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  • Choosing a Wiki for an academic institute

    - by abhishekgupta92
    I need to choose a Wiki. Please someone help. Following are my requirements: 1) Need good control to the access variables 2) LDAP integration support 3) User Group Support 4) Good Themes and Templates Mediawiki has the problem that it does not support Users Groups that intutively. Twiki and Foswiki have a problem that any authenticated user that has write permissions for a topic also have the write to change the particualar permissions for the topic. Else, can someone suggest me where to look for the answer. I know about the WikiMatrix

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  • Choosing a Wiki for an academic institute

    - by abhishekgupta92
    I need to choose a Wiki. Please someone help. Following are my requirements: 1) Need good control to the access variables 2) LDAP integration support 3) User Group Support 4) Good Themes and Templates Mediawiki has the problem that it does not support Users Groups that intutively. Twiki and Foswiki have a problem that any authenticated user that has write permissions for a topic also have the write to change the particualar permissions for the topic. Else, can someone suggest me where to look for the answer. I know about the WikiMatrix

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  • Software Center not Opening at all Error

    - by Newbie
    When I open software from menu, it says "cannot open software database. Please reinstall the software-center package. When I write software-center on terminal, such error comes: 2014-05-28 09:11:20,584 - softwarecenter.ui.gtk3.app - INFO - setting up proxy 'None' 2014-05-28 09:11:20,593 - softwarecenter.ui.gtk3.app - ERROR - xapian open failed Traceback (most recent call last): File "/usr/share/software-center/softwarecenter/ui/gtk3/app.py", line 302, in __init__ if self.db.schema_version() != DB_SCHEMA_VERSION: File "/usr/share/software-center/softwarecenter/db/database.py", line 289, in schema_version return self.xapiandb.get_metadata("db-schema-version") File "/usr/share/software-center/softwarecenter/db/database.py", line 177, in xapiandb self._db_per_thread[thread_name] = self._get_new_xapiandb() File "/usr/share/software-center/softwarecenter/db/database.py", line 190, in _get_new_xapiandb xapiandb = xapian.Database(self._db_pathname) File "/usr/lib/python2.7/dist-packages/xapian/__init__.py", line 3667, in __init__ _xapian.Database_swiginit(self,_xapian.new_Database(*args)) DatabaseCorruptError: /var/cache/software-center/xapian/iamchert: Chert version file should be 28 bytes, actually 0 Now, when I write command sudo apt-get remove software-center dpkg: error: corrupt info database format file '/var/lib/dpkg/info/format' E: Sub-process /usr/bin/dpkg returned an error code (2) I had ubuntu before but it kind of got corrupted. Now, I have freshly reinstalled it and even at start, software center is not opening and this error comes. I hope you have a solution. Thanks.

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  • Have you used nDepend?

    - by Nick Harrison
    Have you Used NDepend? I have often wanted to use it, but never spent the money on it.   I have developed many tools that try to do pieces of what NDepend does, but never with as much success as they reach. Put simply, it is a tool that will allow you to udnerstand and monitor the architecture of your software, and it does it in some pretty amazing ways. One of the most impressive features is something that they call Code Query Language.   It allows you to write queries very similar to SQL to track the performance of various software metrics and use this to identify areas that are out of compliance with your standards and architecture. For instance, once you have analyzed your project, you can write queries such as : SELECT METHODS WHERE IsPublic AND CouldBePrivate  You can also set up such queries to provide warnings if there are records returned.    You can incorporae this into your daily build and compare build against build. There are over 82 metrics included to allow you to view your code in a variety of angles. I have often advocated for a "Code Inventory" database to track the state of software and the ROI on software investments.    This tool alone will take you about 90% of the way there. If you are not using it yet,  I strongly recommend that you do!

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  • External USB hard-drive changing drive letter

    - by Sydius
    I have a Seagate FreeAgent Go external USB hard drive that was mounted but mysteriously decided to reconnect itself: Sep 30 15:07:06 feinman kernel: [243901.551604] usb 1-1.2: USB disconnect, device number 3 Sep 30 15:07:06 feinman kernel: [243901.553828] sd 6:0:0:0: [sdb] Synchronizing SCSI cache Sep 30 15:07:06 feinman kernel: [243901.553893] sd 6:0:0:0: [sdb] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK Sep 30 15:07:10 feinman kernel: [243905.336557] usb 1-1.2: new high-speed USB device number 4 using ehci_hcd Sep 30 15:07:10 feinman kernel: [243905.431219] scsi7 : usb-storage 1-1.2:1.0 Sep 30 15:07:11 feinman kernel: [243906.427207] scsi 7:0:0:0: Direct-Access Seagate FreeAgent Go 0148 PQ: 0 ANSI: 4 Sep 30 15:07:11 feinman kernel: [243906.428303] sd 7:0:0:0: Attached scsi generic sg1 type 0 Sep 30 15:07:11 feinman kernel: [243906.430317] sd 7:0:0:0: [sdc] 625142447 512-byte logical blocks: (320 GB/298 GiB) Sep 30 15:07:11 feinman kernel: [243906.430860] sd 7:0:0:0: [sdc] Write Protect is off Sep 30 15:07:11 feinman kernel: [243906.430865] sd 7:0:0:0: [sdc] Mode Sense: 1c 00 00 00 Sep 30 15:07:11 feinman kernel: [243906.431386] sd 7:0:0:0: [sdc] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA Sep 30 15:07:11 feinman kernel: [243906.493674] sdc: sdc1 Sep 30 15:07:11 feinman kernel: [243906.496109] sd 7:0:0:0: [sdc] Attached SCSI disk It changed from sdb to sdc, causing a number of problems for me. What can I do to further track down the cause? I thought it might be a problem with it sleeping but when I cat /sys/class/scsi_disk/6\:0\:0\:0/allow_restart, I see that it's already 1.

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  • Solving Big Problems with Oracle R Enterprise, Part I

    - by dbayard
    Abstract: This blog post will show how we used Oracle R Enterprise to tackle a customer’s big calculation problem across a big data set. Overview: Databases are great for managing large amounts of data in a central place with rigorous enterprise-level controls.  R is great for doing advanced computations.  Sometimes you need to do advanced computations on large amounts of data, subject to rigorous enterprise-level concerns.  This blog post shows how Oracle R Enterprise enables R plus the Oracle Database enabled us to do some pretty sophisticated calculations across 1 million accounts (each with many detailed records) in minutes. The problem: A financial services customer of mine has a need to calculate the historical internal rate of return (IRR) for its customers’ portfolios.  This information is needed for customer statements and the online web application.  In the past, they had solved this with a home-grown application that pulled trade and account data out of their data warehouse and ran the calculations.  But this home-grown application was not able to do this fast enough, plus it was a challenge for them to write and maintain the code that did the IRR calculation. IRR – a problem that R is good at solving: Internal Rate of Return is an interesting calculation in that in most real-world scenarios it is impractical to calculate exactly.  Rather, IRR is a calculation where approximation techniques need to be used.  In this blog post, we will discuss calculating the “money weighted rate of return” but in the actual customer proof of concept we used R to calculate both money weighted rate of returns and time weighted rate of returns.  You can learn more about the money weighted rate of returns here: http://www.wikinvest.com/wiki/Money-weighted_return First Steps- Calculating IRR in R We will start with calculating the IRR in standalone/desktop R.  In our second post, we will show how to take this desktop R function, deploy it to an Oracle Database, and make it work at real-world scale.  The first step we did was to get some sample data.  For a historical IRR calculation, you have a balances and cash flows.  In our case, the customer provided us with several accounts worth of sample data in Microsoft Excel.      The above figure shows part of the spreadsheet of sample data.  The data provides balances and cash flows for a sample account (BMV=beginning market value. FLOW=cash flow in/out of account. EMV=ending market value). Once we had the sample spreadsheet, the next step we did was to read the Excel data into R.  This is something that R does well.  R offers multiple ways to work with spreadsheet data.  For instance, one could save the spreadsheet as a .csv file.  In our case, the customer provided a spreadsheet file containing multiple sheets where each sheet provided data for a different sample account.  To handle this easily, we took advantage of the RODBC package which allowed us to read the Excel data sheet-by-sheet without having to create individual .csv files.  We wrote ourselves a little helper function called getsheet() around the RODBC package.  Then we loaded all of the sample accounts into a data.frame called SimpleMWRRData. Writing the IRR function At this point, it was time to write the money weighted rate of return (MWRR) function itself.  The definition of MWRR is easily found on the internet or if you are old school you can look in an investment performance text book.  In the customer proof, we based our calculations off the ones defined in the The Handbook of Investment Performance: A User’s Guide by David Spaulding since this is the reference book used by the customer.  (One of the nice things we found during the course of this proof-of-concept is that by using R to write our IRR functions we could easily incorporate the specific variations and business rules of the customer into the calculation.) The key thing with calculating IRR is the need to solve a complex equation with a numerical approximation technique.  For IRR, you need to find the value of the rate of return (r) that sets the Net Present Value of all the flows in and out of the account to zero.  With R, we solve this by defining our NPV function: where bmv is the beginning market value, cf is a vector of cash flows, t is a vector of time (relative to the beginning), emv is the ending market value, and tend is the ending time. Since solving for r is a one-dimensional optimization problem, we decided to take advantage of R’s optimize method (http://stat.ethz.ch/R-manual/R-patched/library/stats/html/optimize.html). The optimize method can be used to find a minimum or maximum; to find the value of r where our npv function is closest to zero, we wrapped our npv function inside the abs function and asked optimize to find the minimum.  Here is an example of using optimize: where low and high are scalars that indicate the range to search for an answer.   To test this out, we need to set values for bmv, cf, t, emv, tend, low, and high.  We will set low and high to some reasonable defaults. For example, this account had a negative 2.2% money weighted rate of return. Enhancing and Packaging the IRR function With numerical approximation methods like optimize, sometimes you will not be able to find an answer with your initial set of inputs.  To account for this, our approach was to first try to find an answer for r within a narrow range, then if we did not find an answer, try calling optimize() again with a broader range.  See the R help page on optimize()  for more details about the search range and its algorithm. At this point, we can now write a simplified version of our MWRR function.  (Our real-world version is  more sophisticated in that it calculates rate of returns for 5 different time periods [since inception, last quarter, year-to-date, last year, year before last year] in a single invocation.  In our actual customer proof, we also defined time-weighted rate of return calculations.  The beauty of R is that it was very easy to add these enhancements and additional calculations to our IRR package.)To simplify code deployment, we then created a new package of our IRR functions and sample data.  For this blog post, we only need to include our SimpleMWRR function and our SimpleMWRRData sample data.  We created the shell of the package by calling: To turn this package skeleton into something usable, at a minimum you need to edit the SimpleMWRR.Rd and SimpleMWRRData.Rd files in the \man subdirectory.  In those files, you need to at least provide a value for the “title” section. Once that is done, you can change directory to the IRR directory and type at the command-line: The myIRR package for this blog post (which has both SimpleMWRR source and SimpleMWRRData sample data) is downloadable from here: myIRR package Testing the myIRR package Here is an example of testing our IRR function once it was converted to an installable package: Calculating IRR for All the Accounts So far, we have shown how to calculate IRR for a single account.  The real-world issue is how do you calculate IRR for all of the accounts?This is the kind of situation where we can leverage the “Split-Apply-Combine” approach (see http://www.cscs.umich.edu/~crshalizi/weblog/815.html).  Given that our sample data can fit in memory, one easy approach is to use R’s “by” function.  (Other approaches to Split-Apply-Combine such as plyr can also be used.  See http://4dpiecharts.com/2011/12/16/a-quick-primer-on-split-apply-combine-problems/). Here is an example showing the use of “by” to calculate the money weighted rate of return for each account in our sample data set.  Recap and Next Steps At this point, you’ve seen the power of R being used to calculate IRR.  There were several good things: R could easily work with the spreadsheets of sample data we were given R’s optimize() function provided a nice way to solve for IRR- it was both fast and allowed us to avoid having to code our own iterative approximation algorithm R was a convenient language to express the customer-specific variations, business-rules, and exceptions that often occur in real-world calculations- these could be easily added to our IRR functions The Split-Apply-Combine technique can be used to perform calculations of IRR for multiple accounts at once. However, there are several challenges yet to be conquered at this point in our story: The actual data that needs to be used lives in a database, not in a spreadsheet The actual data is much, much bigger- too big to fit into the normal R memory space and too big to want to move across the network The overall process needs to run fast- much faster than a single processor The actual data needs to be kept secured- another reason to not want to move it from the database and across the network And the process of calculating the IRR needs to be integrated together with other database ETL activities, so that IRR’s can be calculated as part of the data warehouse refresh processes In our next blog post in this series, we will show you how Oracle R Enterprise solved these challenges.

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  • PHP file_put_contents File Locking

    - by hozza
    The Senario: You have a file with a string (average sentence worth) on each line. For arguments sake lets say this file is 1Mb in size (thousands of lines). You have a script that reads the file, changes some of the strings within the document (not just appending but also removing and modifying some lines) and then overwrites all the data with the new data. The Questions: Does 'the server' PHP, OS or httpd etc. already have systems in place to stop issues like this (reading/writing half way through a write)? i. If it does, please explain how it works and give examples or links to relevant documentation. ii. If not, are there things I can enable or set-up, such as locking a file until a write is completed and making all other reads and/or writes fail until the previous script has finished writing? My Assumptions and Other Information: The server in question is running PHP and Apache or Lighttpd. If the script is called by one user and is halfway through writing to the file and another user reads the file at that exact moment. The user who reads it will not get the full document, as it hasn't been written yet. (If this assumption is wrong please correct me) I'm only concerned with PHP writing and reading to a text file, and in particular, the functions "fopen"/"fwrite" and mainly "file_put_contents". I have looked at the "file_put_contents" documentation but have not found the level of detail or a good explanation of what the "LOCK_EX" flag is or does. The senario is an EXAMPLE of a worst case senario where I would assume these issues are more likely to occur, due to the large size of the file and the way the data is edited. I want to learn more about these issues and don't want or need answers or comments such as "use mysql" or "why are you doing that" because I'm not doing that, I just want to learn about file read/writing with PHP and don't seem to be looking in the right places/documentation and yes I understand PHP is not the perfect language for working with files in this way...

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  • How does one rein in the complexities of web development ?

    - by Rahul
    I have been a server-side programmer for most of my career and have only recently started spending more time on web development. I am amazed at the number of things I need to master in order to write a decent web application. Just to list down a few tools/technologies I need to learn, Server side programming language (Java/JSP, ASP, PHP, Ruby or something else) A decent web framework (for any medium to big size application). HTML & CSS Javascript Javascript library (JQuery/ExtJS etc. primarily for AJAX). Good to know even if not necessary. At least a basic knowledge of web design - layouts, colors, fonts etc. A good understanding of web security. A good understanding of Performance/scalability issues. Testing, browser compatibility issues etc. The list goes on. So, my question to seasoned web developers is - How do you guys manage to learn and keep yourself updated on so many things? While developing a web application, how do you handle the complexities involved in these areas and yet manage to write an application that is well designed, user friendly, secure, performant and scalable. As a web developer, does one have to be a jack of all trades or should one specialize in one or two areas and leave the rest to other members of the team ?

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  • What to choose for a multilingual site with support for Markdown and commenting

    - by Kent
    I want to publish articles at a multilingual site. I want to be able to write an article in two languages and have them available on separate URLs: thesite.foo/english-breakfast thesite.com/engelsk-frukost If the users web browser is set to English I'd like to show a small notice at the top of the Swedish version with a link to the English one. The link should have an appropriate rel attribute for a translation (search for hreflang at http://diveintohtml5.org/semantics.html). There should be a way to list all articles belonging to these sets: Swedish only, English only, Swedish versions + English only, English versions + Swedish only. I'd like to publish these as four RSS-feeds. And I would like to have two versions of the main site, one in Swedish (showing Swedish versions + English only) and one in English (showing English versions). I shall be able to write the articles using Markdown, as that is the formatting language I find most convenient. There should be a way for users to comment. And some kind of way for me to protect myself against comment spam. I am leaning towards learning Drupal. I suspect I'll have to code this behavior myself as a module. To be frank I'd rather work with Java. Is Drupal the way to go? Or is there something more suitable for this project?

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  • Log rotation with automatic *.log file discovery

    - by Mikko Ohtamaa
    I am hosting several websites which each of run their own Python process and write *.log output files, but the directory structure is not standardized. Example: -rw-r--r-- 1 plone plone 125M 2012-08-29 11:35 ./x/var/log/instance-Z2.log -rw-r--r-- 1 plone plone 19M 2012-08-29 00:07 ./zope2.9/y/log/event.log -rw-r--r-- 1 plone plone 188M 2012-08-13 00:09 ./zope2.9/y/log/Z2.log -rw-r--r-- 1 plone plone 137M 2010-11-16 09:41 ./zope2.9/y/log/event.log I'd like to make log rotate autodiscovery these log files and run a log rotation on them, as opposite to manually type in every log file to logrotate conf. Does any existing tools offer this kind of log file discovery and rotation capabilities, without manually specifying each file? If not... then just write a shell script which generates the logrotate conf?

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  • Is there a LOGO interpreter that actually has a turtle?

    - by Tim Post
    This is not a repeat of the now infamous "How do I move the turtle in LOGO?" Recently, I had the following conversation with my five year old daughter: Daughter: Daddy, do you write programs? Me: Yes! Daughter: Daddy, what's a program? Me: A program is a set of instructions that a computer follows. Daughter: Daddy, can I write a program too? Me: Sure! This got me scrambling to think of a very basic language that a five year old could get some satisfaction from mastering rather quickly. I'm ashamed to admit that the first thing that came to mind was this: 10 INPUT "Tell me a secret" A$ 20 PRINT "Wow really? :" A$ 30 GOTO 10 That isn't going to hold a five year old's attention for very long and it requires too much of a lecture. However, moving a turtle around and drawing neat pictures might just work. Sadly, my search for a LOGO interpreter yielded noting but ad ridden sites, flight simulators and a whole bunch of other stuff that I really don't want. I'm hoping to find a cross platform (Java / Python) LOGO interpreter (dare I call it simulator?) with the following features: Can save / replay commands (stored programs) Has an actual turtle Sound effects are a plus Have you stumbled across something like this, if so, can you provide a link? I hate to ask a 'shopping' sort of question, but it seemed much better than "Is LOGO appropriate for a five year old?"

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  • Visual Studio 2010 Modeling and Architecture Tools

    - by MikeParks
    Jennifer Marsman (Microsoft Evangelist) and Cameron Skinner (Microsoft Visual Studio Product Unit Manager) recently stopped by our office while they were passing through Louisville on their tour to give us a presentation on the new Visual Studio 2010 Modeling and Architecture Tools. I checked out these new features when Visual Studio 2010 Beta versions originally rolled out and have been really impressed with this stuff ever since then. So it was pretty cool to actually learn some new techniques from Cameron himself since he helped write the actual code behind some of those features. If you've upgraded to Visual Studio 2010 recently I would highly recommend using the Architecture tools. They're awesome. If you want to make improvements to it, they even have their own SDK for it. There are plenty of blogs out there to show you how to use it. I've been waiting to find a tool that works like this where I can really analyze the code in solutions and projects and see how everything ties together. It's really handy if you're asked to work on a new project and aren't familiar with how it works. Just run the tools, analyze the DLL's, learn how everything works, and then you'll be ready to implement new code! It's a great tool to learn new systems quick and easy and it's all housed within the Visual Studio IDE. I just wanted to write a blog to brag about it a little bit, so I figured I'd throw this up here. It's a must have tool for Developers/Architects. Here's some screenshots of when I was using it earlier:   Thanks everyone! - Mike

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  • Having issues using fdisk and GParted with Lexar 64GB USB, but reading and writing is fine

    - by MetaDark
    I have recently bought a new 64GB Lexar USB with the long model name of LJDV10-64G-000-106, and I am having issues partitioning it. I am able to mount, read and write to the USB without any issues but whenever I try to partition it with GParted it doesn't show up in the dropdown. Also while using the command sudo fdisk -l I receive the error fdisk: unable to seek on /dev/sdc: Invalid argument. This is a brand new USB so I am not sure why I am having these issues, especially since the device is functioning perfectly with read/write. I have tried reformatting it on a windows machine but that does not seem to do anything. For those who want a visual my USB looks almost exactly like But 64GB rather than 8GB Edit: I have just ran GParted from the terminal and I am getting a similar error, but it may give more information on the issue. Could not determine physical sector size for /dev/sdc. Using the logical sector size (512). Invalid argument during seek for read on /dev/sdc Also clearing my USB with /dev/zero fails with the the message $ sudo dd if=/dev/zero of=/dev/sdc bs=1M dd: writing `/dev/sdc': No space left on device 1+0 records in 0+0 records out 0 bytes (0 B) copied, 0.00167254 s, 0.0 kB/s

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  • Am I misunderstanding chown and chmod?

    - by isomorphismes
    I want to either extend the size of my guest partition or figure out how to copy stuff from the guest partition to my normal /home directory. (Because of some other problems I can only run Xorg as guest, but I can log into virtual console as myself or root.) Here's the motivation: I want to torrent a large file. It's larger than my guest filesystem. But I have plenty of space on my real drive, I just can't log into it graphically. So I tried to set up a "pipe" to get the file out of the tmpfs. I did: su -u myself #catch mkdir ~/receiver_dir sudo su cd /tmp/guest-lkj567UIO/ #throw ln -s mario_pipe /home/myself/receiver_dir chown -R guest-lkj567UIO /home/myself/receiver_dir chown -R guest-lkj567UIO /tmp/guest-lkj567UIO/mario_pipe chmod -R a+rw /home/myself/receiver_dir chmod -R a+rw /tmp/guest-lkj567UIO/mario_pipe su -u guest-lkj567UIO cd /tmp/guest-lkj567UIO cd mario_pipe touch something #success! However, when I try to torrent to /tmp/guest-lkj567UIO/mario_pipe, Transmission says I don't have write permissions. But it looks like I just wrote there? And that everybody (a+rw) can write there in fact? Maybe this indicates I don't actually understand chown and chmod but nothing from their man pages pops out.

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  • portable usb harddisk regardless in windows and ubuntu / linux environment

    - by user8184
    I am doing web development mostly in ubuntu. Sometimes i need to go into windows to do other administrative work. Now i am ignorant about file systems. I cannot tell the difference between NTFS and FAT32. My eyes just glaze over the wikipedia articles. All I know is i have been using this 320 Gb portable USB harddisk to save files when I am in ubuntu and when I am in windows. Now i got a situation where sometimes the windows 7 cannot detect the harddisk. I believe it has to do with the file system issue. Or my harddisk is coming apart. To make it easy to backup my files in a portable USB harddisk regardless in ubuntu or windows, please advise me. That means i can go from from linux/ubuntu to portable harddisk read/write files from windows 7 to portable harddisk read/write files the same files. Thank you.

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  • Missing Package: header, Problem with MergeList, The package lists or status file could not be parsed or opened

    - by Inbar Rose
    THIS IS NOT A DUPLICATE OF SIMILAR QUESTIONS (like this) I just had to write that first, there are tons of questions similar to this, all of them have the same redirect to an answer that does not solve my problem, because I don't have the same problem, just the same symptom. I write tests for my companies application. One of these tests tries to upgrade the application from a previous version to a new version to make sure nothing breaks. When I am installing an old version of the application, some weird stuff starts to happen. Sometimes everything goes Okay, and nothing is wrong, other times when trying to install I get this message (company app name censored): E: Encountered a section with no Package: header E: Problem with MergeList /var/lib/apt/lists/XXX-amd64_Packages E: The package lists or status file could not be parsed or opened. Using the solutions provided in the questions similar to this one (like this). Do not help, and the problem keeps repeating itself once it happens the first time. This has led me to believe something is wrong on the apt server where the package is being created, but searching these errors yields no information on anything beyond the "fix" suggested in the question I linked, the only other source of information I could find also did not help (here): So I am asking for information; What is the actual problem? What causes the problem? What can fix the problem? I hope this question is in good format, if there is a problem, or missing information I can move to chat.

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  • Is micro-optimisation important when coding?

    - by BozKay
    I recently asked a question on stackoverflow.com to find out why isset() was faster than strlen() in php. This raised questions around the importance of readable code and whether performance improvements of micro-seconds in code were worth even considering. My father is a retired programmer, I showed him the responses and he was absolutely certain that if a coder does not consider performance in their code even at the micro level, they are not good programmers. I'm not so sure - perhaps the increase in computing power means we no longer have to consider these kind of micro-performance improvements? Perhaps this kind of considering is up to the people who write the actual language code? (of php in the above case). The environmental factors could be important - the internet consumes 10% of the worlds energy, I wonder how wasteful a few micro-seconds of code is when replicated trillions of times on millions of websites? I'd like to know answers preferably based on facts about programming. Is micro-optimisation important when coding? EDIT : My personal summary of 25 answers, thanks to all. Sometimes we need to really worry about micro-optimisations, but only in very rare circumstances. Reliability and readability are far more important in the majority of cases. However, considering micro-optimisation from time to time doesn't hurt. A basic understanding can help us not to make obvious bad choices when coding such as if (expensiveFunction() && counter < X) Should be if (counter < X && expensiveFunction()) (example from @zidarsk8) This could be an inexpensive function and therefore changing the code would be micro-optimisation. But, with a basic understanding, you would not have to because you would write it correctly in the first place.

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  • Can I mark a folder as mountpoint-only?

    - by Collin
    I have a folder ~/nas which I usually use sshfs to mount a network drive on. Today, I didn't realize the share hadn't been mounted yet, and copied some data into it. It took me a bit to realize that I'd just copied data into my own local drive rather than the network share. Is there some way to mark in the system that this folder is supposed to be a mount point, and to not let anyone copy data into it? I tried the permissions solution here: How to only allow a program to write to a directory if it is mounted?, but if I don't have write access I also can't mount anything to it.

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  • Internal hard drive, can't format

    - by user113923
    I cannot format anymore the hard drive of my laptop. Here is how I proceed: I am starting my computer with a USB live drive (Ubuntu 10.04 LTS - the Lucid Lynx). Then I start disk utility and try to format the hard drive - I choosed to format the Master boot record but I get the following error: Error creating partition table: helper exited with exit code 1: Error calling fsync(2) on /dev/sda: Input/output error If I try to delete partitions I get the following error Error erasing: helper exited with exit code 1: In part_del_partition: device_file=/dev/sda, offset=32256 Entering MS-DOS parser (offset=0, size=30005821440) MSDOS_MAGIC found looking at part 0 (offset 32256, size 4096157184, type 0x83) new part entry looking at part 1 (offset 10618836480, size 8414461440, type 0x83) new part entry looking at part 2 (offset 19033297920, size 1077511680, type 0x82) new part entry looking at part 3 (offset 20110809600, size 9895011840, type 0x07) new part entry Exiting MS-DOS parser MSDOS partition table detected got it got disk got partition - part-type=0 Error: Input/output error during write on /dev/sda ped_disk_commit_to_dev() failed If I try to install ubuntu frrom the usb on the hard drive and choose erase and use the entire disk I get the error message Input/output error during write on /dev/sda For side infos I have at the moment 4 partitions on my hard drive: /dev/sda1 (ext2) /dev/sda2 (ext2) /dev/sda3 (swap) /dev/sda1 (ntfs) + /dev/sda (unlocated Space) My ultimate goal is to reinstall ubuntu and have only 2 partitions... I would really appreciate any help here! Thanks JB

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  • HALEVT troubleshooting: VFAT usb storage device gets mounted with root:root user:group

    - by Nova deViator
    Hi, i'm banging my head for number of days around this problem. using Halevt for automounting, everything mostly works, but the only thing is that Halevt mounts external USB storage devices as root. So, as user i cannot write to files on them. Halevt gets run as halevt user on boot through /etc/init.d script. This is Ubuntu Lucid with Awesome WM. No GDM. Running halevt as user seem to not work (halevt runs but doesn't respond on Insert) I know HAL is deprecated and removed and i should probably write my own UDEV rules, but until then it seems there must a be simple hack that enables mounting VFAT/NTFS devices with specific uid/gid. this question/answer helps a lot, but not specifically to the above.

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  • Software development is (mostly) a trade, and what to do about it

    - by Jeff
    (This is another cross-post from my personal blog. I don’t even remember when I first started to write it, but I feel like my opinion is well enough baked to share.) I've been sitting on this for a long time, particularly as my opinion has changed dramatically over the last few years. That I've encountered more crappy code than maintainable, quality code in my career as a software developer only reinforces what I'm about to say. Software development is just a trade for most, and not a huge academic endeavor. For those of you with computer science degrees readying your pitchforks and collecting your algorithm interview questions, let me explain. This is not an assault on your way of life, and if you've been around, you know I'm right about the quality problem. You also know the HR problem is very real, or we wouldn't be paying top dollar for mediocre developers and importing people from all over the world to fill the jobs we can't fill. I'm going to try and outline what I see as some of the problems, and hopefully offer my views on how to address them. The recruiting problem I think a lot of companies are doing it wrong. Over the years, I've had two kinds of interview experiences. The first, and right, kind of experience involves talking about real life achievements, followed by some variation on white boarding in pseudo-code, drafting some basic system architecture, or even sitting down at a comprooder and pecking out some basic code to tackle a real problem. I can honestly say that I've had a job offer for every interview like this, save for one, because the task was to debug something and they didn't like me asking where to look ("everyone else in the company died in a plane crash"). The other interview experience, the wrong one, involves the classic torture test designed to make the candidate feel stupid and do things they never have, and never will do in their job. First they will question you about obscure academic material you've never seen, or don't care to remember. Then they'll ask you to white board some ridiculous algorithm involving prime numbers or some kind of string manipulation no one would ever do. In fact, if you had to do something like this, you'd Google for a solution instead of waste time on a solved problem. Some will tell you that the academic gauntlet interview is useful to see how people respond to pressure, how they engage in complex logic, etc. That might be true, unless of course you have someone who brushed up on the solutions to the silly puzzles, and they're playing you. But here's the real reason why the second experience is wrong: You're evaluating for things that aren't the job. These might have been useful tactics when you had to hire people to write machine language or C++, but in a world dominated by managed code in C#, or Java, people aren't managing memory or trying to be smarter than the compilers. They're using well known design patterns and techniques to deliver software. More to the point, these puzzle gauntlets don't evaluate things that really matter. They don't get into code design, issues of loose coupling and testability, knowledge of the basics around HTTP, or anything else that relates to building supportable and maintainable software. The first situation, involving real life problems, gives you an immediate idea of how the candidate will work out. One of my favorite experiences as an interviewee was with a guy who literally brought his work from that day and asked me how to deal with his problem. I had to demonstrate how I would design a class, make sure the unit testing coverage was solid, etc. I worked at that company for two years. So stop looking for algorithm puzzle crunchers, because a guy who can crush a Fibonacci sequence might also be a guy who writes a class with 5,000 lines of untestable code. Fashion your interview process on ways to reveal a developer who can write supportable and maintainable code. I would even go so far as to let them use the Google. If they want to cut-and-paste code, pass on them, but if they're looking for context or straight class references, hire them, because they're going to be life-long learners. The contractor problem I doubt anyone has ever worked in a place where contractors weren't used. The use of contractors seems like an obvious way to control costs. You can hire someone for just as long as you need them and then let them go. You can even give them the work that no one else wants to do. In practice, most places I've worked have retained and budgeted for the contractor year-round, meaning that the $90+ per hour they're paying (of which half goes to the person) would have been better spent on a full-time person with a $100k salary and benefits. But it's not even the cost that is an issue. It's the quality of work delivered. The accountability of a contractor is totally transient. They only need to deliver for as long as you keep them around, and chances are they'll never again touch the code. There's no incentive for them to get things right, there's little incentive to understand your system or learn anything. At the risk of making an unfair generalization, craftsmanship doesn't matter to most contractors. The education problem I don't know what they teach in college CS courses. I've believed for most of my adult life that a college degree was an essential part of being successful. Of course I would hold that bias, since I did it, and have the paper to show for it in a box somewhere in the basement. My first clue that maybe this wasn't a fully qualified opinion comes from the fact that I double-majored in journalism and radio/TV, not computer science. Eventually I worked with people who skipped college entirely, many of them at Microsoft. Then I worked with people who had a masters degree who sucked at writing code, next to the high school diploma types that rock it every day. I still think there's a lot to be said for the social development of someone who has the on-campus experience, but for software developers, college might not matter. As I mentioned before, most of us are not writing compilers, and we never will. It's actually surprising to find how many people are self-taught in the art of software development, and that should reveal some interesting truths about how we learn. The first truth is that we learn largely out of necessity. There's something that we want to achieve, so we do what I call just-in-time learning to meet those goals. We acquire knowledge when we need it. So what about the gaps in our knowledge? That's where the most valuable education occurs, via our mentors. They're the people we work next to and the people who write blogs. They are critical to our professional development. They don't need to be an encyclopedia of jargon, but they understand the craft. Even at this stage of my career, I probably can't tell you what SOLID stands for, but you can bet that I practice the principles behind that acronym every day. That comes from experience, augmented by my peers. I'm hell bent on passing that experience to others. Process issues If you're a manager type and don't do much in the way of writing code these days (shame on you for not messing around at least), then your job is to isolate your tradespeople from nonsense, while bringing your business into the realm of modern software development. That doesn't mean you slap up a white board with sticky notes and start calling yourself agile, it means getting all of your stakeholders to understand that frequent delivery of quality software is the best way to deal with change and evolving expectations. It also means that you have to play technical overlord to make sure the education and quality issues are dealt with. That's why I make the crack about sticky notes, because without the right technique being practiced among your code monkeys, you're just a guy with sticky notes. You're asking your business to accept frequent and iterative delivery, now make sure that the folks writing the code can handle the same thing. This means unit testing, the right instrumentation, integration tests, automated builds and deployments... all of the stuff that makes it easy to see when change breaks stuff. The prognosis I strongly believe that education is the most important part of what we do. I'm encouraged by things like The Starter League, and it's the kind of thing I'd love to see more of. I would go as far as to say I'd love to start something like this internally at an existing company. Most of all though, I can't emphasize enough how important it is that we mentor each other and share our knowledge. If you have people on your staff who don't want to learn, fire them. Seriously, get rid of them. A few months working with someone really good, who understands the craftsmanship required to build supportable and maintainable code, will change that person forever and increase their value immeasurably.

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  • what kind of memory can be categorized as Modified Memory in Resource Monitor

    - by Kavin
    In Windows 7 and Windows 2008 R2, there is a new Resource Monitor that is very useful and powerful to monitor the system. In the Memory section, I see a section called Modified (orange) The official description is: Memory whose contents must be to disk before it can be used for another purpose. But I am still confused. What kinds of memory is Modified? In which case can we say that this number of memory is Modified? Can anyone give me a specific example? Is the following guess correct? When a program want to write something into disk, it actually write the content to an IO buffer, which is in the memory. After OS flush this area of memory into disk, the memory is modified or standby?

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  • C# Simple Twitter Update

    - by mroberts
    For what it's worth a simple twitter update. using System; using System.IO; using System.Net; using System.Text; namespace Server.Actions { public class TwitterUpdate { public string Body { get; set; } public string Login { get; set; } public string Password { get; set; } public override void Execute() { try { //encode user name and password string creds = Convert.ToBase64String(Encoding.ASCII.GetBytes(string.Format("{0}:{1}", this.Login, this.Password))); //encode tweet byte[] tweet = Encoding.ASCII.GetBytes("status=" + this.Body); //setup request HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://twitter.com/statuses/update.xml"); request.Method = "POST"; request.ServicePoint.Expect100Continue = false; request.Headers.Add("Authorization", string.Format("Basic {0}", creds)); request.ContentType = "application/x-www-form-urlencoded"; request.ContentLength = tweet.Length; //write to stream Stream reqStream = request.GetRequestStream(); reqStream.Write(tweet, 0, tweet.Length); reqStream.Close(); //check response HttpWebResponse response = (HttpWebResponse)request.GetResponse(); //... } catch (Exception e) { //... } } } }

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  • Unable to delete all partitions on flash drive using Windows 7 OS??

    - by irrational John
    Recently I purchased an ADATA C802 8GB flash drive. Since the drive was new I decided to run some of the HD Tune Pro (v4.50) performance tests on it, mostly just for the heck of it. To avoid accidently destroying data HD Tune refuses to write to a drive unless there are no partitions on the drive. If you do attempt to write to a drive with partitions, it posts the message "Writing is disabled. To enable writing please remove all partitions." As you would expect, the ADATA came formatted with a single primary FAT32 partition in the Master Boot Record. But a number of unexpected things happened when I attempted to delete that partition. The first thing I tried was to use the Windows 7 (64-bit) Disk Management tool (diskmgmt.msc) to delete the partition. It would not let me. The context menu choice to delete that volume was not available. Next I opened up a command prompt window with Admin authority and ran diskpart. Diskpart deleted the volume for me. However, when I attempted to run an HD Tune write test on the drive I still got the "Writing is disabled" message. Huh??? So I fired up a utility I have which allows viewing drives at the sector level and verified that the partition table in the Master Boot Record was empty. No partitions. Yet HD Tune still thought there were partitions on the drive? So why was I still getting the "Writing is disabled" message from HD Tune Pro? And why wouldn't the Windows 7 Disk Management tool let me change the partitions on this drive. After doing the above, I plugged the ADATA into my MacBook. I was then able to format it as either a GPT or MBR partitioned drive with no problems. I am not looking for suggestions on how to format this drive. I can do that. What I do not understand and was hoping I might get insight into is why this drive behaves so strangely under Windows 7? And BTW, what's up with HD Tune Pro? BTW, if I plug the drive I formatted on my MacBook back into my Windows 7 64-bit system I still run into road blocks with the Disk Management tool. For example, I cannot delete all the GPT partitions on the ADATA so I can convert it into an MBR drive. I following Microsoft's instructions, the instructions just do not work with this ADATA flash drive. Anyone know what's up with this? It makes no sense to me. Has something changed in Windows 7 (Vista)??

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  • Unmounted root partition

    - by Jack
    My server running Debian lenny has just had a power cut recently and its come back up with the root partition in read only mode. I tried to remount the filesystem in read write mode with mount -n -o remount,rw / which then gave the output mount: block device /dev/hda1 is write-protected, mounting read-only. But now the root filesystem isn't mounted at all so I can't run anything to mount the partition again or any other command for that matter such as shutdown because /bin/ isn't there. Is there anything I can do remotely?

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