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• Ubuntu 13.XX unable to mount USB HDD. Tried everything. I/O error boot sector/file system

  - by XaviGG

  I know that there are many posts related but none of them helped me. I will jump to the last test because it is the one that should work, but it does not. An external HDD with single partition slow NTFS formatted in Windows, empty and clean. Checked for errors, it tells that not errors where found. Moving to Ubutnu 13.04... Gparted throws the first error when trying to read the disk: Input/output error It appears as unknown the content of the disk. Unable to create partition table or format it, getting the same error when trying. If I try to mount it in the terminal it tells me the same, specifying that also there is an I/O error reading the boot sector. I have this problem since I upgraded (always with fresh install) to 13.04. I thought it will be solved by the 13.10 but it has the same behavior. I tried with two different HDD (HD and SSHD) that work perfectly in Windows 7. In 13.04 at least I got a trying of mounting where the icon of the drive started showing and disappearing until finally it disappeared. But now it doesn't even try. Possible causes: -The HDD was my old main HDD, so it had WIN,RECOVERY,SYSTEM,UBU,SWAP partitions. Maybe the way or place where the partition table is defined is not the best for an external HDD but I don't know a lot in that topic. I would appreciate a lot if someone can give me a guideline to convert one of these HDD in a working external HDD. No files to recover, nothing to care about. Just format completely the disk and be able to use it for storing backups without having to move the files first to the windows partition, load windows and then copy them to the external HDD. Because I want to use a file comparator for the backups. Thanks a lot Edit 1: I found an option in Windows to convert it to a dynamic HDD that warns me that I wont be able to run O.S. after changing. I suppose that is what I need because in the current mode I cannot safely extract it. But it tells me an error that it couldn't change the mode.

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• Dual booting windows 8/ubuntu 12.04. Grub doesn't appear and machine never boot in ubuntu

  - by black sensei

  i got a new ACER predator AG3620-UR308 which came with windows 8, so i wanted to run ubuntu 12.04.2 on it as a dual booting. To be honest, i've been doing dual booting for a while now so, i did the right thing. the box came with 2TB HDD. so i made 4 partitions with a raw partition just after the windows installation partition I always do manual installation so even if ubuntu didn't detect windows 8, it was ok for me. So i created swap area and finished the installation etc....Grub was install on the only drive there which is sda. After reboot, grub doesn't even come up.So it always boot in windows 8. I did repeat the installation process twice and yield same result. which is weird because this method always works for me so far.Even the laptop am using to write this post is a dual booting windows 7/ mint nadia installed the same way. Is there anything new in windows 8 that i didn't make provision for? Before starting the installation, all i read about was that , windows 8 should be installed first and ubuntu after. I went ahead and disable secure boot from the BIOS and enabled CSM (don't even know what it means) according to Acer custhelp site . I boot from USB and did fdisk -l bellow is the result: ubuntu@ubuntu:~$ sudo fdisk -l WARNING: GPT (GUID Partition Table) detected on '/dev/sda'! The util fdisk doesn't support GPT. Use GNU Parted. Disk /dev/sda: 2000.4 GB, 2000398934016 bytes 255 heads, 63 sectors/track, 243201 cylinders, total 3907029168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disk identifier: 0x8c361cb5 Device Boot Start End Blocks Id System /dev/sda1 1 3907029167 1953514583+ ee GPT Partition 1 does not start on physical sector boundary. Disk /dev/sdb: 8178 MB, 8178892800 bytes 255 heads, 63 sectors/track, 994 cylinders, total 15974400 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: 0x0006a87e Device Boot Start End Blocks Id System /dev/sdb1 * 2048 15972351 7985152 b W95 FAT32 ubuntu@ubuntu:~$ Can anybody shed some light? thank you in advance

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• More elegant way to avoid hard coding the format of a a CSV file?

  - by dsollen

  I know this is trivial issue, but I just feel this can be more elegant. So I need to write/read data files for my program, lets say they are CSV for now. I can implement the format as I see fit, but I may have need to change that format later. The simply thing to do is something like out.write(For.getValue()+","+bar.getMinValue()+","+fi.toString()); This is easy to write, but obviously is guilty of hard coding and the general 'magic number' issue. The format is hard-coded, requires parsing of the code to figure out the file format, and changing the format requires changing multiple methods. I could instead have my constants specifying the location that I want each variable to be saved in the CSV file to remove some of the 'magic numbers'; then save/load into the an array at the location specified by the constants: int FOO_LOCATION=0; int BAR_MIN_VAL_LOCATION=1; int FI_LOCATION=2 int NUM_ARGUMENTS=3; String[] outputArguments=new String[NUM_ARGUMENTS]; outputArguments[FOO_LOCATION] = foo.getValue(); outputArgumetns[BAR_MIN_VAL_LOCATION] = bar.getMinValue(); outptArguments[FI_LOCATOIN==fi.toString(); writeAsCSV(outputArguments); But this is...extremely verbose and still a bit ugly. It makes it easy to see the format of existing CSV and to swap the location of variables within the file easily. However, if I decide to add an extra value to the csv I need to not only add a new constant, but also modify the read and write methods to add the logic that actually saves/reads the argument from the array; I still have to hunt down every method using these variables and change them by hand! If I use Java enums I can clean this up slightly, but the real issue is still present. Short of some sort of functional programming (and java's inner classes are too ugly to be considered functional) I still have no obvious way of clearly expressing what variable is associated with each constant short of writing (and maintaining) it in the read/write methods. For instance I still need to write somewhere that the FOO_LOCATION specifies the location of foo.getValue(). It seems as if there should be a prettier, easier to maintain, manner for approaching this? Incidentally, I'm working in java at the moment, however, I am interested conceptually about the design approach regardless of language. Some library in java that does all the work for me is definitely welcome (though it may prove more hassle to get permission to add it to the codebase then to just write something by hand quickly), but what I'm really asking is more about how to write elegant code if you had to do this by hand.

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• How can I create a flexible system for tiling a 2D RPG map?

  - by CptSupermrkt

  Using libgdx here. I've just finished learning some of the basics of creating a 2D environment and using an OrthographicCamera to view it. The tutorials I went through, however, hardcoded their tiled map in, and none made mention of how to do it any other way. By tiled map, I mean like Final Fantasy 1, where the world map is a grid of squares, each with a different texture. So for example, I've got a 6 tile x 6 tile map, using the following code: Array<Tile> tiles = new Array<Tile>(); tiles.add(new Tile(new Vector2(0,5), TileType.FOREST)); tiles.add(new Tile(new Vector2(1,5), TileType.FOREST)); tiles.add(new Tile(new Vector2(2,5), TileType.FOREST)); tiles.add(new Tile(new Vector2(3,5), TileType.GRASS)); tiles.add(new Tile(new Vector2(4,5), TileType.STONE)); tiles.add(new Tile(new Vector2(5,5), TileType.STONE)); //... x5 more times. Given the random nature of the environment, for loops don't really help as I have to start and finish a loop before I was able to do enough to make it worth setting up the loop. I can see how a loop might be helpful for like tiling an ocean or something, but not in the above case. The above code DOES get me my final desired output, however, if I were to decide I wanted to move a piece or swap two pieces out, oh boy, what a nightmare, even with just a 6x6 test piece, much less a 1000x1000 world map. There must be a better way of doing this. Someone on some post somewhere (can't find it now, of course) said to check out MapEditor. Looks legit. The question is, if that is the answer, how can I make something in MapEditor and have the output map plug in to a variable in my code? I need the tiles as objects in my code, because for example, I determine whether or not a tile is can be passed through or collided with based on my TileTyle enum variable. Are there alternative/language "native" (i.e. not using an outside tool) methods to doing this?

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• Weird Ubuntu Desktop Boot Partition On External Hard Drive

  - by Magnitus

  I have a Thinkpad with Windows 7. Last time I installed an Ubuntu/Windows dual boot, Windows was never same after and regularly got corrupted so this time, I installed Ubuntu on a separate external hard drive. I took a 500 GB external hard drive and used Windows to shrink the partition on it to 400 GB, freeing 100 GB to install Ubuntu. Then I modified the booting priority of my computer to boot from the external hard drive if present. Then, I installed Ubuntu desktop on the external hard drive using a DVD, picked the most simplistic partitioning scheme I could get away with (didn't go auto as it didn't include the external hard drive as a choice) and voilà. Fast forward some time and I'm trying to refresh my understanding of Linux partitions to install a bunch of servers, so I'm looking at the current partitioning scheme on my external hard drive and find the boot partition puzzling... sda is my integrated hard drive with Windows 7. sdb is my Ubuntu desktop external hard drive. Running parted on sdb, I get this: (parted) print Model: WD My Passport 0740 (scsi) Disk /dev/sdb: 500GB Sector size (logical/physical): 512B/512B Partition Table: msdos Number Start End Size Type File system Flags 1 1049kB 393GB 393GB primary ntfs boot 2 393GB 500GB 107GB extended 5 393GB 425GB 32.8GB logical linux-swap(v1) 6 425GB 500GB 74.6GB logical ext4 At this point, I'm wondering why the ntfs partition is flagged as "boot" and not my ext4 partition which is the partition that contains / (and by extension, /boot since it's not on its own separate partition). Looking at mtab only confirms what I already know: eric@eric-ThinkPad-W530:~$ sudo cat /etc/mtab /dev/sdb6 / ext4 rw,errors=remount-ro 0 0 proc /proc proc rw,noexec,nosuid,nodev 0 0 sysfs /sys sysfs rw,noexec,nosuid,nodev 0 0 none /sys/fs/cgroup tmpfs rw 0 0 none /sys/fs/fuse/connections fusectl rw 0 0 none /sys/kernel/debug debugfs rw 0 0 none /sys/kernel/security securityfs rw 0 0 udev /dev devtmpfs rw,mode=0755 0 0 devpts /dev/pts devpts rw,noexec,nosuid,gid=5,mode=0620 0 0 tmpfs /run tmpfs rw,noexec,nosuid,size=10%,mode=0755 0 0 none /run/lock tmpfs rw,noexec,nosuid,nodev,size=5242880 0 0 none /run/shm tmpfs rw,nosuid,nodev 0 0 none /run/user tmpfs rw,noexec,nosuid,nodev,size=104857600,mode=0755 0 0 none /sys/fs/pstore pstore rw 0 0 systemd /sys/fs/cgroup/systemd cgroup rw,noexec,nosuid,nodev,none,name=systemd 0 0 gvfsd-fuse /run/user/1000/gvfs fuse.gvfsd-fuse rw,nosuid,nodev,user=eric 0 0 /dev/sdb1 /media/eric/My\040Passport fuseblk rw,nosuid,nodev,allow_other,default_permissions,blksize=4096 0 0 My lack of understanding concerning this is not vital to anything (this is only my development desktop partition), but somehow annoys me. Any insight that could shed some light on this would be welcome.

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• Developer career feeling like going back in time every new job [closed]

  - by komediant

  Is there a good category for this question? My background is bachelor in ICT and for a hobby I am programming already since I was around twelve I think. Started with QBasic, Pascal, C, Java et cetera. Currently I am working for about eight/nine years. Half academics/medical and half company world. A few years ago I started with frameworks and I began with Grails (underlying Spring/Hibernate), which was a heavenly job, very productive and no hassle. My previous job I developed in pure Spring/Hibernate Java, which was a bit more writing annotations and XML and no conventions like Grails. But still, I did like Spring/Hibernate a lot and the professional setup with a developmentstreet, versioning, Jenkins/Sonar, log4j and a good IDE like IntellIJ. It felt quite 'clear' and organised, although I knew Grails which felt a bit more productive. But...at my current job almost half the code is pure servlet, hard coded JDBC (connections handled by yourself), scriptlets in all JSP pages, no service layer, no versioning, no Maven, HTML in DAO-layer, JAR-hell, no hot swap deployment locally, every change you have to deploy and hope it works fine on the server. All local development needs ugly scriptlet tags to check which environment it is running. Et cetera. Now and then developers work over in the evening - I don't - and still lots of issues are not solved and new projects are waiting. I hear the developers complaining, but somehow they feel like what they have now is "advanced" or they are in a sort of comfore zone. The lead developer seems open for new things, but half of the times he says he can implement MVC-framework features himself instead of using what is already out there. So in short, I currently feel like I miss all the modern framework techniques and that the company is going so slow forward. I just work here for two months now. What I do now is also code some partially ugly stuff, but it goes in completely into my nature and I feel uncomfortable with it. Coding something takes long(er) than estimated and my manager complains about why it takes so long and I feel ashamed for myself needing so much time. Where I was used to just writing a query I now build up whole try catch methods. My manager knows my complaints and the developers do so too. There will come a meeting to line out plans for 2013 on technology and the issues I and the company are facing. I am not looking for another job yet, it's close to wehre I live and the economy is fragile. Does anyone else have had this kind of career, like feeling going backwards witch technology? And how did you cope with it?

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• Raid superblock missing on single parition. Recovery needed!

  - by user171639

  Ok so I have a 2 TB raid 1 setup that has three partitions: sdc1: linux sdc2: swap sdc3: LVM for data However the LVM will no longer mount. So I thought that I would take the first drive, mount it in linux (ive done this b4), and reset the spare drive to copy the data. Normally I can mount a single drive for data recovery using: sudo su apt-get install mdadm lvm2 mdadm --assemble --scan modprobe dm-mod vgscan vgchange -ay c mount -o ro /dev/c/c /mnt Unfortunately, vgscan doesnot recognize the data partition. It appears as though the superblock on the first drive's data partition was erased while syncing with the second. So now I cannot mount that partition and the second drive is stuck in spare mode. Any ideas? Or a way to force mount the data partition just to copy the data? knoppix@Microknoppix:~$ sudo su root@Microknoppix:/home/knoppix# apt-get install mdadm lvm2 Reading package lists... Done Building dependency tree Reading state information... Done lvm2 is already the newest version. mdadm is already the newest version. 0 upgraded, 0 newly installed, 0 to remove and 551 not upgraded. root@Microknoppix:/home/knoppix# mdadm --assemble --scan mdadm: /dev/md/1 has been started with 1 drive (out of 2). mdadm: /dev/md/0 has been started with 1 drive (out of 2). root@Microknoppix:/home/knoppix# modprobe dm-mod root@Microknoppix:/home/knoppix# vgscan Reading all physical volumes. This may take a while... No volume groups found root@Microknoppix:/home/knoppix# cat /proc/mdstat Personalities : [raid1] md0 : active raid1 sdc1[2] 4193268 blocks super 1.2 [2/1] [U_] md1 : active raid1 sdc2[2] 524276 blocks super 1.2 [2/1] [U_] unused devices: <none> root@Microknoppix:/home/knoppix# mdadm -v --assemble --auto=yes /dev/md2 /dev/sdc3 mdadm: looking for devices for /dev/md2 mdadm: no recogniseable superblock on /dev/sdc3 mdadm: /dev/sdc3 has no superblock - assembly aborted root@Microknoppix:/home/knoppix# dumpe2fs /dev/md0 | grep -i superblock dumpe2fs 1.42.4 (12-Jun-2012) Primary superblock at 0, Group descriptors at 1-1 Backup superblock at 32768, Group descriptors at 32769-32769 Backup superblock at 98304, Group descriptors at 98305-98305 Backup superblock at 163840, Group descriptors at 163841-163841 Backup superblock at 229376, Group descriptors at 229377-229377 Backup superblock at 294912, Group descriptors at 294913-294913 Backup superblock at 819200, Group descriptors at 819201-819201 Backup superblock at 884736, Group descriptors at 884737-884737 root@Microknoppix:/home/knoppix# Notes: I can read the super block from the spare drive. I was gonna try and restore the superblock from one of the backups, but i dont know how or if this would work. I also heard creating a new array (mdadm --create) using the same parameters will not delete the data on the drive but i didnt want to risk it. Recommendations?

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• Can my machine run Ubuntu( kubuntu | xubuntu | mint ) 12.04 WELL?

  - by Steve

  I have a 9 year old computer packing the hardware listed below. My question is, can I run 12.04 ( Ubuntu, Kubuntu, MINT or Xubuntu ) WELL? I was running Ubuntu 10.10 and I upgraded to 12.04 by going through each release via the update manager: 11.04 - 11.10 -12.04 During the installation process for 12.04 I saw an error message that there was an error installing and setting up part of the kernel. Later, when I tried installing a package in synaptic, I got another error message mentioning the kernel. When I rebooted, I got told somehting about my video and graphics was not configured properly and that I would have to do it manually ( like I know ). It gave me the option to enter the system in low graphics mode, but it just hanged. I had an old livecd of Xubuntu 10.10 around so I used that to get into my computer and copy data over to an external hard drive. I think tried to install Xubuntu 10.10 from the livecd, with the option "download updates" checked. The install process moved along a bit, then halted for about 5 hours. I rebooted my machine and tried the Xubuntu 10.10 installer WITHOUT the option to "download updates". The install completed in about 15 minutes. So, all of that is making me wonder if there is someting about 12.04 that does not like my hardware. I'm willing to try again, but only if I know I will not have to spend hours just to get to an error message and a hosed up system like I did last night. I also think I have a lot more RAM than is being reported in the output below. I had extra ram installed last year. I'm not good with the command line readouts, but there seems like there should be a lot more. I wasn't thrilled with Unity. I am willing to try Kubuntu 12.04. Will I run into the same problems? What is the highest version of a *ubuntu can I upgrade to? Thanks CPU Model: Intel(R) Pentium(R) 4 CPU 2.53GHz Frequency: 2533.223 MHz L2 Cache: 512 KB Bogomips: 5066.44 Numbering: family(15) model(2) stepping(7) Flags: fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe up pebs bts cid RAM ~$ free -mt total used free shared buffers cached Mem: 1506 891 615 0 91 521 -/+ buffers/cache: 278 1227 Swap: 1609 0 1609 Total: 3116 891 2225 Video Card 01:00.0 VGA compatible controller: nVidia Corporation NV18 [GeForce4 MX 440 AGP 8x] (rev a2) (prog-if 00 [VGA controller]) Subsystem: ASUSTeK Computer Inc. V9180 Magic Flags: bus master, 66MHz, medium devsel, latency 32, IRQ 16 Memory at fd000000 (32-bit, non-prefetchable) [size=16M] Memory at f0000000 (32-bit, prefetchable) [size=64M] Expansion ROM at fe9e0000 [disabled] [size=128K] Kernel driver in use: nouveau Kernel modules: nouveau, nvidiafb Motherboard Intel 845PE ATX 533FSB DDR333 USB2

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• Why C++ people loves multithreading when it comes to performances?

  - by user1849534

  I have a question, it's about why programmers seems to love concurrency and multi-threaded programs in general. I'm considering 2 main approach here: an async approach basically based on signals, or just an async approach as called by many papers and languages like the new C# 5.0 for example, and a "companion thread" that maanges the policy of your pipeline a concurrent approach or multi-threading approach I will just say that I'm thinking about the hardware here and the worst case scenario, and I have tested this 2 paradigms myself, the async paradigm is a winner at the point that I don't get why people 90% of the time talk about concurrency when they wont to speed up things or make a good use of their resources. I have tested multi-threaded programs and async program on an old machine with an Intel quad-core that doesn't offer a memory controller inside the CPU, the memory is managed entirely by the motherboard, well in this case performances are horrible with a multi-threaded application, even a relatively low number of threads like 3-4-5 can be a problem, the application is unresponsive and is just slow and unpleasant. A good async approach is, on the other hand, probably not faster but it's not worst either, my application just waits for the result and doesn't hangs, it's responsive and there is a much better scaling going on. I have also discovered that a context change in the threading world it's not that cheap in real world scenario, it's infact quite expensive especially when you have more than 2 threads that need to cycle and swap among each other to be computed. On modern CPUs the situation it's not really that different, the memory controller it's integrated but my point is that an x86 CPUs is basically a serial machine and the memory controller works the same way as with the old machine with an external memory controller on the motherboard. The context switch is still a relevant cost in my application and the fact that the memory controller it's integrated or that the newer CPU have more than 2 core it's not bargain for me. For what i have experienced the concurrent approach is good in theory but not that good in practice, with the memory model imposed by the hardware, it's hard to make a good use of this paradigm, also it introduces a lot of issues ranging from the use of my data structures to the join of multiple threads. Also both paradigms do not offer any security abut when the task or the job will be done in a certain point in time, making them really similar from a functional point of view. According to the X86 memory model, why the majority of people suggest to use concurrency with C++ and not just an async aproach ? Also why not considering the worst case scenario of a computer where the context switch is probably more expensive than the computation itself ?

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• How can I improve the battery life under 12.04 on my Inspiron 14z? [duplicate]

  - by cfogelberg

  This question already has an answer here: Tips to extend battery life for laptops and notebooks 24 answers How do I improve the battery life of my Inspiron 14z under Ubuntu 12.04? This laptop gets 4-5 hours of battery life using Windows (e.g. here). I've removed Windows, installed Ubuntu 12.04 and the initial battery life was only 2 hours. With some tweaks (described below) it's still only ~2.5 hours. For reference, the laptop is the latest model of the 14z: i5-3337U processor 32GB MSATA, 500GB HDD (5400rpm) AMD Radeon HD7570M graphics card I have put ext4 partitions on both the SSD and the HDD, and have mounted / to the SSD and /home to the HDD. I also put a 24gb linux swap partition at the start of the HDD, though I figure this won't be used all that much (the laptop has 8gb of RAM). After googling around and reading Ask Ubuntu and other sites extensively, I have done the following steps, and they have improved the battery life ~30 minutes (exact improvement not clear, but battery life is still nowhere near 4-5 hours). Installed Jupiter (and set Performance to "Power Saving") Installed laptop-mode-tools cat /proc/sys/vm/laptop_mode now outputs 5 (previously it output 0) But it's not clear that this will help: AskUbuntu question Turned down the brightness of my screen from full to 1/3 Other things I have heard about but have not tried for fear of frying the laptop or my linux install: Add "pcie_aspm=force" at the end of the line with "quiet splash" in /boot/grub/grub.cfg Enable ALPM, but it may already be enabled in 12.04? Enable i915 framebuffer compression Use a propietary driver for the graphics card? Turn off the graphics card? (what would happen if I relied on the internal Intel bridge?) Use TLP? Spin down the HDD more aggressively (howto, but I think laptop-mode-tools does this already) The only other thing I've noticed is that plastic just above the F5, F6 and F7 keys gets really hot. According to Jupiter my CPU temperature is only 69 celsius and the System Monitor shows CPU load at 7% so I don't think it's the CPU. Maybe it's the graphics card? Also, I've set up MongoDB and LAMP on the machine as well. When I run powertop MongoDB is high in the list, but I'm not sure if that's relevant to battery life because I'm not actually doing anything with MongoDB most of the time. Edit - Additional info as requested $ lspci -nnk | grep -iEA3 "(graphics|vga)" 00:02.0 VGA compatible controller [0300]: Intel Corporation Ivy Bridge Graphics Controller [8086:0166] (rev 09) Subsystem: Dell Device [1028:057f] Kernel driver in use: i915 Kernel modules: i915 -- 02:00.0 VGA compatible controller [0300]: Advanced Micro Devices [AMD] nee ATI Thames [Radeon 7500M/7600M Series] [1002:6841] Subsystem: Dell Device [1028:057f] Kernel driver in use: radeon Kernel modules: radeon

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• Misused mke2fs and cannot boot into system

  - by surlogics

  I installed Ubuntu with WUBI in Windows 7 64bit, and I had installed Mandriva 2011 with a disk. I tried to learn Linux with Ubuntu and misused mke2fs; after I reboot my computer, Windows 7 and Ubuntu has crashed. As I have Mandriva, I boot into Mandriva and found # df -h /dev/sda7 12G 9.8G 1.5G 88% / /dev/sda2 15G 165M 14G 2% /media/logical /dev/sda6 119G 88G 32G 74% /media/2C9E85319E84F51C /dev/sda5 118G 59G 60G 50% /media/D25A6DDE5A6DBFB9 /dev/sda9 100G 188M 100G 1% /media/ae69134a-a65e-488f-ae7f-150d1b5e36a6 /dev/sda1 100M 122K 100M 1% /media/DELLUTILITY /dev/sda3 98G 81G 17G 83% /media/OS # fdisk /dev/sda Command (m for help): p Disk /dev/sda: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 cylinders, total 976773168 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: 0xd24f801e Device Boot Start End Blocks Id System /dev/sda1 2048 206847 102400 6 FAT16 /dev/sda2 * 206848 30926847 15360000 7 HPFS/NTFS/exFAT /dev/sda3 30926848 235726847 102400000 7 HPFS/NTFS/exFAT /dev/sda4 235728864 976771071 370521104 f W95 Ext'd (LBA) /dev/sda5 235728896 481488895 122880000 7 HPFS/NTFS/exFAT /dev/sda6 727252992 976771071 124759040 7 HPFS/NTFS/exFAT /dev/sda7 481500243 506674034 12586896 83 Linux /dev/sda8 506674098 514851119 4088511 82 Linux swap / Solaris /dev/sda9 514851183 727246484 106197651 83 Linux Partition table entries are not in disk order I think I may used the following command mke2fs -j -L "logical"/dev/sda2 but I had forgotten what kind of partition it was before I transfered it into ext3. perhaps ntfs Data was not lost, and I can view my files as I could in Windows. In Mandriva, there are following disks: 117.2 GB hard disk, files in it is the same as my Windows D:, and Ubuntu was installed in it; 119.0 GB hard disk is my G:, with my personal files in it; 12.0 GB is the same with Mandriva / (with means root), 101.3 GB hard disk with nothing but lost+found; DELLUTILITY should be Dell computer utilities pre-installed in my computer; logical is the disk which I had spoiled, I can view nothing but lost+found; and OS is the C: in my Windows. After I boot, grub lets me choose Mandriva or Windows. I chose Windows and it tells me: FILE system type unknown, partition type 0x7 Error 13: Invalid or unsupported executable format I doubt something wrong with windows MBR or something # cat /boot/grub/menu.lst timeout 5 color black/cyan yellow/cyan gfxmenu (hd0,6)/boot/gfxmenu default 0 title linux kernel (hd0,6)/boot/vmlinuz BOOT_IMAGE=linux root=UUID=199581b7-ac7e-4c5f-9888-24c4f213cad8 nokmsboot logo.nologo quiet resume=UUID=34c546e4-9c42-4526-aa64-bbdc0e9d64fd splash=silent vga=788 initrd (hd0,6)/boot/initrd.img title linux-nonfb kernel (hd0,6)/boot/vmlinuz BOOT_IMAGE=linux-nonfb root=UUID=199581b7-ac7e-4c5f-9888-24c4f213cad8 nokmsboot resume=UUID=34c546e4-9c42-4526-aa64-bbdc0e9d64fd initrd (hd0,6)/boot/initrd.img title failsafe kernel (hd0,6)/boot/vmlinuz BOOT_IMAGE=failsafe root=UUID=199581b7-ac7e-4c5f-9888-24c4f213cad8 nokmsboot failsafe initrd (hd0,6)/boot/initrd.img title windows root (hd0,1) makeactive chainloader +1 I can boot into Linux, but not Ubuntu, it boot into Mandriva. I don't have a boot disk. Help me find a way to make it work again.

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• dual boot ubuntu installation mishap

  - by user590849

  I have Windows 7 pc ,where i had 2 partitions, a c drive for my system files and a d drive for my data. I decided to install ubuntu 11.10 a couple of days ago and thought of install it in a separate partition of its own. So i made a separate Linux partition of 30GB. I downloaded ubuntu on my usb stick and installed. During the installation process i was asked where to install ubuntu so i opened up a screen that was similar to this one There were six partitions present ( I had made only 3 partition via windows). Their names were totally different from the ones that i had given in windows. So i selected a drive which had the same size as my Linux partition that i had made in windows ( no other partition had the same size). I clicked on install now and got an error message saying that "There was no root folder set". I set the newly made partition as my root folder and clicked install now. Now out of the 6 partitions that were created 3 were logical ( i had only created 3 partitions in windows). As soon as i clicked install now, the system asked me where i wanted to put my "swap space". I selected one of the logical drives and hit install. Ubuntu successfully installed on my system and at the end it asked me to reboot. I did and got the following error message: "missing operating system". I was shocked. I tried my windows recovery disk ( that i had gotten when i had purchased my laptop) and there i went into startup repair. In the startup repair option i was not able to locate windows. The system asked me to click the "Load drivers" button to load the drivers to my harddrive where windows was installed, but i could not locate any drivers to my harddrive. I tried this several times but to no success. I panicked and installed ubuntu, now this time click "ok" at every step( not worrying about the partition and all). The os installed correctly and i am now able to access my harddrive. NO data within the c drive is lost. All the windows system files are intact. I wish to recover my windows installation. How do i go about it? Thank you in advance. I do not want to format my computer and install windows again.

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• External 1TB WD USB 3.0 HDD is not detecting. Working perfectly find in Windows

  - by Yathi

  My 1TB USB 3.0 was working fine earlier in Ubuntu as well as Windows. But lately it is not at all being detected in Ubuntu. It still works fine in Windows. I did update my Ubuntu to 12.10 but I am not sure if that caused the issue. When I connect my HDD and run dmesg | tail: [ 47.804676] usb 4-3: >Device not responding to set address. [ 48.008575] usb 4-3: >Device not responding to set address. [ 48.212421] usb 4-3: >device not accepting address 9, error -71 [ 48.324451] usb 4-3: >Device not responding to set address. [ 48.528340] usb 4-3: >Device not responding to set address. [ 48.732165] usb 4-3: >device not accepting address 10, error -71 [ 48.844138] usb 4-3: >Device not responding to set address. [ 49.048179] usb 4-3: >Device not responding to set address. [ 49.251881] usb 4-3: >device not accepting address 11, error -71 [ 49.251907] hub 4-0:1.0: >unable to enumerate USB device on port 3 The output of sudo fdisk -l is : Disk /dev/sda: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disk identifier: 0x00030cde Device Boot Start End Blocks Id System /dev/sda1 2048 1332981759 666489856 83 Linux /dev/sda2 1332981760 1953523711 310270976 5 Extended /dev/sda5 1332983808 1349365759 8190976 82 Linux swap / Solaris /dev/sda6 1349367808 1953523711 302077952 7 HPFS/NTFS/exFAT Disk /dev/sdb: 120.0 GB, 120034123776 bytes 255 heads, 63 sectors/track, 14593 cylinders, total 234441648 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: 0x000a2519 Device Boot Start End Blocks Id System /dev/sdb1 * 2048 103368703 51683328 7 HPFS/NTFS/exFAT /dev/sdb2 103368704 154568703 25600000 83 Linux /dev/sdb3 154568704 234440703 39936000 7 HPFS/NTFS/exFAT /dev/sda and /dev/sdb are my 2 internal HDDs. But the external one which should be /dev/sdc is not even being shown though it is connected and the LED on the HDD is glowing. Someone had suggested adding blacklist uas to /etc/modprobe.d/blacklist.conf. Tried that as well. But still not working. Can someone help me out.

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• laptop will not boot after attempting upgrade to 13.10

  - by naerwenya

  I wanted to update my OS to the new 14.04 LTS. I was running 12.04 LTS before and followed the advice that upgrades should be done in steps. I first upgraded to 12.10, which seemed to work fine, and later to 13.10. This was all done through the Software Manager. After the last upgrade, I am no longer able to boot up my computer. The GNU GRUB menu opens up, but after selecting Ubuntu, it just stalls with a blank purple screen. If I select one of the other kernels, it also stalls after "Loading initial ramdisk...". I can't get into the Recovery Menu, either. I'm still rather new to Linux and may have possibly made the situation worse. Unfortunately, nothing has worked yet. I tried reinstalling from a flash drive and on my first attempt, the wizard recognised a previous installation. Unfortunately, the wizard also didn't like how my partitions were set up (I didn't change anything) and gave an error before closing. Unfortunately, I didn't write the error down, but it was about the boot partition. On the next attempt and ever since, the installation wizard has stated that "This computer currently has no detected operating systems." This is strange, because I could see the disk and even access my files when booting up from the USB. At this point, I decided to back up my important files using dropbox. Before losing all my files, I wanted to try the Boot-Repair tool, which also produced no results, and the files are no longer visible when booting from USB. The link to the Boot-Repair log is at http://paste.ubuntu.com/7457249/. If I then proceed through to the "Something else" installation option, I can see that the partitions still exist. This is what they look like: /dev/sda free space (size indicated 1MB) /dev/sda1 efi (33MB of 98 MB used) /dev/sda2 efi (352634MB of 746330MB used) /dev/sda3 swap (3725MB, none used) free space (0MB) Is there any way I might be able to get my computer to work and preserve my files as well?

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• F# Add Constructor to a Record?

  - by akaphenom

  Basically I want to have a single construct to deal with serializing to both JSON and formatted xml. Records workd nicley for serializing to/from json. However XmlSerializer requires a parameterless construtor. I don't really want to have to go through the exercise of building class objects for these constructs (principal only). I was hoping there could be some shortcut for getting a parameterless constructor onto a record (perhaps with a wioth statement or something). I can't get it to behave - has anybody in the community had any luck? module JSONExample open System open System.IO open System.Net open System.Text open System.Web open System.Xml open System.Security.Authentication open System.Runtime.Serialization //add assemnbly reference System.Runtime.Serialization System.Xml open System.Xml.Serialization open System.Collections.Generic [<DataContract>] type ChemicalElementRecord = { [<XmlAttribute("name")>] [<field: DataMember(Name="name") >] Name:string [<XmlAttribute("name")>] [<field: DataMember(Name="boiling_point") >] BoilingPoint:string [<XmlAttribute("atomic-mass")>] [<field: DataMember(Name="atomic_mass") >] AtomicMass:string } [<XmlRoot("freebase")>] [<DataContract>] type FreebaseResultRecord = { [<XmlAttribute("code")>] [<field: DataMember(Name="code") >] Code:string [<XmlArrayAttribute("results")>] [<XmlArrayItem(typeof<ChemicalElementRecord>, ElementName = "chemical-element")>] [<field: DataMember(Name="result") >] Result: ChemicalElementRecord array [<XmlElement("message")>] [<field: DataMember(Name="message") >] Message:string } let getJsonFromWeb() = let query = "[{'type':'/chemistry/chemical_element','name':null,'boiling_point':null,'atomic_mass':null}]" let query = query.Replace("'","\"") let queryUrl = sprintf "http://api.freebase.com/api/service/mqlread?query=%s" "{\"query\":"+query+"}" let request : HttpWebRequest = downcast WebRequest.Create(queryUrl) request.Method <- "GET" request.ContentType <- "application/x-www-form-urlencoded" let response = request.GetResponse() let result = try use reader = new StreamReader(response.GetResponseStream()) reader.ReadToEnd(); finally response.Close() let data = Encoding.Unicode.GetBytes(result); let stream = new MemoryStream() stream.Write(data, 0, data.Length); stream.Position <- 0L stream let test = // get some JSON from the web let stream = getJsonFromWeb() // convert the stream of JSON into an F# Record let JsonSerializer = Json.DataContractJsonSerializer(typeof<FreebaseResultRecord>) let result: FreebaseResultRecord = downcast JsonSerializer.ReadObject(stream) // save the Records to disk as JSON use fs = new FileStream(@"C:\temp\freebase.json", FileMode.Create) JsonSerializer.WriteObject(fs,result) fs.Close() // save the Records to disk as System Controlled XML let xmlSerializer = DataContractSerializer(typeof<FreebaseResultRecord>); use fs = new FileStream(@"C:\temp\freebase.xml", FileMode.Create) xmlSerializer.WriteObject(fs,result) fs.Close() use fs = new FileStream(@"C:\temp\freebase-pretty.xml", FileMode.Create) let xmlSerializer = XmlSerializer(typeof<FreebaseResultRecord>) xmlSerializer.Serialize(fs,result) fs.Close() ignore(test)

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• Regular expression works normally, but fails when placed in an XML schema

  - by Eli Courtwright

  I have a simple doc.xml file which contains a single root element with a Timestamp attribute: <?xml version="1.0" encoding="utf-8"?> <root Timestamp="04-21-2010 16:00:19.000" /> I'd like to validate this document against a my simple schema.xsd to make sure that the Timestamp is in the correct format: <?xml version="1.0" encoding="utf-8"?> <xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="root"> <xs:complexType> <xs:attribute name="Timestamp" use="required" type="timeStampType"/> </xs:complexType> </xs:element> <xs:simpleType name="timeStampType"> <xs:restriction base="xs:string"> <xs:pattern value="(0[0-9]{1})|(1[0-2]{1})-(3[0-1]{1}|[0-2]{1}[0-9]{1})-[2-9]{1}[0-9]{3} ([0-1]{1}[0-9]{1}|2[0-3]{1}):[0-5]{1}[0-9]{1}:[0-5]{1}[0-9]{1}.[0-9]{3}" /> </xs:restriction> </xs:simpleType> </xs:schema> So I use the lxml Python module and try to perform a simple schema validation and report any errors: from lxml import etree schema = etree.XMLSchema( etree.parse("schema.xsd") ) doc = etree.parse("doc.xml") if not schema.validate(doc): for e in schema.error_log: print e.message My XML document fails validation with the following error messages: Element 'root', attribute 'Timestamp': [facet 'pattern'] The value '04-21-2010 16:00:19.000' is not accepted by the pattern '(0[0-9]{1})|(1[0-2]{1})-(3[0-1]{1}|[0-2]{1}[0-9]{1})-[2-9]{1}[0-9]{3} ([0-1]{1}[0-9]{1}|2[0-3]{1}):[0-5]{1}[0-9]{1}:[0-5]{1}[0-9]{1}.[0-9]{3}'. Element 'root', attribute 'Timestamp': '04-21-2010 16:00:19.000' is not a valid value of the atomic type 'timeStampType'. So it looks like my regular expression must be faulty. But when I try to validate the regular expression at the command line, it passes: >>> import re >>> pat = '(0[0-9]{1})|(1[0-2]{1})-(3[0-1]{1}|[0-2]{1}[0-9]{1})-[2-9]{1}[0-9]{3} ([0-1]{1}[0-9]{1}|2[0-3]{1}):[0-5]{1}[0-9]{1}:[0-5]{1}[0-9]{1}.[0-9]{3}' >>> assert re.match(pat, '04-21-2010 16:00:19.000') >>> I'm aware that XSD regular expressions don't have every feature, but the documentation I've found indicates that every feature that I'm using should work. So what am I mis-understanding, and why does my document fail?

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• Searches (and general querying) with HBase and/or Cassandra (best practices?)

  - by alexeypro

  I have User model object with quite few fields (properties, if you wish) in it. Say "firstname", "lastname", "city" and "year-of-birth". Each user also gets "unique id". I want to be able to search by them. How do I do that properly? How to do that at all? My understanding (will work for pretty much any key-value storage -- first goes key, then value) u:123456789 = serialized_json_object ("u" as a simple prefix for user's keys, 123456789 is "unique id"). Now, thinking that I want to be able to search by firstname and lastname, I can save in: f:Steve = u:384734807,u:2398248764,u:23276263 f:Alex = u:12324355,u:121324334 so key is "f" - which is prefix for firstnames, and "Steve" is actual firstname. For "u:Steve" we save as value all user id's who are "Steve's". That makes every search very-very easy. Querying by few fields (properties) -- say by firstname (i.e. "Steve") and lastname (i.e. "l:Anything") is still easy - first get list of user ids from "f:Steve", then list from "l:Anything", find crossing user ids, an here you go. Problems (and there are quite a few): Saving, updating, deleting user is a pain. It has to be atomic and consistent operation. Also, if we have size of value limited to some value - then we are in (potential) trouble. And really not of an answer here. Only zipping the list of user ids? Not too cool, though. What id we want to add new field to search by. Eventually. Say by "city". We certainly can do the same way "c:Los Angeles" = ..., "c:Chicago" = ..., but if we didn't foresee all those "search choices" from the very beginning, then we will have to be able to create some night job or something to go by all existing User records and update those "c:CITY" for them... Quite a big job! Problems with locking. User "u:123" updates his name "Alex", and user "u:456" updates his name "Alex". They both have to update "f:Alex" with their id's. That means either we get into overwriting problem, or one update will wait for another (and imaging if there are many of them?!). What's the best way of doing that? Keeping in mind that I want to search by many fields? P.S. Please, the question is about HBase/Cassandra/NoSQL/Key-Value storages. Please please - no advices to use MySQL and "read about" SELECTs; and worry about scaling problems "later". There is a reason why I asked MY question exactly the way I did. :-)

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• Why does the rename() syscall prohibit moving a directory that I can't write to a different director

  - by Daniel Papasian

  I am trying to understand why this design decision was made with the rename() syscall in 4.2BSD. There's nothing I'm trying to solve here, just understand the rationale for the behavior itself. 4.2BSD saw the introduction of the rename() syscall for the purpose of allowing atomic renames/moves of files. From 4.3BSD-Reno/src/sys/ufs/ufs_vnops.c: /* * If ".." must be changed (ie the directory gets a new * parent) then the source directory must not be in the * directory heirarchy above the target, as this would * orphan everything below the source directory. Also * the user must have write permission in the source so * as to be able to change "..". We must repeat the call * to namei, as the parent directory is unlocked by the * call to checkpath(). */ if (oldparent != dp->i_number) newparent = dp->i_number; if (doingdirectory && newparent) { VOP_LOCK(fndp->ni_vp); error = ufs_access(fndp->ni_vp, VWRITE, tndp->ni_cred); VOP_UNLOCK(fndp->ni_vp); So clearly this check was added intentionally. My question is - why? Is this behavior supposed to be intuitive? The effect of this is that one cannot move a directory (located in a directory that one can write) that one cannot write to another directory that one can write to atomically. You can, however, create a new directory, move the links over (assuming one has read access to the directory), and then remove one's write bit on the directory. You just can't do so atomically. % cd /tmp % mkdir stackoverflow-question % cd stackoverflow-question % mkdir directory-1 % mkdir directory-2 % mkdir directory-1/directory-i-cant-write % echo "foo" > directory-1/directory-i-cant-write/contents % chmod 000 directory-1/directory-i-cant-write/contents % chmod 000 directory-1/directory-i-cant-write % mv directory-1/directory-i-cant-write directory-2 mv: rename directory-1/directory-i-cant-write to directory-2/directory-i-cant-write: Permission denied We now have a directory I can't write with contents I can't read that I can't move atomically. I can, however, achieve the same effect non-atomically by changing permissions, making the new directory, using ln to create the new links, and changing permissions. (Left as an exercise to the reader) . and .. are special cased already, so I don't particularly buy that it is intuitive that if I can't write a directory I can't "change .." which is what the source suggests. Is there any reason for this besides it being the perceived correct behavior by the author of the code? Is there anything bad that can happen if we let people atomically move directories (that they can't write) between directories that they can write?

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• CQRS - Should a Command try to create a "complex" master-detail entity?

  - by Simon Crabtree

  I've been reading Greg Young and Udi Dahan's thoughts on Command Query Responsibilty Separation and a lot of what I read strikes a chord with me. My domain (we track vehicles which are doing deliveries) has the concept of a Route which contains one or more Stops. I need my customers to be able to set these up in our system by calling a webservice, and then be able to retrieve information about a Route and how the vehicle is progressing. In the past I would have "cut-down" DTO classes which closely resemble my domain classes, and the customer would create a RouteDto with an array of StopDto(s), and call our CreateRoute webmethod, passing in the RouteDto. When they query our system by calling the GetRouteDetails method, I would return exactly the same objects to them. One of the appealing aspects of CQRS is that the RouteDto might have all manner of properties that the customer wants to query, but have no business setting when they create a Route. So I create a separate CreateRouteRequest class which is passed in when calling the CreateRoute "command", and a Route DTO class which gets returned as a query result. class Route{ string Reference; List<Stop> Stops; } But I need my customer to provide me with Route AND Stop details when they create a route. As I see it I could either... Give my CreateRouteRequest class a Stops(s) property which is an array of "something" representing the data they need to provide about each stop - but what do I call this class? It's not a Stop as that's what I'm calling the list of DTO inside my Route DTO, but I don't like "CreateStopRequest". I also wonder if I'm stuck in a CRUD mindset here thinking in terms of master-detail information and asking the customer to think like that too. class CreateRouteRequest{ string Reference; ... List<CreateStopRequest> Stops; } or They call CreateRoute, and then make a number of calls to an AddStopToRoute method. This feels a bit more "behavioural" but I'm going to lose the ability to treat creating a route including its stops as a single atomic command. If they create a Route and then try to add a Stop which fails due to some validation problem they're going to have a partially correct Route. The fact that I can't come up with a good name for the list of "StopCreationData" objects I'd be working with in option 1, makes me wonder if there's something I'm missing.

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• Is this a valid pattern for raising events in C#?

  - by Will Vousden

  Update: For the benefit of anyone reading this, since .NET 4, the lock is unnecessary due to changes in synchronization of auto-generated events, so I just use this now: public static void Raise<T>(this EventHandler<T> handler, object sender, T e) where T : EventArgs { if (handler != null) { handlerCopy(sender, e); } } And to raise it: SomeEvent.Raise(this, new FooEventArgs()); Having been reading one of Jon Skeet's articles on multithreading, I've tried to encapsulate the approach he advocates to raising an event in an extension method like so (with a similar generic version): public static void Raise(this EventHandler handler, object @lock, object sender, EventArgs e) { EventHandler handlerCopy; lock (@lock) { handlerCopy = handler; } if (handlerCopy != null) { handlerCopy(sender, e); } } This can then be called like so: protected virtual void OnSomeEvent(EventArgs e) { this.someEvent.Raise(this.eventLock, this, e); } Are there any problems with doing this? Also, I'm a little confused about the necessity of the lock in the first place. As I understand it, the delegate is copied in the example in the article to avoid the possibility of it changing (and becoming null) between the null check and the delegate call. However, I was under the impression that access/assignment of this kind is atomic, so why is the lock necessary? Update: With regards to Mark Simpson's comment below, I threw together a test: static class Program { private static Action foo; private static Action bar; private static Action test; static void Main(string[] args) { foo = () => Console.WriteLine("Foo"); bar = () => Console.WriteLine("Bar"); test += foo; test += bar; test.Test(); Console.ReadKey(true); } public static void Test(this Action action) { action(); test -= foo; Console.WriteLine(); action(); } } This outputs: Foo Bar Foo Bar This illustrates that the delegate parameter to the method (action) does not mirror the argument that was passed into it (test), which is kind of expected, I guess. My question is will this affect the validity of the lock in the context of my Raise extension method? Update: Here is the code I'm now using. It's not quite as elegant as I'd have liked, but it seems to work: public static void Raise<T>(this object sender, ref EventHandler<T> handler, object eventLock, T e) where T : EventArgs { EventHandler<T> copy; lock (eventLock) { copy = handler; } if (copy != null) { copy(sender, e); } }

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• How would you implement this "WorkerChain" functionality in .NET?

  - by Dan Tao

  Sorry for the vague question title -- not sure how to encapsulate what I'm asking below succinctly. (If someone with editing privileges can think of a more descriptive title, feel free to change it.) The behavior I need is this. I am envisioning a worker class that accepts a single delegate task in its constructor (for simplicity, I would make it immutable -- no more tasks can be added after instantiation). I'll call this task T. The class should have a simple method, something like GetToWork, that will exhibit this behavior: If the worker is not currently running T, then it will start doing so right now. If the worker is currently running T, then once it is finished, it will start T again immediately. GetToWork can be called any number of times while the worker is running T; the simple rule is that, during any execution of T, if GetToWork was called at least once, T will run again upon completion (and then if GetToWork is called while T is running that time, it will repeat itself again, etc.). Now, this is pretty straightforward with a boolean switch. But this class needs to be thread-safe, by which I mean, steps 1 and 2 above need to comprise atomic operations (at least I think they do). There is an added layer of complexity. I have need of a "worker chain" class that will consist of many of these workers linked together. As soon as the first worker completes, it essentially calls GetToWork on the worker after it; meanwhile, if its own GetToWork has been called, it restarts itself as well. Logically calling GetToWork on the chain is essentially the same as calling GetToWork on the first worker in the chain (I would fully intend that the chain's workers not be publicly accessible). One way to imagine how this hypothetical "worker chain" would behave is by comparing it to a team in a relay race. Suppose there are four runners, W1 through W4, and let the chain be called C. If I call C.StartWork(), what should happen is this: If W1 is at his starting point (i.e., doing nothing), he will start running towards W2. If W1 is already running towards W2 (i.e., executing his task), then once he reaches W2, he will signal to W2 to get started, immediately return to his starting point and, since StartWork has been called, start running towards W2 again. When W1 reaches W2's starting point, he'll immediately return to his own starting point. If W2 is just sitting around, he'll start running immediately towards W3. If W2 is already off running towards W3, then W2 will simply go again once he's reached W3 and returned to his starting point. The above is probably a little convoluted and written out poorly. But hopefully you get the basic idea. Obviously, these workers will be running on their own threads. Also, I guess it's possible this functionality already exists somewhere? If that's the case, definitely let me know!

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• whats wrong with this php mysql_real_escape_string

  - by skyhigh

  Hi Atomic Number Latin English Abbreviation * check the variables for content */ /*** a list of filters ***/ $filters = array( 'searchtext' => array( 'filter' => FILTER_CALLBACK, 'options' => 'mysql_real_escape_string'), 'fieldname' => array( 'filter' => FILTER_CALLBACK, 'options' => 'mysql_real_escape_string') ); /*** escape all POST variables ***/ $input = filter_input_array(INPUT_POST, $filters); /*** check the values are not empty ***/ if(empty($input['fieldname']) || empty($input['searchtext'])) { echo 'Invalid search'; } else { /*** mysql hostname ***/ $hostname = 'localhost'; /*** mysql username ***/ $username = 'username'; /*** mysql password ***/ $password = 'password'; /*** mysql database name ***/ $dbname = 'periodic_table'; /*** connect to the database ***/ $link = @mysql_connect($hostname, $username, $password); /*** check if the link is a valid resource ***/ if(is_resource($link)) { /*** select the database we wish to use ***/ if(mysql_select_db($dbname, $link) === TRUE) { /*** sql to SELECT information***/ $sql = sprintf("SELECT * FROM elements WHERE %s = '%s'", $input['fieldname'], $input['searchtext']); /*** echo the sql query ***/ echo '<h3>'.$sql.'</h3>'; /*** run the query ***/ $result = mysql_query($sql); /*** check if the result is a valid resource ***/ if(is_resource($result)) { /*** check if we have more than zero rows ***/ if(mysql_num_rows($result) !== 0) { echo '<table>'; while($row=mysql_fetch_array($result)) { echo '<tr> <td>'.$row['atomicnumber'].'</td> <td>'.$row['latin'].'</td> <td>'.$row['english'].'</td> <td>'.$row['abbr'].'</td> </tr>'; } echo '</table>'; } else { /*** if zero results are found.. ***/ echo 'Zero results found'; } } else { /*** if the resource is not valid ***/ 'No valid resource found'; } } /*** if we are unable to select the database show an error ****/ else { echo 'Unable to select database '.$dbname; } /*** close the connection ***/ mysql_close($link); } else { /*** if we fail to connect ***/ echo 'Unable to connect'; } } } else { echo 'Please Choose An Element'; } ? I got this code from phppro.org tutorials site and i tried to run it. It gives Warning: mysql_real_escape_string() [function.mysql-real-escape-string]: A link to the server could not be established. .... Warning: mysql_real_escape_string() [function.mysql-real-escape-string]: Access denied for user 'ODBC'@'localhost' (using password: NO).... I went to php.net and look it up "Note: A MySQL connection is required before using mysql_real_escape_string() otherwise an error of level E_WARNING is generated, and FALSE is returned. If link_identifier isn't defined, the last MySQL connection is used." My questions are: 1-why they put single quotation around mysql_real_escape_string ? 2-They should establish a connection first, then use the $filter array statement with mysql_real_escape_string ?

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• Writing a mini-language with haskell, trouble with "while" statements and blocks { }

  - by Nibirue

  EDIT: problem partially solved, skip to the bottom for update. I'm writing a small language using haskell, and I've made a lot of progress, but I am having trouble implementing statements that use blocks, like "{ ... }". I've implemented support for If statements like so in my parser file: stmt = skip +++ ifstmt +++ assignment +++ whilestmt ifstmt = symbol "if" >> parens expr >>= \c -> stmt >>= \t -> symbol "else" >> stmt >>= \e -> return $ If c t e whilestmt = symbol "while" >> parens expr >>= \c -> symbol "\n" >> symbol "{" >> stmt >>= \t -> symbol "}" >> return $ While c t expr = composite +++ atomic And in the Syntax file: class PP a where pp :: Int -> a -> String instance PP Stmt where pp ind (If c t e) = indent ind ++ "if (" ++ show c ++ ") \n" ++ pp (ind + 2) t ++ indent ind ++ "else\n" ++ pp (ind + 2) e pp ind (While c t) = indent ind ++ "while (" ++ show c ++") \n" ++ "{" ++ pp (ind + 2) t ++ "}" ++ indent ind Something is wrong with the while statement, and I don't understand what. The logic seems correct, but when I run the code I get the following error: EDIT: Fixed the first problem based on the first reply, now it is not recognizing my while statment which I assume comes from this: exec :: Env -> Stmt -> Env exec env (If c t e) = exec env ( if eval env c == BoolLit True then t else e ) exec env (While c t) = exec env ( if eval env c == BoolLit True then t ) The file being read from looks like this: x = 1; c = 0; if (x < 2) c = c + 1; else ; -- SEPARATE FILES FOR EACH x = 1; c = 1; while (x < 10) { c = c * x; x = x + 1; } c I've tried to understand the error report but nothing I've tried solves the problem.

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• Rebuilding array on 3ware 9690SA-8I

  - by Tim Jones

  I have a RAID10 (8x1TB) array on a 3ware 9690 card running on an Ubuntu 1110 server. There was a kernel update so I scheduled a reboot after which the array was inaccessible. I checked the status a drive has died in the array, but the controller has thrown the entire array into an 'inoperable' state instead of simply degraded (what's the point of the RAID now ;-). After taking out the 'dead' drive I run a quick test to find it completely functional without a bad sector to be found. I try to put the drive back in but the array still marks the disk as degraded (remembering serial number or something??) and the entire array as inoperable... So I swap it out for a known working drive (not the same capacity but higher - should still work) and initiate a rebuild with the the new drive as a replacement. This fails instantly with the error "(0x0B:0x0033): Unit busy : Failed to start Rebuild on Unit 0". The unit shouldn't be busy as it is not mounted (the card itself is listed with lshw but the array it provides is not). I'm pretty much at an impasse now, I don't understand how I can have a single drive failure on a RAID10 that makes the entire array inaccessible, degraded I could understand but inaccessible?? I don't think the controller as prior to the reboot it was completely functional.

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• VMWare ESXi, change the default path for a VM

  - by glenatron

  For some reason VMWare ESXi has decided that one of my VMs is on a completely different path to the path it is actually on. So my VM is on /vmfs/volumes/long-guid-here/my-vm-name but when I try to open it I get the message "File < unspecified filename was not found." Which is not really surprising as unspecified filenames are quite difficult to locate. I thought it was just the swap file, which was down in the .vmx file as /vmfs/volumes/long-guid-here/old-vm-name/old-vm-name.vmsd but when I changed that in the vmx it made no difference. What I can't figure out is where VMWare is getting the old-vm-name from- when I look in the "Settings" pane it believes the working file location to be "[datastore-name] old-vm-name\" and I can't find anywhere to change it. Now the files themselves are all named for old-vm-name - so the directory is /my-vm-name/old-vm-name.vmx and so on. Is this the cause of my problems or is there some arcane configuration option elsewhere around the VMWare machine that I need to be tinkering with?

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