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• 2D camera perspective projection from 3D coordinates -- HOW?

  - by Jack

  I am developing a camera for a 2D game with a top-down view that has depth. It's almost a 3D camera. Basically, every object has a Z even though it is in 2D, and similarly to parallax layers their position, scale and rotation speed vary based on their Z. I guess this would be a perspective projection. But I am having trouble converting the objects' 3D coordinates into the 2D space of the screen so that everything has correct perspective and scale. I never learned matrices though I did dig the topic a bit today. I tried without using matrices thanks to this article but every attempt gave awkward results. I'm using ActionScript 3 and Flash 11+ (Starling), where the screen coordinates work like this: Left-handed coordinates system illustration I can explain further what I did if you want to help me sort out what's wrong, or you can directly tell me how you would do it properly. In case you prefer the former, read on. These are images showing the formulas I used: upload.wikimedia.org/math/1/c/8/1c89722619b756d05adb4ea38ee6f62b.png upload.wikimedia.org/math/d/4/0/d4069770c68cb8f1aa4b5cfc57e81bc3.png (Sorry new users can't post images, but both are from the wikipedia article linked above, section "Perspective projection". That's where you'll find what all variables mean, too) The long formula is greatly simplified because I believe a normal top-down 2D camera has no X/Y/Z rotation values (correct ?). Then it becomes d = a - c. Still, I can't get it to work. Maybe you could explain what numbers I should put in a(xyz), c(xyz), theta(xyz), and particularly, e(xyz) ? I don't quite get how e is different than c in my case. c.z is also an issue to me. If the Z of the camera's target object is 0, should the camera's Z be something like -600 ? ( = focal length of 600) Whatever I do, it's wrong. I only got it to work when I used arbitrary calculations that "looked" right, like most cameras with parallax layers seem to do, but that's fake! ;) If I want objects to travel between Z layers I might as well do it right. :) Thanks a lot for your help!

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• Best Practices for serializing/persisting String Object Dictionary entities

  - by Mark Heath

  I'm noticing a trend towards using a dictionary of string to object (or sometimes string to string), instead of strongly typed objects. For example, the new Katana project makes heavy use of IDictionary<string,object>. This approach avoids the need to continually update your entity classes/DTOs and the database tables that persist them with new properties. It also avoids the need to create new derived entity types to support new types of entity, since the Dictionary is flexible enough to store any arbitrary properties. Here's a contrived example: class StorageDevice { public int Id { get; set; } public string Name { get; set; } } class NetworkShare : StorageDevice { public string Path { get; set; } public string LoginName { get; set; } public string Password { get; set; } } class CloudStorage : StorageDevice { public string ServerUri { get; set } public string ContainerName { get; set; } public int PortNumber { get; set; } public Guid ApiKey { get; set; } } versus: class StorageDevice { public IDictionary<string, object> Properties { get; set; } } Basically I'm on the lookout for any talks, books or articles on this approach, so I can pick up on any best practices / difficulties to avoid. Here's my main questions: Does this approach have a name? (only thing I've heard used so far is "self-describing objects") What are the best practices for persisting these dictionaries into a relational database? Especially the challenges of deserializing them successfully with strongly typed languages like C#. Does it change anything if some of the objects in the dictionary are themselves lists of strongly typed entities? Should a second dictionary be used if you want to temporarily store objects that are not to be persisted/serialized across a network, or should you use some kind of namespacing on the keys to indicate this?

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• Rending 2D Tile World (With Player In The Middle)

  - by Mick

  What I have at the moment is a series of data structures I'm using, and I would like to render the world onto the screen (just the visible parts). I've actually already done this several times (lots of rewrites), but it's a bit buggy (rounding seems to make the screen jump ever so slightly every x tiles the player walks past). Basically I've been confusing myself heavily on what I feel should be a pretty simple problem... so here I am asking for some help! OK! So I have a 50x50 array holding the tiles of the world. I have the player position as 2 floats, x ([0, 49]) and y ([0, 49]) in that array. I have the application size exactly in pixels (x and y). I have an arbitrary TILE_SIZE static int (based on screen pixels). What I think is heavily confusing me is using a 2d orthogonal projection in opengl which maps (0,0) to the top left of the screen and (SCREEN_SIZE_X, SCREEN_SIZE_Y) to the bottom right of the screen. gl.glMatrixMode(GL.GL_PROJECTION); gl.glLoadIdentity(); glu.gluOrtho2D(0, getActualWidth(), getActualHeight(), 0); gl.glMatrixMode(GL.GL_MODELVIEW); gl.glLoadIdentity(); The map tiles are set so that the (0,0) in the array is the bottom left. And the player has to be in the middle on the screen (SCREEN_SIZE_X/2, SCREEN_SIZE_Y/2). What I've been doing so far is trying to render 1-2 tiles more all around what would be displayed on the screen so that I don't have to worry about figuring out rendering half a tile from the top left, depending where the player is. It seems like such an easy problem but after spending about 40+hours on it rewriting it many times I think I'm at a point where I just can't think clearly anymore... Any help would be appreciated. It would be great if someone can provide some very basic pseudo code on keeping the player in the middle when your projection is mapped to screen coordinates and only rendering basically the tiles that you would be any be see. Thanks!

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• Accounting for waves when doing planar reflections

  - by CloseReflector

  I've been studying Nvidia's examples from the SDK, in particular the Island11 project and I've found something curious about a piece of HLSL code which corrects the reflections up and down depending on the state of the wave's height. Naturally, after examining the brief paragraph of code: // calculating correction that shifts reflection up/down according to water wave Y position float4 projected_waveheight = mul(float4(input.positionWS.x,input.positionWS.y,input.positionWS.z,1),g_ModelViewProjectionMatrix); float waveheight_correction=-0.5*projected_waveheight.y/projected_waveheight.w; projected_waveheight = mul(float4(input.positionWS.x,-0.8,input.positionWS.z,1),g_ModelViewProjectionMatrix); waveheight_correction+=0.5*projected_waveheight.y/projected_waveheight.w; reflection_disturbance.y=max(-0.15,waveheight_correction+reflection_disturbance.y); My first guess was that it compensates for the planar reflection when it is subjected to vertical perturbation (the waves), shifting the reflected geometry to a point where is nothing and the water is just rendered as if there is nothing there or just the sky: Now, that's the sky reflecting where we should see the terrain's green/grey/yellowish reflection lerped with the water's baseline. My problem is now that I cannot really pinpoint what is the logic behind it. Projecting the actual world space position of a point of the wave/water geometry and then multiplying by -.5f, only to take another projection of the same point, this time with its y coordinate changed to -0.8 (why -0.8?). Clues in the code seem to indicate it was derived with trial and error because there is redundancy. For example, the author takes the negative half of the projected y coordinate (after the w divide): float waveheight_correction=-0.5*projected_waveheight.y/projected_waveheight.w; And then does the same for the second point (only positive, to get a difference of some sort, I presume) and combines them: waveheight_correction+=0.5*projected_waveheight.y/projected_waveheight.w; By removing the divide by 2, I see no difference in quality improvement (if someone cares to correct me, please do). The crux of it seems to be the difference in the projected y, why is that? This redundancy and the seemingly arbitrary selection of -.8f and -0.15f lead me to conclude that this might be a combination of heuristics/guess work. Is there a logical underpinning to this or is it just a desperate hack? Here is an exaggeration of the initial problem which the code fragment fixes, observe on the lowest tessellation level. Hopefully, it might spark an idea I'm missing. The -.8f might be a reference height from which to deduce how much to disturb the texture coordinate sampling the planarly reflected geometry render and -.15f might be the lower bound, a security measure.

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• How can we unify business goals and technical goals?

  - by BAM

  Some background I work at a small startup: 4 devs, 1 designer, and 2 non-technical co-founders, one who provides funding, and the other who handles day-to-day management and sales. Our company produces mobile apps for target industries, and we've gotten a lot of lucky breaks lately. The outlook is good, and we're confident we can make this thing work. One reason is our product development team. Everyone on the team is passionate, driven, and has a great sense of what makes an awesome product. As a result, we've built some beautiful applications that we're all proud of. The other reason is the co-founders. Both have a brilliant business sense (one actually founded a multi-million dollar company already), and they have close ties in many of the industries we're trying to penetrate. Consequently, they've brought in some great business and continue to keep jobs in the pipeline. The problem The problem we can't seem to shake is how to bring these two awesome advantages together. On the business side, there is a huge pressure to deliver as fast as possible as much as possible, whereas on the development side there is pressure to take your time, come up with the right solution, and pay attention to all the details. Lately these two sides have been butting heads a lot. Developers are demanding quality while managers are demanding quantity. How can we handle this? Both sides are correct. We can't survive as a company if we build terrible applications, but we also can't survive if we don't sell enough. So how should we go about making compromises? Things we've done with little or no success: Work more (well, it did result in better quality and faster delivery, but the dev team has never been more stressed out before) Charge more (as a startup, we don't yet have the credibility to justify higher prices, so no one is willing to pay) Extend deadlines (if we charge the same, but take longer, we'll end up losing money) Things we've done with some success: Sacrifice pay to cut costs (everyone, from devs to management, is paid less than they could be making elsewhere. In return, however, we all have creative input and more flexibility and freedom, a typical startup trade off) Standardize project management (we recently started adhering to agile/scrum principles so we can base deadlines on actual velocity, not just arbitrary guesses) Hire more people (we used to have 2 developers and no designers, which really limited our bandwidth. However, as a startup we can only afford to hire a few extra people.) Is there anything we're missing or doing wrong? How is this handled at successful companies? Thanks in advance for any feedback :)

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• "Whole-team" C++ features?

  - by Blaisorblade

  In C++, features like exceptions impact your whole program: you can either disable them in your whole program, or you need to deal with them throughout your code. As a famous article on C++ Report puts it: Counter-intuitively, the hard part of coding exceptions is not the explicit throws and catches. The really hard part of using exceptions is to write all the intervening code in such a way that an arbitrary exception can propagate from its throw site to its handler, arriving safely and without damaging other parts of the program along the way. Since even new throws exceptions, every function needs to provide basic exception safety — unless it only calls functions which guarantee throwing no exception — unless you disable exceptions altogether in your whole project. Hence, exceptions are a "whole-program" or "whole-team" feature, since they must be understood by everybody in a team using them. But not all C++ features are like that, as far as I know. A possible example is that if I don't get templates but I do not use them, I will still be able to write correct C++ — or will I not?. I can even call sort on an array of integers and enjoy its amazing speed advantage wrt. C's qsort (because no function pointer is called), without risking bugs — or not? It seems templates are not "whole-team". Are there other C++ features which impact code not directly using them, and are hence "whole-team"? I am especially interested in features not present in C. Update: I'm especially looking for features where there's no language-enforced sign you need to be aware of them. The first answer I got mentioned const-correctness, which is also whole-team, hence everybody needs to learn about it; however, AFAICS it will impact you only if you call a function which is marked const, and the compiler will prevent you from calling it on non-const objects, so you get something to google for. With exceptions, you don't even get that; moreover, they're always used as soon as you use new, hence exceptions are more "insidious". Since I can't phrase this as objectively, though, I will appreciate any whole-team feature. Appendix: Why this question is objective (if you wonder) C++ is a complex language, so many projects or coding guides try to select "simple" C++ features, and many people try to include or exclude some ones according to mostly subjective criteria. Questions about that get rightfully closed regularly here on SO. Above, instead, I defined (as precisely as possible) what a "whole-team" language feature is, provide an example (exceptions), together with extensive supporting evidence in the literature about C++, and ask for whole-team features in C++ beyond exceptions. Whether you should use "whole-team" features, or whether that's a relevant concept, might be subjective — but that only means the importance of this question is subjective, like always.

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• The term "interface" in C++

  - by Flexo

  Java makes a clear distinction between class and interface. (I believe C# does also, but I have no experience with it). When writing C++ however there is no language enforced distinction between class and interface. Consequently I've always viewed interface as a workaround for the lack of multiple inheritance in Java. Making such a distinction feels arbitrary and meaningless in C++. I've always tended to go with the "write things in the most obvious way" approach, so if in C++ I've got what might be called an interface in Java, e.g.: class Foo { public: virtual void doStuff() = 0; ~Foo() = 0; }; and I then decided that most implementers of Foo wanted to share some common functionality I would probably write: class Foo { public: virtual void doStuff() = 0; ~Foo() {} protected: // If it needs this to do its thing: int internalHelperThing(int); // Or if it doesn't need the this pointer: static int someOtherHelper(int); }; Which then makes this not an interface in the Java sense anymore. Instead C++ has two important concepts, related to the same underlying inheritance problem: virtual inhertiance Classes with no member variables can occupy no extra space when used as a base "Base class subobjects may have zero size" Reference Of those I try to avoid #1 wherever possible - it's rare to encounter a scenario where that genuinely is the "cleanest" design. #2 is however a subtle, but important difference between my understanding of the term "interface" and the C++ language features. As a result of this I currently (almost) never refer to things as "interfaces" in C++ and talk in terms of base classes and their sizes. I would say that in the context of C++ "interface" is a misnomer. It has come to my attention though that not many people make such a distinction. Do I stand to lose anything by allowing (e.g. protected) non-virtual functions to exist within an "interface" in C++? (My feeling is the exactly the opposite - a more natural location for shared code) Is the term "interface" meaningful in C++ - does it imply only pure virtual or would it be fair to call C++ classes with no member variables an interface still?

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• Jenkins: Use it with SSL / https

  - by Tim

  I have a Fedora server running Jenkins which I install via yum. Everything is okay, I can access it with http://ci.mydomain.com. But now, I want to access it with https://ci.mydomain.com, so the login with username and password is encrypted. How can I do this? Best Regards Tim Update My /etc/sysconfig/jenkins file. Starting Jenkins works, but I can not access Jenkins with the webbrowser with https://ci.mydomain.com or http://ci.mydomain.com:443, ... ## Path: Development/Jenkins ## Description: Configuration for the Jenkins continuous build server ## Type: string ## Default: "/var/lib/jenkins" ## ServiceRestart: jenkins # # Directory where Jenkins store its configuration and working # files (checkouts, build reports, artifacts, ...). # JENKINS_HOME="/var/lib/jenkins" ## Type: string ## Default: "" ## ServiceRestart: jenkins # # Java executable to run Jenkins # When left empty, we'll try to find the suitable Java. # JENKINS_JAVA_CMD="" ## Type: string ## Default: "jenkins" ## ServiceRestart: jenkins # # Unix user account that runs the Jenkins daemon # Be careful when you change this, as you need to update # permissions of $JENKINS_HOME and /var/log/jenkins. # JENKINS_USER="jenkins" ## Type: string ## Default: "-Djava.awt.headless=true" ## ServiceRestart: jenkins # # Options to pass to java when running Jenkins. # JENKINS_JAVA_OPTIONS="-Djava.awt.headless=true" ## Type: integer(0:65535) ## Default: 8080 ## ServiceRestart: jenkins # # Port Jenkins is listening on. # JENKINS_PORT="8080" ## Type: integer(1:9) ## Default: 5 ## ServiceRestart: jenkins # # Debug level for logs -- the higher the value, the more verbose. # 5 is INFO. # JENKINS_DEBUG_LEVEL="5" ## Type: yesno ## Default: no ## ServiceRestart: jenkins # # Whether to enable access logging or not. # JENKINS_ENABLE_ACCESS_LOG="no" ## Type: integer ## Default: 100 ## ServiceRestart: jenkins # # Maximum number of HTTP worker threads. # JENKINS_HANDLER_MAX="100" ## Type: integer ## Default: 20 ## ServiceRestart: jenkins # # Maximum number of idle HTTP worker threads. # JENKINS_HANDLER_IDLE="20" ## Type: string ## Default: "" ## ServiceRestart: jenkins # # Pass arbitrary arguments to Jenkins. # Full option list: java -jar jenkins.war --help # JENKINS_ARGS="--httpsPort=443 --httpsKeyStore=/root/.keystore --httpsKeyStorePassword=MYPASSWORD"

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• DNAT to 127.0.0.1 with iptables / Destination access control for transparent SOCKS proxy

  - by cdauth

  I have a server running on my local network that acts as a router for the computers in my network. I want to achieve now that outgoing TCP requests to certain IP addresses are tunnelled through an SSH connection, without giving the people from my network the possibility to use that SSH tunnel to connect to arbitrary hosts. The approach I had in mind until now was to have an instance of redsocks listening on localhost and to redirect all outgoing requests to the IP addresses I want to divert to that redsocks instance. I added the following iptables rule: iptables -t nat -A PREROUTING -p tcp -d 1.2.3.4 -j DNAT --to-destination 127.0.0.1:12345 Apparently, the Linux kernel considers packets coming from a non-127.0.0.0/8 address to an 127.0.0.0/8 address as “Martian packets” and drops them. What worked, though, was to have redsocks listen on eth0 instead of lo and then have iptables DNAT the packets to the eth0 address instead (or using a REDIRECT rule). The problem about this is that then every computer on my network can use the redsocks instance to connect to every host on the internet, but I want to limit its usage to a certain set of IP addresses only. Is there any way to make iptables DNAT packets to 127.0.0.1? Otherwise, does anyone have an idea how I could achieve my goal without opening up the tunnel to everyone? Update: I have also tried to change the source of the packets, without any success: iptables -t nat -A POSTROUTING -p tcp -s 192.168.1.0/24 -d 1.2.3.4 -j SNAT --to-source 127.0.0.1 iptables -t nat -A POSTROUTING -p tcp -s 192.168.1.0/24 -d 127.0.0.1 -j SNAT --to-source 127.0.0.1

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• How can I map a Windows group login to the dbo schema in a database?

  - by Christian Hayter

  I have a database for which I want to restrict access to 3 named individuals. I thought I could do the following: Create a local Windows group on the database server and add the named individuals to it. Create a Windows login in SQL Server mapped to the local Windows group. Map the login to the "dbo" schema in the database, so that the users can access all objects without having to qualify them with the schema name. When I try to do step 3, I get the following error: Msg 15353, Level 16, State 1, Line 1 An entity of type database cannot be owned by a role, a group, an approle, or by principals mapped to certificates or asymmetric keys. I have tried to do this via the IDE, the sp_changedbowner sproc, and the ALTER AUTHORIZATION command, and I get the same error each time. After searching MSDN and Google, I find that this restriction is by design. Great, that's useful. Can anyone tell me: Why this restriction exists? It seems very arbitrary. More importantly, can I accomplish my requirement some other way? Other info that might be pertinent: The server is fully up to date with service packs and hotfixes. All objects in the database are owned by the "dbo" schema, and it's not feasible to change that. The database is running in compatibility level 80, and it's not feasible to change that to 90 yet. I am free to make any other changes (within reason, depending on what they are).

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• What's up with stat on MacOSX/Darwin? Or filesystems without names...

  - by Charles Stewart

  In response to a question I asked on SO, Give the mount point of a path, one respondant suggested using stat to get the device name associated with the volume of a given path. This works nicely on Linux, but gives crazy results on MacOSX 10.4. For my system, df and mount give: cas cas$ df Filesystem 512-blocks Used Avail Capacity Mounted on /dev/disk0s3 58342896 49924456 7906440 86% / devfs 194 194 0 100% /dev fdesc 2 2 0 100% /dev <volfs> 1024 1024 0 100% /.vol automount -nsl [166] 0 0 0 100% /Network automount -fstab [170] 0 0 0 100% /automount/Servers automount -static [170] 0 0 0 100% /automount/static /dev/disk2s1 163577856 23225520 140352336 14% /Volumes/Snapshot /dev/disk2s2 409404102 5745938 383187960 1% /Volumes/Sparse cas cas$ mount /dev/disk0s3 on / (local, journaled) devfs on /dev (local) fdesc on /dev (union) <volfs> on /.vol automount -nsl [166] on /Network (automounted) automount -fstab [170] on /automount/Servers (automounted) automount -static [170] on /automount/static (automounted) /dev/disk2s1 on /Volumes/Snapshot (local, nodev, nosuid, journaled) /dev/disk2s2 on /Volumes/Sparse (asynchronous, local, nodev, nosuid) Trying to get the devices from the mount points, though: cas cas$ df | grep -e/ | awk '{print $NF}' | while read line; do echo $line $(stat -f"%Sdr" $line); done / disk0s3r /dev ???r /dev ???r /.vol ???r /Network ???r /automount/Servers ???r /automount/static ???r /Volumes/Snapshot disk2s1r /Volumes/Sparse disk2s2r Here, I'm feeding each of the mount points scraped from df to stat, outputting the results of the "%Sdr" format string, which is supposed to be the device name: Cf. stat(1) man page: The special output specifier S may be used to indicate that the output, if applicable, should be in string format. May be used in combination with: ... dr Display actual device name. What's going on? Is it a bug in stat, or some Darwin VFS weirdness? Postscript Per Andrew McGregor, try passing "%Sd" to stat for more weirdness. It lists some apparently arbitrary subset of files from CWD...

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• Is there a simple LDAP-to-HTTP gateway out there?

  - by larsks

  We have a local LDAP directory that provides basic contact information about our user community. We would like to integrate this into some third-party hosted services that allow us to implement widgets that run arbitrary Javascript. In order to connect Javascript to our LDAP directory, I would like to set up a simple LDAP-to-HTTP proxy that would accept HTTP GET requests, translate them into an appropriate LDAP query, and respond with directory information as JSON-encoded data. In an ideal world, something like this: GET /[email protected] Would get me something like this: { "cn": "Bob Person", "title": "System Administrator", "sn": "Person", "mail": "[email protected]", "telepehoneNumber": "617-555-1212", "givenName": "Bob" } (And this obviously assumes that the web application has locally configured information about what base DN to use, how to authenticate, etc). I guess I could write one...but surely something like this already exists? UPDATE The consensus seems to be that there isn't a pre-existing solution out there and that I should just get off my lazy derriere and write one. So I did, and it's here. It's not especially pretty, but it works for my prototyping and I figure maybe someone else will find it useful someday.

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• Window Management for Mac OS X

  - by Paolo Maffei

  Ok, I feel dumb. I've put many hours into this and found nothing, yet. When I was using Windows I had this little tool called WinSplit Revolution. What it did was letting you divide your screen into how many and of how much size you choose "virtual monitors". You set one time of you want to divide your monitor, then everytime WinSplit is opened the monitor is automatically divided into Virtual Monitors. Screenshots: http://www.google.com/images?hl=en&q=winsplit%20revolution&um=1&ie=UTF-8&source=og&sa=N&tab=wi&biw=1045&bih=499 I'm now using a 30' which i want almost always divided into 4 equal size "virtual monitors" (plus my mbp 13' those will be 5 1280x800 virtual monitors) Now I've switched to Mac OS X and can't find anything that does just this efficiently. I tried Divvy but I found no way to divide my screen into arbitrary "virtual monitors", I need a couple of clicks to select a 3x3 space on a 9x9 grid. Before starting coding something like this can you tell me if you already know of some software that does window management like this?

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• How to transfer Windows Vista disk image to new machine

  - by Mike Hobbs

  I'm trying to upgrade a user's machine to some better hardware. I know of Easy Transfer, but I'd rather not have to reinstall all the programs that are already present. (Some of which are no longer available, anyway). Instead, I'm trying to transfer the entire disk image from one machine to the other, but I ran into issues. If I copy the partition image over to the new machine using Clonezilla, I get errors on boot saying that I need to insert the Vista install disk and run repair. I do that, but it then says that it is unable to repair whatever it is that's broken. Next, I tried to sysprep the old machine before creating the image, but sysprep fails saying that it encountered some sort of system error. Should it be possible to sysprep any arbitrary machine, or does it only work on a relatively clean install? Could it be a missing driver that is tripping me up? The new machine is a fairly stock desktop that shouldn't need any special drivers beyond what's already present in standard Vista. Are there any foolproof methods for doing this sort of thing?

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• If I scp a file through an intermediate server, is the file stored temporarily on the server?

  - by Blacklight Shining

  For the sake of simplicity (I find it easier to remember names than arbitrary letters), I will dispense with letters and use names to refer to the machines in this scenario. Say I have two machines, applejack and pinkie-pie, each on their own separate LANs and not in the same physical location. I also have a server, cadance, with a direct Internet-facing connection. I want to copy a file from applejack to pinkie-pie, so to avoid dealing with port forwarding and such, I set up an ssh tunnel from pinkie-pie to cadance (ssh -R etc cadance). Now I can connect to pinkie-pie from anywhere, by connecting to cadance and specifying an alternate port to use. I can also easily copy files to pinkie-pie with scp -P $that_port $some_file cadance:$some_path. My understanding of how it works is this: A secure connection is made from applejack to cadance I am authenticated to cadance A secure connection is made from applejack to pinkie-pie that spans the existing reverse tunnel and the new connection from step 1. I am authenticated to pinkie-pie Files are copied directly from applejack to pinkie-pie over this connection. Am I correct here? How secure is this approach? If I'm wrong…are files copied this way decrypted at cadance before being passed on to pinkie-pie? Is there a possibility that traces of unencrypted data could remain on cadance?

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• What's up with stat on Macos/Darwin? Or filesystems without names...

  - by Charles Stewart

  In response to a question I asked on SO, Give the mount point of a path, one respondant suggested using stat to get the device name associated with the volume of a given path. This works nicely on Linux, but gives crazy results on Macos 10.4. For my system, df and mount give: cas cas$ df Filesystem 512-blocks Used Avail Capacity Mounted on /dev/disk0s3 58342896 49924456 7906440 86% / devfs 194 194 0 100% /dev fdesc 2 2 0 100% /dev 1024 1024 0 100% /.vol automount -nsl [166] 0 0 0 100% /Network automount -fstab [170] 0 0 0 100% /automount/Servers automount -static [170] 0 0 0 100% /automount/static /dev/disk2s1 163577856 23225520 140352336 14% /Volumes/Snapshot /dev/disk2s2 409404102 5745938 383187960 1% /Volumes/Sparse cas cas$ mount /dev/disk0s3 on / (local, journaled) devfs on /dev (local) fdesc on /dev (union) on /.vol automount -nsl [166] on /Network (automounted) automount -fstab [170] on /automount/Servers (automounted) automount -static [170] on /automount/static (automounted) /dev/disk2s1 on /Volumes/Snapshot (local, nodev, nosuid, journaled) /dev/disk2s2 on /Volumes/Sparse (asynchronous, local, nodev, nosuid) Trying to get the devices from the mount points, though: cas cas$ df | grep -e/ | awk '{print $NF}' | while read line; do echo $line $(stat -f"%Sdr" $line); done / disk0s3r /dev ???r /dev ???r /.vol ???r /Network ???r /automount/Servers ???r /automount/static ???r /Volumes/Snapshot disk2s1r /Volumes/Sparse disk2s2r Here, I'm feeding each of the mount points scraped from df to stat, outputing the results of the "%Sdr" format string, which is supposed to be the device name: Cf. stat(1) man page: The special output specifier S may be used to indicate that the output, if applicable, should be in string format. May be used in combination with: ... dr Display actual device name. What's going on? Is it a bug in stat, or some Darwin VFS weirdness? Postscript Per Andrew McGregor, try passing "%Sd" to stat for more weirdness. It lists some apparently arbitrary subset of files from CWD...

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• What's up with stat on Mac OS X/Darwin? Or filesystems without names...

  - by Charles Stewart

  In response to a question I asked on SO, Give the mount point of a path, one respondant suggested using stat to get the device name associated with the volume of a given path. This works nicely on Linux, but gives crazy results on Mac OS X 10.4. For my system, df and mount give: cas cas$ df Filesystem 512-blocks Used Avail Capacity Mounted on /dev/disk0s3 58342896 49924456 7906440 86% / devfs 194 194 0 100% /dev fdesc 2 2 0 100% /dev <volfs> 1024 1024 0 100% /.vol automount -nsl [166] 0 0 0 100% /Network automount -fstab [170] 0 0 0 100% /automount/Servers automount -static [170] 0 0 0 100% /automount/static /dev/disk2s1 163577856 23225520 140352336 14% /Volumes/Snapshot /dev/disk2s2 409404102 5745938 383187960 1% /Volumes/Sparse cas cas$ mount /dev/disk0s3 on / (local, journaled) devfs on /dev (local) fdesc on /dev (union) <volfs> on /.vol automount -nsl [166] on /Network (automounted) automount -fstab [170] on /automount/Servers (automounted) automount -static [170] on /automount/static (automounted) /dev/disk2s1 on /Volumes/Snapshot (local, nodev, nosuid, journaled) /dev/disk2s2 on /Volumes/Sparse (asynchronous, local, nodev, nosuid) Trying to get the devices from the mount points, though: cas cas$ df | grep -e/ | awk '{print $NF}' | while read line; do echo $line $(stat -f"%Sdr" $line); done / disk0s3r /dev ???r /dev ???r /.vol ???r /Network ???r /automount/Servers ???r /automount/static ???r /Volumes/Snapshot disk2s1r /Volumes/Sparse disk2s2r Here, I'm feeding each of the mount points scraped from df to stat, outputting the results of the "%Sdr" format string, which is supposed to be the device name: Cf. stat(1) man page: The special output specifier S may be used to indicate that the output, if applicable, should be in string format. May be used in combination with: ... dr Display actual device name. What's going on? Is it a bug in stat, or some Darwin VFS weirdness? Postscript Per Andrew McGregor, try passing "%Sd" to stat for more weirdness. It lists some apparently arbitrary subset of files from CWD...

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• Password Cracking Windows Accounts

  - by Kevin

  At work we have laptops with encrypted harddrives. Most developers here (on occasion I have been guilty of it too) leave their laptops in hibernate mode when they take them home at night. Obviously, Windows (i.e. there is a program running in the background which does it for windows) must have a method to unencrypt the data on the drive, or it wouldn't be able to access it. That being said, I always thought that leaving a windows machine on in hibernate mode in a non-secure place (not at work on a lock) is a security threat, because someone could take the machine, leave it running, hack the windows accounts and use it to encrypt the data and steal the information. When I got to thinking about how I would go about breaking into the windows system without restarting it, I couldn't figure out if it was possible. I know it is possible to write a program to crack windows passwords once you have access to the appropriate file(s). But is it possible to execute a program from a locked Windows system that would do this? I don't know of a way to do it, but I am not a Windows expert. If so, is there a way to prevent it? I don't want to expose security vulnerabilities about how to do it, so I would ask that someone wouldn't post the necessary steps in details, but if someone could say something like "Yes, it's possible the USB drive allows arbitrary execution," that would be great! EDIT: The idea being with the encryption is that you can't reboot the system, because once you do, the disk encryption on the system requires a login before being able to start windows. With the machine being in hibernate, the system owner has already bypassed the encryption for the attacker, leaving windows as the only line of defense to protect the data.

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• tcp connect hangs on SYN_SENT if something listens, gets CONN_REFUSED if nothing listens

  - by Amos Shapira

  I'm hitting a very strange problem - when I try to connect to one of our servers the client hangs with SYN_SENT if something listens on the port (e.g. Apache on port 80, sshd on port 22 or SMTP on port 25) but if I try to connect to a port on which nothing listens then I immediately get a "CONNECTION refused" error. Connecting to other applications (e.g. rsyncd on some arbitrary port) succeeds. I ran tcpdump on the server and see that the SYN packets arrive to it but it only sends a response if nothing listens on that port. e.g.: on the server I run: # tcpdump -nn port 81 06:49:34.641080 IP 10.x.y.z.49829 server.81: S 3966400723:3966400723(0) win 12320 06:49:34.641118 IP server.81 x.y.z.49829: R 0:0(0) ack 3966400724 win 0 But if I listen on this port, e.g. with nc -4lvvv 81 & Then the output of tcpdump is: 06:44:31.063614 IP x.y.z.45954 server.81: S 3493682313:3493682313(0) win 12320 (and repeats until I stop it) The server is CentOS 5, the client is Ubuntu 11.04, the connection is done between two LAN's over per-user TCP OpenVPN. Connection to other servers on that network do not have a problem. Connecting from the other servers on the same network to that server works fine. Connections from other clients in our office over openvpn is also not a problem. What am I missing? Thanks.

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• Monitoring / metric collection for system collectives that change a lot in time (a.k.a. cloud)

  - by Florin Andrei

  When your server fleet doesn't change a lot in time, like when you're using bare-metal hosting, classic monitoring and metric collection solutions (Nagios, Munin) work well. But if the number of systems varies a lot in time, and may in fact vary rapidly, classic software is more difficult to setup and use. E.g., trying to make Nagios (monitoring) keep up with a rapidly evolving cloud infrastructure can be cumbersome. Same for Munin (metric collection). It's not just the configuration, but the way the information is conveyed to the user, or displayed, is inadequate for the cloud. What are some possible alternatives that work well with the cloud? The goals are to collect and display metrics (analog to Munin), and generate alerts when certain metrics go out of bounds or when certain services are unavailable (analog to Nagios), and do everything in a cloud-friendly manner. Some cloud providers offer monitoring / metric collection as services, but not always, and if you use more than one provider you don't want to become too dependent of just one vendor. So provider-independent solutions are required. EDIT: I am asking this question in a general fashion - not limited to any given cloud infrastructure (like OpenStack), but in the general case of using arbitrary cloud providers.

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• Is this a File Header / Magic Number?

  - by Hammer Bro.

  I've got 120,000 files (way more, actually; this is just an arbitrary subset) of an unknown type. Linux file does not identify them (not that they're necessarily Linux files), nor do any other methods I've tried. There are only two hints about them that I currently have. One is that I suspect some compression is employed -- I have metadata that claims the file sizes are always some amount larger than what I observe. The other is that in 100,000 of these files, the first 16 bytes are always: ff ee ee dd 00 00 00 00 01 00 00 00 00 00 00 00 That really looks like a file header/magic number to me, but I just can't place it. Does anyone know what kind of files this would indicate? Alternatively, can anyone convince me that these suspiciously common bytes certainly do not indicate a specific file type? UPDATE I don't know the exact reverse-engineering details, but most of the files in our case are zips after the first 29(? or so) bytes are ignored. So in practice the problem is solved (we know how to process the files) but in theory the question is still unanswered -- I don't know which application routinely prepends about 29 bytes to its zips. [I'm not sure if I should leave the question open or not at this point.]

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• Debugging "clogged" TCP connections

  - by Nikratio

  I'm having trouble with an internet connection that seems to randomly "freeze" arbitrary tcp connections. The connections stay established, but no data is coming through. When this happens, netstat still shows the connection status as ESTABLISHED on both the local computer: Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name Timer tcp 0 53 192.168.0.10:41129 173.255.235.238:143 ESTABLISHED 8219/gnutls-cli on (79.31/13/0) ..and the remote server: Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name Timer tcp 0 0 173.255.235.238:143 68.5.174.98:41129 ESTABLISHED 5303/imapd off (0.00/0/0) However, it seems that no data at all is transferred. If I run strace on the local and remote process, both just show a repeating sequence of select calls (with different fds of course), e.g. select(6, [0 5], NULL, NULL, {0, 50000}) = 0 (Timeout) select(6, [0 5], NULL, NULL, {0, 50000}) = 0 (Timeout) select(6, [0 5], NULL, NULL, {0, 50000}) = 0 (Timeout) The internet connection overall does not seem affected, I can still establish new connections to the same service on the same server without any problems. However, the affected local applications seem to be unaware of the problem and just hang. When I look at a packet capture of this connection on the client side, the last thing that happens is that the client transmits some data, then nothing happens for about 1100 seconds, and then several TCP Retransmission requests go out, with intervals increasing from 4 seconds to 130 seconds. No activity is captured after that. After about 10 minutes, the connection on the remote end disappears from the netstat (I wasn't able to catch any intermediate state), but still stays ESTABLISHED on the local end. Finally, after some more minutes, the local application aborts with a timeout and disappears from the local netstat output as well. Does anyone have a suggestion of how I could debug this further to find out where the problem lies and how to fix it? Additionaly and/or as a temporary workaround: is is there some way to globally reduce the timeout on client and/or server to reduce the time before the local application aborts?

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• Passing two arguments to a command using pipes

  - by firebat

  Usually, we only need to pass one argument: echo abc | cat echo abc | cat some_file - echo abc | cat - some_file Is there a way to pass two arguments? Something like {echo abc , echo xyz} | cat cat `echo abc` `echo xyz` I could just store both results in a file first echo abc > file1 echo xyz > file2 cat file1 file2 But then I might accidentally overwrite a file, which is not ok. This is going into a non-interactive script. Basically, I need a way to pass the results of two arbitrary commands to cat without writing to a file. UPDATE: Sorry, the example masks the problem. While { echo abc ; echo xyz ; } | cat does seem to work, the output is due to the echos, not the cat. A better example would be { cut -f2 -d, file1; cut -f1 -d, file2; } | paste -d, which does not work as expected. With file1: a,b c,d file2: 1,2 3,4 Expected output is: b,1 d,3 RESOLVED: Use process substitution: cat <(command1) <(command2) Alternatively, make named pipes using mkfifo: mkfifo temp1 mkfifo temp2 command1 > temp1 & command2 > temp2 & cat temp1 temp2 Less elegant and more verbose, but works fine, as long as you make sure temp1 and temp2 don't exist before hand.

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• Add and remove letterhead in Word document

  - by Daniel Wolf

  Our company has letterheaded paper (pre-printed paper with our logo on it). Whenever we send something out by mail, we print it on that paper. However, when we send the same document via email, we convert it to a PDF file. Now the problem is: when converting a Word document to PDF, it should contain the letterhead. When printing the same document on paper, it should not (or else the letterhead would be printed twice). Currently, we are using two different Word document templates - one with letterhead, one without. So whenever we want to add or remove the letterhead, we have to create a new document with the other template and copy and paste everything over. Nasty solution. What I'm looking for is some simple way to switch the letterhead on and off. What I've tried so far: Switching the template: There does not seem to be a simple way to switch the template for an existing document. Using a picture watermark: Our letterhead goes all the way to the border of the page. (No printer supports this, of course, but it is fine for export to PDF.) Apparently depending on the current default printer, Word will not allow a borderless watermark, instead shifting the image around. Using the page header: When editing the page header, I can insert pictures at arbitrary positions, which is great. However, I could not find a way (short of macros) to enable/disable just the pictures in the header. (The text should remain there.)

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• How to crop Screen Recordings under Snow Leopard?

  - by willc2

  Quicktime Player for Snow Leopard now allows you record the screen. Awesome! Once you have a movie it will let you trim screen recordings for length. Is there a way to crop the movie's dimensions, either in QT or using some built-in or free software? Update: How to crop to an arbitrary size and aspect ratio? iMovie only seems to let you crop to the aspect ratio of the containing project. Result: Both good answers but since I have QuickTime Player 7 and Photoshop, that's the workflow I choose as the answer. NOTE: If you have Photoshop Extended, you can import a movie, use the crop tool, and Export the cropped movie. Not free or built-in, but convenient. To summarize the instructions from the video link ricbax posted: Open movie in QuickTime Player 7 Copy a frame and Paste it into a new document in Photoshop Draw a rectangular selection around the area to keep and fill with black Invert the selection and fill with white Save as .GIF, with 2 colors Back in QuickTime Player 7, open Movie Properties window Select the Video Track Select the Visual Settings Tab Drag and Drop the 2-color .GIF file onto the Mask drop area (or use choose file button) Export the (now cropped) movie DONE

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