Root Access

2:03 PM

@Bob Is it also job of risk assessment department?

@user2493976 Welcome to Root Access chat for Super Users! I am this channel's helpful chat bot. Please don't ask if you can ask or if anyone's around; just ask your question, and if anyone's free and interested they'll help. For bot commands, type !!listcommands

user2493976

How to calculate the size of the page table from this data?

A computer uses 46–bit virtual address, 32–bit physical address, and a three–level page table organization. The page table base register stores the base address of the first–level table, which occupies exactly one page. Each entry of the first level page table stores the base address of a page of the second–level table. Each entry of the second level page table stores the base address of a page of the third–level table. Each entry of the third level page table stores a page table entry (PTE). The PTE is 32 bits in size. The proces…

Bob

@user2493976 didn't you ask it on SU earlier?

I was on my phone at the time, but I remember thinking it might've been more appropriate on Stack Overflow or Computer Science

though it's a bit borderline for SO, and I'm not sure what exactly CS takes

Braiam

probably more CS than SO

user2493976

@Bob Yes, but i just can't seem to figure out this one

Braiam

2:09 PM

@Bob stop making my chats obsolete!

>:(

Bob

10

A: Homework policy

Policy We do not try to decide which questions are homework, and we don't use a special tag. Users that want to receive hints rather than full answers should say so, and answerers should honor such requests (by not posting details or hiding them in spoiler tags). Other than that, the usual quali...

user2493976

@Bob any resources for solving this would do, I'm not looking for a worked out answrer

Bob

@user2493976 If you were to ask on Computer Science (again, I'm not 100% sure it's on-topic there), I'd recommend you try to generalise the question and maybe provide that block as an example.

user2493976

@Bob ok, thanks

Bob

@Braiam :(

@user2493976 If you would like to find out whether they would take the question, you can ask on their chat room or their meta. Remember, ask if you can ask that kind of question - don't ask the question itself on those places. Well, maybe the chat if they want to answer it there :P

Or you could just post the question and see how it goes.

Braiam

2:16 PM

> Hey professor, I'm not saying that you should tell me the answer, nor that I don't know the answer, but even if I know it I couldn't answer the question because I don't know what is being asked

allquixotic

hi

Bob

@Braiam That's actually a good point. He said somewhere that it was an exam question - it would be worthwhile for @user2493976 to ask his professor or tutors.

@allquixotic hi

flote

@allquixotic hello

ChatBot John Cavil

@ForkrulAssail Welcome to Root Access chat for Super Users! I am this channel's helpful chat bot. Please don't ask if you can ask or if anyone's around; just ask your question, and if anyone's free and interested they'll help. For bot commands, type !!listcommands

Darth Android

@user2493976 The way you solve such a question usually starts with a) figuring out the size of one page of memory, and then b) using the "the first–level table, which occupies exactly one page" fact to determine how many entries fit in the first-level table.

jokerdino

2:19 PM

@ChatBotJohnCavil [helpful] flagged as subjective

allquixotic

!!tell 11728976 no

ChatBot John Cavil

user2493976

@DarthAndroid From this information how is it possible to find out the size of one page of memory?

Darth Android

@user2493976 I'm still not entirely sure on that, but I think it might have to do with the cache information on the end. It's been a few years since I did CPU cache stuff :(

Braiam

@Bob that's what I tell when the exams starts with gliberrish impossible to understand unless you read the mind of who made the exam

flote

2:23 PM

this looks pretty cool

kickstarter.com/projects/1964463742/the-mandate

2

Darth Android

I think you're supposed to figure out how many pages fit in the cache, and then given the 1MB cache size can figure out how big each page is

Bob

@allquixotic government back in full swing? :P

flote

like a dune/mass effect mix

Bob

I was fiddling with SVNKit on Java today. On a Tomcat project.

allquixotic

!!tell 11729076 yes

ChatBot John Cavil

2:24 PM

Bob

Pass in a null username and password expecting an auth exception => it logs in anyway.

Wat.

Hennes

How did you know my user/pass combination!

Bob

Turns out that a "feature" of SVNKit is disk-caching enabled by default. And it stores it in the system-default location, i.e. where the reference SVN command-line client stores it. On Windows, that's %AppData%/Subversion.

Which means it also shares credentials with other SVN clients.

fml.

user2493976

I read that the * metacharacter in UNIX means 0 or more, so if I use ls . shouldn't it match just the "." as well?

flote

@Bob :D nice

Journeyman Geek

2:32 PM

XD

I think thats a wheatie

Bob

@user2493976 You're probably talking about regex

* doesn't mean anything in "unix"

in certain shells, it's a globbing character for filesystem access

user2493976

@Bob not reg ex, i am talking about unix/linux shell

Bob

@user2493976 there is no "unix/linux shell"

allquixotic

@user2493976 ls without any command line args won't list . (the current directory)

Bob

you have dozens, if not hundreds or thousands, of shells available

allquixotic

2:34 PM

you'd have to run ls -a . which would return one result: .

user2493976

@Bob Yes I meant a shell

Hennes

What is with all this ls usage? Real people use magnets or echo * ;-)

Bob

and they do have different interpretations of globbing characters

user2493976

@Bob What does the * mean then in a shell?

Bob

depends which shell

allquixotic

2:36 PM

ls only has special behavior if the argument passed to it gets interpreted specially by the shell, or if it provides a builtin ls implementation that's not compliant with SUS/POSIX standards; otherwise ls should behave equivalently regardless of which shell you're on

Bob

If you were using Bash, tldp.org/LDP/abs/html/globbingref.html

@allquixotic the shell would interpret globbing characters before passing anything to ls, though

allquixotic

actually ls -a . will return the contents of the current directory, which is equivalent to ls -a without the .

just tried it in cygwin :p

@Bob obviously. but I have not yet found a shell that interprets . as a special character

Bob

@user2493976 wait, why are you asking about the * character and giving an example with . ?

@allquixotic I was referring to the * that was part of the question

if you mean how ls * and ls . act, well

user2493976

@Bob thanks, I got the answer there, its mentioned Strings containing * will not match filenames that start with a dot, as, for example, .bashrc. ... I was asking why wasn't that expression ls . not matching the . file

Bob

@user2493976 * has nothing to do with ls .

ls . literally translates to ls on the current directory

allquixotic

2:39 PM

@user2493976 . isn't a file; it's a synonym for the current directory

Bob

that's because . in POSIX refers to the current directory

(wait, is it POSIX? anyway, it's part of the FS access)

if you meant ls *, that * gets expanded by the shell before calling ls

allquixotic

when you pass any directory, even ., to ls, it will look inside that directory and attempt to determine the files and directories that are immediate children of it, and list them out

user2493976

@Bob the original question reads ls .

allquixotic

@Bob the FS layer in modern UNIX derivatives is based on POSIX, yes

Bob

that * would match everything in the current working directory and pass them all to ls, which will then echo them if it's a file or list their contents if it's a directory

allquixotic

2:41 PM

I mean the actual user-facing semantics and behavior, not the implementation details

Oliver Salzburg

Jesus Christ. I just downloaded a 2GB setup file because the live update of the product doesn't work and then I find out that the setup file doesn't even work for all languages. And the language files make up, what? Like 5MB. So now I have to download the 2GB set file for the correct language

user2493976

@Bob oh sorry, the question should have read ls "star dot star"

allquixotic

for instance, the fact that directories are separated by /, the . character for CWD, etc

Bob

@user2493976 your original question mentioned *. why did it do that?

@user2493976 ah. makes more sense, thanks.

Oliver Salzburg

And this line is so slow it takes 40 minutes to download wtf

Someone needs to suffer for this!

Bob

2:42 PM

ls *.* relies on shell globbing

If you're on Bash, Bash will expand *.* and ls will be called on that expansion

ls never sees the *.* (unless there is no expansion available)

user2493976

@Bob yes that part I had read

Bob

@allquixotic I meant, is the behaviour of . and .. defined in POSIX?

allquixotic

ls *.* on Bash or Bourne-derived shells causes ls to receive an ARGV like the following: {"ls", ".", "..", ".emacs", ".bashrc", "dev", "downloads", "somefile.txt"}

user2493976

so what does star dot star mean @Bob?

Simon Sheehan

Fired up my parents stereo from 1991.... this thing sounds beautiful

bass from 1991 is lovely too

allquixotic

2:44 PM

@user2493976 by default, plain old * as a glob character doesn't include files or directories whose name's first character is .

Bob

@user2493976 in Bash, it literally expands to everything in the current working directory that has a . in it

allquixotic

so *.* tells it "include those anyway"

user2493976

@Bob including the "." just ?

allquixotic

actually it's more complicated than that

Bob

@allquixotic doesn't seem to

allquixotic

2:45 PM

ls *.* also traverses subdirectories and lists their contents as well!

Bob

:S

@allquixotic ya

it works on two levels

say you have dir1/ dir2/ and file1 file2 in the current directory

* would expand to be literally equal to dir1/ dir2/ file1 file2

ls * would be literally equal to ls dir1/ dir2/ file1 file2

so ls would proceed to list the contents of dir1/ and dir2/, and list the files file1 and file2

user2493976

excepting files beginning with a . as per the link you shared

Bob

you have the shell expansion first, followed by the ls traversal

allquixotic

and when you pass multiple arguments to ls, it will parse each argument (delimited by a space character on the command line, which causes it to be passed as a separate element in the ARGV array) and do the equivalent action as if you called ls on that argument alone

Bob

@user2493976 yea, that thing is a bit weird

also, *.* would only list files and directories that have a . in them

allquixotic

2:48 PM

so ls abcd "ef gh" supplies ls with an ARGV (command line argument array) like the following: {"ls", "abcd", "ef gh"}

Bob

so dir1/ would not be listed, but dir1.test/ would

allquixotic

@Bob *.* is freaking weird, it's not doing that for me at all

Bob

doubling up shell globbing and ls is usually a weird thing to do

user2493976

I tried it out just now, its not matching directories

@allquixotic I agree

@allquixotic what are you getting?

allquixotic

ls *.* in a directory containing .goodbye, .hello, lol, subdir/ and visible.txt returns just visible.txt

Bob

2:50 PM

@user2493976 it would match if they had a dot in them

because you're specifying <anything>.<anything>

allquixotic

so it matches file or directory names that contain a period except on the first character

Bob

$ ls -a
.              .lesshst         .viminfo                            index.html
..             .pki             .vimrc                              mbox
.bash_history  .profile         Accesses.sql                        old
.bashrc        .screenrc        Hosts.sql                           pyqt
.cache         .sqlite_history  Sessions.sql                        schema.sql
.config        .ssh             awesomium_1_7_2_sdk_linux32.tar.gz  weblog.db
.dbus          .vim             awesomium_v1.7.2_sdk_linux32

$ echo *.*
Accesses.sql Hosts.sql Sessions.sql awesomium_1_7_2_sdk_linux32.tar.gz awesomium_v1.7.2_sdk_linux32 index.html schema.sql weblog.db

Braiam

the * implies that it should be any character, not none character

user2493976

@Bob yes its working now

allquixotic

it's kinda like matching files/directories in the current working directory that match this regex: ^[^.].*\..*$

Bob

2:51 PM

@Braiam any or none

@user2493976 if you want to match dotfiles, .* seems to work

so * and *.* don't work, but .* works

allquixotic

.* will also list the contents of the parent folder because .. is part of .* glob :P

Braiam

@Bob I meant lack of any character like .profile

Bob

@allquixotic that's only if you did ls .*

generally, don't call ls with globbing characters

Braiam

if it had any character be it (space), symbol, etc, it would match it

Bob

use find, or just plain old echo

@Braiam that's special behaviour

* will never match a . if it's the first character

in any other position, it matches anything or nothing

allquixotic

2:54 PM

I just use ls -la -- it takes care of including dotfiles for me

Bob

Bash has special behaviour for globbing dotfiles

(not that other shells might do something different)

Braiam

ms-dos don't agree but that's another thing altogether

allquixotic

lol i remember del *.* in DOS

Bob

@Braiam again, globbing is very shell-dependent

allquixotic

don't even go there please

Bob

2:55 PM

I've been talking about everything in the context of Bash, so far.

(which is also why I really wanted to clarify the shell at the beginning)

csh might do something different, for example

Braiam

@Bob meh, I'm not willing to scroll up :P

Journeyman Geek

er

Bob

@allquixotic rmdir /s is worse :P

@JourneymanGeek wrong person? :P

Journeyman Geek

thats not right

wrong message too

Braiam

.................................................................... O_O

user2493976

2:56 PM

@Bob Uh the link you shared says "Strings containing * will not match filenames that start with a dot, as, for example, .bashrc. " so why does ls .* match them?

Journeyman Geek

@Sathya see the deleted message above

allquixotic

@Bob oh come on!!! he was going to send you a key to download some files over utorrent! why didn't you say "SURE, send it over!" ???

there, solved.

lol

2:57 PM

@allquixotic: utorrent sync uses a shared secret to move files

it works brilliantly

Bob

> Filename expansion can match dotfiles, but only if the pattern explicitly includes the dot as a literal character.

allquixotic

@JourneymanGeek are you Edward Snowden? O_O

Hennes

We have come a long way since 1969. Much prettier suitys.

Bob

@user2493976 read the third note down at the bottom

Journeyman Geek

@allquixotic: no, I'm a small dog. I thought we went through this.

Braiam

2:58 PM

@allquixotic probably, the photo is touched so it looks like a dog... but he isn't a DOG!

allquixotic

@Braiam no, he's a GOD

Snowden has God complex :P

Bob

@JourneymanGeek TIL Edward Snowden is actually a small dog.

allquixotic

@Bob To think; a small dog going "rrrrrraaaaff! grrrrrrraaff raff!" could scare the big scary federal government

Braiam

is quite easy we change of topic... from bash to dogs, to gods to myself...

Journeyman Geek

@allquixotic: I don't have a god complex. Thats cats.

Bob

3:00 PM

@Braiam before you know it, we'll be discussing @JourneymanGeek's fiio amplifier

2

Journeyman Geek

er

allquixotic

@Bob LOL

Journeyman Geek

I don't own fiio headphones

I have one of their amps ;p

user2493976

@Bob thanks

allquixotic

let's talk about headphones and LTE :P

hey, doesn't Windows 8.1 become available for the genpop tomorrow?

Bob

3:00 PM

@allquixotic it's out already

Journeyman Geek

At the moment, I have fisher audio cans. and a suprisingly nice creative headset meant for phones

Bob

came out a few hours ago

Braiam

@allquixotic why should we talk, isn't more easy just to write it in l337?

allquixotic

@Bob O___O

Journeyman Geek

installing it now

Bob

3:01 PM

I'll try installing it over the weekend

Journeyman Geek

downloading the iso

allquixotic

I'll download it for my S Pro and my desktop tonight :)

my Planetside 2 outfit will understand my absence :/

Journeyman Geek

and hoping horrible things don't happen to my deduplicated drive

allquixotic

so will TotalBiscuit's Hearthstone video comment threads

Bob

@allquixotic it's via the store

I never used the store on this laptop :\

Braiam

3:01 PM

poor @Bob

allquixotic

@Bob I use the store constantly on my S Pro, and rarely on my desktop

hopefully the kernel bump doesn't bork Virtual Audio Cable

Bob

on the plus side, my last full disk image is very recent

Journeyman Geek

(the one, now ironically, refered to as the drive of impending doom)

Bob

just before the laptop repair

so if something goes wrong I can just restore

allquixotic

@JourneymanGeek DOID? sounds like a guy with a stuffy nose trying to say DROID

Bob

3:02 PM

@allquixotic sounds like a US gov thing

allquixotic

@Bob IF? with Windows upgrades, something going wrong is almost guaranteed :P

Journeyman Geek

@allquixotic: its the drive off my laptop, it has bad clusters

I use it as a place to store the files that are transient

Bob

@allquixotic hm, perhaps I should wait for HP to release updated drivers

allquixotic

my system runs VMware, Virtual Audio Cable, a crap VPN software with a custom kernel module, AMD's beta graphics drivers, VS2010, Visio 2013, Office Pro 2010, and has every possible Visual C++ and .NET runtime installed... what could possibly go wrong? :D

Bob

not having 8.1 isn't really going to harm me. at all.

Braiam

3:04 PM

meh, I don't understand the advantages of RAID6... is raid 5 for godness sake, just that more expensive!

Bob

@Braiam more redundancy

Journeyman Geek

lol

Bob

the whole point is redundancy

it's in the name for a reason

Braiam

@Bob 2 disks of redundancy... how much are the probabilities that 3 out 4 disk fails?

allquixotic

@Bob it's kind of a misnomer if you're using RAID0 though

Bob

3:05 PM

@allquixotic we don't speak of that here.

allquixotic

@Bob hey, I use RAID0 at home :(

Braiam

@allquixotic you want to get banned of your own chat room??? ummm??

allquixotic

(admittedly only with two disks, which is the best possible case for RAID0)

Bob

@allquixotic boo! death to the heretic! blasphemy!

Braiam

/kb @allquixotic

Bob

3:06 PM

@Braiam RAID5 has a nasty problem known as the write hole

(and RAID0 has a nasty problem known as lose-all-your-data)

Braiam

@Bob that's why I use drobo

allquixotic

@Bob which is reliably solved by either using a hardware RAID controller with a BBU, or ZFS

Bob

@Braiam that's not really comparable with RAID

@allquixotic the first can be considerably more expensive to set up and maintain, and the second can be impractical in a lot of situations, considering it relies on a specific FS

Braiam

who is telling that I want something comparable with RAID?

Bob

also, RAID6 gives you additional redundancy while you're rebuilding a disk

Journeyman Geek

3:08 PM

lol

I use a SSD

Bob

so a disk fails in RAID5 - you've lost your redundancy

if another fails during the rebuild (usually a considerably more stressful time), then you've lost your data

Journeyman Geek

and redundant backups on multiple boxen

(currently using bitorrent sync)

allquixotic

@Bob still, RAID-Z (which is essentially RAID-5 on ZFS) does make RAID5 viable, even without a hardware RAID card... although if it were me I would want the hardware RAID card over RAID-Z

Jimmy Hoffa

@Bob RAID42 has the best characteristics for safety and amazingness. All quantum computing is based around RAID42 bus configurations by default (laws dictate this fact regardless of actual bus implementation)

allquixotic

@JimmyHoffa RAID42? is that even a thing? is that where you have striping with a dedicated parity disk within a set, and then have another set that stripes that across at the bit level?

Bob

3:12 PM

@allquixotic "42"

Braiam

*goes in his time machine to the future and find a RAID 42 article saying that is crap, just to prove that @JimmyHoffa is wrong*

Jimmy Hoffa

@allquixotic RAID42 is when you construct a super computer in the future which goes back in the past to make your data backed up and accessible across timelines. If you have corruption though you can't retrieve the backup for another century.

allquixotic

so D0, D1, D2 = block level striped with parity bits stored in D3, and the {D0/D1/D2, D3} set gets bit-level striped over to another identical set?

troll. I thought you meant actual RAID4+2

Jimmy Hoffa

@allquixotic Welcome to my bridge, I hope you like the carpet. Thankyou please come again.

allquixotic

@JimmyHoffa you didn't happen to be trolling about FP too, did you?

Jimmy Hoffa

3:14 PM

heh no

allquixotic

k

jokerdino

whoop whoop

Braiam

@allquixotic don't believe him, he's trolling you NOW

@Braiam no, YOU are

!!tell 11730505 no

3:15 PM

and what you all don't know is that I am trolling all of you, because I knew from his first mention of RAID42 that he was trolling

jokerdino

I didn't know he was trlling. :/

allquixotic

somehow, recursive trolling / functional trolling seems to make a bit of sense when Jimmy is involved

Journeyman Geek

@allquixotic: setting up raidz properly is tricky tho

Jimmy Hoffa

@jokerdino Mine some qubits and get started on your supercomputer now, you might have it done before you die at which point you'll send it back and have it already! :D

jokerdino

3:16 PM

@JourneymanGeek did you send your assgn yet?

Journeyman Geek

yeah

jokerdino

NOOO

Journeyman Geek

emailed the school with a VERY detailed error report

it was working the next day

Braiam

wait, I can revert a vote in a edited post, but can't revert a edited stared message in chat?!?!

jokerdino

@Braiam yes

allquixotic

3:17 PM

@Braiam a mod can delete it though, or even edit it on your behalf

jokerdino

#nothingtoseehere

allquixotic

a mod should totally edit all my posts, that would be funny. NO

jokerdino

Ahaha, funny.

Sidenote: The rooms I populate are the most friendly and least controversial.

Braiam

that and that you ignore flags :P

jokerdino

Flags are for minions.

Braiam

3:20 PM

^ yeah, I totally agree

Journeyman Geek

image not found ;p

jokerdino

brb -- dinners

Darth Android

@JourneymanGeek Setting it up is easy, getting it to work as efficiently as a RAID5 is not.

Simon Sheehan

@DarthAndroid Efficiency is hard with RAID. Takes more time than people think

Journeyman Geek

@DarthAndroid: I was thinking stuff like needing an SSD for ZIL, for things like dedupe ;p

Bob

3:41 PM

...SURE

store.emprgroup.com.au/…

$100 for a bag of screws

4

allquixotic

@Bob hey, they're screwing you, isn't that what you wanted?

Darth Android

@JourneymanGeek the ZIL isn't as useful as I thought it would be. It's not a write-back cache :(

Psycogeek

@Bob hey if you need some screws, I got a whole bag of them I can send you. They belong in something :-) but hell whatever it was it still works

Bob

lol

Darth Android

And efficiency isn't that hard with raid. Throw 5 drives together and I expect 4X read speed and 1x write speed, maybe faster write speed if you're doing bulk writing.

Bob

3:44 PM

@Psycogeek nah, I was actually looking for a replacement power jack :P

just came across the screws

Darth Android

can't get that kind of performance out of raidz at all.

and I can't figure out why.

Bob

oh, at least HP documents their servicing procedures very well

and publicly releases the manuals

Psycogeek

no tv hasn't gone downhill "Unsafe Sex In The City"

During a visit to the clinic, staff discover there may be more going on downstairs than previously thought. How will this affect her new relationship and will her boyfriend be in danger too? In Exeter, farmer Greg is suffering with pain down below and his new girlfriend won’t sleep with him until staff have got to the bottom of it. The clinic team decide to take chlamydia testing to a young farmers foam party in an attempt to stop STIs spreading like muck.

Maybe the weird thing is not that its on, but that people watch it :-)

Magaluf riddled with STIs? 20-year-old Heather has been suffering with genital warts. That would make me want to watch :-)

Ariane

Question. What would be my simplest, fastest way to boot into another OS for the sole purpose of deleting Windows system files that I can,t get rid of otherwise? Last time I tried, I made an Ubuntu bootable USB key, which kinda did work, but the "deleted" stuff was thrown in a .Trash-999 folder, simply, so I'm not rid of them. And well that was a rather large thing to download (3 times until I got one that worked) for such a simple task.

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