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  • ASMLib

    - by wcoekaer
    Oracle ASMlib on Linux has been a topic of discussion a number of times since it was released way back when in 2004. There is a lot of confusion around it and certainly a lot of misinformation out there for no good reason. Let me try to give a bit of history around Oracle ASMLib. Oracle ASMLib was introduced at the time Oracle released Oracle Database 10g R1. 10gR1 introduced a very cool important new features called Oracle ASM (Automatic Storage Management). A very simplistic description would be that this is a very sophisticated volume manager for Oracle data. Give your devices directly to the ASM instance and we manage the storage for you, clustered, highly available, redundant, performance, etc, etc... We recommend using Oracle ASM for all database deployments, single instance or clustered (RAC). The ASM instance manages the storage and every Oracle server process opens and operates on the storage devices like it would open and operate on regular datafiles or raw devices. So by default since 10gR1 up to today, we do not interact differently with ASM managed block devices than we did before with a datafile being mapped to a raw device. All of this is without ASMLib, so ignore that one for now. Standard Oracle on any platform that we support (Linux, Windows, Solaris, AIX, ...) does it the exact same way. You start an ASM instance, it handles storage management, all the database instances use and open that storage and read/write from/to it. There are no extra pieces of software needed, including on Linux. ASM is fully functional and selfcontained without any other components. In order for the admin to provide a raw device to ASM or to the database, it has to have persistent device naming. If you booted up a server where a raw disk was named /dev/sdf and you give it to ASM (or even just creating a tablespace without asm on that device with datafile '/dev/sdf') and next time you boot up and that device is now /dev/sdg, you end up with an error. Just like you can't just change datafile names, you can't change device filenames without telling the database, or ASM. persistent device naming on Linux, especially back in those days ways to say it bluntly, a nightmare. In fact there were a number of issues (dating back to 2004) : Linux async IO wasn't pretty persistent device naming including permissions (had to be owned by oracle and the dba group) was very, very difficult to manage system resource usage in terms of open file descriptors So given the above, we tried to find a way to make this easier on the admins, in many ways, similar to why we started working on OCFS a few years earlier - how can we make life easier for the admins on Linux. A feature of Oracle ASM is the ability for third parties to write an extension using what's called ASMLib. It is possible for any third party OS or storage vendor to write a library using a specific Oracle defined interface that gets used by the ASM instance and by the database instance when available. This interface offered 2 components : Define an IO interface - allow any IO to the devices to go through ASMLib Define device discovery - implement an external way of discovering, labeling devices to provide to ASM and the Oracle database instance This is similar to a library that a number of companies have implemented over many years called libODM (Oracle Disk Manager). ODM was specified many years before we introduced ASM and allowed third party vendors to implement their own IO routines so that the database would use this library if installed and make use of the library open/read/write/close,.. routines instead of the standard OS interfaces. PolyServe back in the day used this to optimize their storage solution, Veritas used (and I believe still uses) this for their filesystem. It basically allowed, in particular, filesystem vendors to write libraries that could optimize access to their storage or filesystem.. so ASMLib was not something new, it was basically based on the same model. You have libodm for just database access, you have libasm for asm/database access. Since this library interface existed, we decided to do a reference implementation on Linux. We wrote an ASMLib for Linux that could be used on any Linux platform and other vendors could see how this worked and potentially implement their own solution. As I mentioned earlier, ASMLib and ODMLib are libraries for third party extensions. ASMLib for Linux, since it was a reference implementation implemented both interfaces, the storage discovery part and the IO part. There are 2 components : Oracle ASMLib - the userspace library with config tools (a shared object and some scripts) oracleasm.ko - a kernel module that implements the asm device for /dev/oracleasm/* The userspace library is a binary-only module since it links with and contains Oracle header files but is generic, we only have one asm library for the various Linux platforms. This library is opened by Oracle ASM and by Oracle database processes and this library interacts with the OS through the asm device (/dev/asm). It can install on Oracle Linux, on SuSE SLES, on Red Hat RHEL,.. The library itself doesn't actually care much about the OS version, the kernel module and device cares. The support tools are simple scripts that allow the admin to label devices and scan for disks and devices. This way you can say create an ASM disk label foo on, currently /dev/sdf... So if /dev/sdf disappears and next time is /dev/sdg, we just scan for the label foo and we discover it as /dev/sdg and life goes on without any worry. Also, when the database needs access to the device, we don't have to worry about file permissions or anything it will be taken care of. So it's a convenience thing. The kernel module oracleasm.ko is a Linux kernel module/device driver. It implements a device /dev/oracleasm/* and any and all IO goes through ASMLib - /dev/oracleasm. This kernel module is obviously a very specific Oracle related device driver but it was released under the GPL v2 so anyone could easily build it for their Linux distribution kernels. Advantages for using ASMLib : A good async IO interface for the database, the entire IO interface is based on an optimal ASYNC model for performance A single file descriptor per Oracle process, not one per device or datafile per process reducing # of open filehandles overhead Device scanning and labeling built-in so you do not have to worry about messing with udev or devlabel, permissions or the likes which can be very complex and error prone. Just like with OCFS and OCFS2, each kernel version (major or minor) has to get a new version of the device drivers. We started out building the oracleasm kernel module rpms for many distributions, SLES (in fact in the early days still even for this thing called United Linux) and RHEL. The driver didn't make sense to get pushed into upstream Linux because it's unique and specific to the Oracle database. As it takes a huge effort in terms of build infrastructure and QA and release management to build kernel modules for every architecture, every linux distribution and every major and minor version we worked with the vendors to get them to add this tiny kernel module to their infrastructure. (60k source code file). The folks at SuSE understood this was good for them and their customers and us and added it to SLES. So every build coming from SuSE for SLES contains the oracleasm.ko module. We weren't as successful with other vendors so for quite some time we continued to build it for RHEL and of course as we introduced Oracle Linux end of 2006 also for Oracle Linux. With Oracle Linux it became easy for us because we just added the code to our build system and as we churned out Oracle Linux kernels whether it was for a public release or for customers that needed a one off fix where they also used asmlib, we didn't have to do any extra work it was just all nicely integrated. With the introduction of Oracle Linux's Unbreakable Enterprise Kernel and our interest in being able to exploit ASMLib more, we started working on a very exciting project called Data Integrity. Oracle (Martin Petersen in particular) worked for many years with the T10 standards committee and storage vendors and implemented Linux kernel support for DIF/DIX, data protection in the Linux kernel, note to those that wonder, yes it's all in mainline Linux and under the GPL. This basically gave us all the features in the Linux kernel to checksum a data block, send it to the storage adapter, which can then validate that block and checksum in firmware before it sends it over the wire to the storage array, which can then do another checksum and to the actual DISK which does a final validation before writing the block to the physical media. So what was missing was the ability for a userspace application (read: Oracle RDBMS) to write a block which then has a checksum and validation all the way down to the disk. application to disk. Because we have ASMLib we had an entry into the Linux kernel and Martin added support in ASMLib (kernel driver + userspace) for this functionality. Now, this is all based on relatively current Linux kernels, the oracleasm kernel module depends on the main kernel to have support for it so we can make use of it. Thanks to UEK and us having the ability to ship a more modern, current version of the Linux kernel we were able to introduce this feature into ASMLib for Linux from Oracle. This combined with the fact that we build the asm kernel module when we build every single UEK kernel allowed us to continue improving ASMLib and provide it to our customers. So today, we (Oracle) provide Oracle ASMLib for Oracle Linux and in particular on the Unbreakable Enterprise Kernel. We did the build/testing/delivery of ASMLib for RHEL until RHEL5 but since RHEL6 decided that it was too much effort for us to also maintain all the build and test environments for RHEL and we did not have the ability to use the latest kernel features to introduce the Data Integrity features and we didn't want to end up with multiple versions of asmlib as maintained by us. SuSE SLES still builds and comes with the oracleasm module and they do all the work and RHAT it certainly welcome to do the same. They don't have to rebuild the userspace library, it's really about the kernel module. And finally to re-iterate a few important things : Oracle ASM does not in any way require ASMLib to function completely. ASMlib is a small set of extensions, in particular to make device management easier but there are no extra features exposed through Oracle ASM with ASMLib enabled or disabled. Often customers confuse ASMLib with ASM. again, ASM exists on every Oracle supported OS and on every supported Linux OS, SLES, RHEL, OL withoutASMLib Oracle ASMLib userspace is available for OTN and the kernel module is shipped along with OL/UEK for every build and by SuSE for SLES for every of their builds ASMLib kernel module was built by us for RHEL4 and RHEL5 but we do not build it for RHEL6, nor for the OL6 RHCK kernel. Only for UEK ASMLib for Linux is/was a reference implementation for any third party vendor to be able to offer, if they want to, their own version for their own OS or storage ASMLib as provided by Oracle for Linux continues to be enhanced and evolve and for the kernel module we use UEK as the base OS kernel hope this helps.

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  • Clicks counting and crawler bots

    - by Dennis
    I am currently running a small affiliate-program for Facebook users. We use an auto-poster to publish links to fan pages. Every hit is stored in our database and we have included a 24 hour reload block for the IP-addresses. My problem right now is that the PHP script also stores every hit from all the bots that crawls my website. Now I was thinking to block those bots with the robots.txt of my website but I am afraid that this will have a negative effect on my AdSense ads. Does anybody have an idea for me how to work this out?

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  • How do I tackle top down RPG movement?

    - by WarmWaffles
    I have a game that I am writing in Java. It is a top down RPG and I am trying to handle movement in the world. The world is largely procedural and I am having a difficult time tackling how to handle character movement around the world and render the changes to the screen. I have the world loaded in blocks which contains all the tiles. How do I tackle the character movement? I am stumped and can't figure out where I should go with it. EDIT: Well I was abstract with the issue at hand. Right now I can only think of rigidly sticking everything into a 2D array and saving the block ID and the player offset in the Block or I could just "float" everything and move about between tiles so to speak.

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  • Too much delay while sending object over UDP to server

    - by RomZes
    I'm getting 4 sec delay when sending objects over UDP. Working on small game and trying to implement multiplayer. For now just trying to synchronize movements of 2 balls on the screen. StartingPoint.java is my server(first player), that receiving serialized objects (coordinates). SecondPlayer.java is client that sending serialized objects to server. When I'm moving my first object it appears 4 seconds later on different screen. StartingPoint.java @Override public void run() { byte[] receiveData = new byte[256]; byte[] sendData = new byte[256]; // DatagramSocket socketS; try { socket = new DatagramSocket(5000); System.out.println("Socket created on "+ port + " port"); } catch (SocketException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } while(true){ b1.update(this); b3.update(); System.out.println("Starting server..."); //// Receiving and deserializing object try { //socket.setSoTimeout(1000); DatagramPacket packet = new DatagramPacket(buf, buf.length); socket.receive(packet); byte[] data = packet.getData(); ByteArrayInputStream in = new ByteArrayInputStream(data); ObjectInputStream is = new ObjectInputStream(in); // socket.setSoTimeout(300); b1 = (Ball) is.readObject(); } catch (IOException | ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } repaint(); try { Thread.sleep(17); } catch (InterruptedException e) { e.printStackTrace(); } SecondPlayer.java @Override public void run() { while(true){ b.update(); networkSend(); repaint(); try { Thread.sleep(17); } catch (InterruptedException e) { e.printStackTrace(); } } public void networkSend(){ // Serialize to a byte array try { ByteArrayOutputStream bStream = new ByteArrayOutputStream(); ObjectOutputStream oo; oo = new ObjectOutputStream(bStream); oo.writeObject(b); oo.flush(); oo.close(); byte[] bufCar = bStream.toByteArray(); //socket = new DatagramSocket(); //socket.setSoTimeout(1000); InetAddress address = InetAddress.getByName("localhost"); DatagramPacket packet = new DatagramPacket(bufCar, bufCar.length, address, port); socket.send(packet); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); }

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  • ipod not mounting

    - by rls
    Tried to connect my iPod, but got this message: Error mounting: mount: wrong fs type, bad option, bad superblock on /dev/sdb2, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so Have seen links to this here, but beeing rather green, I don't understand much. https://bugs.launchpad.net/ubuntu/+source/util-linux/+bug/734883 What do I do now? The dmesg|tail says [ 2819.709437] sd 6:0:0:0: [sdb] 3901376 4096-byte logical blocks: (15.9 GB/14.8 GiB) [ 2819.710161] sd 6:0:0:0: [sdb] Assuming drive cache: write through [ 2819.735294] sdb: [mac] sdb1 sdb2 [ 2819.738060] sd 6:0:0:0: [sdb] 3901376 4096-byte logical blocks: (15.9 GB/14.8 GiB) [ 2819.738671] sd 6:0:0:0: [sdb] Assuming drive cache: write through [ 2819.738688] sd 6:0:0:0: [sdb] Attached SCSI removable disk [ 2820.420130] sd 6:0:0:0: [sdb] Bad block number requested [ 2820.420167] hfs: unable to find HFS+ superblock [ 2820.612140] sd 6:0:0:0: [sdb] Bad block number requested [ 2820.612191] hfs: unable to find HFS+ superblock

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  • Optimizing a thread safe Java NIO / Serialization / FIFO Queue [migrated]

    - by trialcodr
    I've written a thread safe, persistent FIFO for Serializable items. The reason for reinventing the wheel is that we simply can't afford any third party dependencies in this project and want to keep this really simple. The problem is it isn't fast enough. Most of it is undoubtedly due to reading and writing directly to disk but I think we should be able to squeeze a bit more out of it anyway. Any ideas on how to improve the performance of the 'take'- and 'add'-methods? /** * <code>DiskQueue</code> Persistent, thread safe FIFO queue for * <code>Serializable</code> items. */ public class DiskQueue<ItemT extends Serializable> { public static final int EMPTY_OFFS = -1; public static final int LONG_SIZE = 8; public static final int HEADER_SIZE = LONG_SIZE * 2; private InputStream inputStream; private OutputStream outputStream; private RandomAccessFile file; private FileChannel channel; private long offs = EMPTY_OFFS; private long size = 0; public DiskQueue(String filename) { try { boolean fileExists = new File(filename).exists(); file = new RandomAccessFile(filename, "rwd"); if (fileExists) { size = file.readLong(); offs = file.readLong(); } else { file.writeLong(size); file.writeLong(offs); } } catch (FileNotFoundException e) { throw new RuntimeException(e); } catch (IOException e) { throw new RuntimeException(e); } channel = file.getChannel(); inputStream = Channels.newInputStream(channel); outputStream = Channels.newOutputStream(channel); } /** * Add item to end of queue. */ public void add(ItemT item) { try { synchronized (this) { channel.position(channel.size()); ObjectOutputStream s = new ObjectOutputStream(outputStream); s.writeObject(item); s.flush(); size++; file.seek(0); file.writeLong(size); if (offs == EMPTY_OFFS) { offs = HEADER_SIZE; file.writeLong(offs); } notify(); } } catch (IOException e) { throw new RuntimeException(e); } } /** * Clears overhead by moving the remaining items up and shortening the file. */ public synchronized void defrag() { if (offs > HEADER_SIZE && size > 0) { try { long totalBytes = channel.size() - offs; ByteBuffer buffer = ByteBuffer.allocateDirect((int) totalBytes); channel.position(offs); for (int bytes = 0; bytes < totalBytes;) { int res = channel.read(buffer); if (res == -1) { throw new IOException("Failed to read data into buffer"); } bytes += res; } channel.position(HEADER_SIZE); buffer.flip(); for (int bytes = 0; bytes < totalBytes;) { int res = channel.write(buffer); if (res == -1) { throw new IOException("Failed to write buffer to file"); } bytes += res; } offs = HEADER_SIZE; file.seek(LONG_SIZE); file.writeLong(offs); file.setLength(HEADER_SIZE + totalBytes); } catch (IOException e) { throw new RuntimeException(e); } } } /** * Returns the queue overhead in bytes. */ public synchronized long overhead() { return (offs == EMPTY_OFFS) ? 0 : offs - HEADER_SIZE; } /** * Returns the first item in the queue, blocks if queue is empty. */ public ItemT peek() throws InterruptedException { block(); synchronized (this) { if (offs != EMPTY_OFFS) { return readItem(); } } return peek(); } /** * Returns the number of remaining items in queue. */ public synchronized long size() { return size; } /** * Removes and returns the first item in the queue, blocks if queue is empty. */ public ItemT take() throws InterruptedException { block(); try { synchronized (this) { if (offs != EMPTY_OFFS) { ItemT result = readItem(); size--; offs = channel.position(); file.seek(0); if (offs == channel.size()) { truncate(); } file.writeLong(size); file.writeLong(offs); return result; } } return take(); } catch (IOException e) { throw new RuntimeException(e); } } /** * Throw away all items and reset the file. */ public synchronized void truncate() { try { offs = EMPTY_OFFS; file.setLength(HEADER_SIZE); size = 0; } catch (IOException e) { throw new RuntimeException(e); } } /** * Block until an item is available. */ protected void block() throws InterruptedException { while (offs == EMPTY_OFFS) { try { synchronized (this) { wait(); file.seek(LONG_SIZE); offs = file.readLong(); } } catch (IOException e) { throw new RuntimeException(e); } } } /** * Read and return item. */ @SuppressWarnings("unchecked") protected ItemT readItem() { try { channel.position(offs); return (ItemT) new ObjectInputStream(inputStream).readObject(); } catch (ClassNotFoundException e) { throw new RuntimeException(e); } catch (IOException e) { throw new RuntimeException(e); } } }

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  • All my bandwidth eaten up - report included

    - by Mel
    I have my network bandwidth eaten up totally. Whenever I connect my network, without any application being opened it is always full. I have prepared report of iftop, nethogs and network system monitor. iftop and nethogs My host IP is 192.168.1.203 and all the rest are not known though I have tried to pin 192.168.1.105, it doesn't reply. If possible I would like to block the most disturbing IP which is 192.168.1.105 to block it. but don't know how.

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  • preview form using javascript in popup

    - by user1015309
    please I need some help in previewing a form in popup. I have a form, quite big, so I added the option of preview to show as popup. The lightbox form popup works well, but the problem I now have is function passform ()passing the inputs(textfield, select, checkbox, radio) into the popup page for preview on Click(). Below are my javascript and html codes. I left the css and some html out, because I think they're not needed. I will appreciate your help. Thank you The Javascript function gradient(id, level) { var box = document.getElementById(id); box.style.opacity = level; box.style.MozOpacity = level; box.style.KhtmlOpacity = level; box.style.filter = "alpha(opacity=" + level * 100 + ")"; box.style.display="block"; return; } function fadein(id) { var level = 0; while(level <= 1) { setTimeout( "gradient('" + id + "'," + level + ")", (level* 1000) + 10); level += 0.01; } } // Open the lightbox function openbox(formtitle, fadin) { var box = document.getElementById('box'); document.getElementById('shadowing').style.display='block'; var btitle = document.getElementById('boxtitle'); btitle.innerHTML = formtitle; if(fadin) { gradient("box", 0); fadein("box"); } else { box.style.display='block'; } } // Close the lightbox function closebox() { document.getElementById('box').style.display='none'; document.getElementById('shadowing').style.display='none'; } //pass form fields into variables var divexugsotherugsexams1 = document.getElementById('divexugsotherugsexams1'); var exugsotherugsexams1 = document.form4.exugsotherugsexams1.value; function passform() { divexugsotherugsexams1.innerHTML = document.form4.exugsotherugsexams1.value; } The HTML(with just one text field try): <p><input name="submit4" type="submit" class="button2" id="submit4" value="Preview Note" onClick="openbox('Preview Note', 1)"/> </p> <div id="shadowing"></div> <div id="box"> <span id="boxtitle"></span> <div id="divexugsotherugsexams1"></div> <script>document.write('<PARAM name="SRC" VALUE="'+exugsotherugsexams1+'">')</script> <a href="#" onClick="closebox()">Close</a> </div>

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  • Should I sacrifice code succintness to ensure the narrowest variable scope? [duplicate]

    - by David Scholefield
    This question already has an answer here: Is the usage of internal scope blocks within a function bad style? 3 answers In many languages (e.g. both Perl and Java - which are the two languages I work most with) it is possible to narrow the scope of local variables by declaring them within a block. Although it adds extra code length (the opening and closing block braces), and possibly reduces readability, should I create blocks purely to narrow the scope of variables to the statements that use the variables and to uphold the principle of narrowest scope or does this sacrifice succinctness and readability just to unnecessarily uphold an agreed 'best practice' principle? I usually declare local variables to functions/methods at the start of the function to aid readability, but I could not do this, and just create blocks throughout the function and declare the variables throughout the code - within those blocks - to narrow their scope.

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  • Fuji camera "mounts" but folder not in Dolphin After Kubuntu 13.10 upgrade

    - by user207207
    Fuji camera mount reported in attached devices but not visible in Dolphin After Kubuntu 13.10 upgrade Have reinstalled the driver, and a few other suggestions, for other cameras mounts failing on previous Ubuntu upgrades. I have already spent a couple of hours trying to get my photo's off the camera, very annoying. Worked perfectly in 11.04, 11.10, 12.04, 12.10 and 13.04. dmesg | tail; lsusb; lsb_release -a [ 6181.858786] CPUM: APIC 03 at 00000000fee00000 (mapped at ffffc90009400000) - ver 0x80050010, lint0=0x10700 lint1=0x10400 pc=0x00400 thmr=0x10000 [17261.396236] CPUM: APIC 00 at 00000000fee00000 (mapped at ffffc90000c6a000) - ver 0x80050010, lint0=0x10700 lint1=0x00400 pc=0x00400 thmr=0x10000 [17261.396239] CPUM: APIC 03 at 00000000fee00000 (mapped at ffffc90000c72000) - ver 0x80050010, lint0=0x10700 lint1=0x10400 pc=0x00400 thmr=0x10000 [17261.396241] CPUM: APIC 02 at 00000000fee00000 (mapped at ffffc90000c70000) - ver 0x80050010, lint0=0x10700 lint1=0x10400 pc=0x00400 thmr=0x10000 [17261.396255] CPUM: APIC 01 at 00000000fee00000 (mapped at ffffc90000c6e000) - ver 0x80050010, lint0=0x10700 lint1=0x10400 pc=0x00400 thmr=0x10000 [32456.884907] usb 2-5: new high-speed USB device number 2 using ehci-pci [32457.654046] usb 2-5: New USB device found, idVendor=04cb, idProduct=01e8 [32457.654050] usb 2-5: New USB device strings: Mfr=0, Product=2, SerialNumber=3 [32457.654052] usb 2-5: Product: Digital Camera [32457.654053] usb 2-5: SerialNumber: 4C3230302020091117CAA59WP18548 Bus 002 Device 002: ID 04cb:01e8 Fuji Photo Film Co., Ltd Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 001 Device 003: ID 2013:024f PCTV Systems nanoStick T2 290e Bus 001 Device 002: ID 046d:082d Logitech, Inc. HD Pro Webcam C920 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub No LSB modules are available. Distributor ID: Ubuntu vissibleDescription: Ubuntu 13.10 Release: 13.10 Codename: saucy sudo apt-get install gvfs-bin gvfs-mount gphoto2://[usb:002,002] Error mounting location: Error initializing camera: -108: No such file or directory ...... I have reported a bug in Dolphin, which has been transferred to Solid. Further information : I ran solid-hardware list details udi = '/org/kde/solid/udev/sys/devices/pci0000:00/0000:00:04.1/usb2/2-5' parent = '/org/kde/solid/udev' (string) vendor = '04cb' (string) product = 'Digital Camera' (string) description = 'Camera' (string) Block.major = 189 (0xbd) (int) Block.minor = 137 (0x89) (int) Block.device = '/dev/bus/usb/002/010' (string) Camera.supportedProtocols = {'ptp'} (string list) Camera.supportedDrivers = {'gphoto'} (string list) I still can't get my photo's off, I can see the folders using the Gimp menu. If anyone has got any ideas, I'm willing to try them.

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  • REGISTER TODAY: Oracle Linux and Oracle VM Virtual SysAdmin Day- July 15

    - by Zeynep Koch
    Are you just starting on Oracle Linux or do you still feel you are missing some knowledge on how to configure, install or patch your Oracle Linux? If you answered yes, this event for you. This is our second virtual sysadmin day for Oracle Linux and it had been hugely popular in the past. This is a hands-on experience for all those Sysadmins that are looking for a great training without leaving their office or home. You will learn to: Install Oracle Linux using RPM and yum repositories; create storage volumes, prepare block devices, work with filesystems Create and mount Btrfs in Oracle Linux, work with block devices and snapshots Come and join us on July 15, 9am-12pm Pacific Time for an informative and interactive session. See more details and register 

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  • 'Unable to mount Filesystem' Error

    - by Charles
    Trying to extract data from a 'bricked' Western Digital MyBook Live 2tb drive. I came across a forum that advised to use Ubuntu (booted from a CD) on my Macbook. Managed to download and create a boot CD for Ubuntu (like this little operating system btw). Booted the machine with the CD and plugged the drive (which I had extracted from it's casing and placed into a external USB SATA case & plugged to the laptop). The drive is seen by Ubuntu but each time I click on the drive, it gives me the following error: Unable to mount 2.0 TB Filesystem Error mounting: mount: wrong fs type, bad option, bad superblock on /dev/sdb4, missing codepage or helper program, or other error In some cases useful info is found in syslog -try dmesg | tail or so I am new to this and spent quite some time searching this site to see if I could find a solution to this problem without troubling anyone. I came up with a few that came close but some of the questioners mentioned that they had lost data...which scared me from going further. I need to basically extract 1 particular folder from the drive. If I can get to mount this volume 'sdb4', there is a folder called 'My_Work' which I need to back up. The rest I have/had a copy of. When I typed in dmesg | tail...I got several lines..but I think ones that are relevant are: [ 406.864677] EXT4-fs (sdb4): bad block size 65536 [ 429.098776] hfs: write access to a journaled filesystem is not supported, use the force option at your own risk, mounting read-only [ 439.786365] hfs: write access to a journaled filesystem is not supported, use the force option at your own risk, mounting read-only [ 445.982692] EXT4-fs (sdb4): bad block size 65536 [ 1565.841690] EXT4-fs (sdb4): bad block size 65536 I read somewhere to try/check 'sudo fdisk -l /dev/sdb4'. It gave me the following result: Disk /dev/sdb44: 1995.8 GB, 1995774623744 bytes 255 heads, 63 sectors/track, 242639 cylinders, total 3897997312 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/sdb4 doesn't contain a valid partition table This is where I reached and got frustrated and decided to try & get help on this without digging myself deeper into a hole! I understand that the answer may already be out there. If so, could someone please point me in the right direction. And if not, could someone please resolve (if possible) my situation!

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  • SSH not working from outside network

    - by alexander7567
    Ok.. First off my ISP does not block ports. I run web server just fine from another machine. I have port forwarded port 22. I can access within network but not out of.. I.E. my android. I get "The Operation Timed Out" on ConnectBot. Oh and I have allowed 22 on UFW. To answer what exactly happened was my ISP blocks port 22, even though a while back they told me they do not block any ports.. I changed it to port 27 and it worked without a problem.

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  • Assemble static site from templates? (don't want to reinvent the wheel)

    - by raindog308
    I have a site that is 100% static content (no php, just some javascript). There's several "blocks" like the header, menu, footer, etc. that are the same on each page. Rather than do a lot of copy/pasting, I was thinking of some kind of template system where I could run a CLI command (in php, perl, python, shell, whatever) and have it replace all the block tags with the actual block text. I did see some answers in this question, but those seem oriented towards "we provide the style and layout, you provide the text". In my case, I have everything as far as layout, css, etc. - just want to do a glorified sed. Before I invent the wheel, I was wondering if there was a tool out there already.

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  • Tracing and blocking ip's

    - by Mark
    I was wondering if there is anyway you can block or exclude people from submitting multiple fake ip's online . For example I have a google pay-per-click campaign set up on adwords. I downloaded a program in minutes which enabled me to hide or give out a fake ip address which also allows you to use a different ip each time. I tried this out on my own link on google which in turn got through adwords and I was charged for the click. My question is how would you be able to counter or block someone who continuosly clicks on your link with a different fake ip each time?

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  • In what stage of development should comments be written?

    - by CurtisHx
    I'm a student working an internship at a larger company, writing small business apps in C#. I've noticed that I don't comment my code as I write it. Rather, I comment my code when I'm in the debugging stage of development. As I'm tracking down bugs, I'll run across a block that makes me think "hmm...that might confuse someone in the future. I'd better comment that", and I'll add the appropriate comments. All of my comments are done this way. Is this an appropriate way of commenting? Should comments be written as the code is written? Or does it really matter when the comments are written, as long as they adequately explain why this block is used?

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  • Algorithm for determining grid based on variably sized "blocks"?

    - by Lite Byte
    I'm trying to convert a set of "blocks" in to a grid-like layout. The blocks have a width of either 25%, 33%, 50%, 66%, or 75% of their container and each row of the grid should try to fit as many blocks as possible, up to a total width of 100%. I've discovered that trying to do this while leaving no remaining blocks in the original set is very hard. Eventually, I think my solution will be to upgrade/downgrade various block sizes (based on their priority or something) so they all fit in to a row. Either case, before I do that, I thought I'd check if someone has some code (or a paper) demonstrating a solution to this problem already? And bonus points if the solution incorporates varying block heights in to its calculations :) Thanks!

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  • how did Google Analytics kill my site?

    - by user1813359
    Yesterday I created a google analytics profile for one of my sites and included the JS block in the layout template. What happened next was very strange. Within about 2 minutes, the site had become unreachable. I had been checking the AWStats page for the site when I thought to set up GA. After that had been done, I clicked on the link for 404 stats, which opens in a new tab. It churned for a long while and then showed a nearly blank page, similar to that when Firefox chokes on a badly-formatted XML page, except there was no error msg. But i was logged into the server and could see that that page has a 401 Transitional DTD. Strange! I tried viewing source but it just churned endlessly. I then tried "inspect element" and was able to see an error msg having to do with some internal Firefox lib. Unfortunately, i neglected to copy that. :-( All further attempts to load anything on the site would time out. Firebug's Net panel showed no request being made. Chrome would time out. So, I deleted the GA profile, removed the JS block, and cleared the server cache. No joy. I then removed all google cookies and disabled JS. Still nothing. No luck in any other browser. And now my client couldn't access the site. Terrific. I was able use wget while logged into another server. The retrieved page was fine, and did not contain the GA JS block. However, the two servers are on the same network. (Perhaps a clue.) The server itself was fine. Ping, traceroute looked great. I could SSH in. I tailed the access log and tried a browser request. Nothing. But i forgot to quit and a minute or so later I saw a request from someone else being logged. Later, I could see that requests had been served all day to some people. Now, 24 hours later, the site works once again, but is still unreachable by the client (who is in another city). So, does anyone have some insight into what's going on? Does this have something to do with google's CDN? I don't know very much about how GA works but what I'm seeing reminds me of DNS propagation issues. And why the initial XML error? And why the heck was the site just plain unreachable? What did google do to my site?! Sorry for the length but I wanted to cover everything.

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  • Would you see any use of a Trilean (True, False, ??)

    - by Sybiam
    I don't know if I'm alone but sometimes I have a function that should return true or false. But in some case there would be a third result that would make more sense. In some language theses cases would be handled with integers or with exception. For exemple you want to handle the age of a user if he is over 18 years old. And you have a function like this. if(user.isAdult(country_code)){ //Go On }else{ // Block access or do nothing } But in some case depending how your app is built I could see case where the birthday field is incomplete. Then this function should return something undetermined. switch(user.isAdult()){ case true: // go on break; case undetermined: //Inform user birthday is incomplete case false: //Block access } As i said we can handle that with Exceptions and Int, but I would find it quite sexy to have a true, false, undetermined embeded in the language instead of using some home defined constants.

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  • phpBB - Reducing Spam

    - by user44175
    I've installed phpBB Forums last week and the past 2 days I've been getting users sign up and posting spam chinese emails on each topic. I have:- Added captcha on registration Made sure users have to verify subscription by email before allowing to post What else can I do to stop this from happening? I've banned their IP addresses but this doesn't stop them from using a proxy to keep spamming the forums. I've read I can block all chinese IP addresses through ACP but is this the best step to block all this? Seems to be all chinese spam at the minute, any help would be much appreciated.

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