dir, I must do a cd ~/dir1/dir2 ??

You never put stuff in /home. That's just a place to put all user folders. Your stuff goes into /home/<username>. Most people just use ~ as a shortcut to the full path.

cd in Linux operates the same way as it does in Windows, for the most part.

You just have to deal with a different folder structure and case sensitivity.

7:30 PM

I have a folder named LJC under HOME :)

Your home directory is /home/LJC. The character ~ is a special character that acts as an alias to that. The environment variable $HOME also points to that folder.

I reached the Java folder, yeah!!!! :D

Congrats :)

and heres a question that is not specific to any computer topic

Oliver Salzburg

@Tanner @slhck handled it actually ;)

7:33 PM

@Hennes Not sure if invoking bash that way will change it. Saw the same behavior here, btw.

Oliver Salzburg

Oopse, completely missed this:

Programmers.SE 2013 Moderator Election

is it good to gain random info about computers from the internet and then build up on it (be a script kiddie) or go for a well-structured way to gain knowledge @BenRichards

I mean books and courses that go ground-up

@LittleChild Hard to say. Whatever works best for you. I just wouldn't rely on solely one or the other, in the end (personal opinion). I taught myself until I went to college.

Teaching yourself only goes so far unless you have good resources. Of course when I was young, the Internet wasn't very available to me so it was whatever books I could get my paws on and whatever I figured out from fiddling around on others' computers and reading help documentation.

I find the random learning thingy hard because you have no idea what you know, what you do not know

Yeah, that's one reason why I advocate getting formal education at some point.

7:36 PM

does not have to be formal education, it could be books or a free course online

If you find a good textbook, it can help a lot. I actually used to love the "For Dummies" series of books, as well. I had a few of those for different versions of Windows.

or you could draft your own curriculum and then learn step-bystep

The "For Dummies" line of books actually is very good quality, in my experience. Great for explaining things simply, yet they can have a ton of information and depth.

like, I know I am new to Ubuntu so step 1 - learn to install and uninstall softwares

step 2 - learn the ways to tweak the softwares

step 3 - shell

nothing formal - just organised :)

head First too :)

For me, I didn't draft a curriculum. I just poked and prodded and tweaked. Occasionally broke things, then had to fix them since they were usually on my mom's computer (though occasionally, the school computers) :P

7:39 PM

oh boy :D

Have you any experience with Servlets ?

Not much

I've heard of it. Might have done stuff with them. That's about it :P

ok.. I got the Head First book on it and it uses servlet spec 2.8 while 3.0 is latest

I guess the effort of reading that tome is a waste ?

I dunno. Wasn't useful for my purposes, at least, apparently :P

Just to lighten the mood here:

@BenRichards it is just 2 damn funny :D

@LittleChild Can't. I'm at work :)

7:44 PM

k :)

anyways, c ya :) need to go

half past 1 here :)

See ya

:)

Einsteins Grandson

7:57 PM

hey guys

i have to change settings in here:

c:\WINDOWS\system32\drivers\etc\hosts

@EinsteinsGrandson websphere... cool

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Transcript for

Feb '1321

Root Access

For all you Super Users out there. You have backups, right?

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